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Molecular Base of Acetylcholine and Morphine Analgesia
Abstract
We have previously described the peripheral analgesic effect of dibutyryl cyclic GMP, acetylcholine (ACh) and morphine (Mph) injected into the rat paws. Since ACh induces nitric oxide (NO) release from endothelial cells which is though to stimulate guanylate cyclase (GC) we investigated if NO-cyclic GMP pathway was involved in the analgesia by those agents. Using a modification of the Randall-Selitto rat paw test, it was found that sodium nitroprusside, which releases NO non-enzymatically, blocked rat paw PGE2 induced hyperalgesia. The peripheral analgesic effect of sodium nitroprusside, ACh and morphine was enhanced by intraplantar injection of an inhibitor of cyclic GMP phosphodiesterase (MY5445) and blocked by a GC inhibitor, methylene blue (MB). Peripheral analgesia induced by ACh and morphine, but not by sodium nitroprusside, was blocked by NG-monomethyl-L-arginine (L-NMMA) an inhibitor of the formation of NO from L-arginine. Central effect of morphine as tested by the rat paw and by the tail flick tests was inhibited by intraventricular injection of methylene blue. In addition, the central morphine analgesia was potentiated by My5445. In contrast, with the periphery, the central effect of morphine was not blocked by L-NMMA. Our results demonstrate that NO causes peripheral analgesia via stimulation of GC and supports the suggestion that at this site morphine and acetylcholine analgesia is subsequent to NO release. In the mechanism of the central analgesic effect of morphine, the cGMP system is activated but via NO release, probably by a direct stimulation of the receptors. This is the first demonstration that links peripheral and central analgesic effect of morphine to the stimulation of GC system.
... Intra-articular injection of neostigmine in rats produces moderate analgesia to thermal stimuli, which is allegedly reversible with intra-articular atropine [15]. Preclinical data suggest peripheral antinociceptive effects of acetylcholine [18]. In contrast, some authors reported that neostigmine has no role in the periphery [19]. ...
... A three-point scale was used to test sensory block for cervical C 5 , C 6 , C 7 , and C 8 and thoracic T 1 dermatomes using the pin-prick test (0 = loss of sensation to light touch, 1 = loss of sensation to pinprick, and 2 = normal sensation) [18]. ...
... cGMP plays an antinociceptive activity in nociceptive processing [8]. Thiamine plays an important role in acetyl coenzyme A (Ac-CoA) synthesis (an active acetate component for the production of acetylcholine-Ach) [3], and Ach which is known to be a cholinergic neurotransmitter involved in the mechanism of narcotic analgesic effects [9], mainly contributes to a peripheral analgesia via stimulation of GC similar to morphine [10]. In this study, we aimed to investigate the possible role of L-arginine/ nitric oxide (NO) pathway in the antinociceptive activity of thiamine in p-benzoquinone (PBQ)-induced abdominal constriction test. ...
... As mentioned in the introduction it plays an important role in acetyl CoA synthesis, an active component for the production of Ach [3]. In the antinociceptive action of morphine many findings confirmed the implication of Ach with the participation of central and peripheral involvement of L-arginine/NO/cGMP pathways [9,10,23]. All these findings possess a positive correlation between thiamine and morphine. ...
... dipirone) and NO donors (Cunha et al., 2010;Ferreira et al., 1991b;Lorenzetti and Ferreira, 1985;Sachs et al., 2004). These drugs are able to inhibit the already established hyperalgesia induced by PGE 2 (Cunha et al., 2010Ferreira et al., 1991a;Lorenzetti and Ferreira, 1985;Sachs et al., 2004). Moreover, several studies have demonstrated that the antinociceptive mechanism of these drugs depends on the activation of the L-arginine/NO/guanosine 3, 5-cyclic monophosphate (cGMP)/protein kinase G (PKG)/ATP-sensitive potassium channel pathway (Cunha et al., 2010Ferreira et al., 1991a;Mizokami et al., 2012;Napimoga et al., 2008;Sachs et al., 2004;Santodomingo-Garzon et al., 2006;Vivancos et al., 2003). ...
... These drugs are able to inhibit the already established hyperalgesia induced by PGE 2 (Cunha et al., 2010Ferreira et al., 1991a;Lorenzetti and Ferreira, 1985;Sachs et al., 2004). Moreover, several studies have demonstrated that the antinociceptive mechanism of these drugs depends on the activation of the L-arginine/NO/guanosine 3, 5-cyclic monophosphate (cGMP)/protein kinase G (PKG)/ATP-sensitive potassium channel pathway (Cunha et al., 2010Ferreira et al., 1991a;Mizokami et al., 2012;Napimoga et al., 2008;Sachs et al., 2004;Santodomingo-Garzon et al., 2006;Vivancos et al., 2003). However, the control of inflammatory pain is still a major challenge because of the deleterious side effects attributed to the prolonged use of NSAIDs and opioids, their ineffectiveness in some cases and receptor desensitization in the case of opioids. ...
The activation of nitric oxide (NO) production is an analgesic mechanism shared by drugs such as morphine and diclofenac. Therefore, the controlled release of low amounts of NO seems to be a promising analgesic approach. In the present study, the antinociceptive effect of the ruthenium NO donor [Ru(bpy)2(NO)SO3](PF6) (complex I) was investigated. It was observed that complex I inhibited in a dose (0.3-10mg/kg)-dependent manner the acetic acid-induced writhing response. At the dose of 1mg/kg, complex I inhibited the phenyl-p-benzoquinone-induced writhing response and formalin- and complete Freund's adjuvant-induced licking and flinch responses. Additionally, complex I also inhibited transient receptor potential cation channel subfamily V member 1 (TRPV1)-dependent overt pain-like behavior induced by capsaicin. Complex I also inhibited the carrageenin-induced mechanical hyperalgesia and increase of myeloperoxidase activity (MPO) in paw skin samples. The inhibitory effect of complex I in the carrageenin-induced hyperalgesia, MPO activity and formalin was prevented by the treatment with ODQ, KT5823 and glybenclamide, indicating that complex I inhibits inflammatory hyperalgesia by activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway. The present study demonstrates the efficacy of a novel ruthenium NO donor and its analgesic mechanisms.
... The central analgesic effect of morphine as tested by the rat paw pressure and tail flick tests was inhibited by intracerebroventricular injection of methylene blue and potentiated by an inhibitor of cyclic GMP phosphodiesterase, but it was not blocked by the NOS inhibitors L-NMMA and N-iminoethyl-L-ornithine. 51,52 Therefore, activation of the cyclic GMP system, not via nitric oxide release, may be involved in the mechanism of the central analgesic effect of morphine. Antinociception induced by the muscarinic receptor agonist (ϩ)-cis-dioxolane, but not -endorphin, given supraspinally is likely mediated by the direct activation of an nitric oxide/cyclic GMP system, and the activation by the muscarinic agonist potentiates the antinociception induced by intracerebroventricular -endorphin, but not that by -, ␦-, or -opioid receptor agonists. ...
... 76 Peripheral analgesia induced by acetylcholine and morphine was potentiated by MY5445 and blocked by L-NMMA, whereas central morphine analgesia was potentiated by MY5445 but not affected by L-NMMA, suggesting that nitric oxide causes peripheral analgesia via stimulation of the nitric oxide/guanylyl cyclase system and that the central analgesic effect of morphine is associated with activation of the cyclic GMP system that is not mediated by nitric oxide. 51 Involvement of the L-arginine/nitric oxide/cyclic GMP pathway in peripheral morphine analgesia was also reported. 77,78 FK409, a nitric oxide releaser, alone had no effect on the number of flinches induced by formalin injection in rats; however, when administered after intraplantar morphine, FK409 depressed the agitation behavior, and this inhibitory effect was reversed by naloxone and carboxy-PTIO. ...
Nitric oxide (NO) plays pivotal roles in controlling physiological functions, participates in pathophysiological intervention, and is involved in mechanisms underlying beneficial or untoward actions of therapeutic agents. Endogenous nitric oxide is formed by three isoforms of nitric oxide synthase: endothelial, neurogenic and inducible. The former two are constitutively present mainly in the endothelium and nervous system, respectively, and the latter one is induced by lipopolysaccharides or cytokines mainly in mitochondria and glial cells. Constitutively formed nitric oxide modulates the actions of morphine and related analgesics by either enhancing or reducing antinociception. Tolerance to and dependence on morphine or its withdrawal syndrome are likely prevented by nitric oxide synthase inhibition. Information concerning modulation of morphine actions by nitric oxide is undoubtedly useful in establishing new strategies for efficient antinociceptive treatment and for minimizing noxious and unintended reactions.
... cGMP plays an antinociceptive activity in nociceptive processing [8]. Thiamine plays an important role in acetyl coenzyme A (Ac-CoA) synthesis (an active acetate component for the production of acetylcholine-Ach) [3], and Ach which is known to be a cholinergic neurotransmitter involved in the mechanism of narcotic analgesic effects [9], mainly contributes to a peripheral analgesia via stimulation of GC similar to morphine [10]. In this study, we aimed to investigate the possible role of L-arginine/ nitric oxide (NO) pathway in the antinociceptive activity of thiamine in p-benzoquinone (PBQ)-induced abdominal constriction test. ...
... As mentioned in the introduction it plays an important role in acetyl CoA synthesis, an active component for the production of Ach [3]. In the antinociceptive action of morphine many findings confirmed the implication of Ach with the participation of central and peripheral involvement of L-arginine/NO/cGMP pathways [9,10,23]. All these findings possess a positive correlation between thiamine and morphine. ...
Die Rolle der Aktivierung von Guanylylcyclase bei der Unterdrückung des chemisch induzierten Writhing bei Mäusen mittels Thiamin
Ziel dieser Studie war es, die mögliche Rolle von L-Arginin/Stickoxid (L-Arginin/NO) bei der antinociceptiven Aktivität von Thiamin (Vitamin B1) am p-Benzochinon-induzierten Maus-Writhing-Modell zu untersuchen. Thiamin (ED50: 0.11 mg/kg), L-Arginin (50 mg/kg), NG-Nitro-L-argininmethylester (L-NAME, 75 mg/kg) und Morphin (ED50: 0.13 mg/kg) zeigten bei s.c. Verabreichung eine schmerzlindernde Wirkung (52.4 ± 5.5%, 36.8 ± 7.7%, 27.8 ± 11.1%, 66.1 ±3.5%, in dieser Reihenfolge). Methylenblau (MB, 40 mg/kg, s.c.) verursachte dagegen eine gesteigerte Schmerzempfindung (-32.1 ± 9.9%). Die Verabreichung von Thiamin mit L-Arginin zusammen änderte die durch L-Arginin induzierte Schmerzempfindung (48.9 ± 3.7%) nur unwesentlich. Die Eingabe von Thiamin mit L-NAME und MB zusammen erhöhte die durch L-NAME induzierte schmerzlindernde Wirkung (53.9 ± 3.9%) signifikant und kehrte die durch MB induzierte Schmerzempfindung zur Schmerzlinderung um (46.0 ±4.2%). Gleichzeitige Gabe mit Morphin erhöhte deutlich den durch L-Arginin und L-NAME induzierten schmerzlindernden Effekt (55.9 ± 3.9% und 61.1 ± 5.0%, in dieser Reihenfolge) und kehrte die von MB induzierte Schmerzempfindung signifikant zur Schmerzlinderung um (41.6 ± 8.9%). Gleichzeitige Verabreichung von Thiamin und Morphin produzierte einen antinozizeptiven Effekt (46.0 ± 4.2%). Diese Ergebnisse lassen vermuten, daß die antinozizeptive Wirkung von Thiamin durch die Aktivierung von Guanylylcyclase, vermittelt durch Guanosinmonophosphat (cGMP), hervogerufen werden könnte, wobei cGMP die Beteiligung des zentralen und/oder peripheren L-Arginin/NO/cGMPweges auslösen könnte.
... The control of nitric oxide pathways and neuronal hyperpolarization produce peripheral cholinergic antinociception according to Vitro studies, and other research has proven the presence of acetylcholine receptors in peripheral neurons. Acetylcholine causes analgesia by increasing cyclic GMP through Nitric oxide production (Ferreira et al., 1990) [5]. ...
Background: In our study, we investigated the effect of adding neostigmine to local anesthetic on the supraclavicular brachial plexus block. Patients and Methods: This prospective, randomized, blinded controlled experiment included 80 patients of either sex with an ASA I or II physical status who were planned for forearm operations under ultrasound-assisted supraclavicular brachial plexus block. Participants were separated randomly into two groups and given a supraclavicular block with 25 mL of 0.5% bupivacaine and 1 mL of 0.9 % saline for the control group and 25 mL of 0.5% bupivacaine and 1 mL of neostigmine (0.5mg) for the neostigmine group. Results: In the neostigmine group, sensory and motor blockade began earlier and lasted longer than in the control group. The neostigmine group took substantially longer to seek their first analgesia. The neostigmine group used fewer analgesics in total. At 1, 2, 4, and 6 hours, the neostigmine group had statistically reduced VAS scores than the control group. Conclusion: Patients undergoing forearm procedures benefit from the usage of neostigmine in addition to bupivacaine in ultrasound-assisted supraclavicular brachial plexus block because it reduces the onset of sensory and motor block and lengthens its duration. These results were clear with a dosage of (0.5 mg).
... Pioneering work by Ferreira and his colleagues have demonstrated an important role of NO signaling in modulation of pain [55][56][57]. Further studies have also demonstrated that NO is involved in the antinociceptive action of analgesics such as opioids, nonsteroidal anti-inflammatory drugs, cannabinoids, and xylazine [23]. ...
Objectives
To evaluate the effects of modafinil on neuropathic pain induced by sciatic nerve cuffing in mice, and possible contribution of nitrergic/inflammatory and serotonergic systems.
Methods
Neuropathic pain was induced by applying a polyethylene cuff around the left sciatic nerve. Seven days later, mice received modafinil (50, 100, and 200 mg/kg; intraperitoneal [i.p.]) and morphine (10 mg/kg, i.p.) as control. Mice also received pretreatments of the nonselective nitric oxide (NO) synthase (NOS) inhibitor L-NAME, the selective neuronal NOS inhibitor 7-nitroindazole, the selective inducible NOS inhibitor aminoguanidine, and the selective serotonin reuptake inhibitor citalopram before modafinil (100 mg/kg). von Frey test was used to evaluate mechanical allodynia. Additionally, sciatic nerves were collected for histopathological analysis. Tissue levels of NO metabolites, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were assessed.
Results
Animals whose sciatic nerves were cuffed had a significantly (P<0.001) decreased paw withdrawal threshold (PWT) compared with the sham-operated group. Modafinil (100 mg/kg) and morphine significantly reversed PWT (P<0.001). Pretreatments with L-NAME, 7-nitroindazole, aminoguanidine, and citalopram in different groups markedly reversed analgesic effects of modafinil. Tissue homogenates of Cuffed sciatic nerves showed significantly higher levels of NO metabolites, TNF-α and IL-6 (P<0.001). Modafinil lowered NO metabolites, TNF-α, and IL-6 levels (P<0.001). Histopathology illustrated marked axonal degeneration and shrinkage in the cuffed sciatic nerve, which were improved in the modafinil-treated group.
Conclusions
Modafinil exerts analgesic and neuroprotective effects in cuff-induced neuropathic mice via possible involvement of the nitrergic/inflammatory and serotonergic systems.
... Moreover, analgesic effect of acetylcholine was blocked by intraplantar administration of L-NMMA and methylene blue, an sGC inhibitor, and enhanced by cGMP phosphodiesterase inhibition [121]. Additionally, peripheral antinociception effects of morphine in rats subjected to PGE2-induced hyperalgesia were mediated by NO release via cGMP activation, supporting the hypothesis that peripheral analgesia of morphine and acetylcholine is subsequent to NO output [122]. Our group demonstrated that the antinociceptive effects are mediated by sGC/cGMP/PKG pathway, leading to ATP sensitive K + channel (K ATP ) activation. ...
Nitric oxide (NO) is produced by enzymatic activity of neuronal (nNOS), endothelial (eNOS), and inducible nitric oxide synthase (iNOS) and modulates a broad spectrum of physiological and pathophysiological conditions. The iNOS isoform is positively regulated at transcriptional level and produces high levels of NO in response to inflammatory mediators and/or to pattern recognition receptor signaling, such as Toll-like receptors. In this review, we compiled the main contributions of our group for understanding of the role of NO in sepsis and arthritis outcome and the peripheral contributions of NO to inflammatory pain development. Although neutrophil iNOS-derived NO is necessary for bacterial killing, systemic production of high levels of NO impairs neutrophil migration to infections through inhibiting neutrophil adhesion on microcirculation and their locomotion. Moreover, neutrophil-derived NO contributes to multiple organ dysfunction in sepsis. In arthritis, NO is chief for bacterial clearance in staphylococcal-induced arthritis; however, it contributes to articular damage and bone mass degradation. NO produced in inflammatory sites also downmodulates pain. The mechanism involved in analgesic effect and inhibition of neutrophil migration is dependent on the activation of the classical sGC/cGMP/PKG pathway. Despite the increasing number of studies performed after the identification of NO as an endothelium-derived relaxing factor, the underlying mechanisms of NO in inflammatory diseases remain unclear.
... The relationship between the NO/cGMP pathway and peripheral antinociception was first demonstrated by Ferreira and co-workers (Durate et al., 1990;Ferreira et al., 1991). They showed that the antinociceptive effect of acetylcholine and morphine was blocked by a guanylyl cyclase inhibitor and an NO synthase inhibitor, and was potentiated by a specific cGMP phosphodiesterase inhibitor. ...
... In addition to these three lines of evidence and the present data demonstrating that the HNO scavenger L-cysteine inhibits the antinociceptive effect of AS, we have demonstrated that AS-induced DAF-2DA fluorescence in dorsal root ganglia neurons was sensitive to Lcysteine, which further corroborates AS is delivering nitroxyl to neurons [28]. It is important to mention that similar tools (ODQ, KT5823 and glybenclamide) were used in previous studies demonstrating the anti-hyperalgesic effect and mechanism of NO [9,15,35,39,51] and those inhibitors did not affect the nociceptive behavior induced by PBQ, acetic acid or formalin per se. ...
Background:
Several lines of evidence have indicated that nitric oxide (NO) plays complex and diverse roles in modulation of pain/analgesia. However, the roles of charged and uncharged congeners of NO are less well understood. In the present study, the antinociceptive effect of the nitroxyl (HNO) donor, Angeli's salt (Na2N2O3; AS) was investigated in models of overt pain-like behavior. Moreover, whether the antinociceptive effect of nitroxyl was dependent on the activation of cGMP (cyclic guanosine monophosphate)/PKG (protein kinase G)/ATP-sensitive potassium channels was addressed.
Methods:
The antinociceptive effect of AS was evaluated on phenyl-p-benzoquinone (PBQ)- and acetic acid-induced writhings and via the formalin test. In addition, pharmacological treatments targeting guanylate cyclase (ODQ), PKG (KT5923) and ATP-sensitive potassium channel (glybenclamide) were used.
Results:
PBQ and acetic acid induced significant writhing responses over 20min. The nociceptive response in these models were significantly reduced in a dose-dependent manner by subcutaneous pre-treatment with AS. Furthermore, AS also inhibited both phases of the formalin test. Subsequently, the inhibitory effect of AS in writhing and flinching responses were prevented by ODQ, KT5823 and glybenclamide, although these inhibitors alone did not alter the writhing score. Furthermore, pretreatment with L-cysteine, an HNO scavenger, confirmed that the antinociceptive effect of AS depends on HNO.
Conclusion:
The present study demonstrates the efficacy of a nitroxyl donor and its analgesic mechanisms in overt pain-like behavior by activating the cGMP/PKG/ATP-sensitive potassium channel (K(+)) signaling pathway.
... Foi mostrado que a administração de L-NMMA (N -monometil-L-arginina), um inibidor de NOS, bloqueou a analgesia periférica induzida por acetilcolina (1) . Também foi descrito que a antinocicepção periférica da morfina em ratos submetidos à hiperalgesia induzida por prostaglandina E2 foi mediada por liberação de NO via ativação da GMP-ciclase (2) . Entretanto, há controvérsias com relação ao papel do NO em fenômenos dolorosos, uma vez que a injeção local de NO em humanos produz dor, possivelmente via estimulação local de nociceptores (3) . ...
OBJECTIVE: To study the role of nitric oxide (NO) in the cell influx (CI) and the articular incapacitation (AI) in the zymosan induced-arthritis (ZyA). METHODS: Wistar rats received 1 mg of zymosan (Zy) into the right knee joint, and controls received saline. The AI was evaluated by the Test for AI in rats. After sacrifice, the CI and the release of prostaglandin E2 (PGE2) were assessed in the joint exudate. The joint edema was measured by the wet/dry weight ratio of the articular tissue. Groups were treated i.p. with L-NAME - NO synthase (NOS) inhibitor (LN = 30-300 mg/kg) or aminoguanidine (AG = 30-300 mg/kg) - selective iNOS inhibitor - 30 minutes before or 2 hours after the Zy. RESULTS: Pretreatment with L-NAME or AG dose-dependently inhibited the AI and the CI, but not altering edema or PGE2 release, being maximal for the 100 mg/kg doses of L-N and AG. Coinjection of L-arginine (1g/kg) and LN (100 mg/kg) reversed the inhibition of the AI and of the CI. D-NAME (100 mg/kg) had no effect. Coinjection of naloxone (opioid antagonist) reversed LN or AG effect on the AI. Mean arterial pressure increased (p<0,01) with LN (100 mg/kg), but not with AG (100 mg/ kg). LN and AG (100 mg/kg) given 2 hours after the Zy had no effect. Methylene blue (GMPc inhibitor), but not hemoglobin (NO scavenger) reversed AI and CI (p<0,01). Sodium nitroprusside (NO donor) given 2 hours after Zy reduced significantly AI, but not CI (p<0,01). CONCLUSIONS: The antinociceptive effect of iNOS inhibition in ZyA happens only with a prophylactic administration, due to an anti-inflammatory effect via GMPc, independently of exogenous NO or PGE2 release, but is associated to endogenous opioid release. The administration of an NO donor produces analgesia in ZyA.
... Other modulatory pathways may be involved in the antinociceptive activity of the combinations of morphine and NSAIDs. The NO-cGMP pathway is clearly involved in nociceptive processing [8] and the activation of the system has been suggested to be the target for the analgesic effect of morphine [5], metamizol [13], meloxicam [2], paracetamol [3] and diclofenac [18]. Even if in the present work no NO inhibitors were tested, the modulatory role of this pathway in the spinal cord on the synergism between it morphine and NSAIDs cannot be excluded, since activation of the NO-cGMP pathway at this level seems to induce antinociception [8]. ...
To enhance analgesia, the combinatorial use of analgesic drugs with proven efficacies is a widely-used strategy to reduce adverse side effects. The present study characterizes the antinociceptive interaction of intrathecal morphine co-administered with different NSAIDs using isobolographic analysis.Antinoceptive activity was evaluated using a model for acute visceral pain, the writhing test of mice. The possible involvement of opioid receptors in the mechanism of action of the intrathecal co-administration of morphine and NSAIDs was investigated using the non-selective receptor antagonist naltrexone. The study demonstrated a synergistic antinociception of intrathecal administered combinations of morphine with the following NSAIDs: diclofenac, ketoprofen, meloxicam, metamizol, naproxen, nimesulide, parecoxib and piroxicam. The supra additive effect was obtained with very low doses of each drug and it appeared to be independent of the COX-1 or COX-2 inhibition selectivity of each NSAID and was not significantly modified by intrathecal naltrexone. The findings of the present work suggest that the combination of opioids and NSAIDs has a direct action on spinal nociceptive processing, which may be achieved via mechanisms that are independent of the activation of opioid receptors. The ineffectiveness of naltrexone to reverse the analgesic activity of opioids + NSAIDs combinations indicates that other complex pain regulatory systems are involved in this effect.
... Activation of the nitric oxide-cGMP pathway has been recently implicated in the peripheral analgesia induced by various chemically distinct substances such as opioids, acetylcholine, dipyrone, myrcene (Duarte et al., 1990(Duarte et al., , 1992aFerreira et al., 1991aFerreira et al., ,b, 1992. Analgesia resulting from the systemic application of diclofenac was abolished by pretreatment of the paw or the joint with methylene blue or LNMMA. ...
Indomethacin, a typical cyclo-oxygenase inhibitor, acts as an analgesic by preventing the hyperalgesia induced by prostaglandins during inflammation. Analgesics of the dipyrone type directly block the sensitization of nociceptors. In the present investigation, the analgesic effect of diclofenac was compared with that of indomethacin in two algesimetric tests which permit discrimination between the two types of analgesic: the rat knee joint incapacitation and the rat paw hyperalgesia tests. The analgesics were given either pre- or posttreatment relative to the induction of hyperalgesia with carrageenin or prostaglandin E2. In both tests intraperitoneal pretreatment with indomethacin was equally or slightly more potent than diclofenac. Posttreatment with diclofenac was more effective than posttreatment with indomethacin. This was particularly evident in the paw hyperalgesia test in which posttreatment with indomethacin was not effective while diclofenac caused dose-dependent analgesia. When nociception was induced by PGE2 in both tests, the administration of indomethacin directly into the knee joint or rat paw had no effect while diclofenac continued to cause dose-dependent analgesia. Thus, diclofenac has a direct effect on ongoing hyperalgesia in addition to its ability to block cyclo-oxygenase. Naloxone and N-methyl-nalorphine did not affect diclofenac analgesia, thus indicating that the analgesic effect of the latter is independent of a central or peripheral opioid effect. Local administration of agents which inhibit the formation of nitric oxide (NG-monomethyl-L-arginine) or inhibit the activation of guanylate cyclase by nitric oxide (methylene blue) abolished diclofenac-induced analgesia.(ABSTRACT TRUNCATED AT 250 WORDS)
... Among all the described functions of macrophages in the development of inflammation, the central role-played by these cells on the pathophysiology of inflammatory pain is largely investigated. They perform a pro-nociceptive role secreting chemical mediators such as tumor necrosis factor , prostaglandins , interleukin (IL)-1, IL-6, IL-8, and others [22] in conjunction with other mediators such as acetylcholine and IL-10, which down-regulate inflammatory pain and hyperalgesia [23, 24]. Based on this information and considering that the calciumbinding protein MRP-14 deactivates activated macrophages [14], we decided to investigate the possible activity of this protein in the modulation of inflammatory pain. ...
Macrophages secrete a variety of chemical mediators that play a central role in the pathophysiology of inflammatory pain. Therefore, the activation or deactivation of these cells in an inflammatory focus could modulate the intensity of the algogenic response. Based on these premises and on our previous demonstration that the calcium-binding protein MRP-14, highly expressed in neutrophils, deactivates activated macrophages in vitro, we decided to investigate the role of MRP-14 and of neutrophils in the control of inflammatory pain in mice. Our results show that this protein is endowed with antinociceptive activity. When tested in the writhing model it was able to inhibit pain response but did not change the behavior of the animals in the hot plate test. This observation indicates that MRP-14 down-regulates inflammatory but not central pain. Using a model of acute neutrophilic peritonitis induced by glycogen, a close correlation between neutrophil migration and antinociception was detected. Surgical adrenalectomy demonstrated that the antinociceptive response induced by glycogen was not due to endogenous liberation of glucocorticoids. The treatment of animals either with a monoclonal antibody anti-MRP-14 or a monoclonal antibody that depletes the animals of neutrophils reverts the antinociceptive response observed in the glycogen-induced peritonitis. These data define the calcium-binding protein MRP-14 as a novel mediator for the control of inflammatory pain and consequently discloses an anti-inflammatory role for the neutrophil.
... NO is formed enzymatically from L-arginine by NOS after activation of the NMDA receptor [16]. Ferreira et al. [17,18] have previously reported that morphine-induced analgesia was blocked by L-N'^-monomethylarginine (L-NMMA) and méthylène blue (soluble GG inhibitor), and enhanced by MY5445 (cGlVIP phosphodiesterase inhibitor) concluding that subsequent release of NO causes peripheral analgesia via stimulation of soluble GG at this site of morphine effect. Gonsistent with an antinociceptive mechanism, morphine was found to increase the histamine level in the brain and spinal cord without incomplete understanding of species or strain differences [19][20][21]. ...
Die Rolle von L-Arginin/Stickoxid im Zusammenhang mit der antinozizeptiven Aktivität von Morphin und Mepyramin bei Mäusen
Zur Einschätzung des Einflusses des L-Arginin/Stickoxid (NO)-Stoffwechsels auf die antinozizeptive Aktivität des s.c. injizierten H1-Antagonisten Mepyramin (CAS 59-33-6) und des Opioidrezeptor-Agonisten Morphin (CAS 57-27-2) bei Mäusen wurde der p-Benzoquinon (PBQ)-induzierte abdominale Konstriktionsstest angewendet. Mepyramin (ED50: 5.6 mg/kg) und Morphin (ED50: 0.13 mg/kg) zeigten antinozizeptive Wirkung. Die NO-Vorstufe L-Arginin (CAS 1119-34-2) (50 mg/ kg) zeigte ebenfalls antinozizeptive Wirkung, die ähnlich der von Mepyramin, aber deutlich geringer als diejenige von Morphin war. Der NO-Synthase-Hemmer (NOS) L-NG-Monomethylarginin (L-NMMA) (CAS 53308-83-1) (50 mg/kg) änderte die PBQ-induzierte abdominale Konstriktion nicht signifikant. L-Arginin erhöhte die antinozizeptive Wirkung von Morphin und Mepyramin signifikant. Bei kombinierter Eingabe mit L-NMMA wurde die antinozizeptive Aktivität von Morphin, aber nicht diejenige von Mepyramin, vollständig aufgehoben. L-NMMA in Kombination mit L-Arginin verminderte deutlich die von Morphin und Mepyramin induzierte Antinozizeption. Diese Ergebnissen lassen vermuten, daß Morphin und Mepyramin unter Beteiligung der L-Arginin/NO-Kaskade oder anderer mit der NO-Induktion zusammenhängender nozizeptiver Vorgänge eine periphere Antinozizeption erzeugen.
... On the other hand, there are opposite observations in man that drugs which release NO per se have no effect but are analgaesic or enhance the effect of other analgaesics when tested in models of ongoing pain or hypernociception in humans or in rats. We have proposed that the peripheral analgaesic effect of morphine (Ferreira et al., 1991), dipyrone (Lorenzetti & Ferreira, 1985) and diclofenac (Tonussi & Ferreira, 1994) was associated with the stimulation of the arginine/NO/cGMP pathway. Recently, a family of NSAID containing NO in theFigure 3 Opposite effects of intradermal (a) and subcutaneous (b) injections of SIN-1 on subcutaneous PGE 2 -induced mechanical hypernociception. ...
Nitric oxide has been described either as pronociceptive or antinociceptive. In this investigation, using an electronic pressure-metre, the intradermal and the subcutaneous effects of prostaglandin E2 (PGE2) and agents that mimic or inhibit the arginine/NO/cGMP pathway were compared.
The hypernociceptive effect of the intradermal injection of PGE2 (100 ng) was immediate, peaking within 15–30 min and returning to basal values in 45–60 min. The subcutaneous injection of PGE2 induced a hypernociception with a delayed peak (3 h) plateauing for 4–6 h.
Intradermal administration of 3-morpholino-sydnonimine-hydrochloride (SIN-1) enhanced, while its subcutaneous administration inhibited, subcutaneous hypernociception induced by PGE2. This inhibition was prevented by ODQ (8 μg) but not by NG-monomethyl-L-arginine (L-NMMA) (50 μg).
Intradermal but not subcutaneous administration of L-arginine (1–100 μg), SIN-1 (1–100 μg) and dibutyrylguanosine 3′:5′-cyclic monophosphate (db cGMP) (0.1–100 μg) induced an early (15–30 min) dose-dependent hypernociceptive effect. Intradermal pretreatment with NG-monomethyl-L-arginine (L-NMMA; 50 μg) inhibited the hypernociception induced by L-Arg (10 μg), but not that induced by SIN-1 (10 μg) or db cGMP (10 μg).
Intradermal injection of ODQ (8 μg) antagonized the hypernociception induced by L-arginine and SIN-1, but not that induced by db cGMP.
Considering (a) the different time course of intradermal and subcutaneous PGE2-induced hypernociception, (b) the opposite nociceptive effect of intradermal and subcutaneous administration of SIN-1 (db cGMP) as well as the arginine/NO/cGMP pathway, the existence of different subsets of nociceptive primary sensory neurons in which the arginine/NO/cGMP pathway plays opposing roles is suggested. This hypothesis would explain the apparent contradictory observations described in the literature.
British Journal of Pharmacology (2003) 138, 1351–1357. doi:10.1038/sj.bjp.0705181
... This test was instrumental in the discovery of various seminal findings, which were later confirmed by other nociceptive methods such as formalin-induced flinches (10,11), chemically induced writhing (12,13) and the classical Randall and Selitto method (14). In fact, the modified Randall and Selitto test was used in several pioneering studies of inflammatory nociceptor sensitization (hypernociception): the participation of the cAMP/Ca 2+ pathway in the mechanism of hypernociception (15), the peripheral effect of opiates (16), the cytokine cascade involved in the onset of inflammatory hypernociception (17)(18)(19)(20)(21)(22)(23)(24), the peripheral memory of nociceptor sensitization (25,26), and the spinal retrograde sensitization of primary sensory neurons (27). ...
The objective of the present investigation was to compare the sensitivity of an electronic nociceptive mechanical paw test with classical mechanical tests to quantify the intensity variation of inflammatory nociception. The electronic pressure-meter test consists of inducing the hindpaw flexion reflex by poking the plantar region with a polypropylene pipette tip adapted to a hand-held force transducer. This method was compared with the classical von Frey filaments test and with the rat paw constant pressure test, a modification of the Randall and Selitto test developed by our group. When comparing the three methods, the electronic pressure-meter and the rat paw constant pressure test, but not the von Frey filaments test, detected time vs treatment interactions in prostaglandin E2 (PGE2)-induced hypernociception. Both methods also detected the PGE2-induced hypernociception in dose- (50-400 ng/paw) and time- (1-4 h) dependent manners, and time vs treatment interactions induced by carrageenin (25-400 microg/paw). Furthermore, the electronic pressure-meter test was more sensitive at early times, whereas the constant pressure test was more sensitive at later times. Moreover, the electronic pressure-meter test detected the dose-dependent antinociceptive effect of local indomethacin (30-300 microg/paw) and dipyrone (80-320 microg/paw) on carrageenin- (200 microg/paw) and PGE2- (100 ng/paw) induced hypernociception, respectively, and also detected the ineffectiveness of indomethacin (300 microg) on the effect of PGE2. Our results show that the electronic pressure-meter provides a sensitive, objective and quantitative mechanical nociceptive test that could be useful to characterize new nociceptive inflammatory mediators and also to evaluate new peripheral analgesic substances.
The sensitisation of pain receptors is the common denominator in all types of inflammatory pain. C-Polymodal, high threshold receptors or receptors connected by fine myelinated fibers have long been associated with inflammatory hyperalgesia [1, 2]. In recent years, a new “sleeping” nociceptor associated with certain small afferent fibers has been described in deep visceral innervations (colon and bladder) and in joints [3, 4]. Sleeping nociceptors are not active in normal tissues, but are “switched on” during inflammation. This functional upregulation leads to a clinical state known as hyperalgesia. In such a situation, previously unpainful stimuli become painful.
Biosynthesis of nitric oxide (NO) plays an important role in the regulation of inflammatory responses. NO is a potent vasodilator and inhibits the adhesion of thrombocytes and leukocytes at the endothelium, ensuring optimal perfusion of the inflammed tissue. Depending on the experimental model of inflammation other aspects such as vascular leakage or migration of leukocytes may be stimulated or suppressed by NO synthesis. Within the network of cellular communication NO acts as a paracrine and autocrine mediator, but also affects the production of other mediators, including eicosanoids and oxygen radicals. Direct toxicity of NO is based on the inhibition of mitochondrial respiration and damage of the DNA.
In the case of infection NO supports the immune system by its antimicrobial activity. However, overproduction of NO during septic courses contributes to the development of hyperdynamic shock, septic cardiomyopathy and hepatocellular insufficiency. NO biosynthesis may also interfere with metabolic performane of the liver during lokal inflammatory responses of hepatitis or rejection episodes following liver transplantation. Induction of NO biosynthesis was also demonstrated in autoimmune diseases such as diabetes mellitus type I and ulcerative colitis. In the pathophysiology of diabetes mellitus NO not only inhibits the release of insulin but may also be responsible for the destruction of pancreatic islet cells. The functional relevance of NO production in ulcerative colitis remains to be uncovered.
Objectives: Nitric oxide (NO) is an intercellular neuromodulator synthetized by NO synthetase (NOS). L-arginine (L-ARG) is converted to ornithine and NO by NOS and is involved in the L-ARG-NO pathway of nociceptive transmission and/or modulation in the CNS and in the periphery. In the present work, the antinociceptive activity of L-ARG was determined and the effects of non selective and selective opioid antagonists was evaluated. Material and methods: The dose-response curve for the antinociceptive effect of intraperitoneal (i.p.) L-ARG was determined in CF-1 mice, using the acetic acid writhing test. The dose-response curves were repeated after pretreatment with the following opioid receptor antagonists: Naloxone and naltrexone (non selective), naltrindole (δ antagonist) y norbinaltorphimine (κ antagonist). The antinociceptive activity of a single dose of L-ARG administered intrathecally (i.t.) and intracerebro-ventricularly (i.c.v.) was determined by the same algesiometric test. Results: L-ARG i.p. exhibited a dose-dependent antinociceptive activity, with an ED 50 of 4,65 mg,kg -5 NOS inhibition significatively reduced the antinociceptive effect of L-ARG. The administration by the i.t. and i.c.v, routes of a dose approximately 45 times lower (0,16 and 0,15 mg.kg -1) produced a comparable antinociceptive effect. The pretreatment with all opioid receptor antagonists significantly displaced the dose-response curve for the antinociceptive activity of L-ARG to the right, indicating a pharmacologic antagonism. Conclusions: Systemically administered L-ARG, through NO formation and activation of cyclic GMP induce antinociception probably by a direct effect on peripheral nociceptors, additionally activating spinal and supraspinal antinociceptive mechanisms. The relation between systemic, intrathecal and intracerebroventricular equipotent doses suggests that a major part of the acción is exerted in the CNS. The synthesis and release of NO facilitates in some way the activation of opioid receptors at spinal and supraspinal levels and confirms the modulating action of NO in nociception.
Previous work has shown that nitric oxide (NO) mediates the antinociceptive effect of Crotalus durissus terrificus venom on carrageenin-induced hyperalgesia. In the present study the role of constitutive neuronal or of inducible form of nitric oxide synthase on venom effect was determined. The rat paw prostaglandin E2 (PGE2)-induced mechanical hyperalgesia model was used for nociceptive evaluation. The venom (200 μg/kg) administered per oz immediately before prostaglandin induced antinociception that persisted for 120 h. The characterisation of the antinociceptive effect of the venom in this model of hyperalgesia showed that κ and δ-opioid receptors are involved in this effect. 7-nitroindazole (7-NI), a neuronal nitric oxide synthase (NOS) inhibitor, but not L-N6-(1-iminoethyl)lysine (L-NIL), an inhibitor of the inducible form of NOS, injected by intraplantar (i.pl.) route, antagonized the antinociceptive effect of the venom. The i.pl. administration of 1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), a seletive guanylate cyclase inhibitor, blocked antinociception, whereas Rp-cGMP triethylamine, a cGMP-dependent protein kinase inhibitor, partially reversed this effect. These data indicate that peripheral κ- and δ-opioid receptors are involved in the antinociceptive effect of Crotalus durissus terrificus on prostaglandin E2-induced hyperalgesia. Peripheral nitric oxide, generated by neuronal NO synthase, and cGMP/PKc are responsible, at least partially, for the molecular mechanisms of venom effect.
Background and Objectives
Neostigmine has shown analgesic benefit when used as an adjunct to epidural or intrathecal anesthesia and analgesia, but evidence of benefit in the peripheral nervous system is controversial. This study aimed to determine if neostigmine 1 mg added to intravenous regional anesthesia (IVRA) provided any advantage in terms of intraoperative anesthesia or postoperative analgesia.
Methods
We recruited 54 patients booked for hand surgery into this randomized, double-blind study. For the IVRA technique, patients were administered 3 mg/kg of 0.5% lidocaine (maximum 45 mL). The treatment group (group N) had 1 mg neostigmine added to lidocaine before dilution. The control group (group C) had no additives to the IVRA solution. At the completion of surgery and after transfer to the recovery room, patients had verbal response pain scores measured at 30 minutes, 1 hour, and 2 hours after cuff deflation. Time to first request for analgesic, side effects, and analgesic consumption at 24 hours were also recorded.
Results
Significantly more patients in group N had motor block at 5 and 10 minutes after injection of study solution. There were no other significant differences in sensory block onset, intraoperative anesthesia, postoperative analgesia, or adverse effects between groups.
Conclusions
Neostigmine 1 mg provides no anesthetic or analgesic advantage when added to IVRA for upper limb surgery.
The aim of the present study was to investigate the role of the peripheral cholinergic system in patients with sympathetically maintained pain (SMP). Thirty-three patients with SMP were given Bier's block with 0.6 mg of atropine in 10 ml of saline or 10 ml of saline in a randomised double-blind manner. Pain intensity, pain relief and mood were assessed before and after each block using the visual analogue scale (VAS). In addition pain intensity was assessed at the same time using a categorical scale (CS). There was at least 1 week between each injection, and during this week the patients reported their pain intensity daily, using the CS. Three patients failed to complete both wings of the study and thus the results of the remaining 30 patients were analysed using the Mann-Whitney U test and the Wilcoxon signed-rank test. No significant difference was found between atropine and saline on any parameter.
G protein-coupled (GPCRs) and ionotropic receptors play an important role in normal and pathological pain transmission and
modulation. Activation of these receptors either directly or indirectly further activates intracellular second messenger pathways
to enhance or suppress nociceptive processing. These second messenger pathways are important both in the periphery as well
as in the central nervous system in mediating pain states. Major second messengers associated with GPCRs are cAMP, cGMP, inositol
triphosphate (IP3), Ca2+and diacylglyceride (DAG). These second messengers transmit the signals mainly by activating protein kinases, such as protein
kinase A (by cAMP), protein kinase G (by cGMP), and protein kinase C (by DAG/ IP3). Ionotropic receptors also activate components
of second messenger systems by increasing calcium influx. Preclinical data show that peripheral injury or inflammation activates
cAMP-protein kinase A (PKA) and/ or DAG/IP3-PKC cascade in the periphery and/ or central nervous system (CNS), which leads
to pain. The cyclic GMP-PKG system has been shown to either facilitate or inhibit nociception. However, the exact role of
the cGMP-PKG pathway in nociception is unclear at this point, although there is sufficient evidence to show its involvement
in the modulation of nociception. Experimental evidences suggest that, despite the ubiquitous distribution of these pathways
throughout living cells, their selective modullation could lead to novel therapies in pain conditions.
This study investigated the role of the cholinergic system in the modulation of inflammatory and neuropathic pain. The paw pressure test was used with inflammatory pain induced by intraplantar injection of carrageenan and neuropathic pain induced by sciatic nerve constriction. All drugs were locally administered into the right hindpaw of rats. Neostigmine, an acetylcholinesterase inhibitor (2, 4, 8 or 16 μg), inhibited the inflammatory pain induced by carrageenan (250 μg/paw), but not the hyperalgesia induced by prostaglandin E₂ (2 μg/paw). Neostigmine (8 μg) increased the nociceptive threshold only in the treated paw, suggesting only a local effect. The muscarinic antagonist atropine (150, 300 and 600 μg) caused a reduction in the nociceptive threshold induced by carrageenan (125 μg/paw), but not by prostaglandin E₂ (1 μg/paw). Atropine significantly decreased the nociceptive threshold only in the treated paw. On the other hand, in the presence of neuropathic pain, atropine (300 μg) did not alter the nociceptive threshold induced by constriction of the sciatic nerve. This study suggests that a peripheral endogenous cholinergic system involving muscarinic receptors may be activated during inflammation as a modulatory negative feedback control of inflammatory pain.
Previous work from our group showed that intrathecal (i.t.) administration of substances such as glutamate, NMDA, or PGE(2) induced sensitization of the primary nociceptive neuron (PNN hypernociception) that was inhibited by a distal intraplantar (i.pl.) injection of either morphine or dipyrone. This pharmacodynamic phenomenon is referred to in the present work as "teleantagonism". We previously observed that the antinociceptive effect of i.t. morphine could be blocked by injecting inhibitors of the NO signaling pathway in the paw (i.pl.), and this effect was used to explain the mechanism of opioid-induced peripheral analgesia by i.t. administration. The objective of the present investigation was to determine whether this teleantagonism phenomenon was specific to this biochemical pathway (NO) or was a general property of the PNNs. Teleantagonism was investigated by administering test substances to the two ends of the PNN (i.e., to distal and proximal terminals; i.pl. plus i.t. or i.t. plus i.pl. injections). We found teleantagonism when: (i) inhibitors of the NO signaling pathway were injected distally during the antinociception induced by opioid agonists; (ii) a nonselective COX inhibitor was tested against PNN sensitization by IL-1beta; (iii) selective opioid-receptor antagonists tested against antinociception induced by corresponding selective agonists. Although the dorsal root ganglion seems to be an important site for drug interactions, the teleantagonism phenomenon suggests that, in PNNs, a local sensitization spreads to the entire cell and constitutes an intriguing and not yet completely understood pharmacodynamic property of this group of neurons.
The role of the L-arginine-NO-cGMP pathway in morphine-induced central analgesia was investigated in two nociceptive tests: PGE2-induced hind paw hyperalgesia and tail-flick. The central analgesic effect of morphine was potentiated by MY5445, a specific cGMP phosphodiesterase inhibitor. I.c.v. injections of morphine or carbachol caused dose-dependent analgesia, which was prevented by methylene blue, an inhibitor of guanylate cyclase. The NO synthase inhibitor, N-iminoethyl-L-ornithine, prevented carbachol-induced analgesia, but did not affect morphine-induced analgesia. Our results suggest that activation of cGMP may underlies analgesia induced by morphine and carbachol. The activation of guanylate cyclase by carbachol seems to depend on the L-arginine-NO pathway, but that caused by morphine remains to be further characterized.
Understanding of the organization and function of a newly identified neuronal messenger molecule, nitric oxide, has progressed rapidly. Nitric oxide synthase has been purified and molecularly cloned from brain. Its localization is exclusively neuronal and endothelial. The catalytic activity of nitric oxide synthase accounts for the NADPH diaphorase staining of neurons that are uniquely resistant to toxic insults and neurodegenerative disorders. Nitric oxide has diverse functions. In platelets it inhibits their aggregation, in macrophages it mediates cytotoxicity, and in blood vessels it acts as a vasodilator. In the nervous system nitric oxide may be the retrograde transmitter in long-term potentiation. It is the "neurotransmitter" of cerebral vasodilator nerves and the inhibitory "neurotransmitter" of the motor neurons of the intestines. Nitric oxide in situations of excessive production may function as a neurotoxin, suggesting a role for nitric oxide in neurodegenerative disorders.
A new behavioral test is described in which quantitation is independent of the observer and is sensitive to all classes of analgesics. A computer-assisted device measures the period during which a rat hind paw fails to touch the surface of a rotating cylinder for 1 min (paw elevation time). Intra-articular injection of carrageenin induces a progressive and dose-dependent incapacitation of the limb. The maximum paw elevation time is attained 3-4 h after carrageenin challenge. The model showed dose-dependent sensitivity to (a) a central acting opiate (morphine, ID50 = 1.5 mg/kg, i.p.), (b) cyclooxygenase inhibitors (indomethacin, ID50 = 0.8 mg/kg, i.p.; diclofenac, ID50 = 0.22 mg/kg, i.p.), and (c) peripheral analgesics which directly antagonize nociceptor hypersensitivity: dipyrone (ID50 = 21 mg/kg, i.p.), N-methyl-nalorphine (ID50 = 14 mg/kg, i.p.) and BW443C (ID50 = 17.5 mg/kg, i.p.). The knee-joint carrageenin incapacitation was also blocked by the sympatholytics, propranolol and guanethidine. After the blockade by either indomethacin or guanethidine, intra-articular injections of prostaglandin E2 or dopamine, respective, reversed carrageenin-induced incapacitation. These results suggest that during inflammatory articular incapacitation cyclooxygenase and sympathomimetic mediators are involved, as has been suggested for the rat paw carrageenin hyperalgesia test and formalin test.
We report the development of a 'second-messenger' model in an attempt to re-evaluate the role of K+ as a desensitising agent. Despite unequivocal validation of the effectiveness of potassium-based dentifrices in the management of dentine hypersensitivity, the mechanism(s) of action of K+ remains unclear. Although experimental paradigms of the Nernst equation demonstrate a direct inhibitory effect of K+ ion upon nerve conduction, in vivo considerable constraints can be argued to preclude this mechanism of action. Indeed, measurements of solution velocity within individual dentinal tubules obtained by scanning electrochemical microscopy indicate that outward movement of tubular fluid may represent a far greater barrier to the inward diffusion of K+ ions than previously estimated from measurements of hydraulic conductance across bulk dentine. Despite such probable limited penetration of dentine tubules, K+ ions may desensitise deeply-located nerve terminals through activation of a second-messenger transduction pathway that is capable of controlling the gain of K+-evoked effects which remain physically restricted to the more superficial aspects of the tubule. In addition to a direct effect upon transmembrane potential K+ can also indirectly attenuate neural activity through effects upon levels of the endogenously-synthesised free radical, nitric oxide (NO). Stimulation of the release of NO by K+ has been observed using a variety of cell preparations, which include endothelium, smooth muscle, adrenal medulla, hypothalamus and cerebellum. Importantly, a growing number of studies now report that an increase in the production of NO is associated with analgesia through a modulation of nociceptive input and a downregulation of sensitised nociceptors, most likely achieved through an increase in intraneural content of cGMP. The clinical role of a K+-evoked liberation of NO as a principal mechanism in the management of dentine hypersensitivity is supported by recent findings which include: (1) the localisation of NADPH-diaphorase activity and inducible nitric oxide synthase (iNOS) immunoreactivity within odontoblasts, their processes in dentine, and the subodontoblast layer of the pulp; (2) iNOS causes a sustained release of large (nanomolar) amounts of NO; (3) NO is freely diffusible and capable of displaying remarkably potent effector actions at distant target cells; (4) the actions of NO may be enhanced by endogenous carrier molecules such as S-nitrosothiols; (5) the synthesis of NO can be evoked by concentrations of K+ ion far less (i.e. <1 mM) than those required for direct inhibitory effects upon neural activity.
The acetylcholinesterase inhibitor neostigmine has shown peripherally mediated analgesic action in recent preclinical and clinical studies. The present study investigates the effectiveness of adding neostigmine to a local anesthetic, mepivacaine, in patients receiving axillary brachial plexus block for upper extremity surgery.
In a double-blind, randomized study 34 patients were assigned to the treatment group: Neostigmine (NM) (500 microg) + mepivacaine (M) (500 mg) (NM, n = 17) as drugs for the plexus block, or to control group: mepivacaine (500 mg) + saline (0.9%, 1 mL) (M, n = 17).
The onset and duration of sensory and motor block was similar in both groups. Patients receiving NM had significantly lower pain ratings [visual analogue scores (VAS): 14.7 +/- 9.9 vs 32.4 +/-23.5; P < .05] 24 hours after surgery, and a lower number of patients in the NM group needed supplemental analgesics during the first 24 hours postoperatively. No adverse events were recorded for either group.
Peripherally administered neostigmine improves postoperative analgesia in axillary brachial plexus block.
The antinociceptive effect of Crotalus durissus terrificus venom was investigated in a model of inflammatory hyperalgesia induced by carrageenin. The rat paw pressure test was applied before and 3 h after the intraplantar (i.pl.) injection of carrageenin. The venom administered per os before and 1 or 2 h after carrageenin blocked hyperalgesia. When carrageenin was injected in both hind paws and naloxone into one hind paw, antinociception was abolished only in the paw injected with naloxone. D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr amide (CTOP) and nor-binaltorphimine, antagonists of micro- and kappa-opioid receptors, respectively, did not alter the effect of the venom. N,N-diallyl-Tyr-Aib-Aib-Phe-Leu (ICI 174,864), an antagonist of delta-opioid receptors, antagonised this effect. Prolonged administration of the venom did not induce tolerance to this antinociceptive effect. N(G)-methyl-L-arginine (L-NMMA) and methylene blue, inhibitors of nitric oxide synthase and soluble guanylate cyclase, respectively, injected i.pl., antagonised antinociception. These data indicate that both delta-opioid receptors and nitric oxide participate in the mediation of the peripheral antinociceptive effect of C. durissus terrificus venom.
Inflammatory signs and symptoms of redness, swelling, heat and pain are due to the effects of inflammatory mediators released during the inflammatory response. Depending on the type of injurious stimuli and the tissue involved, the array of mediators may differ but eicosanoids are involved in the genesis of inflammatory pain. They are responsible for the hypersensitisation of the nociceptors (allodynialhyperalgesia). The basic mechanism of analgesic action of nonsteroidal anti-inflammatory drugs results from the inhibition of prostaglandin synthesis (prostacyclin or PGE2), thus preventing nociceptor threshold lowering. Because there is a temporal hierarchy in the release of inflammatory mediators, there are several targets for the action of peripheral acting analgesics before and after the inhibition of prostaglandin synthesis. Blockade of the release and inhibition of inducible cyclooxygenase explain the analgesic action of glucocorticoids. Nimesulide also has an inhibitory action on the cascade of hypersensitising cytokines. Some analgesics, such as dipyrone, flurbiprofen or diclofenac, act directly upon ongoing inflammatory hypersensitisation. Those analgesics restore the nociceptor by stimulating the arginine/NO/cGMP/K(ATP) channel pathway.
The role of peripheral potassium channels on the antinociceptive effect of Crotalus durissus terrificus venom, a mixed delta- and kappa-opioid receptor agonist, was investigated in hyperalgesia induced by carrageenin or prostaglandin E(2). Rat paw pressure test was applied before and 3 h after the intraplantar (i.pl.) injection of the nociceptive stimuli. Oral administration of venom 2 h after carrageenin or prostaglandin E(2) induces antinociception. Local pretreatment with 4-aminopyridine and tetraethylammonium (blockers of voltage-dependent K(+) channel) or charybdotoxin and apamin (inhibitors of large- and small-conductance Ca(2+)-activated K(+) channel, respectively) did not modify venom effect. On the other hand, glybenclamide, an inhibitor of ATP-sensitive K(+) channel abolished antinociception induced by the venom. Glybenclamide also inhibited the antinociceptive effect of [D-Pen(2.5)] enkephalin (DPDPE), a delta opioid receptor agonist, but did not modify the effect of (+)-trans-(1R,2R)-U-50488 (U50488), a kappa opioid receptor agonist. Diazoxide and pinacidil, two ATP-sensitive K(+) channel openers, injected by intraplantar route, induced a long-lasting increment of pain threshold of the animals and produced antinociception in both models of hyperalgesia. These results suggest that the antinociceptive effect of crotalid venom is mediated by activation of ATP-sensitive K(+) channels at peripheral afferent neurons.
Previous work has shown that nitric oxide (NO) mediates the antinociceptive effect of Crotalus durissus terrificus venom on carrageenin-induced hyperalgesia. In the present study the role of constitutive neuronal or of inducible form of nitric oxide synthase on venom effect was determined. The rat paw prostaglandin E(2) (PGE(2))-induced mechanical hyperalgesia model was used for nociceptive evaluation. The venom (200 microg/kg) administered per oz immediately before prostaglandin induced antinociception that persisted for 120 h. The characterisation of the antinociceptive effect of the venom in this model of hyperalgesia showed that kappa and delta-opioid receptors are involved in this effect. 7-nitroindazole (7-NI), a neuronal nitric oxide synthase (NOS) inhibitor, but not L-N(6)-(1-iminoethyl)lysine (L-NIL), an inhibitor of the inducible form of NOS, injected by intraplantar (i.pl.) route, antagonized the antinociceptive effect of the venom. The i.pl. administration of 1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), a selective guanylate cyclase inhibitor, blocked antinociception, whereas Rp-cGMP triethylamine, a cGMP-dependent protein kinase inhibitor, partially reversed this effect. These data indicate that peripheral kappa- and delta-opioid receptors are involved in the antinociceptive effect of Crotalus durissus terrificus on prostaglandin E(2)-induced hyperalgesia. Peripheral nitric oxide, generated by neuronal NO synthase, and cGMP/PKc are responsible, at least partially, for the molecular mechanisms of venom effect.
The development of COX-2 selective inhibitors has opened a new era of clinical investigation in NSAIDs. Discussion of the established concepts of inflammation and therapeutical uses of these drugs has changed the rationale for its clinical use and therapeutic labeling of these drugs. A comprehensive discussion across basic science and clinical areas involved in each of these concepts is presented. This led to a remarkable re-evaluation of our insights on their traditionally proposed mechanisms of analgesia, their side-effects, and the clinical indication of NSAIDs as "over the counter" pain killers. This may shift physicians toward a more rational use of this drug class.
The final step in the direct restoration of the nociceptor threshold by peripheral administration of morphine and dipyrone was recently suggested to result from the opening of ATP-sensitive K(+) channels (K(ATP)(+)). This channel is known to be open either directly by cGMP or indirectly via protein kinase G (PKG) stimulation. In the present study, it was shown that the blockade was caused by a specific PKG inhibitor (KT5823) of the antinociceptive effect of morphine and dipyrone on acute hypernociception and of dipyrone on persistent hypernociception. It was also shown that, in both models, KT5823 prevented the peripheral antinociceptive effect of an analogue of cGMP, the nitric oxide (NO) donor (S-nitroso-n-acetyl-d,l-penicilamine). However, in acute hypernociception, KT5823 did not prevent the peripheral antinociceptive effect of diazoxide (a direct K(ATP)(+) opener). In persistent hypernociception, the sensitization plateau was induced by daily injections of prostaglandin E(2) (PGE(2), 100 ng) into the rat paw for 14 days. After cessation of PGE(2) injections, the pharmacological blockade of persistent hypernociception led to a quiescent phase in which a rather small stimulus restored the hypernociceptive plateau. In this phase, glibenclamide (which specifically closes K(ATP)(+)) fully restored persistent hypernociception, as did injection of PGE(2). Thus, the activation of the arginine/NO/cGMP pathway causes direct blockade of acute and persistent hypernociception by opening K(ATP)(+) via the stimulation of PKG. Analgesic stimulators of the neuronal arginine/NO/cGMP/PKG/K(ATP)(+) pathway constitute a previously undescribed well defined class of peripheral analgesics with a mechanism of action different from either glucocorticoids or inhibitors of cyclooxygenases.
Neostigmine has shown analgesic benefit when used as an adjunct to epidural or intrathecal anesthesia and analgesia, but evidence of benefit in the peripheral nervous system is controversial. This study aimed to determine if neostigmine 1 mg added to intravenous regional anesthesia (IVRA) provided any advantage in terms of intraoperative anesthesia or postoperative analgesia.
We recruited 54 patients booked for hand surgery into this randomized, double-blind study. For the IVRA technique, patients were administered 3 mg/kg of 0.5% lidocaine (maximum 45 mL). The treatment group (group N) had 1 mg neostigmine added to lidocaine before dilution. The control group (group C) had no additives to the IVRA solution. At the completion of surgery and after transfer to the recovery room, patients had verbal response pain scores measured at 30 minutes, 1 hour, and 2 hours after cuff deflation. Time to first request for analgesic, side effects, and analgesic consumption at 24 hours were also recorded.
Significantly more patients in group N had motor block at 5 and 10 minutes after injection of study solution. There were no other significant differences in sensory block onset, intraoperative anesthesia, postoperative analgesia, or adverse effects between groups.
Neostigmine 1 mg provides no anesthetic or analgesic advantage when added to IVRA for upper limb surgery.
Patients with osteoarthritis (OA) may experience severe pain, progressive loss of movement function, and disability. Many pain-relieving medications are not effective, and are not able to improve the existing pathology.
This review summarizes (1) the pathology, mechanisms of pain production, and conservative management of OA with respect to pain; and (2) explains the role of nitric oxide (NO) in pain reduction and production, especially as related to OA.
NO is produced in biologic cells by a family of enzymes referred to as the nitric oxide synthases (NOSs). The beneficial or harmful effects of different isoforms, constitutive NOS (cNOS) and inducible NOS (iNOS), respectively, suggest dual effects of NO in biologic structures. The harmful effects of NO are most often reported in the literature. We suggest that (1) NO via the beneficial cNOS pathway is decreased in joint structures exposed to chronic load-induced stresses and biochemical change-induced stresses, (2) monochromatic infrared light energy at an 890 nm wavelength, applied at the skin surface, is absorbed into blood vessels and stimulates production of NO in joints by the beneficial cNOS pathway, (3) NO from the cNOS pathway may help decrease the detrimental effects of NO induced by iNOS and produced in OA pathology, and (4) NO-based intervention may produce substantial pain relief without undesirable side effects by increasing circulation, decreasing nerve irritation, and decreasing inflammation in joints. KEY MESSAGES: (1) The roles of NO in nociception are dual and complex. (2) NO via cNOS, produced transiently in small amounts, can bring dramatic relief to people with painful OA.
Different kinds of stress induce distinct antinociceptive properties that may be related or unrelated to the endogenous opioid system. Nitric oxide (NO) has been implicated in stress-activated mechanisms. NO also plays an important role in the modulation of nociceptive responses and has many functional interactions with opioidergic pathways. The present study examined the role of NO in two distinct opioid-mediated and nonopioid types of antinociception induced by footshock stress and assessed by the tail flick latency in mice. Brief and continuous footshock (3 min) induced a naloxone-insensitive antinociception that was not altered by either L-NAME (10 mg/kg), aminoguanidine (100 mg/kg) or L-arginine (60 mg/kg). In contrast, prolonged and intermittent footshock (30 min) induced a naloxone-reversible antinociceptive effect that was blocked by L-NAME (2-10 mg/kg) but not by aminoguanidine (100 mg/kg). L-Arginine (20 and 60 mg/kg) also did not alter this type of antinociception. Morphine (1 mg/kg) induced a mild antinociceptive effect in nonstressed animals that was potentiated by L-NAME (2 mg/kg) but not affected by aminoguanidine (100 mg/kg). The same dose of morphine increased the antinociceptive effect of prolonged and intermittent footshock but this increase was inhibited by L-NAME (2 mg/kg) but not by aminoguanidine. In conclusion, NO of constitutive origin is selectively involved in an opioid-mediated type of footshock stress antinociception in mice.
Endothelium-derived relaxing factor (EDRF) is a labile humoral agent released by vascular endothelium that mediates the relaxation induced by some vasodilators, including acetylcholine and bradykinin. EDRF also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to vascular endothelium. These actions of EDRF are mediated through stimulation of the soluble guanylate cyclase and the consequent elevation of cyclic guanosine 3',5'-monophosphate. EDRF has been identified as nitric oxide (NO). The pharmacology of NO and EDRF is indistinguishable; furthermore, sufficient NO is released from endothelial cells to account for the biological activities of EDRF. Organic nitrates exert their vasodilator activity following conversion to NO in vascular smooth muscle cells. Thus, NO may be considered the endogenous nitrovasodilator. NO is synthesized by vascular endothelium from the terminal guanido nitrogen atom(s) of the amino acid L-arginine. This indicates the existence of an enzymic pathway in which L-arginine is the endogenous precursor for the synthesis of NO. The discovery of the release of NO by vascular endothelial cells, the biosynthetic pathway leading to its generation, and its interaction with other vasoactive substances opens up new avenues for research into the physiology and pathophysiology of the vessel wall.
Nitric oxide (NO) released by vascular endothelial cells accounts for the relaxation of strips of vascular tissue1 and for the inhibition of platelet aggregation2 and platelet adhesion3 attributed to endothelium-derived relaxing factor4. We now demonstrate that NO can be synthesized from L-arginine by porcine aortic endothelial cells in culture. Nitric oxide was detected by bioassay5, chemiluminescence1 or by mass spectrometry. Release of NO from the endothelial cells induced by bradykinin and the calcium ionophore A23187 was reversibly enhanced by infusions of L-arginine and L-citrulline, but not D-arginine or other close structural analogues. Mass spectrometry studies using 15N-labelled L-arginine indicated that this enhancement was due to the formation of NO from the terminal guanidino nitrogen atom(s) of L-arginine. The strict substrate specificity of this reaction suggests that L-arginine is the precursor for NO synthesis in vascular endothelial cells.
Prostaglandins stimulate cAMP increase in several biological systems including CNS. The possible participation of a cAMP/Ca2+ related mechanism in prostaglandin induced hyperalgesia in the rat paw, as measured by a modification of the Randall-Selitto method was investigated. A serie of agents was administered in the paw in an attempt to change either Ca2+ or cyclic AMP concentration at the nociceptive terminations. PGE2, dibutyryl cyclic AMP, isoprenaline, noradrenaline, adrenaline, Ca2+ionophore (A23187), BaCl2 caused a dose dependent hyperalgesia. The hyperalgesic effect of these substances was enhanced by methyl-xanthines. Cyclic GMP as well as agents which interfere with Ca2+ influx (verapamil and lanthanum) were local analgesics in normal and hyperalgesic paws.
The peripheral and central effects of some non-steroid anti-inflammatory drugs, aspirin, indomethacin, paracetamol and phenacetin were studied by comparing their intraplantar and intracerebroventricular effects on hyperalgesia induced by carrageenin injected into the rat paw. Hyperalgesia was measured by a modification of the Randall-Selitto test. The agents tested had antialgesic effects when given by any route. Their intraventricular administration enhanced the antialgesic effect of anti-inflammatory drugs administered into the paw. Previous treatment of one paw with carrageenin reduced the oedema caused by a second injection of carrageenin in the contralateral paw. In contrast, it had no effect on the intensity of hyperalgesia but shortened the time necessary for it to reach a plateau. Administration of a prostaglandin antagonist (SC-19220) in the cerebral ventricles, in the rat paw or in both sites, significantly inhibited the hyperalgesia evoked by carrageenin. The maximal hyperalgesic effect of intraplantar injections of prostaglandin E2 could be further enhanced by its cerebroventricular administration. It was suggested that carrageenin hyperalgesia has a peripheral and a central component and that the cyclo-oxygenase inhibitors used may exert an antialgesic effect by preventing the hyperalgesia induced by a peripheral and/or central release of prostaglandins.
The role of l ‐arginine in the basal and stimulated generation of nitric oxide (NO) for endothelium‐dependent relaxation was studied by use of N G ‐monomethyl l ‐arginine ( l ‐NMMA), a specific inhibitor of this pathway.
l ‐Arginine (10–100 μ m ), but not d ‐arginine (100 μ m ), induced small but significant endothelium‐dependent relaxations of rings of rabbit aorta. In contrast, l ‐NMMA (1–300 μ m ) produced small, endothelium‐dependent contractions, while its enantiomer N G ‐monomethyl‐ d ‐arginine (d‐NMMA; 100 μ) had no effect.
l ‐NMMA (1–300 μ m ) inhibited endothelium‐dependent relaxations induced by acetylcholine (ACh), the calcium ionophore A23187, substance P or l ‐arginine without affecting the endothelium‐independent relaxations induced by glyceryl trinitrate or sodium nitroprusside.
The inhibition of endothelium‐dependent relaxation by l ‐NMMA (30 μ m ) was reversed by l ‐arginine (3–300 μ m ) but not by d ‐arginine (300 μ m ) or a number of close analogues (100 μ m ).
The release of NO induced by ACh from perfused segments of rabbit aorta was also inhibited by l ‐NMMA (3–300 μ m ), but not by d ‐NMMA (100 μ m ) and this effect of l ‐NMMA was reversed by l ‐arginine (3–300 μ m ).
These results support the proposal that l ‐arginine is the physiological precursor for the basal and stimulated generation of NO for endothelium‐dependent relaxation.
Oral methylnalorphine ( methylnalorphinium ) caused a dose-dependent selective inhibition of inflammatory hyperalgesia (measured in the rat by a modified version of the Randall- Selitto test) without affecting the oedema. When subcutaneously injected, repeated doses of morphine for 5 days caused progressive analgesic tolerance. Tolerance was not observed after similar treatment with methylnalorphinium or methylmorphinium . Animals displaying analgesic tolerance to systemic morphine did not exhibit tolerance to the local ( intraplantar ) injection of morphine, methylnalorphinium or methylmorphinium . In contrast with nalorphine and other opiates, methylnalorphinium did not reduce intestinal transit in mice. Methylnalorphinium , a mixed opiate agonist-antagonist devoid of central effects, might be considered the prototype of an ideal peripheral analgesic since it was orally active, did not affect intestinal transit and did not cause analgesic tolerance.
Intracerebral administration of morphine into either nucleus reticularis paragigantocellularis (NRPG) or nucleus raphe magnus (NRM) of rats produced analgesia, as measured by the tail flick test. NRPG was more sensitive to morphine and the effect was dose dependent. The narcotic antagonist naloxone blocked these analgesic effects of morphine. The effect of intracerebral injection of naloxone on the analgesia produced by systemically administered morphine was examined. Morphine was administered subcutaneously (2.86 mg/kg) and naloxone was microinjected 35 min later. Microinjection of 5 micrograms of naloxone into NRM was found to be more effective in reversing in analgesia produced by morphine than naloxone microinjected into more lateral sites, including NRPG. Lesions of NRPG did not attenuate the analgesia produced by systemically administered morphine, whereas lesions of NRM did attenuate this analgesia. The analgesia produced by morphine administered into NRPG was blocked by lesions of NRM. Cinanserin, a serotonergic blocker, blocked the effects of morphine microinjected into NRM but not effects of morphine injected into NRPG. Phenoxybenzamine partially blocked the effects of morphine injected into NRPG but not the effects of morphine injected into NRM. These results show that both nuclei are sensitive to morphine, exert their effects by different synaptic mechanisms and that NRPG does not make an appreciable contribution to the analgesia produced by systemically administered morphine.
On the mode of analgesic action of Tyr-D-arg-Gly-Phe [4-NO2] Pro-NH (443c)
- B B Lorenzetti
- S H Ferreira
- BB Lorenzetti
Larginine is the physiological precursor for formation of nitric oxide in the endothelium-dependent relaxation
- R M J Palmer
- D D Rees
- S Moncada
- RMJ Palmer