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Morphine and cocaine influence on CRF biosynthesis in the rat central nucleus of amygdala
Abstract
The central nucleus of the amygdala is a CRF-containing limbic brain site which mediates both fear-like and avoidance behaviors; moreover it has been hypothesized that atypical stress responses may contribute to compulsive drug use. Therefore, we studied in rat amygdala the level of CRF mRNA by in situ hybrydization, and the level of the peptide using immunocytochemistry after acute and chronic administration of morphine and cocaine and after their withdrawal. Acute injection of morphine (20 mg/kg i.p.) increased CRF mRNA level, but did not change significantly CRF immunoreactivity in the central nucleus of the amygdala. Chronic morphine administration significantly increased the level of CRF mRNA 3, 24 and 48 h after the last dose. Both, acute and chronic cocaine administration increased CRF mRNA, but the peptide level was decreased only after acute cocaine administration. However, in the late withdrawal (48 h after the last dose of cocaine) both mRNA and the peptide levels tended to decrease. The above data suggest that amygdalar CRF system activity is potently activated after administration of morphine and cocaine, and that activation of this system observed at the time of withdrawal from morphine may be responsible for aversion and anxiety related to these states; therefore a CRF1 receptor may be a target for prospective pharmacotherapies of the withdrawal from abused drugs.
... While hypothalamic CRF may play a role in the very onset of drug selfadministration, extrahypothalamic sources of CRF, particularly within the extended amygdala and other limbic structures, might be implicated in the negative reinforcement mechanisms associated with later stages of drug dependence [Koob, 2010]. Multiple lines of evidence have demonstrated that, while acute drug exposure yields a transient elevation of CRF expression in multiple brain regions [Zhou et al., 1996, Maj et al., 2003, chronic drug exposure results in an overactivation of the CRF system, which is central to the drug dependence and withdrawal phenotypes observed upon cessation of drug intake [Zorrilla et al., 2001, Zhou et al., 2003, Sommer et al., 2008, George et al., 2007, Caberlotto et al., 2004. During the progression of drug dependence, drug exposure disrupts the HPA axis negative feedback mechanisms [Zhou et al., 1996], resulting in a blunted response [Koob and Kreek, 2007]. ...
... However, when the drug is subsequently withdrawn, CRF release in the extended amygdala increases, accompanied by somatic and psychological withdrawal signs [Richter and Weiss, 1999, Olive et al., 2002, Merlo Pich et al., 1995. Particularly striking across multiple drugs of abuse is the elevation of CRF in the central nucleus of the amygdala (CeA) at various withdrawal time points, which could be observed in rats not only when assessing levels of messenger RNA (mRNA) expression [Caberlotto et al., 2004, Maj et al., 2003, Sommer et al., 2008 and protein content [Zorrilla et al., 2001], but also as an elevation of CRF released into the extracellular space [Rodriguez de Fonseca et al., 1997, Richter and Weiss, 1999, George et al., 2007. Similar to the CeA, increased CRF release has also been observed in the lateral bed nucleus of the stria terminalis (BNST) during alcohol withdrawal in rats [Olive et al., 2002], suggesting an elevated activation of CRF signaling throughout the whole structure of the extended amygdala. ...
... CRF might also be implicated in OUDs. For instance, early (8-48 h) morphine withdrawal is associated with increased CRF mRNA expression in the central nucleus of the amygdala (CeA) and the paraventricular nucleus of the hypothalamus (PVN), brain regions implicated in the effects of substances of abuse [Ingallinesi et al., 2012, Maj et al., 2003, Papaleo et al., 2007. CRF signaling is mediated by two types of receptors, named CRF 1 and CRF 2 [Hauger et al., 2003]. ...
The neurobiology underlying poor social behavior of opiate users and dependent individuals remains largely unknown, hampering the development of noveleffective therapies for opiate use disorders. However, recent pre-clinical evidence suggests that the corticotropin-releasing factor (CRF) system might be involved.In this light, we employed the three-chamber (3-CH) task and genetic/pharmacological approaches to assess the impact of morphine administrationand withdrawal upon social behavior in mice with regard to the CRF system. In a first set of experiments, we found that male subjects displayed increasedhostility-driven pseudo-social interest during opiate withdrawal, indicative of longlasting effects of chronic drug administration upon normal social functioning. On theother hand, female subjects displayed lower social interest during opiate withdrawal, a phenotype that more straightforwardly replicates what observed in humans.Notably, CRF1 receptor-deficiency completely rescued the latter social deficit, adding to the growing evidence linking the CRF system to substance-induced behavioraldysfunctions. In a second set of experiments, we investigated the initial effects of morphine more widely on naturally” rewarding activities. We found that a single, acuteadministration of a relatively low dose of the drug was sufficient to produce brain reward and at the same time to induce profound deficits in social interest and fooddriven motivation, providing initial experimental evidence of “hijacking” of brain reward systems by substances of abuse. Interestingly, systemic administration of the CRF receptor antagonist antalarmin completely reversed the latter social deficit, indicating a critical role of the CRF system in mediating substance-induced decreased interest for “naturally” rewarding activities and strengthening the notion of a therapeutic potential for CRF-targeting pharmacological agents.
... While hypothalamic CRF may play a role in the very onset of drug selfadministration, extrahypothalamic sources of CRF, particularly within the extended amygdala and other limbic structures, might be implicated in the negative reinforcement mechanisms associated with later stages of drug dependence [Koob, 2010]. Multiple lines of evidence have demonstrated that, while acute drug exposure yields a transient elevation of CRF expression in multiple brain regions [Zhou et al., 1996, Maj et al., 2003, chronic drug exposure results in an overactivation of the CRF system, which is central to the drug dependence and withdrawal phenotypes observed upon cessation of drug intake [Zorrilla et al., 2001, Zhou et al., 2003, Sommer et al., 2008, George et al., 2007, Caberlotto et al., 2004. During the progression of drug dependence, drug exposure disrupts the HPA axis negative feedback mechanisms [Zhou et al., 1996], resulting in a blunted response [Koob and Kreek, 2007]. ...
... However, when the drug is subsequently withdrawn, CRF release in the extended amygdala increases, accompanied by somatic and psychological withdrawal signs [Richter and Weiss, 1999, Olive et al., 2002, Merlo Pich et al., 1995. Particularly striking across multiple drugs of abuse is the elevation of CRF in the central nucleus of the amygdala (CeA) at various withdrawal time points, which could be observed in rats not only when assessing levels of messenger RNA (mRNA) expression [Caberlotto et al., 2004, Maj et al., 2003, Sommer et al., 2008 and protein content [Zorrilla et al., 2001], but also as an elevation of CRF released into the extracellular space [Rodriguez de Fonseca et al., 1997, Richter and Weiss, 1999, George et al., 2007. Similar to the CeA, increased CRF release has also been observed in the lateral bed nucleus of the stria terminalis (BNST) during alcohol withdrawal in rats [Olive et al., 2002], suggesting an elevated activation of CRF signaling throughout the whole structure of the extended amygdala. ...
... CRF might also be implicated in OUDs. For instance, early (8-48 h) morphine withdrawal is associated with increased CRF mRNA expression in the central nucleus of the amygdala (CeA) and the paraventricular nucleus of the hypothalamus (PVN), brain regions implicated in the effects of substances of abuse [Ingallinesi et al., 2012, Maj et al., 2003, Papaleo et al., 2007. CRF signaling is mediated by two types of receptors, named CRF 1 and CRF 2 [Hauger et al., 2003]. ...
The neurobiology underlying poor social behavior of opiate users and dependent individuals remains largely unknown, hampering the development of novel effective therapies for opiate use disorders. However, recent pre-clinical evidence suggests that the corticotropin-releasing factor (CRF) system might be involved. In this light, we employed the three-chamber (3-CH) task and genetic/pharmacological approaches to assess the impact of morphine administration and withdrawal upon social behavior in mice with regard to the CRF system. In a first set of experiments, we found that male subjects displayed increased hostility-driven pseudo-social interest during opiate withdrawal, indicative of long lasting effects of chronic drug administration upon normal social functioning. On the other hand, female subjects displayed lower social interest during opiate withdrawal, a phenotype that more straightforwardly replicates what observed in humans. Notably, CRF1 receptor-deficiency completely rescued the latter social deficit, adding to the growing evidence linking the CRF system to substance-induced behavioral dysfunctions. In a second set of experiments, we investigated the initial effects of morphine more widely on naturally rewarding activities. We found that a single, acute administration of a relatively low dose of the drug was sufficient to produce brain reward and at the same time to induce profound deficits in social interest and food-driven motivation, providing initial experimental evidence of hijacking of brain reward systems by substances of abuse. Interestingly, systemic administration of the CRF receptor antagonist antalarmin completely reversed the latter social deficit, indicating a critical role of the CRF system in mediating substance-induced decreased interest for naturally rewarding activities and strengthening the notion of a therapeutic potential for CRF-targeting pharmacological agents.
... The paraventricular nucleus of the hypothalamus (PVN) of the HPA axis and the extended amygdala contain a large number of CRF cell bodies (Swanson et al., 1983). Alterations in CRF mRNA (Zhou et al., 1996(Zhou et al., , 2003a(Zhou et al., , 2003bMaj et al., 2003;Erb et al., 2004;Mantsch et al., 2007;Rudoy et al., 2009) and peptide content (Sarnyai et al., 1995;Richter and Weiss, 1999;Zorrilla et al., 2001;Maj et al., 2003) have been reported in these brain regions at different time points following chronic cocaine administration. The majority of these studies have investigated male rats. ...
... The paraventricular nucleus of the hypothalamus (PVN) of the HPA axis and the extended amygdala contain a large number of CRF cell bodies (Swanson et al., 1983). Alterations in CRF mRNA (Zhou et al., 1996(Zhou et al., , 2003a(Zhou et al., , 2003bMaj et al., 2003;Erb et al., 2004;Mantsch et al., 2007;Rudoy et al., 2009) and peptide content (Sarnyai et al., 1995;Richter and Weiss, 1999;Zorrilla et al., 2001;Maj et al., 2003) have been reported in these brain regions at different time points following chronic cocaine administration. The majority of these studies have investigated male rats. ...
... Expanded by a thorough time-course analysis during withdrawal and by the addition of females treated in parallel to males, the present results support previous findings and extend those results in several ways. For example, 2 studies found an increase in CRF mRNA in the CeA of male rats 24 hours post cocaine (Maj et al., 2003;Erb et al., 2004), which is replicated here. In contrast, other studies have found an increase in CRF mRNA in the amygdala at 48 hours, not 24 hours, post cocaine (Zhou et al., 2003a;Rudoy et al., 2009). ...
Background:
Cocaine withdrawal activates stress systems. Females are more vulnerable to relapse to cocaine use and more sensitive to withdrawal-induced negative affect. Delta opioid receptors (DOR) modulate anxiety-like behavior during cocaine withdrawal in rats. This study measured the time course of gene regulation of one of the main stress peptides, CRF, and its type 1 receptor in male and female rats, as well as the ability of the DOR agonist SNC80 to normalize cocaine withdrawal-induced changes in CRF mRNA.
Methods:
Rats were injected with cocaine or saline 3 times daily for 14 days. Brains were collected 30 minutes, 24 hours, 48 hours, 7 days, and 14 days following the last injection. The paraventricular nucleus of the hypothalamus (PVN), central amygdala (CeA), and bed nucleus of the stria terminalis (BNST) were processed for qRT-PCR measurement of CRF and CRFR1 mRNA. Additional rats received SNC80 during early cocaine withdrawal, and CRF mRNA was measured in the CeA.
Results:
CRF mRNA was elevated in the CeA at 24 hours and the PVN at 48 hours of cocaine withdrawal in males and females. Significant sex differences in cocaine-induced CRF upregulation were found in the BNST at 30 minutes and 24 hours. SNC80 administration attenuated the increase in CRF mRNA in the CeA of female rats only.
Conclusions:
CRF mRNA regulation during cocaine withdrawal is sex-, time- and brain region-dependent. Administration of a DOR agonist during early withdrawal may ameliorate stress-related negative affect in females by abrogating the induction of CRF mRNA.
... Substantial preclinical data implicate extended amygdala CRF-CRF 1 systems in excessive or addiction-like consumption. While acute drug exposure only yields a transient elevation of CRF expression (Maj, Turchan, Smialowska, & Przewlocka, 2003;Zhou et al., 1996), chronic exposure leads to more sustained overactivation following cessation of drug use (Caberlotto, Rimondini, Hansson, Eriksson, & Heilig, 2004;George et al., 2007;Sommer et al., 2008;Zhou, Spangler, Ho, & Kreek, 2003;Zorrilla, Valdez, & Weiss, 2001). For example, in vivo microdialysis showed that acute withdrawal from chronic administration or self-administration of drugs of abuse increases extracellular CRF in the extended amygdala, a stress-like response Richter, Zorrilla, Basso, Koob, & Weiss, 2000). ...
... Similarly, extracellular CRF levels increased in the CeA during precipitated withdrawal from chronic nicotine (George et al., 2007), opioids , or cannabinoids (Rodriguez de Fonseca et al., 1997) as well as during withdrawal from binge cocaine self-administration (Richter & Weiss, 1999). Increased CeA CRF mRNA also has been seen at various withdrawal time points (Caberlotto et al., 2004;Maj et al., 2003;Roberto et al., 2010;Sommer et al., 2008). The high levels of CRF release at early withdrawal time points can paradoxically yield low tissue content of CRF peptide (Funk, O'Dell, Crawford, & Koob, 2006;Maj et al., 2003;Sarnyai et al., 1995;Zorrilla et al., 2001) because CRF synthesis may lag behind release, resulting in transient depletion of CRF levels. ...
... Increased CeA CRF mRNA also has been seen at various withdrawal time points (Caberlotto et al., 2004;Maj et al., 2003;Roberto et al., 2010;Sommer et al., 2008). The high levels of CRF release at early withdrawal time points can paradoxically yield low tissue content of CRF peptide (Funk, O'Dell, Crawford, & Koob, 2006;Maj et al., 2003;Sarnyai et al., 1995;Zorrilla et al., 2001) because CRF synthesis may lag behind release, resulting in transient depletion of CRF levels. ...
Drug addiction is a complex disorder that is characterized by compulsivity to seek and take the drug, loss of control in limiting intake of the drug, and emergence of a withdrawal syndrome in the absence of the drug. The transition from casual drug use to dependence is mediated by changes in reward and brain stress functions and has been linked to a shift from positive reinforcement to negative reinforcement. The recruitment of brain stress systems mediates the negative emotional state produced by dependence that drives drug seeking through negative reinforcement mechanisms, defined as the “dark side” of addiction. In this chapter we focus on behavioral and cellular neuropharmacological studies that have implicated brain stress systems (i.e., corticotropin-releasing factor [CRF]) in the transition to addiction and the predominant brain regions involved. We also discuss the implication of CRF recruitment in compulsive eating disorders.
... Similar reductions in CRF-like immunoreactivity in the amygdala (Zorrilla et al., 2001), and increases in dialysate CRF concentrations in the CeA (Richter and Weiss, 1999), are seen in the 12 h following a 12-h cocaine self-administration session; together, these results are also indicative of increased peptide release. Accordingly, decreased CRF receptor binding in the amygdala (Ambrosio et al., 1997), and increased CRF mRNA expression in the amygdala (Zhou et al., 2003b;2010), and CeA specifically (Erb et al., 2004;Maj et al., 2003), have been observed within the first 48 h of cocaine withdrawal. ...
... Potential Brain Loci where eCBs and CRF Interact to Mediate Anxiety As described in Chapter 1, the BNST (Lee and Davis, 1997;Sahuque et al., 2006) and BLA (Sajdyk et al., 1999;Walker et al., 2009) have been identified as regions important for mediating i.c.v. CRF-induced anxiety, and the CeA as critical for the expression of cocaine withdrawal-induced anxiety (Sarnyai et al., 1995;Zhou et al., 1996;Zorrilla et al., 2001;Erb et al., 2003;Maj et al., 2003). In contrast, the brain sites involved in the effects of CB 1 receptor agonists and antagonists on anxiety are unclear. ...
... This additional efficacy of AM251 could be explained by the specific brain substrates underlying these behaviours. Indeed, consistent with other behaviours effectively modified by AM251, cocaine-induced expression of sensitization and withdrawalinduced anxiety are both associated with heightened CRF transmission within the CeA (Richter et al., 1995;Maj et al., 2003), and are both reliant on intact BLA function (Kalivas and Alesdatter, 1993;Harris et al., 2006). Moreover, the inability of AM251 to interfere with both footshock-and, in the present work, cocaine-induced reinstatement of cocaine seeking, is in line with evidence that neither condition for reinstatement recruits CRF transmission in the CeA (Erb and Stewart, 1999;McFarland and Kalivas, 2001), nor is either dependent on the BLA (McFarland et al., 2004;McFarland and Kalivas, 2001). ...
... The present study therefore tested the hypothesis that LgA rats exhibit regional differences in CRF tissue content relative to ShA rats in the amygdala and dorsal raphe (DR), CRF-rich structures that subserve mood and arousal (Cummings et al. 1983; Palkovits, Brownstein & Vale 1985). Passive cocaine administration is known to increase CeA CRF release, depleting CRF tissue content (Richter et al. 1995; Maj et al. 2003 ), but the effects of selfadministered cocaine are unknown. Therefore, cocaine self-administration was hypothesized here to alter tissue CRF content in the CeA, with greater changes expected in LgA rats. ...
... Increased immunoreactivity was not observed in the CeA of LgA rats as compared with ShA rats at any time-point. This negative result is consistent with studies that observed changes in CeA CRF peptide or mRNA levels only after acute, and not repeated, cocaine exposure (Maj et al. 2003; Zhou et al. 2003). Increased extracellular CeA CRF immunoreactivity was observed previously using in vivo microdialaysis ~12 hours following 'binge-like' (12-hour session) cocaine access (Richter & Weiss 1999), but that study reflected interstitial (rather than whole tissue) CRF levels, and did not involve a repeated history of LgA cocaine exposure. ...
... A final result was that CRF levels in the CeA and DR were higher 3 hours after the cocaine self-administration session than immediately before or after the session. These results extend upon studies that showed that passive exposure to cocaine acutely activates amygdalar CRF systems (Sarnyai et al. 1993; Zhou et al. 1996; Maj et al. 2003) by finding that voluntary cocaine self-administration also results in CRF system activation, and that the DR CRF system is involved as well. One interpretation of these data is that the delayed rise in CRF concentrations reflects the time needed to complete cocaine exposure-induced CRF synthesis (Zhou et al. 1996; Maj et al. 2003) or, alternatively, a rapid rise in CRF synthesis secondary to withdrawal from cocaine access (Zhou et al. 2003; Erb et al. 2004; Rudoy, Reyes & Van Bockstaele 2009). ...
Cocaine-induced neuroadaptation of stress-related circuitry and increased access to cocaine each putatively contribute to the transition from cocaine use to cocaine dependence. The present study tested the hypothesis that rats receiving extended versus brief daily access to cocaine would exhibit regional differences in levels of the stress-regulatory neuropeptide corticotropin-releasing factor (CRF). A secondary goal was to explore how CRF levels change in relation to the time since cocaine self-administration. Male Wistar rats acquired operant self-administration of cocaine and were assigned to receive daily long access (6 hours/day, LgA, n=20) or short access (1 hour/day, ShA, n=18) to intravenous cocaine self-administration (fixed ratio 1, ~0.50 mg/kg/infusion). After at least 3 weeks, tissue CRF immunoreactivity was measured at one of three timepoints: pre-session, post-session or 3 hours post-session. LgA, but not ShA, rats showed increased total session and first-hour cocaine intake. CRF immunoreactivity increased within the dorsal raphe (DR) and basolateral, but not central, nucleus of the amygdala (BLA, CeA) of ShA rats from pre-session to 3 hours post-session. In LgA rats, CRF immunoreactivity increased from pre-session to 3 hours post-session within the CeA and DR but tended to decrease in the BLA. LgA rats showed higher CRF levels than ShA rats in the DR and, pre-session, in the BLA. Thus, voluntary cocaine intake engages stress-regulatory CRF systems of the DR and amygdala. Increased availability of cocaine promotes greater tissue CRF levels in these extrahypothalamic brain regions, changes associated here with a model of cocaine dependence.
... These brain regions include those known to be involved in reward pathways, such as the nucleus accumbens (NAc), ventral tegmental area (VTA), caudate putamen, and frontal cortex (FC). Cocaine has been shown to affect the expression of a number of neuropeptides or peptide precursors, including substance P (Hanson et al. 1989;Hurd and Herkenham 1992;Arroyo et al. 2000;Adams et al. 2001), dynorphin (Hurd and Herkenham 1992;Werme et al. 2000;Shippenberg et al. 2007), nociceptin/orphanin FQ (Romualdi et al. 2007;Lutfy et al. 2008), neurotensin/neuromedin N (Adams et al. 2001), thyrotropin-releasing hormone (Sevarino and Primus 1993;Eugene et al. 2002), secretogranin II (Kuzmin and Johansson 1999), neuropeptide Y (Wahlestedt et al. 1991;Westwood and Hanson 1999), vasopressin, oxytocin (Sarnyai et al. 1992), and corticotropin-releasing factor (Maj et al. 2003). ...
... The peptidomics analyses compared 4 distinct pools of cocaine-and saline-treated mice (each pool representing 3-4 different mice), and this was performed for four different brain regions. The dose of cocaine (10 mg/kg once per day) and length of treatment (7 days) were based on previous studies (Hanson et al. 1989;Wahlestedt et al. 1991;Hurd and Herkenham 1992;Sarnyai et al. 1992;Sevarino and Primus 1993;Kuzmin and Johansson 1999;Westwood and Hanson 1999;Arroyo et al. 2000;Werme et al. 2000;Adams et al. 2001;Eugene et al. 2002;Maj et al. 2003;Romualdi et al. 2007;Shippenberg et al. 2007;Lutfy et al. 2008). Brain regions were labeled with isotopic tags as shown (Fig. S1); two of the replicates (runs 1 and 3) had the labels reversed relative to the other two replicates (runs 2 and 4) to control for possible differences because of the isotopic tags. ...
To identify neuropeptides that are regulated by cocaine, we used a quantitative peptidomic technique to examine the relative levels of neuropeptides in several regions of mouse brain following daily intraperitoneal administration of 10 mg/kg cocaine or saline for 7 days. A total of 102 distinct peptides were identified in one or more of the following brain regions: nucleus accumbens, caudate putamen, frontal cortex, and ventral tegmental area. None of the peptides detected in the caudate putamen or frontal cortex were altered by cocaine administration. Three peptides in the nucleus accumbens and seven peptides in the ventral tegmental area were significantly decreased in cocaine‐treated mice. Five of these ten peptides are derived from pro SAAS , a secretory pathway protein and neuropeptide precursor. To investigate whether pro SAAS peptides contribute to the physiological effects of psychostimulants, we examined acute responses to cocaine and amphetamine in the open field with wild‐type ( WT ) and pro SAAS knockout ( KO ) mice. Locomotion was stimulated more robustly in the WT compared to mutant mice for both psychostimulants. Behavioral sensitization to amphetamine was not maintained in pro SAAS KO mice and these mutants failed to sensitize to cocaine. To determine whether the rewarding effects of cocaine were altered, mice were tested in conditioned place preference ( CPP ). Both WT and pro SAAS KO mice showed dose‐dependent CPP to cocaine that was not distinguished by genotype. Taken together, these results suggest that pro SAAS ‐derived peptides contribute differentially to the behavioral sensitization to psychostimulants, while the rewarding effects of cocaine appear intact in mice lacking pro SAAS .
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... The corticotropinreleasing factor (CRF) system and the closely related hypothalamus-pituitary-adrenal (HPA) axis are major stressresponsive systems that are activated by stimulant drugs (Koob, 2008;Piazza and Le Moal, 1998). For instance, the prototype stimulant drug cocaine increases the expression and the extracellular levels of CRF in the central nucleus of the amygdala (CeA), a brain region implicated in the stress response and the effects of substances of abuse (Maj et al., 2003;Richter et al., 1995). Cocaine also activates the HPA axis, as revealed by increased CRF expression in the paraventricular nucleus of the hypothalamus (PVN) and elevated plasma levels of corticotropin (ACTH) and corticosterone, the main glucocorticoid hormone in rodents (Rivier and Lee, 1994;Rivier and Vale, 1987;Sarnyai et al., 1992). ...
... Accordingly, in either rats or mice cocaine may elicit anxiety-like, risk assessment and stereotyped behavior, suggesting increased negative emotional responses to threat (Blanchard et al., 1998;Rogerio and Takahashi, 1992;Yang et al., 1992). Cocaine also increases the activity of brain extra-hypothalamic CRF systems and of the HPA axis (Maj et al., 2003;Richter et al., 1995;Rivier and Lee, 1994). Notably, hypothalamic CRF circuits are thought to underlie the increased HPA axis activity produced by stimulant drugs. ...
Stimulant drugs produce reward but also activate stress-responsive systems. The corticotropin-releasing factor (CRF) and the related hypothalamus-pituitary-adrenal (HPA) axis stress-responsive systems are activated by stimulant drugs. However, their role in stimulant drug-induced reward remains poorly understood. Herein, we report that CRF1 receptor-deficient (CRF1-/-), but not wild-type, mice show conditioned place preference (CPP) responses to a relatively low cocaine dose (5 mg/kg, i.p.). Conversely, wild-type, but not CRF1-/-, mice display CPP responses to a relatively high cocaine dose (20 mg/kg, i.p.), indicating that CRF1 receptor-deficiency alters the rewarding effects of cocaine. Acute pharmacological antagonism of the CRF1 receptor by antalarmin also eliminates cocaine reward. Nevertheless, CRF1-/- mice display higher stereotypy responses to cocaine than wild-type mice. Despite the very low plasma corticosterone concentration, CRF1-/- mice show higher nuclear glucocorticoid receptor (GR) levels in the brain region of the hippocampus than wild-type mice. Full rescue of wild-type-like corticosterone and GR circadian rhythm and level in CRF1-/- mice by exogenous corticosterone does not affect CRF1 receptor-dependent cocaine reward but induces stereotypy responses to cocaine. These results indicate a critical role for the CRF1 receptor in cocaine reward, independently of the closely related HPA axis activity.
... Besides, non-opioid drugs have been applied to decrease the signs of morphine withdrawal by manipulating specific neurotransmitter re-uptake or affecting cerebral amino acids with the advantages like longer duration of action and lesser side effects in comparison with opioid agents. 5,6,9,[13][14][15] The present study shows that increasing the intervals of morphine injections without changing the dosages and irregular instead of regular injection reduces the symptoms of withdrawal syndrome significantly. We can justify that through increasing the intervals by adding 6 hours to dosage intervals in each time of injection, the central nervous system (CNS) does not encounter regular morphine intake and its award activating system abolishes and can provide a condition to reduce morphine dependence. ...
... The origin of this activity is in cellular events, because morphine dependence increase HPA axis activity with changes in gene expression in selective neurons of the paraventricular nucleus. 13 Our study showed that morphine doses in the dependent positive control group caused a significant increase in the blood cortisol in comparison with the independent negative control group during the withdrawal syndrome period. This result is arguable with the increasing level of stress in mice and consequently with increasing the cortisol secretion in the withdrawal period and dependency level in mice. ...
Morphine withdrawal usually results in unsuccessful outcomes. Despite partial benefits from alternative substances such as methadone, its use may not lead to the desired result due to the lack of mental tranquility during the withdrawal period. In this study, by means of an animal model, morphine itself was used to manage morphine dependence. Forty mice were divided into 5 groups, in which 4 groups became dependent by increasing daily doses of morphine for 7 days (15-45 mg/kg). Afterwards, the animals received morphine for 14 days by either of the following regimens:
• Once daily 45 mg/kg (positive controls)
• Increasing the interval (each time 6 hours longer than the previous interval)
• Irregular interval in every 36, 12 and 24 hours until the 21th day
• 12, 24, 36 hours decreasing doses (each time 2.5 mg/kg less than the former dosage).
Negative controls received saline solution only. On day 22, total withdrawal index (TWI) was determined by injecting 3 mg/kg of naloxone. Thereafter, blood samples were taken for the measurement of cortisol and glucose levels. TWI significantly decreased in all test groups in comparison with the positive control animals (P
... Negative affect observed during drug abstinence is timed with neurobiological responses that mediate negative affective states (Koob, 2013(Koob, , 2020. For example, following repeated exposure to morphine, there are increases in norepinephrine-induced modulation of the extended amygdala (Aston-Jones et al., 1999;Delfs et al., 2000;Smith and Aston-Jones, 2008), activation of the amygdalar corticotrophin-releasing factor (CRF) system (Heinrichs et al., 1995;Maj et al., 2003), norepinephrine release in the extended amygdala (Fuentealba et al., 2000;Aston-Jones and Harris, 2004), and decreases in dopamine transmission (Diana et al., 1995). Also, following repeated exposure to cocaine, the lateral habenula, a brain region whose increased activity is correlated with aversive states , has increased activation 15 min after repeated cocaine administration (Jhou et al., 2013), with evidence suggesting that this increase in cocaine-induced lateral habenula activation lasts until abstinence day 2 in rodents with a history of cocaine self-administration (Neumann et al., 2014). ...
The conditioned place preference (CPP) paradigm is a well-established model utilized to study the role of context associations in reward-related behaviors, including both natural rewards and drugs of abuse. In this review article, we discuss the basic history, various uses, and considerations that are tied to this technique. There are many potential takeaway implications of this model, including negative affective states, conditioned drug effects, memory, and motivation, which are all considered here. We also discuss the neurobiology of CPP including relevant brain regions, molecular signaling cascades, and neuromodulatory systems. We further examine some of our prior findings and how they integrate CPP with self-administration paradigms. Overall, by describing the fundamentals of CPP, findings from the past few decades, and implications of using CPP as a research paradigm, we have endeavored to support the case that the CPP method is specifically advantageous for studying the role of a form of Pavlovian learning that associates drug use with the surrounding environment.
... There could be several possibilities by which R121919 could be limiting engagement in cue-reinforced opioid seeking. Mechanistically, CRF and CRFR1 receptor expression is altered in the amygdala and extended amygdala after chronic drug use and withdrawal (Maj et al., 2003;Sommer et al., 2008;Roberto et al., 2017). We speculate that R121919 could be attenuating the enhanced transmission at BNST CRFR1 receptors to promote disengagement from opioid seeking. ...
The time-dependent increase in cue-triggered opioid seeking, termed “incubation of opioid craving,” is modeled in rodents by examining responding for opioid-associated cues after a period of forced abstinence. With opioid drugs, withdrawal symptoms may heighten cue reactivity by recruiting brain systems involved in both reward seeking and stress responses. Corticotropin releasing factor (CRF) in the bed nucleus of the stria terminalis (BNST) is a critical driver of stress-induced relapse to drug seeking. Here, we sought to determine whether BNST CRF receptor 1 (CRFR1) signaling drives incubation of opioid craving in opioid dependent and non-dependent rats. First, we tested whether BNST CRFR1 signaling drives incubation of opioid craving in rats with short-access fentanyl self-administration experience (2.5 μg/kg/infusion, 3 h/day for 10 days). On Day 1 of forced abstinence, we gave bilateral intra-BNST vehicle injections to all rats and measured lever responding for opioid cues in the absence of fentanyl infusions. On Day 30 of forced abstinence, we gave an identical test after bilateral intra-BNST injections of vehicle or CRFR1 receptor antagonist, R121919 (1 μg/0.3 μL/hemisphere). Vehicle treated rats showed greater responding for opioid associated cues on Day 30 relative to Day 1, and this incubation effect was prevented by intra-BNST R121919 on Day 30. Next, we incorporated an opioid-dependence procedure to investigate whether BNST CRFR1 signaling drives opioid cue-reactivity to a greater extent in opioid-dependent relative to non-dependent rats. We trained rats to self-administer fentanyl for 5 days before initiating the dependence phase and resuming daily fentanyl self-administration sessions for 10 days. We gave intra-BNST R121919 or vehicle injections before testing during acute (Day 5) or protracted (Day 30) withdrawal. During acute withdrawal, antagonizing BNST CRFR1 decreased the number of press bouts without affecting bout size or duration. These patterns of responding with R121919 treatment resulted in less fentanyl-associated conditioned reinforcement during test. Together, these findings suggest a role for BNST CRFR1 signaling in driving cue-reinforced opioid seeking after periods of forced abstinence.
... Notably, deregulated brain CRF activity might underlie the stress-like properties of substance dependence and withdrawal (Koob, 2008). Accordingly, early (3-48 hr) phases of morphine withdrawal were associated with increased CRF mRNA expression in the central nucleus of the amygdala and in the paraventricular nucleus of the hypothalamus, brain regions relevant to the addictive-like properties of substances of abuse (Ingallinesi, Rouibi, Le Moine, Papaleo, & Contarino, 2012;Maj, Turchan, Smialowska, & Przewlocka, 2003;Papaleo, Kitchener, & Contarino, 2007). CRF signaling is mediated by two types of receptors, termed CRF 1 and CRF 2 (Hauger et al., 2003). ...
Poor sociability and aggressive behavior are key clinical features of opioid use disorders. The corticotropin‐releasing factor (CRF) system may mediate behavioral effects of substances of abuse but its implication in substance‐induced social behavior deficits and outward‐directed hostility remains largely unknown. CRF signaling is mediated by two receptor types, termed CRF1 and CRF2. The present study aimed at understanding the role for the CRF1 receptor in social and aggressive behavior induced by withdrawal from repeated opiate administration. Thus, wild‐type (CRF1+/+), CRF1 receptor heterozygous (CRF1+/−), and null mutant (CRF1−/−) female and male mice were treated with saline or escalating doses of morphine (20‐100 mg/kg, i.p.) during six consecutive days and tested in the three‐chamber task for sociability (i.e., preference for an unfamiliar same‐sex conspecific vs. an object) 7 days after the last administration. Moreover, aggressive biting behavior toward the unfamiliar conspecific was assessed during the three‐chamber test. Opiate withdrawal disrupted sociability in CRF1+/+ and CRF1+/−, but not in CRF1−/−, female mice, without affecting aggressive biting behavior in any genotype. In contrast, opiate withdrawal did not affect sociability but increased aggressive biting behavior in male mice, independently of CRF1 receptor‐deficiency. Nevertheless, in opiate‐withdrawn CRF1+/+, but not CRF1+/− and CRF1−/−, male mice, sociability directly correlated with aggressive biting behavior, suggesting a role for the CRF1 receptor in hostility‐linked social approach. These findings demonstrate the implication of the CRF1 receptor in social behavior deficits associated with repeated opiate administration and withdrawal, revealing a new potential target for the treatment of opioid use disorders.
... These results are similar to previous studies showing escalating doses of morphine over 6 days induce anxiety-like behaviors in the marble burying task (Becker et al., 2017). Additionally, our observed morphine-induced anxiety-like behavior is timed with anxiogenic neurobiological responses that occur during acute opioid abstinence including, increases in norepinephrine release in the extended amygdala (Fuentealba et al., 2000;Aston-Jones and Harris, 2004), norepinephrine-induced modulation of the extended amygdala (Aston- Jones et al., 1999;Delfs et al., 2000;Smith and Aston-Jones, 2008), activation of the amygdalar corticotrophin-releasing factor (CRF) system (Heinrichs et al., 1995;Maj et al., 2003), and decreases in dopamine transmission (Diana et al., 1995). However, the observed morphine-induced anxiety-like behavior may be dependent upon morphine exposure as it has been shown that morphine does not elicit anxiety-like behaviors following three morphine injections (10 mg/kg) occurring every other day (Benturquia et al., 2007). ...
Patients suffering from opioid use disorder often relapse during periods of abstinence, which is posited to be caused by negative affective states that drive motivated behaviors. Here, we explored whether conditioning mice with morphine in a conditioned place preference (CPP) training paradigm evoked anxiety-like behavior during morphine abstinence. To do this, mice were conditioned with morphine (10 mg/kg, i.p.) for 5 days. Twenty-four hours following conditioning, anxiety levels were tested by measuring time in the open arms of the elevated plus-maze. The next day, mice were placed in the three-compartment chamber to measure morphine-induced CPP. Our results show that following morphine conditioning, mice spent significantly less time in the open arm of the elevated plus-maze and expressed robust morphine CPP on CPP test day. Furthermore, we found that an acute treatment with (R,S)-ketamine (10 mg/kg, i.p.), a medication demonstrating promise for preventing anxiety-related phenotypes, 30 min before testing on post-conditioning day 1, increased time spent in the open arm of the elevated plus-maze in saline- and morphine-conditioned mice. Additionally, we found that the second injection of ketamine 30 min before CPP tests on post-conditioning day 2 prevented morphine-induced CPP, which lasted for up to 28 days post-conditioning. Furthermore, we found that conditioning mice with 10% (w/v) sucrose using an oral self-administration procedure did not evoke anxiety-like behavior, but elicited robust CPP, which was attenuated by ketamine treatment 30 min before CPP tests. Overall, our results suggest that the ketamine-induced block of morphine CPP may not be attributed solely to alleviating negative affective states, but potentially through impaired memory of morphine-context associations.
... Corticotrophin-releasing factor (CRF), synthesized by hypothalamic neurons, is a potent inhibitor of the GnRH pulse generator. Central administrations of CRF decrease the GnRH concentration in hypophyseal portal system and mean plasma LH/sex steroid concentrations (26)(27)(28). While suppression of LH secretion, by CRF injection, or a variety of stressful stimuli, increasing the CRF/cortisol secretions, can be reversed by CRF antagonists (29). ...
Bachground:
The inhibitory effects of morphine and the stimulatory influence of kisspeptin signaling have been demonstrated on gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) release. Hypothalamic kisspeptin is involved in relaying the environmental and metabolic information to reproductive axis. In the present study, the role of kisspeptin/ GPR54 signaling system was investigated on relaying the inhibitory influences of morphine on LH hormone secretion.
Materials and methods:
In this experimental study, 55 wistar male rats weighing 230-250 g were sub-grouped in 11 groups (in each group n=5) receiving saline, kisspeptin (1 nmol), peptide234 (P234, 1 nmol), morphine (5 mg/kg), naloxone (2 mg/kg), kisspeptin/P234, morphine/naloxone, kisspeptin/morphine, kisspeptin/naloxone, P234/morphine or P234/naloxone respectively. Blood samples were collected via tail vein. Mean plasma (LH) concentrations and mean relative KiSS1 or GPR54 mRNA levels were determined by radioimmunoassay (RIA) and real time reverse transcriptase-polymerase chain reaction (RT-PCR), respectivwely.
Results:
Morphine significantly decreased mean plasma LH concentration and mean relative KiSS1 gene expression compared to saline; while it did not significantly decrease mean relative GPR54 gene expression compared to saline. Naloxone significant increased mean LH level and mean relative KiSS1 gene expression compared to saline; while it did not significantly increase mean relative GPR54 gene expression compared to saline. Injections of kisspeptin plus morphine significantly increased mean LH concentration compared to saline or morphine, while simultaneous infusions of them significantly declined mean plasma LH level compared to kisspeptin. In kisspeptin/naloxone group mean plasma LH level was significantly increased compared to saline or naloxone. Co-administration of P234/morphine significantly decreased mean LH concentration compared to saline.
Conclusion:
Down regulation of KiSS1 gene expression may be partly involved in the mediating the inhibitory effects of morphine on reproductive axis.
... Cocaine has been shown to increase circulating plasma levels of CRF (Goeders, 1997;Rivier and Vale, 1987;Sarnyai et al., 2001) and produce changes in CRF peptide or mRNA levels within the extended amygdala (Maj et al., 2003;Richter et al., 1995;Zhou et al., 1996). Indeed, both the CeA and the BNST contain CRF-immunoreactive cells bodies, terminals and receptors (Cassell and Gray, 1989;Sakanaka et al., 1986;Swanson et al., 1983) and CRF signaling within the extended amygdala has been correlated with behavioral responses to fearful and/or anxiogenic stimuli (Funk et al., 2006). ...
... However, the present results indicate that neither cocaine withdrawal nor CRF 2 receptor-deficiency influence the expression of the dopamine and norepinephrine synthesis enzyme TH in the VTA or the LC, suggesting that it might not be involved in cocaine withdrawal-induced cognitive vulnerability to stress. Cocaine withdrawal and stressors also increase CRF activity in the CeA and the PVN (Koob, 1999;Richter and Weiss, 1999;Maj et al., 2003). However, despite the resilience of cocaine-withdrawn CRF 2 −/− mice to the stressor used herein, the present data indicate no effect of CRF 2 receptor-deficiency in CeA-CRF and PVN-CRF expression. ...
Psychostimulant drug abuse, dependence and withdrawal are associated with cognitive dysfunction and impact stress-sensitive systems. The corticotropin-releasing factor (CRF) system orchestrates stress responses via CRF1 and CRF2 receptors and is implicated in substance use disorders. However, CRF2 role in psychostimulant drug-induced cognitive dysfunction remains to be elucidated. In the present study, wild-type and CRF2-/- mice are injected with cocaine and memory assessed by the novel object recognition (NOR) task throughout relatively long periods of drug withdrawal. Following recovery from the drug-induced memory deficits, the mice are stressed prior to the NOR task and brain gene expression evaluated by in situ hybridization. Cocaine impairs NOR memory in wild-type and CRF2-/- mice. However, following cocaine withdrawal NOR memory deficits last less time in CRF2-/- than in wild-type mice. Furthermore, a relatively mild stressor induces the re-emergence of NOR deficits in long-term cocaine-withdrawn wild-type but not CRF2-/- mice. Cocaine-withdrawn mice show a genotype-independent higher c-fos expression in the NOR memory-relevant perirhinal cortex than drug-naïve mice. However neither genotype nor drug withdrawal affect the expression of tyrosine hydroxylase in the ventral tegmental area or the locus coeruleus and CRF in the central nucleus of the amygdala or the paraventricular nucleus of the hypothalamus, brain regions implicated in stress and drug responses. These data indicate a new role for the CRF2 receptor in cognitive deficits induced by cocaine withdrawal, both as regards to their duration and their re-induction by stress. Interestingly, prototypical brain stress systems other than CRF do not appear to be involved.
... Moreover, in drugdependent male animals, the recruitment of CRF activity seems to serve a motivational role in that CRF and NA receptor blockade reduce the motivational effects of drug withdrawal (Delfs et al., 2000;Heinrichs et al., 1995;Schulteis et al., 1994). Further, extracellular CRF is increased in the CeA during acute drug withdrawal (George et al., 2007;Maj et al., 2003;Merlo Pich et al., 1995;Richter and Weiss, 1999;Rodriguez de Fonseca et al., 1997;Zorrilla et al., 2012). The CeA sends a CRF-containing projection to the BNST that appears to be critical for stress-induced reinstatement to drug seeking behavior in male animals (Erb et al., 2001). ...
... Acute withdrawal from morphine (12 h) or cocaine (24 h) enhanced the expression of Orx mRNA (Zhou et al., 2006Zhou et al., , 2008), and opiate antagonist-precipitated morphine withdrawal activated Orx neurons and Orx gene expression (Georgescu et al., 2003). In parallel, extracellular CRF (Merlo-Pich et al., 1995; Rodríguez de Fonseca et al., 1997; Richter & Weiss, 1999) and CRF mRNA (Maj et al., 2003) levels increased in the CeA during withdrawal. Moreover, recent reports show that an increase in the ICSS threshold induced by precipitated nicotine withdrawal or alcohol withdrawal was blocked by i.c.v. or intra-CeA injection of a CRF antagonist (Bruijnzeel et al., 2007Bruijnzeel et al., , 2009Bruijnzeel et al., , 2010 Marcinkiewcz et al., 2009). ...
Although orexin-A peptide was recently found to inhibit the brain reward system, the exact neural substrates for this phenomenon remain unclear. The aim of the present study was to investigate the role of orexin neurons in intra-cranial self-stimulation behavior and to clarify the pathways through which orexin-A inhibits the brain reward system. Immunohistochemical examination using Fos, a neuronal activation marker, revealed that the percentage of activated orexin cells was very low in the lateral hypothalamus even in the hemisphere ipsilateral to self-stimulation, suggesting that orexin neurons play only a small part, if any, in performing intra-cranial self-stimulation behavior. Intra-ventral tegmental area administration of orexin-A (1.0 nmol) significantly increased the intra-cranial self-stimulation threshold. Furthermore, the threshold-increasing effects of intra-ventral tegmental area or intracerebroventricular orexin-A were inhibited by administration of the nonspecific corticotropin-releasing factor receptor antagonist, d-Phe-CRF 12–41 (20 lg). Following intra-ventral tegmental area infusion of orexin-A, the percentage of cells double-labeled with corticotropin-releasing factor and Fos antibodies increased in the central nucleus of the amygdala but not in the bed nucleus of the stria terminalis, and brain microdialysis analyses indicated that dopamine efflux in both the central nucleus of the amygdala and bed nucleus of the stria terminalis were enhanced. Taken together, the present findings suggest that intra-ventral tegmental area or intracerebroventricular administration of orexin-A exerts its threshold-increasing effect via subsequent activation of the corticotropin-releasing factor system.
... The central amygdala (CeA) appears to contribute to the use of a number of different drugs. Acute and chronic alcohol/drug exposures and withdrawal increase CRF biosynthesis in the CeA (Merlo et al., 1995;Rodriguez de et al., 1997;Richter and Weiss, 1999;Maj et al., 2003;George et al., 2007;Zorrilla et al., 2012) and the CeA sends a CRF-containing projection to the BNST that is critical for stress-induced reinstatement (Erb et al., 2001). Therefore, an understanding of drug/alcohol interactions with CeA CRF neurocircuitry may provide an insight into an important interface between stress and addiction A series of studies have shown that EtOH enhances GABAergic neurotransmission in the CeA via a CRF type 1 receptor (CRFR1)-dependent mechanism (Roberto et al., 2003Roberto et al., , 2010Nie et al., 2009). ...
Stress and anxiety play an important role in the development and maintenance of drug and alcohol addiction. The bed nucleus of the stria terminalis (BNST), a brain region involved in the production of long-term stress-related behaviors, plays an important role in animal models of relapse, such as reinstatement to previously extinguished drug-seeking behaviors. While a number of neurotransmitter systems have been suggested to play a role in these behaviors, recent evidence points to the neuropeptide corticotropin releasing factor (CRF) as being critically important in BNST-mediated reinstatement behaviors. Although numerous studies indicate that the BNST is a complex brain region with multiple afferent and efferent systems and a variety of cell types, there has only been limited work to determine how CRF modulates this complex neuronal system at the circuit level. Recent work from our lab and others have begun to unravel these BNST neurocircuits and explore their roles in CRF-related reinstatement behaviors. This review will examine the role of CRF signaling in drug addiction and reinstatement with an emphasis on critical neurocircuitry within the BNST that may offer new insights into treatments for addiction.
... Indeed, ethanol-dependent rats exhibit increased extracellular release of CRF in the CeA during withdrawal and the administration of a CRF receptor antagonist into the CeA is able to block escalated ethanol self-administration during withdrawal (Funk et al, 2006;Merlo Pich et al, 1995). Analogously, opiate-dependent animals show increased CRF expression in the CeA during withdrawal (Maj et al, 2003) and blockade of CRF receptors in the CeA, but not the BNST, reduces the behavioral signs of withdrawal (Heinrichs et al, 1995;McNally and Akil, 2002). A key role for CRF-CRF 1 system in the CeA has also been demonstrated in nicotine dependence. ...
Highly palatable foods and dieting are major contributing factors for the development of compulsive eating in obesity and eating disorders. We previously demonstrated that intermittent access to palatable food results in corticotropin-releasing factor-1 (CRF 1) receptor antagonist-reversible behaviors, which include excessive palatable food intake, hypophagia of regular chow, and anxiety-like behavior. However, the brain areas mediating these effects are still unknown. Male Wistar rats were either fed chow continuously for 7 days/week (Chow/Chow group), or fed chow intermittently 5 days/week, followed by a sucrose, palatable diet 2 days/week (Chow/Palatable group). Following chronic diet alternation, the effects of microinfusing the CRF 1 receptor antagonist R121919 (0, 0.5, 1.5 μg/side) in the central nucleus of the amygdala (CeA), the basolateral nucleus of the amygdala (BlA), or the bed nucleus of the stria terminalis (BNST) were evaluated on excessive intake of the palatable diet, chow hypophagia, and anxiety-like behavior. Furthermore, CRF immunostaining was evaluated in the brain of diet cycled rats. Intra-CeA R121919 blocked both excessive palatable food intake and anxiety-like behavior in Chow/Palatable rats, without affecting chow hypophagia. Conversely, intra-BlA R121919 reduced the chow hypophagia in Chow/Palatable rats, without affecting excessive palatable food intake or anxiety-like behavior. Intra-BNST treatment had no effect. The treatments did not modify the behavior of Chow/Chow rats. Immunohistochemistry revealed an increased number of CRF-positive cells in CeA-but not in BlA or BNST-of Chow/Palatable rats, during both withdrawal and renewed access to the palatable diet, compared with controls. These results provide functional evidence that the CRF-CRF 1 receptor system in CeA and BlA has a differential role in mediating maladaptive behaviors resulting from palatable diet cycling.
... For example, the hypothalamo-pituitary-adrenal (HPA) axis, a system activated following stress, is associated with drug administration and withdrawal (Bruijnzeel and Gold, 2005;Sinha, 2008). Specifically, both cocaine administration and withdrawal increases CRF mRNA in the rat central nucleus of amygdala (Richter and Weiss, 1999;Maj et al., 2003); conversely, CRF antisera or receptor antagonists injected intracerebroventricularly (i.c.v.) blocks both cocaine-induced hyperactivity and cocaine withdrawal-induced anxiety-like behavior (Sarnyai et al., 1992(Sarnyai et al., , 1995Basso et al., 1999). The locus coeruleus (LC)-norepinephrine system is involved in a variety of behavioral effects of addictive drugs (Weinshenker and Schroeder, 2006;Sofuoglu and Sewell, 2008). ...
There is high comorbidity between stress-related psychiatric disorders and addiction, suggesting they may share one or more common neurobiological mechanisms. Because of its roles in both depressive and addictive behaviors, the galanin system is a strong candidate for such a mechanism. In this study, we tested if galanin and its receptors are involved in stress-associated behaviors and drug addiction. Mice were exposed to 21 days of chronic restraint stress (CRS); subsequently, mRNA levels of galanin, galanin receptors, and the rate-limiting enzymes for synthesis of monoamine autoreceptors were measured in the nucleus accumbens by qRT-PCR. Moreover, we tested the effects of this stress on morphine-induced addictive behaviors. We found that CRS induced anxiety and depression-like behaviors, impaired the formation and facilitated the extinction process in morphine-induced conditioned place preference (CPP), and also blocked morphine-induced behavioral sensitization. These behavioral results were accompanied by a CRS-dependent increase in the mRNA expression of galanin, galanin receptor 1 (GalR1), tyrosine hydroxylase (TH), tryptophan hydroxylase 2, and 5-HT1B receptor. Interestingly, treatment with a commonly used antidepressant, fluoxetine, normalized the CRS-induced behavioral changes based on reversing the higher expression of galanin and TH while increasing the expression of GalR2 and α2A-adrenceptor. These results indicate that activating the galanin system, with corresponding changes to noradrenergic systems, following chronic stress may modulate stress-associated behaviors and opiate addiction. Our findings suggest that galanin and galanin receptors are worthy of further exploration as potential therapeutic targets to treat stress-related disorders and drug addiction.
... However, there is substantial evidence that CRF influences psychostimulant as well as opiate self-administration and withdrawal. Several studies (Erb et al. 2005; Maj et al. 2003; Zorrilla et al. 2001) have shown that the levels of CRF mRNA and of some CRF-like protein in the amygdala are altered during self-administration and withdrawal from cocaine and morphine. One study (Richter and Weiss 1999) of cocaine–self-administering rats reported increased CRF in the animals’ amygdala during cocaine withdrawal. ...
Stress-that is, any type of stimulus that challenges the organism's normal internal balance-induces a physiologic response involving a variety of hormones and other signaling molecules that act on, among other organs, the brain. This stress response also can influence the progression of alcohol and other drug (AOD) addiction through various stages. For example, AODs can directly activate the stress response. In turn, certain stress hormones (i.e., glucocorticoids and corticotrophin-releasing factor) also act on the brain system that mediates the rewarding experiences associated with AOD use (i.e., the mesocorticolimbic dopamine system). Moreover, elevated glucocorticoid levels and stress increase AOD self-administration in certain animal models. During a later stage of the addiction process, in contrast, excessive and/or prolonged stress may impair the reward system, inducing heavier AOD use to maintain the rewarding experience. During the final stage of addiction, when the addicted person experiences withdrawal symptoms if no drug is consumed, chronic AOD use results in gross impairment of the normal stress response and other signaling mechanisms in the brain, resulting in a state of anxiety and internal stress. At this stage, people continue to use AODs mainly to relieve this negative-affect state.
... Therefore, morphine abuse and subsequent withdrawal cause a negative emotional state and psychiatric side effects, including depression and anxiety [2]. Many studies have demonstrated that morphine withdrawal causes depression-and anxiety-related disorders in humans and corresponding behavioral responses in animals [3,4]. Importantly, depression and anxiety that occur during morphine abstinence often lead to relapse to morphine use in humans [5]. ...
The purpose of this study was to evaluate whether berberine (BER) administration could attenuate depression- and anxiety-like behaviors and increase corticotrophin-releasing factor (CRF) and tyrosine hydroxylase (TH) expression following chronic morphine withdrawal in rats. Male rats were exposed to chronic, intermittent, escalating morphine (10~50 mg/kg) for 10 days. After the last morphine injection, depression- and anxiety-like beahvior associated with morphine discontinuation persisted for at least three days during withdrawal without any change in ambulatory activity. Daily BER administration significantly decreased immobility in the forced swimming test and increased open-arm exploration in the elevated plus maze test. BER administration also significantly blocked the increase in hypothalamic CRF expression and TH expression in the locus coeruleus (LC) and the decrease in hippocampal brain-derived neurotrophic factor (BDNF) mRNA expression. Taken together, these findings demonstrated that BER administration significantly reduced morphine withdrawal-associated behaviors following discontinuation of repeated morphine administration in rats, possibly through modulation of hypothalamic CRF and the central noradrenergic system. BER may be a useful agent for treating or alleviating complex withdrawal symptoms and preventing morphine use relapses.
... Given that CRH gene has a CRE motif in its promoter sequence, it might be proposed that FosB/DFosB accumulation in CRH neurons can mediate the morphine-induced changes in CRH levels, as reported for cocaine effects [42], especially in the CeA and the BNST, where, for the first time, we reported an enhancement in the number of CRH-positive neurons during morphine dependence. Supporting this hypothesis, an increase in CRH mRNA levels has been described in the CeA after chronic administration of morphine [43]. However, the number of CRH-positive neurons was unchanged in the PVN after chronic morphine treatment. ...
Chronic use of drugs of abuse profoundly alters stress-responsive system. Repeated exposure to morphine leads to accumulation of the transcription factor ΔFosB, particularly in brain areas associated with reward and stress. The persistent effects of ΔFosB on target genes may play an important role in the plasticity induced by drugs of abuse. Recent evidence suggests that stress-related hormones (e.g., glucocorticoids, GC) may induce adaptations in the brain stress system that is likely to involve alteration in gene expression and transcription factors. This study examined the role of GC in regulation of FosB/ΔFosB in both hypothalamic and extrahypothalamic brain stress systems during morphine dependence. For that, expression of FosB/ΔFosB was measured in control (sham-operated) and adrenalectomized (ADX) rats that were made opiate dependent after ten days of morphine treatment. In sham-operated rats, FosB/ΔFosB was induced after chronic morphine administration in all the brain stress areas investigated: nucleus accumbens(shell) (NAc), bed nucleus of the stria terminalis (BNST), central amygdala (CeA), hypothalamic paraventricular nucleus (PVN) and nucleus of the solitary tract noradrenergic cell group (NTS-A(2)). Adrenalectomy attenuated the increased production of FosB/ΔFosB observed after chronic morphine exposure in NAc, CeA, and NTS. Furthermore, ADX decreased expression of FosB/ΔFosB within CRH-positive neurons of the BNST, PVN and CeA. Similar results were obtained in NTS-A(2) TH-positive neurons and NAc pro-dynorphin-positive neurons. These data suggest that neuroadaptation (estimated as accumulation of FosB/ΔFosB) to opiates in brain areas associated with stress is modulated by GC, supporting the evidence of a link between brain stress hormones and addiction.
... Indeed, functional antagonism of brain CRF neurotransmission attenuates stress-induced reinstatement of ethanol-or cocaine-seeking behavior 11,12 , decreases ethanol selfadministration 13 and reverses anxiety-like behavior 14 induced by ethanol-withdrawal in rats. Accordingly, cessation of ethanol or cocaine intake elevates CRF activity in the amygdala and in the bed nucleus of the stria terminalis [15][16][17][18] , brain regions implicated in the behavioral effects of substance withdrawal. In mammals, CRF-like signaling is peer-00682812, version 1 -27 Mar 2012 4 transmitted by two receptor pathways, termed CRF 1 and CRF 2 19 . ...
The opiate withdrawal syndrome is a severe stressor that powerfully triggers addictive drug intake. However, no treatment yet exists that effectively relieves opiate withdrawal distress and spares stress-coping abilities. The corticotropin-releasing factor (CRF) system mediates the stress response, but its role in opiate withdrawal distress and bodily strategies aimed to cope with is unknown. CRF-like signaling is transmitted by two receptor pathways, termed CRF(1) and CRF(2). Here, we report that CRF(2) receptor-deficient (CRF(2)(-/-)) mice lack the dysphoria-like and the anhedonia-like states of opiate withdrawal. Moreover, in CRF(2)(-/-) mice opiate withdrawal does not increase the activity of brain dynorphin, CRF and periaqueductal gray circuitry, which are major substrates of opiate withdrawal distress. Nevertheless, CRF(2) receptor-deficiency does not impair brain, neuroendocrine and autonomic stress-coping responses to opiate withdrawal. The present findings point to the CRF(2) receptor pathway as a unique target to relieve opiate withdrawal distress without impairing stress-coping abilities.Molecular Psychiatry advance online publication, 27 September 2011; doi:10.1038/mp.2011.119.
... Acute withdrawal from morphine (12 h) or cocaine (24 h) enhanced the expression of Orx mRNA (Zhou et al., 2006(Zhou et al., , 2008, and opiate antagonist-precipitated morphine withdrawal activated Orx neurons and Orx gene expression (Georgescu et al., 2003). In parallel, extracellular CRF (Merlo-Pich et al., 1995;Rodríguez de Fonseca et al., 1997;Richter & Weiss, 1999) and CRF mRNA (Maj et al., 2003) levels increased in the CeA during withdrawal. Moreover, recent reports show that an increase in the ICSS threshold induced by precipitated nicotine withdrawal or alcohol withdrawal was blocked by i.c.v. or intra-CeA injection of a CRF antagonist (Bruijnzeel et al., 2007(Bruijnzeel et al., , 2010Marcinkiewcz et al., 2009). ...
Although orexin-A peptide was recently found to inhibit the brain reward system, the exact neural substrates for this phenomenon remain unclear. The aim of the present study was to investigate the role of orexin neurons in intra-cranial self-stimulation behavior and to clarify the pathways through which orexin-A inhibits the brain reward system. Immunohistochemical examination using Fos, a neuronal activation marker, revealed that the percentage of activated orexin cells was very low in the lateral hypothalamus even in the hemisphere ipsilateral to self-stimulation, suggesting that orexin neurons play only a small part, if any, in performing intra-cranial self-stimulation behavior. Intra-ventral tegmental area administration of orexin-A (1.0 nmol) significantly increased the intra-cranial self-stimulation threshold. Furthermore, the threshold-increasing effects of intra-ventral tegmental area or intracerebroventricular orexin-A were inhibited by administration of the nonspecific corticotropin-releasing factor receptor antagonist, d-Phe-CRF(12-41) (20 μg). Following intra-ventral tegmental area infusion of orexin-A, the percentage of cells double-labeled with corticotropin-releasing factor and Fos antibodies increased in the central nucleus of the amygdala but not in the bed nucleus of the stria terminalis, and brain microdialysis analyses indicated that dopamine efflux in both the central nucleus of the amygdala and bed nucleus of the stria terminalis were enhanced. Taken together, the present findings suggest that intra-ventral tegmental area or intracerebroventricular administration of orexin-A exerts its threshold-increasing effect via subsequent activation of the corticotropin-releasing factor system.
... Rats provided with alternating 5-day/2-day access to standard laboratory chow and the palatable diet spent less time on the open arms of the elevated plus-maze and more time within the withdrawal chamber in a defensive withdrawal task when tested during the chow phase of their diet cycle [53, 54] . The increase in anxietylike behavior was accompanied by increased expression of the stress-related neuropeptide corticotropin-releasing factor (CRF) in the central nucleus of the amygdala (CeA), a system that also is activated during withdrawal from alcohol5556575859, opiates60616263, cocaine [64], cannabinoids [65],and nicotine [66, 67]. Pretreatment with the selective CRF 1 antagonist R121919 blocked the food withdrawal-associated anxiety at doses that did not alter behavior of chow-fed controls686970. ...
In drug addiction, the transition from casual drug use to dependence has been linked to a shift away from positive reinforcement and toward negative reinforcement. That is, drugs ultimately are relied on to prevent or relieve negative states that otherwise result from abstinence (e.g., withdrawal) or from adverse environmental circumstances (e.g., stress). Recent work has suggested that this "dark side" shift also is a key in the development of food addiction. Initially, palatable food consumption has both positively reinforcing, pleasurable effects and negatively reinforcing, "comforting" effects that can acutely normalize organism responses to stress. Repeated, intermittent intake of palatable food may instead amplify brain stress circuitry and downregulate brain reward pathways such that continued intake becomes obligatory to prevent negative emotional states via negative reinforcement. Stress, anxiety and depressed mood have shown high comorbidity with and the potential to trigger bouts of addiction-like eating behavior in humans. Animal models indicate that repeated, intermittent access to palatable foods can lead to emotional and somatic signs of withdrawal when the food is no longer available, tolerance and dampening of brain reward circuitry, compulsive seeking of palatable food despite potentially aversive consequences, and relapse to palatable food-seeking in response to anxiogenic-like stimuli. The neurocircuitry identified to date in the "dark" side of food addiction qualitatively resembles that associated with drug and alcohol dependence. The present review summarizes Bart Hoebel's groundbreaking conceptual and empirical contributions to understanding the role of the "dark side" in food addiction along with related work of those that have followed him.
... We have shown that DYN is localized in axon terminals in the locus coeruelus (LC) (Reyes et al., 2007b, the major norepinephrine containing nucleus that innervates almost all levels of the neuraxis (Foote et al., 1983, Aston-Jones et al., 1984, Aston-Jones et al., 1991. While it is known that interactions of stress and opioid substrates occur in various brain regions that may play a role in drug dependence and withdrawal (McNally and Akil, 2002, Houshyar et al., 2003, Maj et al., 2003, the LC is one site at which opioids and stress substrates may interact to have global effects on behavior. ...
The endogenous opioid peptides, met- or leu-enkephalin, and corticotropin-releasing factor (CRF) regulate noradrenergic neurons in the locus coeruleus (LC) in a convergent manner via projections from distinct brain areas. In contrast, the opioid peptide dynorphin (DYN) has been shown to serve as a co-transmitter with CRF in afferents to the LC. To further define anatomical substrates targeting noradrenergic neurons by DYN afferents originating from limbic sources, anterograde tract-tracing of biotinylated dextran amine (BDA) from the central amygdaloid complex was combined with immunocytochemical detection of DYN and tyrosine hydroxylase (TH) in the same section of tissue. Triple labeling immunocytochemistry was combined with electron microscopy in the LC where BDA was identified using an immunoperoxidase marker, and DYN and TH were distinguished by the use of sequential immunogold labeling and silver enhancement to produce different sized gold particles. Results show direct evidence of a monosynaptic pathway linking amygdalar DYN afferents with LC neurons. To determine whether DYN-containing amygdalar LC-projecting neurons colocalize CRF, retrograde tract-tracing using fluorescent latex microspheres injected into the LC was combined with immunocytochemical detection of DYN and CRF in single sections in the central amygdala. Retrogradely labeled neurons from the LC were distributed throughout the rostro-caudal extent of the central nucleus of the amygdala (CeA) as previously described. Cell counts showed that approximately 42% of LC-projecting neurons in the CeA contained both DYN and CRF. Taken with our previous studies showing monosynaptic projections from amygdalar CRF neurons to noradrenergic LC cells, the present study extends this by showing that DYN and CRF are co-transmitters in monosynaptic projections to the LC and are poised to coordinately impact LC neuronal activity.
In bipolar disorder, manic or depressive episodes and mixed states are frequently marked by psychotic symptoms. Moreover, psychosis may occur after substance use disorder, often intervening with the effect of making the clinical picture indistinguishable from that of a primary psychosis. Cannabinoids, stimulants, hallucinogens, alcohol and poly-use most commonly develop psychosis induced by the non-medical use of substances. Among substance use disorder users, it has not yet been ascertained whether opioids exert a psychotic effect. Still, some authors have supported the view that opioids have antidepressant, antipanic and antipsychotic effects. It has also been hypothesized that affective disorders, coupled with genetic disposition rather than affective disturbance or psychosis, result in bipolar psychosis or schizoaffective disorder, respectively. In the history of chronic psychotics, heroin use is relatively infrequent. Chronic use of psychotogenic substances and autonomous chronicity of psychotic symptoms may root in a bipolar substrate. Substance use among people with schizophrenia cannot always be justified in terms of dysphoria. Still, the number of depressive symptoms can significantly influence the risk rate for alcohol, cannabinoid use or poly-use. Dual disorder psychotic heroin-addicted patients usually enter treatment with more severe psychopathological aspects and a shorter, less severe addiction history than their non-psychotic peers suggesting that these patients are likely to benefit from opioid medication. These data indirectly confirm the antipsychotic effects of opioids and Khantzian’s self-medication hypothesis. For further confirmation, patients affected by chronic psychosis and anxiety disorders tend to progress from a psychiatric disorder to a substance use disorder. In contrast, patients with mood disorders are initially affected by drug addiction. As far as dual disorder is concerned, it is advisable to employ agents that do not heavily affect dopamine metabolism in an inhibitory way since the worsening of use hampers the effectiveness upon psychotic symptoms. On the other hand, when the tie with substances is more robust, their use may amplify as a direct consequence of dopamine antagonism, as a compensatory mechanism effective throughout the reward pathway. Novel antipsychotics seem to permit equivalent effectiveness on psychotic symptoms without promoting drug use, at least to the same extent, and might have anticraving properties.KeywordsVulnerabilityNeurotransmitter pathwayChronic psychosisSchizoaffective disorderProneness to substance use disorderProneness to psychosisDopamine metabolismSelf-medication hypothesisNegative symptomsTherapeutic proposals
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
The second volume of Behavioral Genetics of the Mouse provides a comprehensive overview of the major genetically modified mouse lines used to model human neurobehavioral disorders; from disorders of perception, of autonomous and motor functions to social and cognitive syndromes, drug abuse and dependence as well as neurodegenerative pathologies. Mouse models obtained with different types of genetic manipulations (i.e. transgenic, knockout/in mice) are described in their pathological phenotypes, with a special emphasis on behavioral abnormalities. The major results obtained with many of the existing models are discussed in depth highlighting their strengths and limitations. A lasting reference, the thorough reviews offer an easy entrance into the extensive literature in this field, and will prove invaluable to students and specialists alike.
Background
Opioid misuse is hypothesized to compromise the ability to regulate negative emotions, as manifested through visceral and peripheral physiological signals. However, neurophysiological impairment of top-down cognitive emotion regulation in opioid misuse has not previously been shown.
Methods
Patients with chronic pain who had been taking opioids for 90 days or longer (N=149; Female n=98) underwent a negative emotion regulation task with electroencephalography (EEG). Participants were instructed to view or reappraise negative images presented for 3 s. Using a validated cutoff score on the Current Opioid Misuse Measure, participants were classified as exhibiting aberrant drug-related behavior consistent with opioid misuse (MISUSE+) or as being low risk for opioid misuse (MISUSE-). Participants reported their general opioid craving in the past week and craving in response to negative emotions.
Results
We observed a group X condition interaction (p=0.003), such that the MISUSE- group decreased the late positive potential (LPP) of the EEG during reappraisal whereas the MISUSE+ group showed increased LPP during reappraisal. This deficit in negative emotion regulation remained significant after controlling for an array of potential confounding variables, including opioid dose, pain, and depression. Heightened LPP during reappraisal was associated with more severe opioid craving.
Conclusions
Opioid misuse can occasion top-down deficits in emotional regulation that begin as early as 400 milliseconds after presentation of negative stimuli. It remains unknown whether emotion dysregulation is the cause, correlate, or consequence of opioid misuse. Nonetheless, targeting emotion dysregulation in opioid misuse with reappraisal-focused interventions may represent an important treatment approach.
Highly palatable foods and substance of abuse have intersecting neurobiological, metabolic and behavioral effects relevant for understanding vulnerability to conditions related to food (e.g., obesity, binge eating disorder) and drug (e.g., substance use disorder) misuse. Here, we review data from animal models, clinical populations and epidemiological evidence in behavioral, genetic, pathophysiologic and therapeutic domains. Results suggest that consumption of highly palatable food and drugs of abuse both impact and conversely are regulated by metabolic hormones and metabolic status. Palatable foods high in fat and/or sugar can elicit adaptation in brain reward and withdrawal circuitry akin to substances of abuse. Intake of or withdrawal from palatable food can impact behavioral sensitivity to drugs of abuse and vice versa. A robust literature suggests common substrates and roles for negative reinforcement, negative affect, negative urgency, and impulse control deficits, with both highly palatable foods and substances of abuse. Candidate genetic risk loci shared by obesity and alcohol use disorders have been identified in molecules classically associated with both metabolic and motivational functions. Finally, certain drugs may have overlapping therapeutic potential to treat obesity, diabetes, binge-related eating disorders and substance use disorders. Taken together, data are consistent with the hypotheses that compulsive food and substance use share overlapping, interacting substrates at neurobiological and metabolic levels and that motivated behavior associated with feeding or substance use might constitute vulnerability factors for one another.
This article is part of the special issue on ‘Vulnerabilities to Substance Abuse’.
Compulsive eating is prevalent in binge-type eating disorders, present in some obese individuals, and often conceptualized in relation to the recently operationalized construct of food addiction. Compulsive eating putatively involves escalated intake of highly preferred foods, finickiness toward otherwise acceptable alternatives, increased effort and time spent to obtain preferred foods, eating behavior despite incorrect or adverse outcomes, and eating of palatable food in order to soothe abstinence- and stress-induced negative emotional states. We review theoretical and empirical bases for an opponent-process affective dysregulation model of compulsive eating, adapted from the addiction field, whereby intermittent, extended access to palatable food progressively dampens reward circuitry and potentiates activation of stress circuitry. We then detail corresponding protocols for two rodent models of intermittent, extended access to palatable food, describe methods for assessing compulsive-like outcomes, and discuss possible adaptations that can be used to understand better the prevention, biology, and treatment of compulsive eating.
The transition from casual drug use to dependence involves a shift from positive to negative reinforcement. This “dark side” shift also is implicated in food addiction. Palatable food intake initially has pleasurable and comforting effects that can normalize stress responses. But, repeated, intermittent intake can downregulate brain reward pathways and recruit brain circuitry, yielding negative emotional behavior when the food is not eaten, tolerance, palatable food-seeking despite aversive consequences, and heightened stress-induced relapse to palatable food-seeking. The results support an affective dysregulation model whereby intake becomes obligatory to prevent negative emotions, which show high comorbidity with addiction-like eating. Such negative emotions also may trigger impulsive palatable food intake via negative urgency. Neurobiological changes resemble many from substance-use disorders, including corticotropin-releasing factor, hypocretin, dopamine, opioid, and endocannabinoid systems in mesolimbic, extended amygdala and inhibitory frontal circuitry. We synthesize conceptual and empirical contributions to illuminate the “dark side” in food addiction.
Drug addiction is a major public health concern in the United States costing taxpayers billions in health care costs, lost productivity and law enforcement. However, the availability of effective treatment options remains limited. The development of novel therapeutics will not be possible without a better understanding of the addicted brain. Studies in both clinical and preclinical models indicate that chronic drug use leads to alterations in the body and brain's response to stress. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis may shed light on the ability of stress to increase vulnerability to relapse. Further, within both the HPA axis and limbic brain regions, corticotropin-releasing factor (CRF) is critically involved in the brain's response to stress. Alterations in both central and peripheral CRF activity seen following chronic drug use provide a mechanism by which substance use can alter stress reactivity, thus mediating addictive phenotypes. While many reviews have focused on how stress alters drug-mediated changes in physiology and behavior, the goal of this review is to focus on how substance use alters responses to stress.
Opiate use disorders are associated with impaired cognitive function and altered stress-responsive systems. The corticotropin-releasing factor (CRF) system mediates stress responses via CRF1 and CRF2 receptors and may be implicated in substance use disorders. However, the specific role for each of the two known CRF receptor subtypes in cognitive impairment induced by opiate administration and withdrawal remains to be elucidated. In the present study, CRF1-/-, CRF2-/- and their respective wild-type mice are injected with escalating doses of morphine and cognitive function assessed by the novel object recognition (NOR) memory task throughout relatively long periods of opiate withdrawal. Early (2 days) phases of opiate withdrawal impair NOR memory in wild-type, CRF1-/- and CRF2-/- mice. However, the duration of opiate withdrawal-induced NOR memory deficits is prolonged in CRF1-/- but shortened in CRF2-/- mice, as compared to their respective wild-type mice, indicating opposite roles for the two CRF receptor subtypes. Nevertheless, following apparent recovery, exposure to an environmental stressor induces the reemergence of NOR memory deficits in long-term opiate-withdrawn wild-type but not CRF1-/- or CRF2-/- mice, indicating an essential role for both CRF receptor subtypes in stress vulnerability. These findings bring initial evidence of a complex physiopathological role for the CRF system in cognitive deficits and the long-lasting vulnerability induced by opiate drugs.
Stimulant-related disorders are characterized by emotional-like, cognitive and social dysfunction that may contribute to the maintenance of the disease. In addition, stimulant use and withdrawal may alter brain stress systems. The corticotropin-releasing factor (CRF) system is a major stress coordinator hypothesized to contribute to substance-related disorders. CRF signalling is mediated by two receptor types, named CRF1 and CRF2. The specific role of each of the CRF receptors in negative affective-like, cognitive and social dysfunction associated with stimulant administration and withdrawal remains largely unknown. The present study demonstrates that the CRF1 receptor-deficiency increases the anxiety-like behaviour induced by intermittent administration of escalating doses of cocaine (5-20 mg/kg, i.p.), as assessed by the elevated plus maze. In addition, the same cocaine regimen induces novel object recognition (NOR) and sociability deficits, which are unaffected by CRF2 receptor-deficiency. However, CRF2 receptor-deficiency effectively shortens the duration of the NOR and sociability deficit induced by cocaine withdrawal. Furthermore, following the apparent recovery of NOR and sociability performances during relative long-term (42 days) cocaine withdrawal, CRF2 receptor-deficiency eliminates the stress-induced re-emergence of NOR and sociability deficit. Stressed cocaine-withdrawn mice show a genotype-independent higher c-fos mRNA expression in the perirhinal cortex, a brain region mediating NOR performance, than stressed drug-naïve mice. However, neither genotype nor drug withdrawal affects the expression of tyrosine hydroxylase in the ventral tegmentale area and the locus coeruleus, CRF in the amygdala and the paraventricular nucleus of the hypothalamus and dynorphin in the nucleus accumbens shell. The latter results suggest that stress vulnerability during long-term cocaine withdrawal is not due to alterations in stress-coping mechanisms. The present study provides initial evidence of a critical role for the CRF system in cognitive and sociability deficits and vulnerability induced by stimulant administration and withdrawal, suggesting new therapeutic strategies for substance-related disorders.
Heightened anxiety and sensitivity to stress following chronic cocaine use are likely to increase an individual's susceptibility for relapse to drug-seeking behavior. Thus, it is important to investigate the neural mechanisms responsible for the regulation of anxiety during cocaine withdrawal and stress-induced relapse in order to identify potential targets for pharmacological intervention. This chapter will address the involvement of several neurotransmitter systems in regulating anxiety during cocaine withdrawal and stress-induced relapse mechanisms. The distinct roles of the dopamine, serotonin, corticotropin releasing factor, norepinephrine, and opioid systems in regulating the negative consequences of cocaine withdrawal and the effects of stress in eliciting relapse to drug use will be discussed. In addition, a section detailing the potential role of other neuropeptides like cholecystokinin and neuropeptide Y in cocaine withdrawal-induced anxiety and stress-induced relapse is included. It is important to consider the roles of these brain-signaling systems separately, as well as integrated in a network that functions in regulating anxiety during cocaine withdrawal and the effects of stress on drug abuse and relapse to drug use. By targeting these regulatory mechanisms, potential pharmacological targets may be identified in support of the prevention of relapse to drug use.
Mice have become invaluable as a model species to investigate the visual system, visual behavior and eye disease. The reasons for this include: relative genetic similarity to humans, the ability to generate transgenic animals, their convenience and cost as laboratory animals, and the extensive variety of proven behavioral tests. It is therefore not surprising that in recent years, mice have been central to some of the most important findings in the visual sciences. After more than 200 years of classifying the cells of the mammalian eye, it was accepted that detection of light occurred in two types of photoreceptor cells located in the outer retina, the rods and cones. Russell Foster and colleagues showed there must be a third class of photoreceptor cell in the eye. These cells have since been identified as intrinsically photosensitive retinal ganglion cells. This remarkable discovery was only possible because genetic manipulation created mice completely lacking rod and cone photoreceptors, and robust behavioral assays for mice had already been established. Mouse models of eye disease have also been at the leading edge of pre-clinical therapy development. Efficacy in cell replacement therapy has relied heavily on mouse models of retinal degeneration, where the variety of disease phenotypes has allowed progressive testing of cell capabilities for survival, integration, and restoration of function. However, the most remarkable success story comes from development of RPE65 gene replacement therapy. Finally, the retina is the most accessible part of the immune privileged central nervous system, and is therefore a powerful model for broader studies of neuronal circuitry and how disorders of neural circuits relate to behavior.
The intake of psychostimulant drugs may induce cognitive dysfunction and negative affective-like states, and is associated with increased activity of stress-responsive systems. The corticotropin-releasing factor (CRF) system mediates neuroendocrine, behavioural and autonomic responses to stressors, and might be implicated in substance-related disorders. CRF signalling is mediated by two receptor types, named CRF1 and CRF2.
The present study aims to elucidate the role for the CRF1 receptor in cognitive dysfunction and anxiety-like states induced by cocaine.
The genetic inactivation of the CRF1 receptor (CRF1+/- and CRF1-/-) does not influence recognition memory in drug-naïve mice, as assessed by the novel object recognition (NOR) test. Moreover, the chronic administration of escalating doses of cocaine (5-20 mg/kg, i.p.) induces NOR deficits, which are unaffected by CRF1 receptor-deficiency. However, the same drug regimen reveals an anxiety-like vulnerability to cocaine in CRF1-/- but not in wild-type or CRF1+/- mice, as assessed by the elevated plus maze test.
The present findings indicate dissociation of cognitive dysfunction and anxiety-like states induced by cocaine. Moreover, they unravel a novel mechanism of vulnerability to psychostimulant drugs.
Altered motivational processes are key features of drug dependence and withdrawal, yet their neural mechanisms remain largely unknown. The present study shows that genetic disruption of the corticotropin-releasing factor receptor-2 (CRF2-/-) does not impair motivation for palatable food in drug-naïve mice. However, CRF2 receptor-deficiency effectively reduces the increase in palatable food-driven motivation induced by opiate withdrawal. Indeed, both in male and female wild-type mice, withdrawal from escalating morphine doses (20-100 mg/kg) induces a dramatic and relatively long-lasting (6 days) increase in palatable food-driven operant behavior under a progressive ratio (PR) schedule of reinforcement. In contrast, either male or female morphine-withdrawn CRF2-/- mice show smaller and shorter (2 days) increases in motivation than wild-type mice. Nevertheless, CRF2 receptor-deficiency does not impair the ability to discriminate reinforced behavior prior to, during the partial opiate withdrawal periods occurring between morphine injections and following drug discontinuation, indicating preserved cognitive function. Moreover, CRF2 receptor-deficiency does not affect the ambulatory or body weight effects of intermittent morphine injections and withdrawal. These results provide initial evidence of a gender-independent and specific role for the CRF2 receptor in the motivational effects of opiate withdrawal.
Negative symptoms, conceptualized as clinical manifestations of schizophrenia, and subsequently described in other psychiatric disorders, include the loss of normal arousal, drive and affective reactivity. In the field of substance abuse, an interesting analogy can be detected between negative symptoms, in their classical meaning, and the amotivational syndrome (AS), which has been described as a form of chronic cannabis intoxication. AS also shows a close resemblance to the reward deficiency syndrome (RDS) of alcoholics and stimulant abusers, and to the post-withdrawal syndrome (PWS) of detoxified heroin addicts. A variety of substances share a common tropism for the dopaminergic system, leading to a state of hypophoria, which seems to represent a common pathway for chronic substance abusers. In the light of these convergences, a common treatment principle for addictive disorders can be enunciated. This consists in resorting to pro-dopaminergic drugs, that are supposed to replace damaged functions and control craving, and in avoiding anti-dopaminergic drugs, that are expected to exacerbate craving and impede the reversal of the reward deficiency.
The endocannabinoid (eCB) system is an important regulator of the stress response and mediates several stress-related behaviors, including anxiety. Despite anatomical evidence that eCBs interact with the principle stress peptide, corticotropin-releasing factor (CRF), few data exist that address functional interactions between these systems. Accordingly, we examined the effects of the CB1 receptor antagonist, AM251, on behavioral anxiety induced by (1) exogenous CRF, and (2) withdrawal from chronic cocaine exposure (mediated by CRF). After behavioral testing, we collected blood and assessed plasma corticosterone levels. In Experiment 1, male Long-Evans rats were pretreated with AM251 (0, 10, 100, or 200 μg, i.c.v.), followed by CRF (0 or 0.5 μg, i.c.v.), before testing for anxiety-like behavior in the elevated plus maze (EPM). In Experiment 2, rats were exposed to cocaine (20 mg/kg, i.p.) or saline for 14 consecutive days. Forty-eight hours following cocaine exposure, rats were pretreated with AM251 (0, 10, or 100 μg, i.c.v.) and tested in the EPM. AM251 produced an anxiogenic response at the highest dose, but reversed the behavioral anxiety induced by CRF and withdrawal from chronic cocaine in a dose-dependent manner. AM251 also increased plasma corticosterone levels, but did so irrespective of CRF treatment or cocaine preexposure. Our findings suggest that the anxiogenic effects of CRF and cocaine withdrawal are mediated, at least in part, by CB1 receptor transmission, and provide evidence in support of eCB-CRF interactions that are independent of the hypothalamic-pituitary-adrenal axis.
There is a high degree of overlap between brain regions involved in processing natural rewards and drugs of abuse. "Non-drug" or "behavioral" addictions have become increasingly documented in the clinic, and pathologies include compulsive activities such as shopping, eating, exercising, sexual behavior, and gambling. Like drug addiction, non-drug addictions manifest in symptoms including craving, impaired control over the behavior, tolerance, withdrawal, and high rates of relapse. These alterations in behavior suggest that plasticity may be occurring in brain regions associated with drug addiction. In this review, I summarize data demonstrating that exposure to non-drug rewards can alter neural plasticity in regions of the brain that are affected by drugs of abuse. Research suggests that there are several similarities between neuroplasticity induced by natural and drug rewards and that, depending on the reward, repeated exposure to natural rewards might induce neuroplasticity that either promotes or counteracts addictive behavior.
The theory is advanced that the common denominator of a wide range of addictive substances is their ability to cause psychomotor activation. This view is related to the theory that all positive reinforcers activate a common biological mechanism associated with approach behaviors and that this mechanism has as one of its components dopaminergic fibers that project up the medial forebrain bundle from the midbrain to limbic and cortical regions. Evidence is reviewed that links both the reinforcing and locomotor-stimulating effects of both the psychomotor stimulants and the opiates to this brain mechanism. It is suggested that nicotine, caffeine, barbiturates, alcohol, benzodiazepines, cannabis, and phencyclidine-each of which also has psychomotor stimulant actions-may activate the dopaminergic fibers or their output circuitry. The role of physical dependence in addiction is suggested to vary from drug to drug and to be of secondary importance in the understanding of compulsive drug self-administration.
Corticotropin-releasing factor (CRF) is a major hypophysiotropic peptide regulating pituitary-adrenal response to stress, and it is also widely expressed in the central nervous system. The recent cloning of cDNAs encoding the human and rat CRF receptors has enabled us to map the distribution of cells expressing CRF receptor mRNA in rat brain and pituitary by in situ hybridization. Receptor expression in the forebrain is dominated by widespread signal throughout all areas of the neo-, olfactory, and hippocampal cortices. Other prominent sites of CRF receptor mRNA expression include subcortical limbic structures in the septal region and amygdala. In the diencephalon, low levels of expression are seen in a few discrete ventral thalamic and medial hypothalamic nuclei. CRF receptor expression in hypothalamic neurosecretory structures, including the paraventricular nucleus and median eminence, is generally low. In the brainstem, certain relay nuclei associated with the somatic (including trigeminal), auditory, vestibular, and visceral sensory systems, constituted prominent sites of CRF receptor mRNA expression. In addition, high levels of this transcript are present in the cerebellar cortex and deep nuclei, along with many precerebellar nuclei. In the pituitary, moderate levels of CRF receptor mRNA expression were detected throughout the intermediate lobe and in a subset of cells in the anterior lobe identified as corticotropes by concurrent immunolabeling. Overall, the central distribution of CRF receptor mRNA expression is similar to, though more expansive than, that of regions reported to bind CRF, and it shows limited overlap with loci expressing CRF-binding protein. Interestingly, CRF receptor mRNA is low or undetectable in several cell groups implicated as central sites of CRF action.
The development of addiction and vulnerability to relapse following withdrawal is proposed to be the result of neuroadaptive processes within the central nervous system that oppose the acute reinforcing actions of drugs of abuse. These changes lead to impairment in the mechanisms that mediate positive reinforcement and the emergence of affective changes such as anxiety, dysphoria, and depression during withdrawal. Considerable evidence exists implicating perturbations in DA and 5-HT transmission in the nucleus accumbens--neurochemical systems that are activated by cocaine and ethanol self-administration and deficient during withdrawal--as potential substrates for these affective changes. In addition, growing evidence suggests that enhanced CRF release in the central nucleus of the amygdala represents a mechanism underlying the anxiogenic and stress-like consequences of withdrawal that are common to all drugs of abuse. A growing body of evidence also implicates dysregulation of the non-neuroendocrine CRF stress system within the central nucleus of the amygdala as a common factor in the anxiogenic and aversive consequences of withdrawal from drugs of abuse. Moreover, a possible link may exist between long-lasting abnormalities in CRF function in the CeA and vulnerability to relapse during protracted abstinence. Another presumably critical element contributing to the chronic relapsing nature of drug addiction is the learned responses to drug-related stimuli. The long-lasting efficacy of drug- and alcohol-associated contextual stimuli in eliciting drug-seeking behavior in animal models of relapse resembles the endurance of conditioned cue reactivity and cue-induced cocaine craving in humans and confirms a significant role of learning factors in the long-lasting addictive potential of cocaine. With cocaine, D1-dependent neural mechanisms within the medial prefrontal cortex and basolateral amygdala may be important substrates for the motivating effects of drug-related environmental stimuli. With ethanol, available data suggest a role for opioid receptors in the mediation of conditioned drug-seeking behavior. Finally, conditioning factors (i.e., exposure to drug-associated stimuli) and stress can interact to augment vulnerability to relapse. This finding emphasizes that it will be important to consider the simultaneous effects of multiple environmental triggers for relapse in the development of treatment and medication strategies.
Despite prolonged abstinence, prior drug dependence is accompanied by lasting changes in physiology, psychosocial functioning and vulnerability to relapse. One proposed mechanism for these alterations is dysregulation of corticotropin-releasing factor (CRF) neurocircuitry.
To determine regional brain CRF content and HPA-axis activity during protracted cocaine and ethanol withdrawal in dependent rats.
To study protracted ethanol withdrawal, rats ( n=22) were fed a nutritionally complete, ethanol (10% v/v) liquid diet for 3-4 weeks. Controls ( n=12) were pair-fed an isocaloric, ethanol-free formulation. To study protracted cocaine withdrawal, rats ( n=23) self-administered cocaine (0.25 mg/infusion; FR-5) daily for 3 weeks during 3-h sessions and subsequently were allowed to self-administer cocaine during two 12-h "binge" sessions. Controls ( n=6) received yoked saline infusions. Regional brain CRF-like-immunoreactivity (CRF-LI), plasma ACTH-LI and CORT-LI levels were determined from 1 day to 6 weeks post-withdrawal.
Both ethanol- and cocaine-withdrawn rats initially exhibited reduced CRF-LI content in the amygdala followed by a progressive increase culminating in elevated levels 6 weeks post-withdrawal. Ethanol-withdrawn rats also initially had reduced hippocampal, frontal cortical and hypothalamic CRF-LI levels and time-dependent reductions in basal CORT levels. Cocaine-withdrawn rats showed time-dependent elevations in frontal cortical CRF-LI and basal CORT levels.
Protracted withdrawal from ethanol or cocaine is associated with altered limbic CRF-LI and circulating CORT levels beyond the detoxification stage. The delayed nature of some changes suggests that they may not represent residual effects of acute withdrawal, but rather emerging manifestations of a separate process, such as allostatic load.
Previous studies have suggested a role for corticotropin-releasing factor (CRF) in the central nucleus of the amygdala (CeA) in the aversive and anxiogenic effects of withdrawal from opiates and ethanol. To test whether this role of CRF extends to cocaine withdrawal as well, the release of CRF in rat amygdala was monitored by intracranial microdialysis during a 12-hour session of intravenous cocaine self-administration and subsequent 12-hour cocaine withdrawal period. Cocaine self-administration tended to lower dialysate CRF concentrations to approximately 75% of CRF levels in controls. In contrast, subsequent cocaine withdrawal produced a profound increase in CRF release, which reached peak levels of approximately 400% of baseline between 11 and 12 hours post-cocaine. These results provide evidence that cocaine withdrawal activates CRF neurons in the amygdala, a site that has been implicated in emotional and anxiogenic effects of stress and drug withdrawal syndromes. Synapse 32:254–261, 1999. © 1999 Wiley-Liss, Inc.
Understanding the neurobiological mechanisms of addiction requires an integration of basic neuroscience with social psychology, experimental psychology, and psychiatry. Addiction is presented as a cycle of spiralling dysregulation of brain reward systems that progressively increases, resulting in compulsive drug use and a loss of control over drug-taking. Sensitization and counteradaptation are hypothesized to contribute to this hedonic homeostatic dysregulation, and the neurobiological mechanisms involved, such as the mesolimbic dopamine system, opioid peptidergic systems, and brain and hormonal stress systems, are beginning to be characterized. This framework provides a realistic approach to identifying the neurobiological factors that produce vulnerability to addiction and to relapse in individuals with a history of addiction.
The possible effects on the morphine withdrawal signs of the nonspecific corticotropin-releasing factor (CRF) receptor antagonist -helical CRF, the selective CRF receptor subtype 1 antagonist CP-154,526 and the selective CRF receptor subtype 2 antagonist antisauvagine-30 (AS-30) were investigated in rats. The most withdrawal signs, including jumping, teeth chatter, writhing, shakes, lacrimation, piloerection, irritability and diarrhoea, were attenuated by pretreatment with -helical CRF (10 µg i.c.v.) and CP-154,526 (30 mg/kg i.p.). However, no morphine withdrawal signs except for diarrhea were significantly affected by pretreatment with AS-30 (10 µg, i.c.v.). To investigate the possible role of different CRFR antagonists (-helical CRF, CP-154,526 and AS-30) in relapse to opiate dependence, the 28-day extinction of morphine-conditioned place preference (CPP) was used. The morphine-CPP disappeared following a 28-day extinction and then was reactivated by a single injection of 10 mg/kg morphine. Pretreatment with -helical CRF (10 µg, i.c.v.) and CP-154,526 (30 mg/kg, i.p.) could significantly block this reactivation of morphine-CPP. In contrast, pretreatment with AS-30 (1 or 10 µg i.c.v.) did not affect this reactivation of morphine-CPP. The present study demonstrated that activation of the CRF receptor is involved in morphine withdrawal signs and relapse to morphine dependence, and that the role of CRF receptor subtypes 1 and 2 in withdrawal and reactivation of morphine dependence is not identical. CRF receptor subtype 1, but not subtype 2, is largely responsible for the action of the CRF system on opiate dependence. These results suggest that the CRF receptor antagonists, particularly the CRF receptor subtype 1 antagonist, might be of some value in the treatment and prevention of drug dependence.
Previous studies indicate that corticotropin-releasing factor (CRF) contributes to the anxiety-like and aversive states associated with drug-induced withdrawal. The present study extends this work by analyzing the CRF receptor subtype involved in withdrawal responses. First, the influence of a selective CRF receptor-1 (CRF-R1) antagonist, CP-154,526, on opiate withdrawal behavior was examined. Pretreatment with the CRF-R1 antagonist significantly attenuated several behavioral signs of naltrexone-induced morphine withdrawal, including writhing, chewing, weight loss, lacrimation, salivation, and irritability, measured during the first hour of withdrawal. Next the expression of CRF-R1 was determined as a second measure of the involvement of this receptor in opiate withdrawal. Naltrexone-induced morphine withdrawal resulted in down-regulation of CRF-R1 mRNA in several brain regions, including the frontal cortex, parietal cortex, striatum, nucleus accumbens, and amygdala, but not in the hypothalamus or periaqueductal gray. Expression of CRF-R2, the other major CRF receptor subtype, was not down-regulated significantly by withdrawal in any of the regions examined, although morphine alone significantly increased levels of this receptor subtype. Taken together, the behavioral and receptor regulation findings indicate that CRF-R1 is the primary mediator of the actions of the CRF system on opiate withdrawal, although it is possible that CRF-R2 contributes to the response.
The development of addiction and vulnerability to relapse following withdrawal is proposed to be the result of neuroadaptive processes within the central nervous system that oppose the acute reinforcing actions of drugs of abuse. These changes lead to impairment in the mechanisms that mediate positive reinforcement and the emergence of affective changes such as anxiety, dysphoria, and depression during withdrawal. Considerable evidence exists implicating perturbations in DA and 5-HT transmission in the nucleus accumbens—neurochemical systems that are activated by cocaine and ethanol self-administration and deficient during withdrawal—as potential substrates for these affective changes. In addition, growing evidence suggests that enhanced CRF release in the central nucleus of the amygdala represents a mechanism underlying the anxiogenic and stress-like consequences of withdrawal that are common to all drugs of abuse. A growing body of evidence also implicates dysregulation of the non-neuroendocrine CRF stress system within the central nucleus of the amygdala as a common factor in the anxiogenic and aversive consequences of withdrawal from drugs of abuse. Moreover, a possible link may exist between long-lasting abnormalities in CRF function in the CeA and vulnerability to relapse during protracted abstinence. Another presumably critical element contributing to the chronic relapsing nature of drug addiction is the learned responses to drug-related stimuli. The long-lasting efficacy of drug- and alcohol-associated contextual stimuli in eliciting drug-seeking behavior in animal models of relapse resembles the endurance of conditioned cue reactivity and cue-induced cocaine craving in humans and confirms a significant role of learning factors in the long-lasting addictive potential of cocaine. With cocaine, D1-dependent neural mechanisms within the medial prefrontal cortex and basolateral amygdala may be important substrates for the motivating effects of drug-related environmental stimuli. With ethanol, available data suggest a role for opioid receptors in the mediation of conditioned drug-seeking behavior. Finally, conditioning factors (i.e., exposure to drug-associated stimuli) and stress can interact to augment vulnerability to relapse. This finding emphasizes that it will be important to consider the simultaneous effects of multiple environmental triggers for relapse in the development of treatment and medication strategies.
Corticotropin-releasing factor (CRF) may mediate some of the neuroendocrine and behavioral responses to cocaine. In this study, the distribution of CRF-like immunoreactivity (CRF-LI) was determined in the hypothalamus and in several extrahypothalamic brain regions after acute cocaine administration in handled rats. CRF-LI decreased dose-dependently with cocaine administration in the hypothalamus and in the basal-forebrain structures. A small dose of cocaine (7.5 mg/kg) decreased CRF-LI in the hippocampus and in the frontal cortex. A significant, selective, dose-dependent increase in CRF-LI was found in the amygdala after cocaine injection. None of the investigated doses of cocaine altered CRF-LI in the striatum. These results suggest that acute cocaine administration alters brain CRF systems to contribute behavioral and neuroendocrine responses to cocaine.
The hypothesis that brain noradrenergic systems have a broad biological function which is related to human fear or anxiety is reviewed. Data from studies of the function of the nucleus locus coereleus in non-human primates are presented in the context of recent anatomical, physiological, pharmacological, and animal behavioral experiments. Implications are suggested for the treatment of anxiety, drug addictions, pain, and psychosomatic diseases.
Anxiety is a key symptom of the cocaine withdrawal syndrome in human addicts, and it is considered to be one of the major factors in precipitating relapse to chronic cocaine abuse. Corticotropin-releasing factor (CRF) plays an important role in the pathophysiology of anxiety and depression, and it may also be involved in the acute behavioral and neuroendocrine actions of cocaine. The role of endogenous CRF in cocaine withdrawal-induced anxiety was investigated in the present study. Animals were subjected to chronic cocaine (20 mg/kg, intraperitoneally, once a day for 14 days) administration. Rats tested 30 min after the last cocaine injection did not show withdrawal anxiety on the elevated plus maze or any alterations in brain CRF levels. Withdrawal (48 h) from chronic cocaine administration produced an intense anxiety-like behavior characterized by decreased open arm exploration. Immunoreactive CRF (CRF-LI) levels were selectively altered in the hypothalamus, in the amygdala and in the basal forebrain structures at the time of the behavioral anxiety, reflecting an increased activity of brain CRF systems. Daily intracerebroventricular (i.c.v.) pretreatment with an immunoserum raised against CRF completely prevented the development of anxiety induced by cocaine withdrawal. These data suggest that extrahypothalamic-limbic CRF hypersecretion may be involved in the development of anxiety related to cocaine withdrawal and that the CRF system may be a useful target for new pharmacotherapies for cocaine withdrawal and relapse.
A 35S-labeled 48-base synthetic oligonucleotide complementary to a portion of the rat corticotropin-releasing factor (CRF) mRNA was used for in situ hybridization histochemistry. CRF-synthesizing cells were located in the paraventricular nucleus of the hypothalamus. These cells were observed in the medial parvocellular subdivision where there was a 90% increase in the amount of CRF mRNA per unit volume after adrenalectomy.
Injection of N-methyl-D-aspartate (NMDA, 7.5 micrograms) kainate (1 microgram) or quisqualate (2 micrograms) into the rat dorsal hippocampus induced wet-dog shakes and convulsions. As shown by an in situ immunohistochemical analysis, 3 h after the excitatory amino acids injections the rats displayed a bilateral profound elevation of the proenkephalin and prodynorphin mRNA levels in dentate gyrus granule cells (2-3 or 1.5-2 fold higher than control levels, respectively). Pretreatment of rats with D-amino-phosphonovalerate (D-APV, 10 micrograms), a selective antagonist of NMDA receptor, prevented the behavioral and biochemical changes evoked by NMDA. The changes in the behavior and gene expression evoked by kainate or quisqualate were diminished in rats which received 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX, 2 micrograms), a putative antagonist of quisqualate and kainate receptors. The study demonstrated that activation of NMDA, quisqualate or kainate receptors in the hippocampus induced seizures associated with a marked increase in the proenkephalin (PENK) and the prodynorphin (PDYN) gene expression in the rat dentate gyrus.
Drugs of abuse are very powerful reinforcers, and even in conditions of limited access (where the organism is not dependent) these drugs will motivate high rates of operant responding. This presumed hedonic property and the drugs' neuropharmacological specificity provide a means of studying the neuropharmacology and neuroanatomy of brain reward. Three major brain systems appear to be involved in drug reward--dopamine, opioid and GABA. Evidence suggests a midbrain-forebrain-extrapyramidal circuit with its focus in the nucleus accumbens. Data implicating dopamine and opioid systems in indirect sympathomimetic and opiate reward include critical elements in both the nucleus accumbens and ventral tegmental areas. Ethanol reward appears to depend on an interaction with the GABAA receptor complex but may also involve common elements such as dopamine and opioid peptides in this midbrain-forebrain-extrapyramidal circuit. These results suggest that brain reward systems have a multidetermined neuropharmacological basis that may involve some common neuroanatomical elements.
The control of hypothalamic-pituitary-adrenocortical (HPA) activity by opioids seems to involve stimulatory and inhibitory pathways. The purpose of the present study was to determine the acute and chronic effects of selective mu- and delta-opioid agonists, administered centrally (i.c.v.) on pituitary-adrenocortical activity in the rat. The mu-agonist DAGO ([D-Ala2,N-MePhe4,Gly-ol5]enkephalin; 0.75 nmol i.c.v.) and the delta-agonist DPDPE ([D-Pen2,5]enkephalin; 194 nmol i.c.v.) both stimulated corticosterone release when administered acutely. Chronic administration of DAGO and DPDPE resulted in the development of tolerance to their neuroendocrine effects. These data suggest that both mu- and delta-opioid receptors are involved in the regulation of HPA activity under physiological conditions and during opiate abuse.
There are a number of repetitive behaviors which have in common what appears to be a decrease in an individual's capacity to choose to discontinue them. The taxonomy we select to categorize these behaviors depends on our objectives. Broad definition which label as 'addictions' both repetitive use of drugs and repetitive behaviors not related to drug use call attention to the loss of flexibility that the behaviors have in common. However, such broad definitions may overemphasize the value of general behavioral approaches to change and obscure the fact that seemingly similar behaviors can be dramatically changed by very different specific interventions; (for example, nicotine gum for cigarette smoking, clomipramine for obsessive compulsive disorder.) It is also possible that calling both compulsive hair-pulling and daily heroin use 'addictive disorders' may trivialize the concept of addiction and lead to an erosion of public support for research and intervention in the chemical addictions.
The effect of hypoxia on plasma met-enkephalin and catecholamine levels was studied in chronically catheterized fetal sheep. Maternal and fetal hypoxia was maintained for 20 min. We found hypoxia significantly increased the plasma levels of large mol wt met-enkephalin containing peptides from 1755 +/- 229 pg/mL during baseline to 4408 +/- 1426 pg/mL by 15 minutes of hypoxia. The levels of the met-enkephalin pentapeptide were unchanged during hypoxia from a baseline value of 168 +/- 56 pg/mL. Norepinephrine and epinephrine levels increased 5- and 10-fold, respectively, by 15 min of hypoxia. These observations suggest cosecretion of the large mol wt met-enkephalin peptides with catecholamines during stress in developing animals.
Selective unilateral 6-hydroxydopamine lesion of the nigrostriatal dopaminergic neurones in rats resulted, 12 to 90 days later, in a marked increase in the number of neuropeptide Y (NPY)-immunoreactive perikarya in the ipsilateral deafferented striatum compared to the contralateral intact side in the same animal and to both sides in control animals. The staining intensity of most positive cells also appeared to be enhanced in the deafferented striatum. These effects which can be interpreted as resulting from an increase in the intraneuronal levels of NPY may be accounted for by an increased production or a decreased metabolization of the peptide in the striatum deafferented from its dopaminergic input. The results therefore provide morphological evidence that the NPY-containing neuronal system of the striatum may undergo tonic influence from nigrostriatal dopaminergic afferents.
The use of avidin-biotin interaction in immunoenzymatic techniques provides a simple and sensitive method to localize antigens in formalin-fixed tissues. Among the several staining procedures available, the ABC method, which involves an application of biotin-labeled secondary antibody followed by the addition of avidin-biotin-peroxidase complex, gives a superior result when compared to the unlabeled antibody method. The availability of biotin-binding sites in the complex is created by the incubation of a relative excess of avidin with biotin-labeled peroxidase. During formation of the complex, avidin acts as a bridge between biotin-labeled peroxidase molecules; and biotin-labeled peroxidase molecules, which contains several biotin moieties, serve as a link between the avidin molecules. Consequently, a "lattice" complex containing several peroxidase molecules is likely formed. Binding of this complex to the biotin moieties associated with secondary antibody results in a high staining intensity.
Using intracranial microdialysis, the effect of repeated cocaine (30 mg/kg i.p.) versus saline administration for 10 consecutive days upon basal and stimulated release of corticotropin-releasing factor (CRF) was examined in the central amygdaloid nucleus (CeA) of anesthetized rats. No significant differences in basal CRF levels between daily cocaine and saline treated groups were found. However, after cocaine challenge (10 mg/kg i.p.) the increase in CRF overflow was significantly greater in cocaine- as opposed to saline-pretreated rats (266 +/- 55.4% versus 149 +/- 8.5% of basal levels). Local administration of 4-aminopyridine produced a significant increase in CRF efflux (195 +/- 58.5%) in daily cocaine-treated rats with only a weak response in the control group (127 +/- 30.9%). These data demonstrate that repeated administration of cocaine enhances cocaine-induced release of CRF in the rat CeA. The sensitization of CRF release may play a significant role in psychostimulant-induced sensitization phenomena.
The effect of catecholamine depletion or blockade of dopaminergic or noradrenergic receptors on the neuropeptide Y immunoreactivity was studied in the rat brain cortex using immunohistochemical methods. Neuropeptide Y immunoreactive neurons were counted and the mean density of stained neurons per microscopic field was calculated. It was found that monoamine depletion by reserpine, the blockade of dopaminergic receptors by haloperidol or the specific D1 receptor blockade by SCH23390 caused a significant increase in the neuropeptide Y immunoreactivity in the cortex studied, after 24 h, evaluated as the density of immunoreactive neurons. No significant changes were observed after the blockade of alpha or beta adrenergic receptors (by phenoxybenzamine or propranolol, respectively). Specific D2 receptor blockade by sulpiride induced an insignificant increase only. The results suggest the existence of an inhibitory dopaminergic control of the neuropeptide Y content, mainly via D1 receptors, in neurons of the rat brain cortex.
Other workers have established that cocaine injections increase the levels of dynorphin peptides in the caudate putamen and substantia nigra of the rat brain. Using a quantitative solution hybridization protection assay for mRNA, we detected a significant increase in the concentration of prodynorphin mRNA in caudate putamen extracts of rats injected with cocaine following a 'binge' administration pattern designed to mimic human cocaine abuse. Increased prodynorphin mRNA was observed at the earliest time-point studied (50 h) and the lowest dose (10 mg/kg/day) of cocaine tested and persisted through the 14 day period studied. No prodynorphin mRNA was detected in the substantia nigra.
1. The effects of morphine tolerance and abstinence on the characteristics of N-methyl-D-aspartate (NMDA) receptors, labeled with [3H]MK-801, were determined in the brain regions and spinal cord of the rat. 2. Male Sprague-Dawley rats were rendered tolerant to and physically dependent on morphine by subcutaneous implantation of six morphine pellets during a 7-day period. In tolerant (non-abstinent) rats, the pellets were left intact at the time of sacrificing, whereas in the abstinent rats the pellets were removed 16 hr prior to sacrificing. 3. The binding of [3H]MK-801, an NMDA receptor antagonist, to membranes prepared from spinal cord and brain regions (cortex, striatum, amygdala, hippocampus, hypothalamus, midbrain and pons-medulla) was determined using 5 nM concentration of the ligand in the presence of 30 microM glycine and 50 microM of glutamate. 4. In non-abstinent morphine tolerant rats, the binding of [3H]MK-801 was decreased by 40 and 33% in the midbrain and spinal cord, respectively, in comparison with their placebo controls. In morphine abstinent rats, the binding of [3H]MK-801 was decreased by 42, 29 and 50% in hypothalamus, midbrain and spinal cord, respectively, in comparison with their placebo controls. The binding of [3H]MK-801 to other brain regions and spinal cord of morphine tolerant and abstinent rats did not differ from their respective placebo controls. 5. Thus, these studies demonstrate, for the first time, that in the presence of glutamate and glycine, NMDA receptors of selected brain regions and spinal cord are down-regulated in rats treated chronically with morphine.
High doses of stimulants of abuse, such as methamphetamine and cocaine, cause significant increases in the content of neurotension- and dynorphin-like immunoreactivity in the striatum and nucleus accumbens (approximately 200-600% of control) in the rat. These changes in neuropeptide content are caused by stimulation of dopamine D1 receptors and prevented by the glutamate NMDA receptor antagonist, MK 801. Stimulation of the NMDA receptor with N-methyl-D-aspartate results in increases in the neuropeptide levels like that caused by methamphetamine and cocaine. These findings demonstrate that stimulants of abuse profoundly influence neurotensin and dynorphin pathways associated with extrapyramidal and limbic structures by an interaction of activated dopamine D1 and glutamate NMDA receptors.
Changes in the spinal expression of the opioid precursor prodynorphin, which has been implicated in the response to peripheral inflammation, were examined with semi-quantitativein situ hybridization histochemistry in rats subjected to collagen II-induced arthritis. The effects of glucocorticos-teroid treatment on the basal and inflammation-induced prodynorphin expression were evaluated. Collagen II-induced arthritis caused a 16-fold increase in prodynorphin mRNA levels which comprised all neurons expressing low levels under normal conditions. In the superficial dorsal horn, one group of neurons of a large size reacted with a dramatic increase of prodynorphin mRNA, while another group of small neurons exhibited a moderate elevation of prodynorphin mRNA levels. In the deep dorsal horn of arthritic rats, most prodynorphin neurons were large and showed high prodynorphin mRNA levels. Systemic treatment with the glucocorticosteroid budesonide attenuated the arthritis-induced increase of prodynorphin mRNA expression in a topospecific manner. The budesonide-induced reduction of prodynorphin mRNA levels was more pronounced in the deep dorsal horn than in the superficial dorsal horn. Budesonide treatment of control animals caused a small, but significant increase in prodynorphin mRNA levels in the superficial laminae I/II without affecting prodynorphin mRNA levels in the deep dorsal horn. The degree of arthritis correlated closely with spinal prodynorphin mRNA levels.
The expression of the neurokinin 1 (NK1) receptor (i.e. substance P receptor) gene in spinal cord was studied in rats subjected to unilateral inflammation by semi-quantitative in situ hybridization analysis. Low levels of NK1 receptor mRNA were detected in many neurones throughout the grey matter. Relatively strong labelling was observed in large motoneurones and a subpopulation of superficial dorsal horn neurones. Six days after Freund's adjuvant-induced unilateral hindpaw inflammation, NK1 receptor mRNA levels in lamina I/II of the dorsal horn ipsilateral to the inflamed paw increased almost two fold compared with the contralateral side. These data suggest an inflammation-induced increase of NK1 receptor synthesis in intrinsic spinal cord neurones involved in nociceptive neurotransmission.
Corticotropin-releasing hormone (CRH) is a 41-amino acid neuropeptide which increases the transcription of the proopiomelanocortin (POMC) gene, as well as the biosynthesis and secretion of POMC-derived peptides. Using a specific human CRH radioimmunoassay we have shown that human T-lymphocytes contain immunoreactive CRH. We studied the effects of phytohemagglutinin (PHA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on the biosynthesis of CRH in human T-lymphocyte cell cultures. A significant increase in CRH mRNA levels was observed in human lymphocytes after 12 h of PHA/TPA treatment, while the levels decreased after 22 h. These findings could imply an immunomodulatory role for CRH that could be due to autocrine and/or paracrine interactions.
Endogenous central corticotropin-releasing factor (CRF) may be involved in the neuroendocrine and behavioral responses to cocaine. In the present study, levels of CRF mRNA were measured in the hypothalamus and in several extrahypothalamic brain regions after different regimens of "binge"-pattern cocaine administration. Male Fischer rats were injected with saline or cocaine (15 mg/kg, 1 hr x 3/day) at the beginning of the light cycle, to approximate the manner in which cocaine is often abused by humans, both in terms of temporal pattern and in relation to circadian rhythm. Cocaine administered in this binge regimen produced time-dependent alterations of CRF mRNA levels in the hypothalamus. There was a significant increase in CRF mRNA levels on day 1, which returned to base-line levels on day 2, with elevated plasma corticosterone levels on both days. CRF receptor type 1 and prooplomeianocortin mRNA levels in the anterior lobe of the pituitary were not significantly altered after acute cocaine injections on day 1 or day 2. On day 14 of chronic binge-pattern cocaine administration, decreased hypothalamic CRF mRNA levels and an attenuated elevation in plasma corticosterone levels were found. After 10 days of withdrawal from 14-day binge cocaine, CRF mRNA returned to basal levels. CRF mRNA levels in the amygdala were also significantly increased on day 1 and returned to basal values on day 2. Chronic (14-day) binge cocaine administration did not alter CRF mRNA levels in the amygdala. These results suggest that the attenuated response in the hypothalamic-pituitary-adrenal axis to chronic binge cocaine administration is coupled to the cocaine-induced decreases in CRF gene expression in the hypothalamus and that activation of CRF gene expression in extrahypothalamic regions may have implications for a molecular understanding of the behavioral responses to cocaine.
The aim of this study was to investigate the consequences of partial vs. complete serotonergic (5-HT) depletions on the immunoreactivity of striatal interneurons containing neuropeptide Y (NPY). Taking into account the plasticity of the monoaminergic neurons, the effects of various doses of 5,7-dihydroxytryptamine (5,7-DHT) injected into the anterior raphe nuclei and P-chlorophenylalanine (PCPA) administration were compared in the dorsal (caudate-putamen) and the ventral (nucleus accumbens) striatum. Twenty days after administering 5,7-DHT injections inducing a substantial but partial decrease in the striatal 5-HT concentrations (about 80%), we detected a significant decrease in the number of NPY immunoreactive cells. In contrast, the PCPA inhibition of serotonin synthesis in the neurons spared by the partial lesion or the near-complete neurotoxic lesion induced an increase in the number of striatal NPY neurons. These results suggest that complex adaptive mechanisms are probably responsible for the changes in striatal NPY reactivity observed after a partial lesion and that these neurons can adapt according to the extent of 5-HT depletion. Upon comparing the NPY responses in the dorsal and ventral components of the striatal complex, no main differences were observed; while in the caudate-putamen, the changes were primarily found to occur in the medial zone. This finding is discussed here with reference to the topographical effects of dopaminergic or glutamatergic deafferentation. Finally, these results suggest that a complete interruption of the 5-HT transmission may lead to an increase in the intracellular NPY level, which may be associated with a decrease in the release of the peptide. It can therefore be postulated that serotonergic neurons normally exert a positive influence on NPY striatal neurons.
Cocaine, as does exposure to other physiological stressors, releases brain corticotropin releasing factor (CRF), and this release habituates during the course of repeated cocaine administration in animals. Due to the many signs of anxiety and responses to stress that are produced by cocaine withdrawal in humans, the present study was designed to assess the effects of chronic cocaine and its withdrawal on regional 125I-Tyr-oCRF binding to the CRF1 receptor in brains of male Lewis rats. Cocaine or saline was intravenously infused for 10 days in a regimen that resembled a self-administration paradigm (1 mg/kg every 12 min for 2 h each day). Tissues were harvested either 15 min after or 10 days after the last cocaine infusion, and the brains were sectioned and prepared for CRF1 receptor autoradiography. Compared with findings in saline controls, there was a 31% lower level of CRF binding sites in the basolateral nucleus of the amygdala immediately after the last cocaine infusion, but not 10 days later. Neuroendocrine and non-neuroendocrine mechanisms associated with CRF1 receptors do not appear to contribute to long-term withdrawal effects.
The influence of the L-type calcium channel antagonist nimodipine on both the activity of noradrenergic neurons projecting to the hypothalamus and the pituitary-adrenal response during morphine tolerance and withdrawal was analysed. Tissue concentration of hypothalamic noradrenaline (NA) and its metabolite 3-methoxy-4-hydroxy-phenylethylen-glycol (MHPG) were determined by high-pressure liquid chromatography. Plasma corticosterone concentration (a marker of pituitary-adrenal activity) was measured by radioimmunoassay. Rats rendered tolerant to morphine decreased hypothalamic MHPG concentration, and reduced hypothalamic NA turnover. Chronic infusion of nimodipine concurrently with morphine prevented the decrease in NA turnover during tolerance. After naloxone administration to tolerant rats we found a striking parallelism between an increased activity of the hypothalamic-pituitary-adrenal axis and an enhanced activity of noradrenergic neurons projecting to the hypothalamus. However, hypothalamic NA turnover and MHPG concentration, both elevated during withdrawal, returned to control levels in rats infused chronically with nimodipine, concomitantly with a reduction of the secretion of corticosterone. Taken together, these data indicate that increased noradrenergic neuronal activity in the hypothalamic nerve terminals is associated with the neuroendocrine morphine withdrawal syndrome and suggest that an up-regulated calcium system might contribute to the activation of these neurons.
Understanding the neurobiological mechanisms of addiction requires an integration of basic neuroscience with social psychology, experimental psychology, and psychiatry. Addiction is presented as a cycle of spiralling dysregulation of brain reward systems that progressively increases, resulting in compulsive drug use and a loss of control over drug-taking. Sensitization and counteradaptation are hypothesized to contribute to this hedonic homeostatic dysregulation, and the neurobiological mechanisms involved, such as the mesolimbic dopamine system, opioid peptidergic systems, and brain and hormonal stress systems, are beginning to be characterized. This framework provides a realistic approach to identifying the neurobiological factors that produce vulnerability to addiction and to relapse in individuals with a history of addiction.
High densities of nerve cells containing corticotropin-releasing hormone (CRH) are located in the central nucleus of the amygdala (CeA) and paraventricular nucleus (PVN) of the hypothalamus. These brain regions play an important role in activating autonomic, behavioral, and endocrine responses to stress. This study was conducted to provide needed information concerning the acute effects of stress on CeA and PVN CRH mRNA expression. Rats were exposed to restraint stress for 1 h and brains collected after a 1-h post-stress interval. CRH mRNA expression occurring in the CeA and PVN was examined using in situ hybridization techniques. Densitometric analysis revealed that acute restraint stress produced significant increases in CRH mRNA levels in the PVN and in the rostral CeA region. In addition, the area in the rostral CeA encompassing high CRH mRNA signals increased significantly after stress. Results provide clear evidence that CRH neurons in the CeA and PVN exhibit rapid increases in CRH mRNA expression after exposure to stress.
Corticotropin-releasing hormone messenger RNA expression in the amygdala of rats after adrenalectomy and bilateral lesions of the hypothalamic paraventricular nucleus was examined by in situ hybridization histochemistry. Corticotropin-releasing hormone messenger RNA-containing cells are abundant in the intermediate subdivision of the central amygdaloid nucleus. Some corticotropin-releasing hormone-labeled cells are scattered in other subdivisions of the central nucleus and throughout the anterior amygdaloid area. Five days after bilateral adrenalectomy, the number of corticotropin-releasing hormone messenger RNA-containing cells was reduced both in the central nucleus and the anterior area of the amygdala. This reduction was prevented by corticosterone replacement and contrasts sharply with the known rise of corticotropin-releasing hormone messenger RNA in the paraventricular nucleus after adrenalectomy. Corticotropin-releasing hormone messenger RNA expression in the amygdala was up-regulated in rats with six-week bilateral lesions of the paraventricular nucleus. This elevation in corticotropin-releasing hormone messenger RNA was not influenced by adrenalectomy or corticosterone, and it did not correlate with plasma levels of adrenocorticotrophic hormone or corticosterone. The possible direct innervation of the amygdala by the paraventricular nucleus is supported by the demonstration of labeled axons from the paraventricular nucleus to the amygdala after injection of an anterograde tracer, Phaseolus vulgaris leucoagglutinin, into the paraventricular nucleus. Labeled fibers take two courses: through the lateral hypothalamus–ventral amygdalofugal path and through the stria terminalis.
The prodynorphin system is implicated in the neurochemical mechanism of psychostimulants. To elucidate the activity of the endogenous prodynorphin system upon treatment with psychostimulants, we investigated the effect of single and repeated cocaine and amphetamine on the prodynorphin messenger RNA level, the prodynorphin-derived peptide α-neoendorphin tissue level, and its in vitro release in the nucleus accumbens and striatum of rats. The density of κ opioid receptors in those brain regions was also assessed. Rats were injected with cocaine following a “binge” administration pattern, 20 mg/kg i.p. every hour for 3 h, one (single treatment) or five days (chronic treatment). Amphetamine, 2.5 mg/kg i.p. was administered once (single treatment) or twice a day for five days (chronic treatment).
Both the locus coeruleus (LC) and the amygdala have been implicated in aspects of opiate dependence and withdrawal. The LC is known to be one of the most sensitive sites for precipitating withdrawal behaviors after local opiate antagonist infusions in morphine-dependent subjects. The amygdala is also known to mediate antagonist-induced withdrawal behaviors and aversive motivational states. The goal of the present study was to evaluate directly the ability of noradrenergic agonists and glutamatergic antagonists to attenuate naloxone-precipitated withdrawal behaviors when infused into the LC or the central nucleus of the amygdala (CeA). The alpha-2-noradrenergic agonists clonidine or ST-91 were infused into the CeA to compare the effects of noradrenergic activation in the CeA to the attenuation of withdrawal previously observed in rats infused with clonidine into the LC, since the LC and CeA are known to contain co-localized opiate and noradrenergic receptors. The effects of microinfusions of the non-NMDA excitatory amino acid antagonist 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX) were also infused into the LC and CeA since opiate withdrawal is associated with increased glutamatergic transmission. Intra-CeA clonidine or ST-91 (2.4 microg/0.5 microl or 1.0 microl) produced significant reductions primarily in the occurrence of irritability. Conversely, intra-CeA or intra-LC infusions of CNQX (2.5 microg/0.5 microl) significantly attenuated naloxone-precipitated withdrawal, an effect similar to the attenuation previously observed after intra-LC clonidine infusions. These data demonstrate the specific behavioral effects of altering glutamatergic and noradrenergic neurotransmission in the LC or CeA during naloxone-precipitated opiate withdrawal. Elucidation of the neuroanatomical circuitry involved in opiate withdrawal should increase our understanding of the neuroadaptations associated with drug dependence and subsequent withdrawal behavior.
Previous studies have suggested a role for corticotropin-releasing factor (CRF) in the central nucleus of the amygdala (CeA) in the aversive and anxiogenic effects of withdrawal from opiates and ethanol. To test whether this role of CRF extends to cocaine withdrawal as well, the release of CRF in rat amygdala was monitored by intracranial microdialysis during a 12-hour session of intravenous cocaine self-administration and subsequent 12-hour cocaine withdrawal period. Cocaine self-administration tended to lower dialysate CRF concentrations to approximately 75% of CRF levels in controls. In contrast, subsequent cocaine withdrawal produced a profound increase in CRF release, which reached peak levels of approximately 400% of baseline between 11 and 12 hours post-cocaine. These results provide evidence that cocaine withdrawal activates CRF neurons in the amygdala, a site that has been implicated in emotional and anxiogenic effects of stress and drug withdrawal syndromes.
The effect of reserpine, a monoamine-depleting agent, on the neuropeptide Y (NPY) immunoreactivity was studied immunohistochemically in the amygdaloid complex (amygdala) of rat brain. It was found that reserpine, at a dose of 10 mg/kg i.p., after 24 h, enhanced the NPY immunoreactivity in amygdala neurons, which was expressed as an increase in the staining intensity and in the number of immunoreactive neurons visible in that structure. The obtained results suggest that monoamines take part in the regulation of NPY expression in amygdala neurons of rat brain, and that elimination of these monoaminergic regulation leads to an increase in the NPY content in that structure.
The present study was carried out to evaluate the effect of morphine, cocaine and ethanol on the density of opioid receptors in the nucleus accumbens and striatum of rat brain. The animals were injected i.p. with morphine in a single dose 20 mg/kg, or twice daily for 10 days in increasing doses of 20-100 mg/kg. Cocaine was administered in a dose of 60 mg/kg/day following the "binge" paradigm, every hour for 3 h, one day (single treatment) or five days (chronic treatment). Ethanol was administered in drinking water at increasing concentrations of 1-6% v/v, for one month. As shown by receptor autoradiography, single morphine and cocaine administration did not influence the binding density of the selective ligand of delta2 receptors [3H]Ile5,6deltorphin b, but single administration of cocaine decreased binding density of a highly selective antagonist of delta receptors, [3H]H-Tyr-Tic psi[CH2-NH]Phe-Phe-OH. Repeated morphine administration decreased the receptor density after both ligands of the delta receptor in the nucleus accumbens after 3, 24 and 48 h, and in the striatum after 24 and 48 h. The density of [3H]Ile5,6deltorphin b binding remained unchanged in both structures following repeated cocaine administration. After repeated cocaine administration either no changes (3 h) or a decrease in the binding of [3H]H-Tyr-Tic psi[CH2-NH]Phe-Phe-OH in the nucleus accumbens and striatum were observed after 24 and 48 h. Ethanol did not influence the binding density of [3H]H-Tyr-Tic psi[CH2-NH]Phe-Phe-OH and [3H]Ile5,6deltorphin b in the nucleus accumbens and striatum at any time-point studied. In the nucleus accumbens and striatum, no changes were found in the binding density of [3H]Tyr-D-Ala-Gly-MePhe-Gly-ol following single or repeated morphine administration. At 3 h after single or repeated "binge" cocaine administration, the binding of [3H]Tyr-D-Ala-Gly-MePhe-Gly-ol was not changed in either structure, but after 24 h the density of mu opioid receptors was decreased in both structures. Ethanol given to rats in drinking water decreased the binding of [3H]Tyr-D-Ala-Gly-MePhe-Gly-ol at the time of exposure to ethanol, yet in the nucleus accumbens only. Ethanol withdrawal decreased the density of the mu receptor in both structures after 24, 48 and 96 h. The above data indicate that repeated administration of morphine evokes a long-lasting down-regulation of the density of delta1 and delta2 opioid receptors, whereas cocaine affects in a similar way only the delta1 subtype in the nucleus accumbens, and to a lesser extent in the striatum. A long-term intake of ethanol solution down-regulates mu opioid receptors in both structures, but has no effect on any type of delta receptors. Thus changes in the particular opioid receptor depend on the type of drug used. Furthermore, the most profound changes are observed after late withdrawal, which may play some role in maintaining the state of dependence.
The influence of dopaminergic denervation on neuropeptide Y and corticotropin-releasing factor-containing neurons in the amygdala was investigated in rats by examining the effects of a selective, unilateral 6-hydroxydopamine lesion of mesencephalic dopaminergic neurons in both the substantia nigra and the ventral tegmental area on these peptides and their messenger RNA expression, observed eight to 10 days after the lesion. The studies were conducted by immunocytochemical and in situ hybridization methods. Neuropeptide Y or corticotropin-releasing factor-immunoreactive neurons were counted in sections of the amygdala under a microscope, and the messenger RNA expression was measured as optical density units in autoradiograms. A significant increase in both neuropeptide Y and corticotropin-releasing factor messenger RNA expression was found in the amygdala on the lesioned side in comparison with the contralateral one, as well as with the ipsilateral side of vehicle-injected controls. Immunohistochemical studies showed that the number of neuropeptide Y-immunoreactive neurons increased in the whole amygdala on the lesioned side. At the same time, the number of corticotropin-releasing factor-immunoreactive neurons grouped in the central amygdaloid nucleus declined, and so did the staining intensity. The obtained results indicate that dopaminergic denervation stimulates the synthesis of neuropeptide Y and corticotropin-releasing factor in rat amygdala, but the peptide levels are differently regulated, which points to a diverse release of these peptides.
The neuropeptide corticotropin-releasing factor (CRE) and related neuropeptides not only mediate hormonal responses to stressors but also have a neurotropic role in the central nervous system to mediate behavioral responses to stressors. CRF antagonists effectively block CRF responses and have effects opposite those of CRF in many stress-related situations. Recent advances suggest that in addition to CRF itself there is another CRF-related neuropeptide, urocortin, that may be involved in stress-related responses, particularly those involving appetite. At least two CRF receptors have been discovered to date, CRF-1 and CRF-2. CRF may be involved in various aspects of the addiction cycle associated with drugs of abuse. CRF appears to be activated during stress-induced reinstatement of drug taking as well as acute withdrawal from all major drugs of abuse. CRF is hypothesized to be part of an allostatic change leading to vulnerability to relapse during prolonged abstinence from drugs of abuse.
The possible effects on the morphine withdrawal signs of the nonspecific corticotropin-releasing factor (CRF) receptor antagonist alpha-helical CRF, the selective CRF receptor subtype 1 antagonist CP-154,526 and the selective CRF receptor subtype 2 antagonist antisauvagine-30 (AS-30) were investigated in rats. The most withdrawal signs, including jumping, teeth chatter, writhing, shakes, lacrimation, piloerection, irritability and diarrhoea, were attenuated by pretreatment with alpha-helical CRF (10 microg i.c.v.) and CP-154,526 (30 mg/kg i.p.). However, no morphine withdrawal signs except for diarrhea were significantly affected by pretreatment with AS-30 (10 microg, i.c.v.). To investigate the possible role of different CRFR antagonists (alpha-helical CRF, CP-154,526 and AS-30) in relapse to opiate dependence, the 28-day extinction of morphine-conditioned place preference (CPP) was used. The morphine-CPP disappeared following a 28-day extinction and then was reactivated by a single injection of 10 mg/kg morphine. Pretreatment with alpha-helical CRF (10 microg, i.c.v.) and CP-154, 526 (30 mg/kg, i.p.) could significantly block this reactivation of morphine-CPP. In contrast, pretreatment with AS-30 (1 or 10 microg i. c.v.) did not affect this reactivation of morphine-CPP. The present study demonstrated that activation of the CRF receptor is involved in morphine withdrawal signs and relapse to morphine dependence, and that the role of CRF receptor subtypes 1 and 2 in withdrawal and reactivation of morphine dependence is not identical. CRF receptor subtype 1, but not subtype 2, is largely responsible for the action of the CRF system on opiate dependence. These results suggest that the CRF receptor antagonists, particularly the CRF receptor subtype 1 antagonist, might be of some value in the treatment and prevention of drug dependence.
The central nucleus of the amygdala is a CRF-containing limbic brain site which mediates both fear-like and avoidance behaviors, and intra-amygdala administration of a CRF antagonist blocks the increase in anxiogenic-like behavior characteristic of ethanol withdrawal. In order to evaluate the role of brain CRF in negative motivational states associated with other classes of abused drugs, the present studies examined the effects of suppression of amygdala CRF systems on the characteristic aversive state of precipitated withdrawal in morphine-dependent subjects. In a place conditioning paradigm, administration of a CRF antagonist, alpha-belical CRF (9-41) [250ng], bilaterally into the central nucleus of amygdala, reversed the withdrawal-induced conditioned place aversion produced by injection of the opiate antagonist, methylnaloxonium [500ng], into the same site. In a conditioned operant suppression paradigm, impairment of CRF neurons by immuno-targeted toxins administered into the central nucleus of amygdala, one month prior to testing, attenuated the decrease in response rate produced by exposure to distinctive sensory cues associated previously with systemic administration of naloxone [25µg/kg s.c.] in morphine-dependent subjects. These results indicate that suppression of intra-amygdala CRF systems weakens the aversive stimulus properties of conditioned opiate withdrawal, and suggest a general role for CRF in coordinating behavioral responses to negative motivational effects of drug withdrawal.
A vast body of evidence points to the role of the limbic system in the mechanism of drug dependence. Opioid peptides localized in the limbic system may play a role in central effects of substances of abuse. The goal of the present study was to investigate the influence of acutely and chronically administered drugs of abuse, cocaine and amphetamine on biosynthesis of prodynorphin and proenkephalin in the rat amygdala, the structure involved in the mechanism of drug addiction. Acute injection of cocaine (20 mg/kg ip every hour for 3 h) or amphetamine (2.5 mg/kg) did not changed or decreased the level of proenkephalin mRNA in the central nucleus of the amygdala. In contrast, the level of prodynorphin mRNA was significantly increased in this structure after cocaine. Repeated cocaine administration (20 mg/kg ip every hour for 3 h, for 5 days) had no effect on the proenkephalin and prodynorphin mRNA in the central nucleus of the amygdala. Chronic amphetamine (2.5 mg/kg twice daily for 5 days) administration decreased proenkephalin and increased prodynorphin mRNA level in the central nucleus of the amygdala (at 24 and 48 h). Moreover, significant increase in prodynorphin mRNA level was observed in the hippocampal dentate gyrus after acute (cocaine) and chronic (cocaine, amphetamine) administration of the psychostimulants. The observed adaptive changes in the activity of two opioid systems in two structures of the limbic system, central nucleus of amygdala and hippocampus, may contribute to the neurochemical mechanism of drug addiction after psychostimulants. These studies also indicate that the changes in opioid gene expression in the central nucleus of the amygdala are not parallel to those observed in the nucleus accumbens after cocaine and amphetamine, which suggests that peptidergic systems in the structures of extended amygdala might be regulated by different neurochemical mechanisms after psychostymulant administration.
Effects of acute and chronic administration of l-and d-opioid agonists on the
- M L Gonzalvez
- M V Milanes
- M L Vargas
Gonzalvez, M.L., Milanes, M.V., Vargas, M.L., 1991. Effects of acute and chronic administration of l-and d-opioid agonists on the hypothalamic–pituitary–adrenocortical (
Drug dependence: stress and dysre-gulation of brain reward pathways
- M J Kreek
- G F Koob
Kreek, M.J., Koob, G.F., 1998. Drug dependence: stress and dysre-gulation of brain reward pathways. Drug Alcohol Depend. 51, 23–47.
Effect of 6-hydroxydopamine on neuro-peptide Y and corticotropin releasing factor expression in rat amygdala
- S Smiałowska
- M Bajkowska
- M Przewlocka
- B Maj
- M Turchan
- J Przewlocki
S Smiałowska, M., Bajkowska, M., Przewlocka, B., Maj, M., Turchan, J., Przewlocki, R., 1999. Effect of 6-hydroxydopamine on neuro-peptide Y and corticotropin releasing factor expression in rat amygdala. Neuroscience 94, 1125–1132.