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Neurobiological activity of Parawixin 10, a novel anticonvulsant compound isolated from Parawixia bistriata spider venom (Araneidae: Araneae)
Abstract
The neurobiological activity of Parawixin 10, isolated from Parawixia bistriata spider venom, was investigated. Cannulas were implanted in the lateral ventricles of Wistar rats (200-250 g, n=6-8 per group) to perform anticonvulsant and behavioral assays, and synaptosomes from cerebral cortices of male Wistar rats were used for neurochemical studies. The results indicate that pretreatment with Parawixin 10 prevents the onset of seizures induced with kainic acid, N-methyl-D-aspartate, and pentylenetetrazole in a dose-response manner. Lower doses of Parawixin 10 significantly increased the latency to onset of kainic acid-, pentylenetetrazole-, and N-methyl-D-aspartate-induced seizures. There were maximum increases of 79% in L-[(3)H]glutamine uptake and 40% in [(3)H]glycine uptake; [(3)H]GABA uptake did not change. The findings demonstrate that this novel compound from P. bistriata venom exerts a pharmacological effect on the glutamatergic and glycinergic systems.
... In previous studies, Parawixin10 was demonstrated to be neuroprotective and to [191] . Intracerebroventricular injections 10 min before insults [192] Offers neuroprotection and anticonvulsant properties and prevents onset of seizures [190][191][192] Pilocarpine-induced limbic seizure model in rats. ...
... In previous studies, Parawixin10 was demonstrated to be neuroprotective and to [191] . Intracerebroventricular injections 10 min before insults [192] Offers neuroprotection and anticonvulsant properties and prevents onset of seizures [190][191][192] Pilocarpine-induced limbic seizure model in rats. ...
... Administration route: right lateral ventricle injections 60 min after induction of SE, and then daily for four days Chronic administration of Parawixin10 results in neuroprotection, increased latency of recurrent seizures, and decreased duration and severity of seizures [193] J.L. Green et al. have anticonvulsant properties in an in vivo model of intrahippocampal injection of NMDA [191]. In another study, pretreatment with Para-wixin10 prevented the onset of seizures induced by kainic acid, NMDA, and PTZ [192]]. Another study demonstrated that chronic administration of Parawixin10 in the pilocarpine-induced rat model of epilepsy resulted in neuroprotection, increased the latency of recurrent seizures, and decreased duration and severity of seizures, with no behavioral deficits analyzed by the Morris water maze approach [193]. ...
Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.
... It has anticonvulsant effect in rats submitted to acute chemical induction of seizures by kainic acid and N-methyl-D-aspartate (NMDA) (icv) and PTZ (ip). the uptake of L-Glu and glycine using SRCC and also stimulated the release of GABA. [9] In recent decades, great efforts have been employed in an attempt to discover new substances or associations between existing substances that could be more effective to block processes of nerve tissue injury, such as chronic and ischemic processes, which resulting from vascular changes in animal models or clinical trials. [10,11] However, so far no drug or politherapeutical scheme could block the death of neurons arising from these injuries. ...
... Spider collection and venom fractionation was performed et ., [9] were collected in the Ribeirão Preto region (São Paulo, homogenized in acetonitrile/milli-Q water (1:1; v/v), and centrifuged at 8000.g for 10 min at 4°C. Supernatants cut-off (Millipore, Microcon, USA) under centrifugation extract was lyophilized, weighed, and submitted to fractionation. ...
... Next, a linear gradient from 1% to 60% CH 3 CN for weighed, and used in bioassays. [9] CH 3 CN: ...
Background:
Parawixia bistriata is a semi-colonial spider found mainly in southeastern of Brazil. Parawixin 10 (Pwx 10) a compound isolated from this spider venom has been demonstrated to act as neuroprotective in models of injury regulating the glutamatergic neurotransmission through glutamate transporters.
Objectives:
The aim of this work was to evaluate the neuroprotective effect of Pwx 10 in a rat model of excitotoxic brain injury by N-methyl-D-aspartate (NMDA) injection.
Material and methods:
Male Wistar rats have been used, submitted to stereotaxic surgery for saline or NMDA microinjection into dorsal hippocampus. Two groups of animals were treated with Pwx 10. These treated groups received a daily injection of the Pwx 10 (2.5 mg/μL) in the right lateral ventricle into rats pretreated with NMDA, always at the same time, each one starting the treatment 1 h or 24 h. Nissl staining was performed for evaluating the extension and efficacy of the NMDA injury and the neuroprotective effect of Pwx 10.
Results:
The treatment with Pwx 10 showed neuroprotective effect, being most pronounced when the compound was administrated from 1 h after NMDA in all hippocampal subfields analyzed (CA1, CA3 and hilus).
Conclusion:
These results indicated that Pwx 10 may be a good template to develop therapeutic drugs for treating neurodegenerative diseases, reinforcing the importance of continuing studies on its effects in the central nervous system.
... The venom of Parawixia bistriata spiders has been intensively investigated in our laboratory (Fontana et al. 2003; Beleboni et al. 2006;Fachim et al. 2011;Forster et al. 2020). In this search for new anticonvulsant and neuroprotective compounds, several toxins were isolated from the venom of P. bistriata, including Parawixin-11. ...
... induced by kainic acid, NMDA, and PTZ in a dose-response manner. These authors also showed a increase of 79% in [3H]-L-Glu uptake and 40% in [3H]-Gly uptake in the rat's cortical synaptosomes (Fachim et al. 2011). These evidences and the results of this study lead us to suggest that the Parawixin-11 is also a polyamine, although magnetic resonance is required to elucidate chemical structure. ...
The pharmacological treatment of epilepsy is often complex, involving lack of efficacy in several patients due to individual characteristics and profound side effects from current drugs such as sedation, motor impairment and teratogenesis. In the context of drug development for epilepsy, animal venoms represent an important source of new neuroactive molecules acting in different targets such as ion channels and neurotransmitter receptor. In this work we investigated the antiepileptic potential of compounds isolated from the venom of Parawixia bistriata spider. One compound, named here as Parawixin-11, revealed anticonvulsivant effect against seizures induced by bicuculline, pentylenetetrazole, strychnine, pilocarpine and NMDA in a dose-response manner. We also investigated whether the intracerebroventricular administration of Parawixin-11 induced significant motor or cognitive impairment in rats submitted to three tests: open field, rotarod and Morris water maze. No difference was observed on exploration or movement when animals were treated with either 0.3, 0.2 or 0.1 ug of Parawixin-11. An increased latency to find platform was observed in the acquisition phase of the Morris water maze test even though no difference in retention of spatial memory was observed. Considering that Parawixin-11 was more potent against NMDA induced crisis, we hypothesize that this molecule might be modulating the glutamatergic system, consistent with the mechanism of several spider polyamines.
... Our group has elucidated several biological and pharmacological activities of compounds isolated from the venom of the social spider Parawixia bistriata (P. bistriata) [14,15]. Some of these compounds display anxiolytic, anticonvulsant and neuroprotective effects, by acting on L-Glu and GABA (gamma-Aminobutyric acid) transporters [11,16,17]. ...
... We hypothesized that the observed neuroprotection resulted from previously reported activities of Parawixin1 and Parawixin2 in glutamate and GABA transporters, respectively [18,23]. Furthermore, Parawixin1 was shown to increase the function of Excitatory Amino Acid Transporter 2 (EAAT2), the main subtype of L-Glu transporter, which could explain the neuroprotective effects observed in the current work, due to the enhancement of transporter action that results in a lower amount of L-Glu in extracellular space, and consequent reductions of Ca 2+ influx and cell death [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Parawixin2 was shown to reduce GABA and Glycine uptake, but did not modulate the activity of Na + , K + or Ca 2+ ions or of GABA receptors in synaptosomes from the cerebral cortex of rats [18]. ...
Background
L-Glutamate (L-Glu), the major excitatory neurotransmitter in the mammalian Central Nervous System (CNS), is essential to cognitive functions. However, when L-Glu is accumulated in large concentrations at the synaptic cleft, it can induce excitotoxicity that results in secondary damage implicated in many neurological disorders. Current therapies for the treatment of neurological disorders are ineffective and have side effects associated with their use; therefore, there is a need to develop novel treatments. In this regard, previous studies have shown that neuroactive compounds obtained from the venom of the spider Parawixia bistriata have neuroprotective effects in vitro and in vivo. In this sense, this work aimed to evaluate potential neuroprotective effects of fraction RT10, obtained from this spider venom, on primary cultures of neuron and glial cells subjected to glutamate excitotoxicity insults.
Methods
Primary cultures of neurons and glia were obtained from the cerebral tissue of 1-day-old postnatal Wistar rats. After 7 days in vitro (DIV), the cultures were incubated with fraction RT10 (0.002; 0.02; 0.2 and 2 µg/µL) or riluzole (100 µM) for 3-hours before application of 5 mM L-Glu. After 12 hours, the resazurin sodium salt (RSS) test was applied to measure metabolic activity and proliferation of living cells, whereas immunocytochemistry for MAP2 was performed to measure neuronal survival. In addition, the cells were immunolabeled with NeuN and GFAP in baseline conditions.
Results
In the RSS tests, we observed that pre-incubation with RT10 before the excitotoxic insults from L-Glu resulted in neuroprotection, shown by a 10% reduction in the cell death level. RT10 was more effective than riluzole, which resulted in a cell-death reduction of 5%. Moreover, qualitative analysis of neuronal morphology (by MAP2 staining, expressed as fluorescence intensity (FI), an indirect measure of neuronal survival) indicate that RT10 reduced the toxic effects of L-Glu, as shown by a 38 % increase in MAP2 fluorescence when compared to L-Glu insult. On the other hand, the riluzole treatment resulted in 17% increase of MAP2 fluorescence; therefore, the neuroprotection from RT10 was more efficacious.
Conclusion
RT10 fraction exhibits neuroprotective effects against L-Glu excitotoxicity in neuron-glia cultured in vitro.
... In this respect, an unidentified factor related to the generation of HPLC fractions could be responsible for the anticonvulsive effects. However, the fractionation technique applied here has been extensively used, and no study reported an association between the fractionation process and the anticonvulsive action [39,[42][43][44] or other pharmacological effects [45][46][47][48][49][50][51]. Furthermore, the fact that all of the fractions have anticonvulsant potential is surprising, but not unlikely. ...
... L-glutamate receptors and transporters are logical targets for anticonvulsant drugs, as they mediate the majority of excitatory synapses in the human brain. Parawixin 10, a toxin extracted from P. bistriata, exerts its anticonvulsant activity by increasing glutamate uptake [44]. However, this mechanism is not common for antiepileptic drugs due to the wide range of side effects [9,59,61]. ...
Natural products, sources of new pharmacological substances, have large chemical diversity and architectural complexity. In this context, some toxins obtained from invertebrate venoms have anticonvulsant effects. Epilepsy is a neurological disorder that affects about 65 million people worldwide, and approximately 30% of cases are resistant to pharmacological treatment. Previous studies from our group show that the denatured venom of the ant Dinoponera quadriceps (Kempt) protects mice against bicuculline (BIC)-induced seizures and death. The aim of this study was to investigate the anticonvulsant activity of compounds isolated from D. quadriceps venom against seizures induced by BIC in mice. Crude venom was fractionated by high-performance liquid chromatography (HPLC) resulting in six fractions referred to as DqTx1–DqTx6. A liquid chromatography-mass spectrometry (LC/MS) analysis revealed a major 431 Da compound in fractions DqTx1 and DqTx2. Fractions DqTx3 and DqTx4 showed a compound of 2451 Da and DqTx5 revealed a 2436 Da compound. Furthermore, the DqTx6 fraction exhibited a major component with a molecular weight of 13,196 Da. Each fraction (1 mg/mL) was microinjected into the lateral ventricle of mice, and the animals were observed in an open field. We did not observe behavioral alterations when the fractions were given alone. Conversely, when the fractions were microinjected 20 min prior to the administration of BIC (21.6 nM), DqTx1, DqTx4, and DqTx6 fractions increased the latency for onset of tonic-clonic seizures. Moreover, all fractions, except DqTx5, increased latency to death. The more relevant result was obtained with the DqTx6 fraction, which protected 62.5% of the animals against tonic-clonic seizures. Furthermore, this fraction protected 100% of the animals from seizure episodes followed by death. Taken together, these findings indicate that compounds from ant venom might be a potential source of new anticonvulsants molecules.
... Moreover, the TsTX-I, a scorpion neurotoxin isolated from T. serrulatus venom, promoted short and long epileptic-like discharges when injected in the hippocampus of rats (Teixeira et al 2010). On the other hand, conversely, to the proconvulsant action of the P. bistriata spider crude venom, toxins isolated from this venom, such as Parawixin 10, blocked generalized seizures induced by kainic acid, N-methyl-D-aspartate, and pentylenetetrazole in rats (Fachim et al 2011). In addition, Parawixin 2 is a potent anticonvulsant against chemically induced acute seizures (Liberato et al 2006, Gelfuso et al 2007), and showed similar effects against pentylenetetrazol (PTZ)induced kindling (Gelfuso et al 2013). ...
... Notwithstanding, this mechanism is believed to be involved in the activity of some antiepileptic drugs (Macdonald & Kelly 1995, Kwan et al 2001, Mortari et al 2007 ). An example of venom toxin with anticonvulsant potential whose mechanism of action includes modulation of glutamatergic transmission is the Parawixin 10, which increases glutamate uptake (Fachim et al 2011). There are several antiepileptic drugs that act on the GABA A receptor, enhancing the action of GABA or acting as agonists. ...
Epilepsy affects at least 50 million people worldwide, and the available treatment is associated with various side effects. Approximately 20-30% of the patients develop seizures that persist despite careful monitored treatment with antiepileptic drugs. Thus, there is a clear need for the development of new antiepileptic drugs, and the venoms can be an excellent source of probes. In this context, while there are studies on venoms from snakes, scorpions, and spiders, little is known regarding venom from ants. The aim of this study was to investigate the potential pro- and anticonvulsant effects of the venom from the ant Dinoponera quadriceps (Kempf) in Swiss mice. After the injection of the crude venom (DqTx-5, 50, and 500 mg/mL) in the lateral ventricle of mice, we observed a reduction of exploration and grooming behaviors, as well as an increase in immobility duration. In addition, the crude venom induced procursive behavior and tonic-clonic seizures at the highest concentration. Conversely, the preadministration of the denatured venom (AbDq) at the concentration of 2 mg/mL protected the animals against tonic-clonic seizures (66.7%) and death (100%) induced by administration of bicuculline. Taken together, the findings demonstrate that D. quadriceps venom might be potential source of new pro- and anticonvulsants molecules.
... The crude venom of P. bistriata and its chromatographic fractions have been characterized, with some components such as beta-carbolines, polyamines, and phosphatases already having been identified. Diverse biological and pharmacological activities were described, such as insecticidal, anxiolytic, and anticonvulsant activities, reversible inhibition of A and B type monoamine-oxidases, inhibition of GABA and glycine transporters, and increased glutamate uptake [15][16][17][18][19][20][21][22]. ...
... The biochemical, proteomic, and functional characterization of Parawixia bistriata venom presented in this study confirms the presence of various nonprotein toxins of low molecular weight previously described in advanced neurochemical and pharmacological research [15][16][17][18][19][20][21][22], revealing novel enzymatic and biological activities, as well as enzymatically active and inactive protein components of high molecular weight not characterized in previous studies. ...
Toxins purified from the venom of spiders have high potential to be studied pharmacologically and biochemically. These biomolecules may have biotechnological and therapeutic applications. This study aimed to evaluate the protein content of Parawixia bistriata venom and functionally characterize its proteins that have potential for biotechnological applications. The crude venom showed no phospholipase, hemorrhagic, or anti-Leishmania activities attesting to low genotoxicity and discrete antifungal activity for C. albicans. However the following activities were observed: anticoagulation, edema, myotoxicity and proteolysis on casein, azo-collagen and fibrinogen. The chromatographic and electrophoretic profiles of the proteins revealed a predominance of acidic, neutral and polar proteins, highlighting the presence of proteins with high molecular masses. Five fractions were collected using cation exchange chromatography, with the P4 fraction standing out as that of highest purity. All fractions showed proteolytic activity. The crude venom and fractions P1, P2 and P3 showed larvicidal effects on A. aegypti. Fraction P4 showed the presence of a possible metalloprotease (60 kDa) that has high proteolytic activity on azo-collagen and was inhibited by EDTA. The results presented in this study demonstrate the presence of proteins in the venom of P. bistriata with potential for biotechnological applications.
... However, the important mode of action for Parawixin-10 has yet to be pinpointed and thus requires further investigation and studies. 25 Additional study on P. bistrata venom fraction, RT10, which comprised of Parawixins 1 and 2, demonstrated neuroprotective effects on neuron-glia primary culture against high L-glutamate concentrations. 26 ...
Epilepsy affects millions of people worldwide, and there is an urgent need to develop safe and effective therapeutic agents. Animal venoms contain diverse bioactive compounds like proteins, peptides, and small molecules, which may possess medicinal properties against epilepsy. In recent years, research has shown that venoms from various organisms such as spiders, ants, bees, wasps, and conus snails have anticonvulsant and antiepileptic effects by targeting specific receptors and ion channels. This review underscores the significance of purified proteins and toxins from these sources as potential therapeutic agents for epilepsy. In conclusion, this review emphasizes the valuable role of animal venoms as a natural resource for further exploration in epilepsy treatment research.
... Maximal electroshock-induced seizures in albino Wistar rats (i) Exhibited the anticonvulsant activity in maximal electroshockinduced seizures by reducing epileptic seizures [76] (ii) Increased Gamma-Aminobutyric Acid (GABA) release (iii) Decreased lipid peroxidation and acetylcholinesterase activity (iv) Increased GSH level Phragmanthera austroarabica extract Pentylenetetrazol-kindled mouse (i) Reduced seizures and cortical malondialdehyde level [77] (ii) Enhanced cortical GSH (iii) Reduced the percentage of pyknotic neurons in the hippocampus (iv) Increased the percentage of viable neurons Parawixin 10, a compound isolated from Parawixia bistriata spider venom A rat excitotoxicity model of brain injury by kainic acid, N-methyl-D-aspartate, and pentylenetetrazol (i) Decreased glial proliferation in all hippocampal subfields studied, as well as the preservation of cell layers [78,79] (ii) Prevented the onset of seizures induced with kainic acid, N-methyl-D-aspartate, and pentylenetetrazol (iii) Increased the latency to the onset of kainic acid-, pentylenetetrazol-, and N-methyl-D-aspartate-induced seizures White rose (Rosa hybrida) petal extract Kainic acid-induced mouse and in HB1. ...
Alzheimer's Disease (AD) and other memory-related difficulties have both been treated successfully with herbs. Dementia is a neurodegenerative disease that causes the gradual deterioration of affective and cognitive capacities over time. Many factors, including poor cerebral blood flow, poison toxicity, mitochondrial dysfunction, oxidative injury, and, in some cases, the coexistence of other diseases like Alzheimer's Disease (AD), Huntington's Disease (HD), Parkinson's Syndrome (PD), and Attention Deficit Hyperactivity Disorder (ADHD), have been linked to Dementia (ADHD). Although semi-synthetic pharmaceuticals have been shown to be effective in treating Alzheimer's disease and dementia caused by AD, many of these drugs come with unwanted side effects. Therefore, traditional medicine provides a selection of plant-derived lead compounds that may prove useful in future medical research. This research examines the use of ayurvedic plants in the treatment of neurodegenerative diseases in various parts of the world. Also, it has been found that plants can protect the brain system from the damaging effects of proinflammatory cytokines including IL-6, IL-1b, and TNF-a by increasing antioxidant activity, decreasing oxidant levels, and blocking the breakdown of acetylcholinesterase. The most important ayurveda medicinal herbs and the biochemical effects they have have been highlighted. This suggests that the above medicinal herbs and their active ingredients have therapeutic potential in treating neurodegenerative disorders, such as Alzheimer's disease. and sadness, all of which have been associated to neuroinflammation and neurotransmitter dysregulation.
... Recently, researchers focused on potential neurobiological activities of peptide vaccine. 12 Dementia is a clinical syndrome caused by disorders that affect the brain. 13,14 Alzheimer's disease (AD) is the most common type of dementia. ...
Antioxidant agents and cholinesterase inhibitors are the foremost drugs for the treatment of Alzheimer’s disease (AD). In this study, a new peptide from Ziziphus jujuba fruits was investigated for its inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes as well as antioxidant activity. This peptide was introduced as a new peptide and named Snakin-Z. The Snakin-Z displayed considerable cholinesterase inhibition against AChE and BChE. The half maximal inhibitory concentration (IC50) values of Snakin-Z against AChE and BChE are 0.58 + 0.08 and 0.72 + 0.085 mg/mL, respectively. This peptide has 80% enzyme inhibitory activity on AChE and BChE at 1.5 mg/mL. The Snakin-Z also had the high antioxidant activity (IC50 ¼ 0.75 + 0.09 mg/mL). Thus, it is suggested that Snakin-Z may be beneficial in the treatment of AD. However, more detailed researches are still required as in vivo testing its anticholinesterase and antioxidant activities.
... Kluge et al., 2008;Agnarsson et al., 2010;Blackledge, 2012), genomics (Babb et al., 2017), pharmacology and medicine (e.g. Rash and Hodgson, 2002;Liberato et al., 2006;Fachim et al., 2011;Pineda et al., 2017), and it has been a popular object for phylogenetic speculations (e.g. Simon, 1892;Kaston, 1964;Lehtinen, 1978;Levi, 1978;Heimer and Nentwig, 1983;Levi and Coddington, 1983;Eberhard, 1990;Coddington and Levi, 1991;Shear, 1994). ...
... Epilepsy refers to any type of disease characterized by the occurrence of spontaneous and recurrent seizures, caused by paroxysmal discharges of brain neurons, affecting about 700.000 people in the United States and around 5 million people worldwide, representing approximately 1% of the world's population. It is believed that dysfunctions in the chemical balance of neurotransmitters may be the main cause of both development and maintenance of epileptiform electrical activity [30][31][32][33]. ...
Background:
Studies on toad poison are relevant since they are considered a good source of toxins that act on different biological systems. Among the molecules found in the toad poison, it can be highlighted the cardiotonic heterosides, which have a known mechanism that inhibit Na⁺/K⁺-ATPase enzyme. However, these poisons have many other molecules that may have important biological actions. Therefore, this work evaluated the action of the low molecular weight components from Rhinella schneideri toad poison on Na⁺/K⁺-ATPase and their anticonvulsive and / or neurotoxic effects, in order to detect molecules with actions of biotechnological interest.
Methods:
Rhinella schneideri toad (male and female) poison was collected by pressuring their parotoid glands and immediately dried and stored at -20 °C. The poison was dialysed and the water containing the low molecular mass molecules (< 8 kDa) that permeate the dialysis membrane was collected, frozen and lyophilized, resulting in the sample used in the assays, named low molecular weight fraction (LMWF). Na⁺/K⁺ ATPase was isolated from rabbit kidneys and enzyme activity assays performed by the quantification of phosphate released due to enzyme activity in the presence of LMWF (1.0; 10; 50 and 100 µg/mL) from Rhinella schneideri poison. Evaluation of the L-Glutamate (L-Glu) excitatory amino acid uptake in brain-cortical synaptosomes of Wistar rats was performed using [3H]L-glutamate and different concentration of LMWF (10⁻⁵ to 10 µg/µL). Anticonvulsant assays were performed using pentylenetetrazole (PTZ) and N-methyl-D-aspartate (NMDA) to induce seizures in Wistar rats (n= 6), which were cannulated in the lateral ventricle and treated with different concentration of LMWF (0.25; 0.5; 1.0; 2.0; 3.0 and 4.0 µg/µL) 15 min prior to the injection of the seizure agent.
Results:
LMWF induced a concentration-dependent inhibition of Na⁺/K⁺-ATPase (IC50% = 107.5 μg/mL). The poison induces an increased uptake of the amino acid L-glutamate in brain-cortical synaptosomes of Wistar rats. This increase in the L-glutamate uptake was observed mainly at the lowest concentrations tested (10⁻⁵ to 10⁻² µg/µL). In addition, this fraction showed a very relevant central neuroprotection on seizures induced by PTZ and NMDA.
Conclusions:
LMWF from Rhinella schneideri poison has low molecular weight compounds, which were able to inhibit Na⁺/K⁺-ATPase activity, increase the L-glutamate uptake and reduced seizures induced by PTZ and NMDA. These results showed that LMWF is a rich source of components with biological functions of high medical and scientific interest.
... Experimental neurological approaches investigate the complex neurobiological mechanisms involved in epileptogenesis and the maintenance of seizures, 25 the development of new antiepileptic drugs, 9,18,20 alterations in synaptic plasticity, 26,50 the neurophysiological and neuropharmacological bases of the postictal immobility syndrome, 8,12 the characteristics of ictal and postictal states, 31 and postsurgical recovery skills. 5,40 None of these lines of research, however, are related to the resection of relevant cortical regions or disconnection of cortical tracts in animals undergoing acute and chronic models of generalized, multifocal, or limbic epileptic induction and cortical reorganization. ...
OBJECTIVE
The objective of this study was to describe a new experimental model of hemispherotomy performed on laboratory animals.
METHODS
Twenty-six male young adult Wistar rats were distributed into two groups (surgery and control). The nonfluorescent anterograde neurotracer biotinylated dextran amine (BDA; 10,000 MW) was microinjected into the motor cortex area (M1) according to The Rat Brain in Stereotaxic Coordinates atlas to identify pathways and fibers disconnected after the experimental hemispherectomy. SPECT tomographic images of 99m Tc hexamethylpropyleneamine oxime were obtained to verify perfusion in functioning areas of the disconnected and intact brain. A reproducible and validated surgical procedure is described in detail, including exact measurements and anatomical relationships. An additional 30 rodents (n = 10 rats per group) were divided into naïve, sham, and hemispherotomy groups and underwent the rotarod test.
RESULTS
Cortico-cortical neural pathways were identified crossing the midline and contacting neuronal perikarya in the contralateral brain hemisphere in controls, but not in animals undergoing hemispherotomy. There was an absence of perfusion in the left side of the brain of the animals undergoing hemispherotomy. Motor performance was significantly affected by brain injuries, increasing the number of attempts to maintain balance on the moving cylinder in the rotarod test at 10 and 30 days after the hemispherotomy, with a tendency to minimize the motor performance deficit over time.
CONCLUSIONS
The present findings show that the technique reproduced neural disconnection with minimal resection of brain parenchyma in young adult rats, thereby duplicating the hemispherotomy procedures in human patients.
... Recently, researchers focused on potential neurobiological activities of peptide vaccine. 12 Dementia is a clinical syndrome caused by disorders that affect the brain. 13,14 Alzheimer's disease (AD) is the most common type of dementia. ...
Greetings, and thank you for publishing with SAGE Publications. Your article has been copyedited, and we have a few queries for you. Please address these queries when you send your proof corrections to the production editor. Thank you for your time and effort. Please assist us by clarifying the following queries: No. Query Remarks 1 Please check that (a) all authors are listed in the proper order; (b) clarify which part of each author's name is his or her surname; and (c) verify that all author names are correctly spelled/punctuated and are presented in a manner consistent with any prior publications and (d) provide the degree(s) for all the authors here and in the correspondence field. 2 Please provide department name (if any) for affiliation 3. 3 Please provide supplier location for 'Sigma'. 4 Please check whether http://aps.unmc.edu/AP/main.php can be moved to the reference list and if moved to the reference list please provide the complete details in the list and appropriate reference number in superscript in the text. 5 Please verify whether the conflicting interest and funding statements are accurate and correct. Abstract Antioxidant agents and cholinesterase inhibitors are the foremost drugs for the treatment of Alzheimer's disease (AD). In this study, a new peptide from Ziziphus jujuba fruits was investigated for its inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes as well as antioxidant activity. This peptide was introduced as a new peptide and named Snakin-Z. The Snakin-Z displayed considerable cholinesterase inhibition against AChE and BChE. The half maximal inhibitory concentration (IC50) values of Snakin-Z against AChE and BChE are 0.58 + 0.08 and 0.72 + 0.085 mg/mL, respectively. This peptide has 80% enzyme inhibitory activity on AChE and BChE at 1.5 mg/mL. The Snakin-Z also had the high antioxidant activity (IC50 ¼ 0.75 + 0.09 mg/mL). Thus, it is suggested that Snakin-Z may be beneficial in the treatment of AD. However, more detailed researches are still required as in vivo testing its anticholinesterase and antioxidant activities.
... Recently, researchers focused on potential neurobiological activities of peptide vaccine. 12 Dementia is a clinical syndrome caused by disorders that affect the brain. 13,14 Alzheimer's disease (AD) is the most common type of dementia. ...
Antioxidant agents and cholinesterase inhibitors are the foremost drugs for the treatment of Alzheimer's disease (AD). In this study, a new peptide from Ziziphus jujuba fruits was investigated for its inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes as well as antioxidant activity. This peptide was introduced as a new peptide and named Snakin-Z. The Snakin-Z displayed considerable cholinesterase inhibition against AChE and BChE. The half maximal inhibitory concentration (IC50) values of Snakin-Z against AChE and BChE are 0.58 ± 0.08 and 0.72 ± 0.085 mg/mL, respectively. This peptide has 80% enzyme inhibitory activity on AChE and BChE at 1.5 mg/mL. The Snakin-Z also had the high antioxidant activity (IC50 = 0.75 ± 0.09 mg/mL). Thus, it is suggested that Snakin-Z may be beneficial in the treatment of AD. However, more detailed researches are still required as in vivo testing its anticholinesterase and antioxidant activities.
Glutamate transporters, or excitatory amino acid transporters (EAATs), are key proteins that regulate the excitatory tone in the central nervous system (CNS) by clearing synaptic glutamate, maintaining extracellular glutamate concentrations low enough to prevent receptor desensitization and/or glutamate-mediated excitotoxicity. Dysregulation of the function and/or expression of the EAATs is implicated in several diseases, including epilepsy, stroke, traumatic brain injury, drug abuse disorders, neurodegenerative disorders, and neuropathic pain, among others. In this chapter, we will discuss the regulatory mechanisms of EAATs in health and disease states. We will discuss post-translational modifications, trafficking deficits, reverse transport, and other regulatory processes. We will also discuss current approaches on potential therapeutic strategies targeting these transporters for many neuropsychiatric diseases.
Network pharmacology is an emerging pioneering approach in the drug discovery process, which is used to predict the therapeutic mechanism of compounds using various bioinformatic tools and databases. Emerging studies have indicated the use of network pharmacological approaches in various research fields, particularly in the identification of possible mechanisms of herbal compounds/ayurvedic formulations in the management of various diseases. These techniques could also play an important role in the prediction of the possible mechanisms of neuroprotective compounds. The first part of the chapter includes an introduction on neuroprotective compounds based on literature. Further, network pharmacological approaches are briefly discussed. The use of network pharmacology in the prediction of the neuroprotective mechanism of compounds is discussed in detail with suitable examples. Finally, the chapter concludes with the current challenges and future prospectives.
Antiepileptic drugs have been successfully treating epilepsy and providing individuals sustained seizure freedom. However, about 30% of the patients with epilepsy present drug resistance, which means they are not responsive to the pharmacological treatment. Considering this, it becomes extremely relevant to pursue alternative therapeutic approaches, in order to provide appropriate treatment for those patients and also improve their quality of life. In the light of that, this review aims to discuss some innovative options for the treatment of epilepsy, which are currently under investigation, addressing strategies that go from therapeutic compounds to clinical procedures. For instance, peptides derived from animal venoms, such as wasps, spiders, and scorpions, demonstrate to be promising antiepileptic molecules, acting on a variety of targets. Other options are cannabinoids and compounds that modulate the endocannabinoid system, since it is now known that this network is involved in the pathophysiology of epilepsy. Furthermore, neurostimulation is another strategy, being an alternative clinical procedure for drug‐resistant patients who are not eligible for palliative surgeries. This article reviews the most innovative treatments for epilepsy, given the great percentage of drug resistant patients. The topics addressed include neuromodulation, peptides derived from animal venoms, cannabinoids and nanoparticles.
Innovative materials and technologies applied to biomedical studies have been developed along the last 20 years varying their delivery systems. Devices, implants, microneedles, transdermal and mucoadhesive patches, scaffolds, micro and nanoparticles have received considerable attention for their controlled and sustained release system applied to wide range of diseases. The drug delivery systems and administration routes including oral, nasal, ocular, topical and/or local (i.e.skin ointments and patches) and systemic delivery (i.e.intravenous injection) have been investigated along the few years. According with the literature, oral delivery is the most used administration route for small-molecules and pharmaceutical formulations due the non-invasive nature and they are mainly associated with the drug and genes delivery using synthetic compounds until the present moment. Few researchers combine the development of technologies with the natural therapeutic approach as phytochemical and natural products. However, they show the importance to push the boundaries of the scientific knowledge regarding the use of natural sources to target biological sites and improve patients compliance.
The South-American social spider Parawixia bistriata produces a venom containing complex organic compounds with intriguing biological activities. The crude venom leads to paralysis in termites and stimulates L-glutamate uptake and inhibits GABA uptake in rat brain synaptosomes. Glutamate is the major neurotransmitter at the insect neuromuscular junction and at the mammalian central nervous system, suggesting a modulation of the glutamatergic system by the venom. Parawixin1, 2, and 10 (Pwx1, 2 and 10) are HPLC fractions that demonstrate this bioactivity. Pwx1 stimulates L-glutamate uptake through the main transporter in the brain, EAAT2, and is neuroprotective in in vivo glaucoma models. Pxw2 inhibits GABA and glycine uptake in synaptosomes and inhibits seizures and neurodegeneration, and Pwx10 increases L-glutamate uptake in synaptosomes and is neuroprotective and anticonvulsant, shown in in vivo epilepsy models. Herein, we investigated the low molecular mass compounds in this venom and have found over 20 small compounds and 36 unique acylpolyamines with and without amino acid linkers. The active substances in fractions Pwx1 and Pwx2 require further investigation. We elucidated and confirmed the structure of the active acylpolyamine in Pwx10. Both, fraction Pwx10 and the synthesized component enhance the activity of transporters EAAT1 and EAAT2, and importantly, offer in vitro neuroprotection against excitotoxicity in primary cultures. This data suggests that compounds with this mechanism could be developed into therapies for disorders in which L-glutamate excitotoxicity is involved.
In recent years, natural products, which originate from plants, animals, and fungi, together with their bioactive compounds have been intensively explored and studied for their therapeutic potentials for various diseases such as cardiovascular, diabetes, hypertension, reproductive, cancer, and neurodegenerative diseases. Neurodegenerative diseases, including Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis are characterized by the progressive dysfunction and loss of neuronal structure and function that resulted in the neuronal cell death. Since the multifactorial pathological mechanisms are associated with neurodegeneration, targeting multiple mechanisms of actions and neuroprotection approach, which involves preventing cell death and restoring the function to damaged neurons, could be promising strategies for the prevention and therapeutic of neurodegenerative diseases. Natural products have emerged as potential neuroprotective agents for the treatment of neurodegenerative diseases. This review focused on the therapeutic potential of natural products and their bioactive compounds to exert a neuroprotective effect on the pathologies of neurodegenerative diseases.
Spider venoms are a complex cocktail containing hundreds of biologically active compounds resulting in a potent weapon to subdue their prey and for predator deterrence. Some spider toxins are valuable instruments for studying the physiological, pharmacological, and molecular mechanisms of nervous system of invertebrates and vertebrates. Neuroactive compounds from spider venoms have become valuable as therapeutic tools due to their extremely high specificity and potency for interaction with ion channels, receptors for neurotransmitters, and/or transporters of neurotransmitters. The study of these molecules allowed the identification and characterization of new receptors and ionic channels and also established the three-dimensional structure of receptors. It has been used in the development of new bioinsecticides as well as for drugs and therapeutic methods for the disturbances in the functioning of the nervous system.
Spider venoms are a complex cocktail containing hundreds of biologically active compounds resulting in a potent weapon to subdue their prey and for predator deterrence. Some spider toxins are valuable instruments for studying the physiological, pharmacological, and molecular mechanisms of nervous system of invertebrates and vertebrates. Neuroactive compounds from spider venoms have become valuable as therapeutic tools due to their extremely high specificity and potency for interaction with ion channels, receptors for neurotransmitters, and/or transporters of neurotransmitters. The study of these molecules allowed the identification and characterization of new receptors and ionic channels and also established the three-dimensional structure of receptors. It has been used in the development of new bioinsecticides as well as for drugs and therapeutic methods for the disturbances in the functioning of the nervous system.
The impact of neurological disorders in society is growing with alarming estimations for an incidence increase in the next decades. These disorders are generally chronic and can affect individuals early during productive life, imposing real limitations on the performance of their social roles. Patients can have their independence, autonomy, freedom, self-image, and self-confidence affected. In spite of their availability, drugs for the treatment of these disorders are commonly associated with side effects, which can vary in frequency and severity. Currently, no effective cure is known. Nowadays, the biopharmaceutical research community widely recognizes arthropod venoms as a rich source of bioactive compounds, providing a plethora of possibilities for the discovery of new neuroactive compounds, opening up novel and attractive opportunities in this field. Several identified molecules with a neuropharmacological profile can act in the central nervous system on different neuronal targets, rendering them useful tools for the study of neurological disorders. In this context, this review aims to describe the current main compounds extracted from arthropod venoms for the treatment of five major existing neurological disorders: stroke, Alzheimer's disease, epilepsy, Parkinson's disease, and pathological anxiety.
Invertebrate venoms have attracted considerable interest as a potential source of bioactive substances, especially neurotoxins. These molecules have proved to be extremely useful tools for the understanding of synaptic transmission events, and they have contributed to the design of novel drugs for the treatment of neurological disorders and pain. In this context, as epilepsy involves neuronal substrates, which are sites of action of many neurotoxins; venoms may be particularly useful for antiepileptic drug (AED) research. Epilepsy is a chronic disease whose treatment consists of controlling seizures with antiepileptics that very often induce strong undesirable side effects that may limit treatment. Here, we review the vast, but yet unexplored, world of neurotoxins from invertebrates used as probes in pharmacological screening for novel and less toxic antiepileptics. We briefly review (1) the molecular basis of epilepsy, as well as the sites of action of commonly used anticonvulsants (we bring a comprehensive review of the elements from invertebrate venoms which are mostly studied in neuroscience research and may be useful for drug development); (2) peptides from conus snails; (3) peptides and polyamine toxins from spiders and wasps; and (4) peptides from scorpions.
NMDA receptors require both L-glutamate and the coagonist glycine for efficient channel activation. The glycine binding site of these heteromeric receptor proteins is formed by regions of the NMDAR1 (NR1) subunit that display sequence similarity to bacterial amino acid binding proteins. Here, we demonstrate that the glutamate binding site is located on the homologous regions of the NR2B subunit. Mutation of residues within the N-terminal domain and the loop region between membrane segments M3 and M4 significantly reduced the efficacy of glutamate, but not glycine, in channel gating. Some of the mutations also decreased inhibition by the glutamate antagonists, D-AP5 and R-CPP. Homology-based molecular modeling of the glutamate and glycine binding domains indicates that the NR2 and NR1 subunits use similar residues to ligate the agonists' alpha-aminocarboxylic acid groups, whereas differences in side chain interactions and size of aromatic residues determine ligand selectivity.
Venomous animals have evolved a vast array of peptide toxins for prey capture and defence. These peptides are directed against a wide variety of pharmacological targets, making them an invaluable source of ligands for studying the properties of these targets in different experimental paradigms. A number of these peptides have been used in vivo for proof-of-concept studies, with several having undergone preclinical or clinical development for the treatment of pain, diabetes, multiple sclerosis and cardiovascular diseases. Here we survey the pharmacology of venom peptides and assess their therapeutic prospects.
Glutamate is the principal excitatory neurotransmitter in the nervous system. Inactivation of synaptic glutamate is handled by the glutamate transporter GLT1 (also known as EAAT2; refs 1, 2), the physiologically dominant astroglial protein. In spite of its critical importance in normal and abnormal synaptic activity, no practical pharmaceutical can positively modulate this protein. Animal studies show that the protein is important for normal excitatory synaptic transmission, while its dysfunction is implicated in acute and chronic neurological disorders, including amyotrophic lateral sclerosis (ALS), stroke, brain tumours and epilepsy. Using a blinded screen of 1,040 FDA-approved drugs and nutritionals, we discovered that many beta-lactam antibiotics are potent stimulators of GLT1 expression. Furthermore, this action appears to be mediated through increased transcription of the GLT1 gene. beta-Lactams and various semi-synthetic derivatives are potent antibiotics that act to inhibit bacterial synthetic pathways. When delivered to animals, the beta-lactam ceftriaxone increased both brain expression of GLT1 and its biochemical and functional activity. Glutamate transporters are important in preventing glutamate neurotoxicity. Ceftriaxone was neuroprotective in vitro when used in models of ischaemic injury and motor neuron degeneration, both based in part on glutamate toxicity. When used in an animal model of the fatal disease ALS, the drug delayed loss of neurons and muscle strength, and increased mouse survival. Thus these studies provide a class of potential neurotherapeutics that act to modulate the expression of glutamate neurotransmitter transporters via gene activation.
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. After release from glutamatergic nerve terminals, glial and neuronal glutamate transporters remove glutamate from the synaptic cleft to terminate synaptic transmission and to prevent neuronal damage by excessive glutamate receptor activation. In this issue of Molecular Pharmacology, Fontana et al. (p. 1228) report on the action of a venom compound, Parawixin1, on excitatory amino acid transporters (EAATs). They demonstrate that this agent selectively affects a glial glutamate transporter, EAAT2, by specifically increasing one particular step of the glutamate uptake cycle. Disturbed glutamate homeostasis seems to be a pathogenetic factor in several neurodegenerative disorders. Because EAAT2 is a key player in determining the extracellular glutamate concentration in the mammalian brain, drugs targeting this protein could prevent glutamate excitotoxicity without blocking glutamatergic transmission. Its specificity and selectivity makes Parawixin1 a perfect starting point to design small molecules for the treatment of pathological conditions caused by alterations of glutamate homeostasis.
In this article we describe an in vivo anticonvulsant effect from denatured crude venom and partially isolated fractions from two spiders: Parawixia bistriata and Scaptocosa raptoria. Intracerebroventricular injections of these venoms and fractions abolished rat convulsive tonic-clonic seizures induced by picrotoxin, bicuculline and pentylenetetrazole, and also, inhibited GABA uptake in synaptosomes of rat cerebral cortex. The venoms described in this work seems to be promising tools for the study of the GABAergic system, and may be a potential source for new anticonvulsant drugs.
Calcium enters the cytoplasm mainly via voltage-activated calcium channels (VACC), and this represents a key step in the regulation of a variety of cellular processes. Advances in the fields of molecular biology, pharmacology and electrophysiology have led to the identification of several types of VACC (referred to as T-, N-, L-, P/Q- and R-types). In addition to possessing distinctive structural and functional characteristics, many of these types of calcium channels exhibit differential sensitivities to pharmacological agents. In recent years a large number of toxins, mainly small peptides, have been purified from the venom of predatory marine cone snails and spiders. Many of these toxins have specific actions on ion channels and neurotransmitter receptors, and the toxins have been used as powerful tools in neuroscience research. Some of them (ω-conotoxins, ω-agatoxins) specifically recognize and block certain types of VACC. They have common structural backbones and some been synthesized with identical potency as the natural ones. Natural, synthetic and labeled calcium channel toxins have contributed to the understanding of the diversity of the neuronal calcium channels and their function. In particular, the toxins have been useful in the study of the role of different types of calcium channels on the process of neurotransmitter release. Neuronal calcium channel toxins may develop into powerful tools for diagnosis and treatment of neurological diseases.
When electrical stimulation is periodically applied to any one of a number of forebrain sites, there is a progressive development and intensification of elicited motor seizures which can culminate in the development of an epileptic syndrome characterized by spontaneously recurring motor seizures; however, spontaneous motor seizures have been observed in relatively few kindled animals. In the present experiment rats received amygdaloid stimulation about 300 times during a 134-day period. The initial development and intensification of elicited clonic motor seizures progressed as others have described it; however, with continued stimulation running fits were eventually elicited in most of the subjects, and seizures with a tonic component were elicited in a few. Spontaneous motor seizures similar to those elicited by stimulation were observed in 16 of the 18 kindled subjects. Thus, rather than being an idiosyncratic response of a few kindled rats, spontaneous motor seizures appear to be a reliable manifestation of long-term amygdaloid kindling.
Polyamine amide toxins obtained from venous of spiders and wasps interact selectively with ionotropic glutamate receptors (GLU-R) of vertebrate central nervous systems. The sites and modes of action of these polyamine amide toxins are reviewed with particular reference to their structure-activity relationships. Qualitatively, their effects on GLU-R are identical to those exerted by polyamines such as spermine, but the polyamine amides are more potent. These compounds (a) potentiate and (b) antagonize GLU-R, the latter arising through open channel block. For the N-methyl-D-aspartate receptor this non-competitive antagonism probably arises through binding of toxin to the Mg2+ site(s) located in the channel gated by this receptor. Similarities and differences between GLU-R in vertebrates and in invertebrates with respect to their interactions with polyamines and polyamine amide toxins are discussed. In both groups the low specificity of these compounds is illustrated by their antagonism at nicotinic acetylcholine receptors in addition to GLU-R. Electrophysiological studies, including those employing Xenopus oocytes, are reviewed and future prospects for the use of polyamine amides in therapy are discussed.
1.1. The Lowry, Rosebrough, Farr, and Randall method for protein assay has been modified so as to give a higher color yield with bovine serum albumin and with five other pure proteins.2.2. Under the new conditions there is direct proportionality between absorbance at 650 nm and weight of protein within the range 15–110 μg.
N. Kawai, A. Miwa and T. Abe. Specific antagonism of the glutamate receptor by an extract from the venom of the spider Araneus ventricosus. Toxicon 21, 439 - 441, 1983. - A venom sac extract selectively and irreversibly suppressed excitatory postsynaptic potentials in the lobster neuromuscular junction without affecting inhibitory postsynaptic potentials. Glutamate-induced depolarization of the postsynaptic membrane was blocked by the venom extract, whereas membrane depolarization by aspartate was unaffected.
We report the solution structure of mu-agatoxin-I (mu-Aga-I) and model structures of the closely related mu-agatoxin-IV (mu-Aga-IV) which were isolated from venom of the American funnel web spider, Agelenopsis aperta. These toxins, which modify the kinetics of neuronal voltage-activated sodium channels in insects, are C-terminally amidated peptides composed to 36 amino acids, including four internal disulfide bonds. The structure of mu-Aga-I was determined by NMR and distance geometry/molecular dynamics calculations. Structural calculations were carried out using 256 interresidue NOE-derived distance restraints and 25 angle restraints obtained from vicinal coupling constants. The peptide contains eight cysteines involved in disulfide bonds, the pairings of which were uncertain and had to be determined from preliminary structure calculations. The toxin has an average rmsd of 0.89 A for the backbone atoms among 38 converged conformers. The structure consists of a well-defined triple-stranded beta-sheet involving residues 7-9, 20-24, and 30-34 and four tight turns. A homologous peptide, mu-Aga-IV, exhibited two distinct and equally populated conformations in solution, which complicated spectral analysis. Analysis of sequential NOE's confirmed that the conformers arose from cis and trans peptide bonds involving a proline at position 15. Models were developed for both conformers based on the mu-Aga-I structure. Our structural data show that the mu-agatoxins, although specific modifiers of sodium channels, share common secondary and tertiary structural motifs with phylogenetically diverse peptide toxins targeting a variety of channel types. The mu-agatoxins add voltage-sensitive sodium channel activity to a growing list of neurotoxic effects elicited by peptide toxins which share the same global fold yet differ in their animal origin and ion channel selectivity.
In a recent electrophysiological experiment, we showed the deep cerebellar nuclei to be a major source of excitatory input to the superior colliculus. Furthermore, target neurons in the colliculus were found, in every case, to receive convergent tonic inhibitory input from the substantia nigra pars reticulata. In the present study, we investigated these effects in the awake rat. We asked whether circling behaviour, induced by unilateral injection of a GABA antagonist into the lateral colliculus, could be suppressed by concurrent cerebellar inactivation. Rats were chronically implanted with bilateral guide cannulae located above the superior colliculus and deep cerebellar nuclei. Bicuculline methiodide (25 pmol) was microinjected unilaterally into intermediate layers of the colliculus at increasing depths until an optimal contralateral circling response was elicited. This behaviour was taken as the "baseline response" and was the first of three treatments. The second was an identical manipulation of the colliculus with a concurrent 200-nl microinjection of 1 M GABA into the contralateral deep cerebellar nuclei. The third was a repeat of BIC alone into the colliculus or, if rotation had been suppressed by more than 50% on test 2, the treatment was collicular BIC plus deep cerebellar saline. This latter treatment was used as a control for possible non-pharmacological injection effects. The effect of cerebellar GABA at 26 sites (17 within cerebellar nuclei and 9 outside) on BIC-induced rotation at 15 collicular sites was studied in ten animals. Only GABA injections at sites that fell within the cerebellar nuclei significantly reduced turning (P < 0.0001). A full behavioural analysis showed that this was a specific suppression of turning, not the result of general motor impairment. These results provide clear behavioral evidence that opposing, convergent influences from the basal ganglia and cerebellum interact in the lateral superior colliculus to control head and body movements. They furthermore suggest that the tonic deep cerebellar excitation of the superior colliculus could be the driving force in the expression of rotation induced by manipulations of the basal ganglia.
The termination of chemical neurotransmission in the CNS involves the rapid removal of neurotransmitter from synapses by specific transport systems. Such mechanism operates for the three major amino acid neurotransmitters glutamate, gamma-aminobutyric acid (GABA) and glycine. To date, five different high-affinity Na(+)-dependent glutamate (Glu) transporters have been cloned: GLT1, GLAST, EAAC1, EAAT4 and EAAT5. The first two are expressed mainly by glial cells, and seem to be the predominant Glu transporters in the brain. A major function of Glu uptake in the nervous system is to prevent extracellular Glu concentrations from raising to neurotoxic levels in which glial transporters seem to play a critical role in protecting neurons from glutamate-induced excitotoxicity. Under particular conditions, glial GluTs have been shown to release Glu by reversal of activity, in a Ca(2+)--and energy-independent fashion. Furthermore, an activity of these transporters as ion channels or transducing units coupled to G-proteins has recently been reported. The localization, stoichiometry, and regulation of glial GluTs are outlined, as well as their possible contributions to nervous system diseases as ALS, AD and ischemic damage.
Glial cells possess transport systems for the three major amino acid neurotransmitters glutamate, gamma-aminobutyric acid (GABA) and glycine, involved in the arrest of neurotransmission mediated by these compounds. Two glycine transporters have been cloned: GLYT1, mainly expressed by glial cells and shown to colocalize with NMDA receptors, and GLYT2, exclusively expressed by neurons and colocalized with the inhibitory glycine receptors. The way in which the regulation of extracellular glycine concentration by glial glycine transporters affects physiological and pathological conditions is discussed. The presence, differential pharmacology and specific regulation of glycine transporters in glial cells strongly support an important role for glia in the modulation of both, excitatory and inhibitory neurotransmission.
Brain tissue has a remarkable ability to accumulate glutamate. This ability is due to glutamate transporter proteins present in the plasma membranes of both glial cells and neurons. The transporter proteins represent the only (significant) mechanism for removal of glutamate from the extracellular fluid and their importance for the long-term maintenance of low and non-toxic concentrations of glutamate is now well documented. In addition to this simple, but essential glutamate removal role, the glutamate transporters appear to have more sophisticated functions in the modulation of neurotransmission. They may modify the time course of synaptic events, the extent and pattern of activation and desensitization of receptors outside the synaptic cleft and at neighboring synapses (intersynaptic cross-talk). Further, the glutamate transporters provide glutamate for synthesis of e.g. GABA, glutathione and protein, and for energy production. They also play roles in peripheral organs and tissues (e.g. bone, heart, intestine, kidneys, pancreas and placenta). Glutamate uptake appears to be modulated on virtually all possible levels, i.e. DNA transcription, mRNA splicing and degradation, protein synthesis and targeting, and actual amino acid transport activity and associated ion channel activities. A variety of soluble compounds (e.g. glutamate, cytokines and growth factors) influence glutamate transporter expression and activities. Neither the normal functioning of glutamatergic synapses nor the pathogenesis of major neurological diseases (e.g. cerebral ischemia, hypoglycemia, amyotrophic lateral sclerosis, Alzheimer's disease, traumatic brain injury, epilepsy and schizophrenia) as well as non-neurological diseases (e.g. osteoporosis) can be properly understood unless more is learned about these transporter proteins. Like glutamate itself, glutamate transporters are somehow involved in almost all aspects of normal and abnormal brain activity.
A number of neurotoxins derived from arthropod venoms are known to show highly selective effects on nervous tissue. These neurotoxins have been proved to be extremely useful tools to investigate either convulsive or anticonvulsive mechanisms in the nervous system. In the present work, intracerebroventricular injection of the crude venom from the spider Parawixia bistriata (Araneae, Araneidae) in rats induced convulsive limbic seizures (head and forelimb myoclonus, as well as rearing and falling). Neuroethological analysis showed that the limbic seizures induced by the venom were different from those induced by kainic acid. Intravenous injection of the same venom did not induce seizures, but the neuroethological analysis showed an intensification of grooming behavior similar to a displaced activity. In conclusion, our experiments point that crude venom of P. bistriata may contain convulsant neurotoxins probably acting in limbic system structures. The mechanism of action of these neurotoxins may be different from simple activation of glutamatergic kainate receptors, as evidenced by a comparative neuroethological analysis of seizures induced by either venom or kainic acid.
Antiepileptic drugs (AEDs) cover a broad spectrum of pathological conditions ranging from seizures following congenital or acquired brain disorders to behavioural and psychiatric disorders and recently neuropathic pain. The need for novel antiepileptics raises from the expanding field of indications as well as from the fact, that special seizure types are refractory to common AEDs. In addition, many of the conventional antiepileptic drugs exhibit an unfavourable side-effect profile. Since there is growing evidence, that NMDA receptor activation might play a crucial role in epilepsy, NMDA receptor antagonists have become compounds of interest in preventing and treating seizures. This review focuses on NMDA receptor antagonistic compounds, which are already in use for the treatment of epileptic seizures (i. e. MgSO4, felbamate) and compounds in clinical trials (i. e. remacemide, ADCI). Further interest is put on NMDA antagonists in preclinical and biological testing (memantine, dizocilpine, conantokins, Co101244/PD174494, ifenprodil, arcaine, L-701,324, eliprodil, CGP40116, LY235959, LY233053, MRZ2/576, LU73068, 4-Cl-KYN). Some of the latter compounds are predominantely of academic interest (i. e. 4-Cl-KYN), others (i. e. dizocilpine, LY235959, LY233053) might be of therapeutical value when combined with conventional AEDs. In order to reduce adverse effects in antiepileptic medication using NMDA antagonists, special interest will be focused on subtype selective compounds. In this respect, Co101244, a novel potent and selective NR1/2B NMDA receptor antagonist might be a lead for therapeutically promising compounds.
The present experiments investigated the effect of a neurotoxin purified from the venom of the spider Phoneutria nigriventer. This toxic component, P. nigriventer toxin 3-6 (PnTx3-6), abolished Ca(2+)-dependent glutamate release with an IC(50) of 74.4nM but did not alter Ca(2+)-independent secretion of glutamate when brain cortical synaptosomes were depolarized by KCl (33mM). This effect was most likely due to interference with the entry of calcium through voltage activated calcium channels (VACC), reducing the increase in the intrasynaptosomal free calcium induced by membrane depolarization with an IC(50) of 9.5nM. We compared the alterations induced by PnTx3-6 with the actions of toxins known to block calcium channels coupled to exocytosis. Our results indicate that PnTx3-6 inhibition of glutamate release and intrasynaptosomal calcium involves P/Q type calcium channels and this toxin can be a valuable tool in the investigation of calcium channels.
We investigated the consequences of pentylenetetrazole (PTZ) kindling on cognitive capacities of rats in a Morris water maze assessing spatial reference memory and in the spontaneous alternation test used as an index of working memory. The emotional consequences of PTZ kindling were also evaluated in an elevated plus maze test. Results indicated that PTZ kindled rats were not different from controls in mastering the water maze. However, PTZ kindled rats did not persist in searching the platform when evaluated at the end of learning. This suggests an altered place memory, although alternative explanations, like reduced anxiety, may be involved. Indeed, such anxiolytic activity was observed in a separate group of kindled rats evaluated in the plus maze test. No significant effect of PTZ kindling was noted in the spontaneous alternation test. These results question the generalization of previous results obtained in learning tests using electric shocks and illustrate the complexity of the PTZ model for the study of the behavioral consequences of kindling.
In this study, we examined the effects of crude venom from the spider Parawixia bistriata on glutamate and GABA uptake into synaptosomes prepared from rat cerebral cortex. Addition of venom to cortical synaptosomes stimulated glutamate uptake and inhibited GABA uptake in a concentration-dependent manner.
The venom was fractionated using reverse-phase high-performance liquid chromatography on a preparative column. The fraction that retained glutamate uptake-stimulating activity was further purified on a reverse-phase analytical column followed by ion-exchange chromatography.
The active fraction, referred to as PbTx1.2.3, stimulated glutamate uptake in synaptosomes without changing the KM value, and did not affect GABA uptake. Additional experiments showed that the enhancement of glutamate uptake by PbTx1.2.3 occurs when ionotropic glutamate receptors or voltage-gated sodium and calcium channels are completely inhibited or when GABA receptors and potassium channels are activated, indicating that the compound may have a direct action on the transporters.
In an experimental model for glaucoma in which rat retinas are subjected to ischemia followed by reperfusion, PbTx1.2.3 protected neurons from excitotoxic death in both outer and inner nuclear layers, and ganglion cell layers.
This active spider venom component may serve as a basis for designing therapeutic drugs that increase glutamate clearance and limit neurodegeneration.
British Journal of Pharmacology (2003) 139, 1297–1309. doi:10.1038/sj.bjp.0705352
Glycine acts as a necessary coagonist for glutamate at the NMDA receptor (NMDAR) complex by binding to the strychnine-insensitive glycine-B binding site on the NR1 subunit. The fact that glycine is normally found in the brain and spinal cord at concentrations that exceed those required to saturate this site has led to the speculation that glycine normally saturates NMDAR-containing synapses in vivo. However, additional lines of evidence suggest that synaptic glycine may be efficiently regulated in synaptic areas by the glycine transporter type 1 (GlyT1). The recent description of a potent and selective GlyT1 inhibitor (N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine [NFPS]) provides a tool for evaluation of the hypothesis that inhibition of GlyT1 may increase synaptic glycine and thereby potentiate NMDAR function in vivo. In the present study, we found that (+)-NFPS demonstrated >10-fold greater activity in an in vitro functional glycine reuptake assay relative to the racemic compound. In vivo, (+/-)-NFPS significantly enhanced long-term potentiation in the hippocampal dentate gyrus induced by high-frequency electrical stimulation of the afferent perforant pathway. Furthermore, (+)-NFPS induced a pattern of c-Fos immunoreactivity comparable with the atypical antipsychotic clozapine and enhanced prepulse inhibition of the acoustic startle response in DBA/2J mice, a strain with low basal levels of prepulse inhibition. Collectively, these data suggest that selective inhibition of GlyT1 can enhance NMDAR-sensitive activity in vivo and also support the idea that GlyT1 may represent a novel target for developing therapeutics to treat disorders associated with NMDAR hypofunction.
Since 1922 when Wu proposed the use of the Folin phenol reagent for
the measurement of proteins (l), a number of modified analytical pro-
cedures ut.ilizing this reagent have been reported for the determination
of proteins in serum (2-G), in antigen-antibody precipitates (7-9), and
in insulin (10).
Although the reagent would seem to be recommended by its great sen-
sitivity and the simplicity of procedure possible with its use, it has not
found great favor for general biochemical purposes.
In the belief that this reagent, nevertheless, has considerable merit for
certain application, but that its peculiarities and limitations need to be
understood for its fullest exploitation, it has been studied with regard t.o
effects of variations in pH, time of reaction, and concentration of react-
ants, permissible levels of reagents commonly used in handling proteins,
and interfering subst.ances. Procedures are described for measuring pro-
tein in solution or after precipitation wit,h acids or other agents, and for
the determination of as little as 0.2 y of protein.
It has previously been shown that the denatured crude extract of Agelaia vicina wasp venom inhibits glutamate and GABA uptake in rat cerebral cortex synaptosomes. To identify the components responsible for these effects, the neurotoxin AvTx 7 (molecular weight of 1210 Da) was isolated from A. vicina venom and its effects on glutamate neurotransmission investigated. AvTx 7 inhibits glutamate uptake in a dose-dependent and uncompetitive manner. AvTx 7 was found to stimulate the glutamate release in the presence of calcium and sodium channel blockers, suggesting that its action is not mediated through these channels. AvTx 7 potentiates glutamate release in the presence of K(+) channel blockers tetraethylammonium and 4-aminopyridine, indicating that the toxin may act through these drugs-sensible K(+) channels. We suggest that AvTx 7 can be a valuable tool to enhance our understanding of K(+) channels' involvement in the release of glutamate.
The use of toxins as novel molecular probes to study the structure-function relationship of ion-channels and receptors as well as potential therapeutics in the treatment of wide variety of diseases is well documented. The high specificity and selectivity of these toxins have attracted a great deal of interest as candidates for drug development. This review highlights the involvement of the proteins and peptide toxins as well as non-proteinaceous compounds derived from both venomous and non-venomous animals, in anti-nociception and anti-inflammation. The possible mechanisms of these potential therapeutic agents and possible clinical applications in the treatment of pain and inflammation are also summarized.
Ligand-gated ion channels, or ionotropic receptors, constitute a group of membrane-bound proteins that regulate the flux of ions across the cell membrane. In the brain, ligand-gated ion channels mediate fast neurotransmission. They are crucial for normal brain function and involved in many diseases in the brain. Historically, natural products have been used extensively in biomedical studies and ultimately as drugs or leads for drug design. In studies of ligand-gated ion channels, natural products have been essential for the understanding of their structure and function. In the following a short survey of natural products and their use in studies of ligand-gated ion channels is given.
L-glutamate serves as the primary excitatory neurotransmitter in the mammalian CNS, where it can contribute to either neuronal communication or neuropathological damage through the activation of a wide variety of excitatory amino acid (EAA) receptors. By regulating the levels of extracellular L-glutamate that have access to these receptors, glutamate uptake systems hold the potential to effect both normal synaptic signaling and the abnormal over-activation of the receptors that can trigger excitotoxic pathology. Among the various membrane transporters that are capable of translocating this dicarboxylic amino acid, the majority of glutamate transport in the CNS, particularly as related to excitatory transmission, is mediated by the high-affinity, sodium-dependent, excitatory amino acid transporters (EAATs). At least 5 subtypes of EAATs have been identified, each of which exhibits a distinct distribution and pharmacology. Our growing appreciation for the functional significance of the EAATs is closely linked to our understanding of their pharmacology and the consequent development of inhibitors and substrates with which to delineate their activity. As was the case with EAA receptors, conformationally constrained glutamate mimics have been especially valuable in this effort. The success of these compounds is based upon the concept that restricting the spatial positions that can be occupied by required functional groups can serve to enhance both the potency and selectivity of the analogues. In the instance of the transporters, useful pharmacological probes have emerged through the introduction of additional functional groups (e.g., methyl, hydroxyl, benzyloxy) onto the acyclic backbone of glutamate and aspartate, as well as through the exploitation of novel ring systems (e.g., pyrrolidine-, cyclopropyl-, azole-, oxazole-, and oxazoline-based analogues) to conformationally lock the position of the amino and carboxyl groups. The focus of the present review is on the pharmacology of the EAATs and, in particular, the potential to identify those chemical properties that differentiate the processes of binding and translocation (i.e., substrates from non-substrate inhibitors), as well as strategies to develop glutamate analogues that act selectively among the various EAAT subtypes.
Several investigations demonstrate that neurotoxins isolated from venoms of spiders and wasps may exert specific and selective activity on structures of the mammalian CNS. In the present work we examine the neurological effects of the low molecular weight compounds of the denatured venom of the neotropical social wasp Polybia occidentalis in freely moving rats. Central administration of denatured venom decreased the duration of exploratory, elevation and grooming behaviours on the open field. Moreover, denatured venom inhibited convulsing action of bicuculline (ED50 57 microg/microl), picrotoxin (ED50 75 microg/microl) and kainic acid (ED50 44 microg/microl), although it was ineffective against pentylenetetrazole-induced seizures. Despite of its inhibitory activity, toxic effects on motor performance examined in the rotarod test were not found, not even in extremely high doses. Also, denatured venom moderately reduced the spontaneous locomotor activity at anticonvulsant doses. These findings may indicate that the denatured venom has anticonvulsant activity with scarce propensity to cause neurological side-effects. Further studies are necessary to isolate the active compound and establish its mechanism of action.
The major contribution of this work is the isolation of a neuroprotective compound referred to as 2-amino-5-ureidopentanamide (FrPbAII) (M(r) = 174) from Parawixia bistriata spider venom and an investigation of its mode of action. FrPbAII inhibits synaptosomal GABA uptake in a dose-dependent manner and probably does not act on Na(+), K(+), and Ca(2+) channels, GABA(B) receptors, or gamma-aminobutyrate:alpha-ketoglutarate aminotransferase enzyme; therefore, it is not directly dependent on these structures for its action. Direct increase of GABA release and reverse transport are also ruled out as mechanisms of FrPbAII activities as well as unspecific actions on pore membrane formation. Moreover, FrPbAII is selective for GABA and glycine transporters, having slight or no effect on monoamines or glutamate transporters. According to our experimental glaucoma data in rat retina, FrPbAII is able to cross the blood-retina barrier and promote effective protection of retinal layers submitted to ischemic conditions. These studies are of relevance by providing a better understanding of neurochemical mechanisms involved in brain function and for possible development of new neuropharmacological and therapeutic tools.
The aims of the present study were to investigate the anticonvulsant activity and behavioral toxicity of FrPbAII using freely moving Wistar rats. Moreover, the effectiveness of this compound against chemical convulsants was compared to that of the inhibitor of the GABAergic uptake, nipecotic acid. Our results show that FrPbAII was effective against seizures induced by the i.c.v. injection of pilocarpine (ED(50) = 0.05 microg/animal), picrotoxin (ED(50) = 0.02 microg/animal), kainic acid (ED(50) = 0.2 microg/animal) and the systemic administration of PTZ (ED(50) = 0.03 microg/animal). The anticonvulsant effect of FrPbAII differed from that of nipecotic acid in potency, as the doses needed to block the seizures were more than 10 folds lower. Toxicity assays revealed that in the rotarod, the toxic dose of the FrPbAII is 1.33 microg/animal, and the therapeutic indexes were calculated for each convulsant. Furthermore, the spontaneous locomotor activity of treated animals was not altered when compared to control animals but differed from the animals treated with nipecotic acid. Still, FrPbAII did not induce changes in any of the behavioral parameters analyzed. Finally, when tested for cognitive impairments in the Morris water maze, the i.c.v. injection of FrPbAII did not alter escape latencies of treated animals. These findings indicate that the novel GABA uptake inhibitor is a potent anticonvulsant with mild side-effects when administered to Wistar rats.
This study was aimed at determining the effects of FrPbAII (174 Da), a novel isolated component from Parawixia bistriata spider venom, in the CNS of Wistar rats. Considering that FrPbAII inhibits the high affinity GABAergic uptake in a dose-dependent manner, its anxiolytic and anticonvulsant effects were analyzed in well-established animal models. Injection of FrPbAII in the rat hippocampus induced a marked anxiolytic effect, increasing the occupancy in the open arms of the elevated plus maze (EC(50)=0.09 microg/microl) and increasing the time spent in the lit area of the light-dark apparatus (EC(50)=0.03 microg/microl). Anxiolytic effects were also observed considering the number of entries in the open arms of the EPM and in the lit compartment of the light-dark box. Interestingly, when microinjected bilaterally in the SNPr of freely moving rats, FrPbAII (0.6 microg/microl) effectively prevented seizures induced by the unilateral GABAergic blockade of Area tempestas (bicuculline, 0.75 microg/microl). This anticonvulsant effect was similar to that evoked by muscimol (0.1 microg/microl) and baclofen (0.6 microg/microl), but differed from that of the specific GAT1 inhibitor, nipecotic acid (0.7 microg/microl). This difference could be accounted either for the parallel action of FrPbAII over glycinergic transporters or to an inspecific activity on GABAergic transporters. Data from the present investigation might be pointing to a novel compound with interesting and yet unexplored pharmacological potential.
It is widely accepted that glycine transporters of the GLYT1 type are situated on astrocytes whereas GLYT2 are present on glycinergic neuronal terminals where they mediate glycine uptake. We here used purified preparations of mouse spinal cord nerve terminals (synaptosomes) and of astrocyte-derived subcellular particles (gliosomes) to characterize functionally and morphologically the glial versus neuronal distribution of GLYT1 and GLYT2. Both gliosomes and synaptosomes accumulated [3H]GABA through GAT1 transporters and, when exposed to glycine in superfusion conditions, they released the radioactive amino acid not in a receptor-dependent manner, but as a consequence of glycine penetration through selective transporters. The glycine-evoked release of [3H]GABA was exocytotic from synaptosomes but GAT1 carrier-mediated from gliosomes. Based on the sensitivity of the glycine effects to selective GLYT1 and GLYT2 blockers, the two transporters contributed equally to evoke [3H]GABA release from GABAergic synaptosomes; even more surprising, the 'neuronal' GLYT2 contributed more efficiently than the 'glial' GLYT1 to mediate the glycine effect in [3H]GABA releasing gliosomes. These functional results were largely confirmed by confocal microscopy analysis showing co-expression of GAT1 and GLYT2 in GFAP-positive gliosomes and of GAT1 and GLYT1 in MAP2-positive synaptosomes. To conclude, functional GLYT1 are present on neuronal axon terminals and functional GLYT2 are expressed on astrocytes, indicating not complete selectivity of glycine transporters in their glial versus neuronal localization in the spinal cord.
Previous studies have shown that a compound purified from the spider Parawixia bistriata venom stimulates the activity of glial glutamate transporters and can protect retinal tissue from ischemic damage. To understand the mechanism by which this compound enhances transport, we examined its effects on the functional properties of glutamate transporters after solubilization and reconstitution in liposomes and in transfected COS-7 cells. Here, we demonstrate in both systems that Parawixin1 promotes a direct and selective enhancement of glutamate influx by the EAAT2 transporter subtype through a mechanism that does not alter the apparent affinities for the cosubstrates glutamate or sodium. In liposomes, we observed maximal enhancement by Parawixin1 when extracellular sodium and intracellular potassium concentrations are within physiological ranges. Moreover, the compound does not enhance the reverse transport of glutamate under ionic conditions that favor efflux, when extracellular potassium is elevated and the sodium gradient is reduced, nor does it alter the exchange of glutamate in the absence of internal potassium. These observations suggest that Parawixin1 facilitates the reorientation of the potassium-bound transporter, the rate-limiting step in the transport cycle, a conclusion further supported by experiments showing that Parawixin1 does not stimulate uptake by an EAAT2 transport mutant (E405D) defective in the potassium-dependent reorientation step. Thus, Parawixin1 enhances transport through a novel mechanism targeting a step in the transport cycle distinct from substrate influx or efflux and provides a basis for the design of new drugs that act allosterically on transporters to increase glutamate clearance.
Therapeutic potential of venom peptides [3] Strømgaard K. Natural products as tools for studies of ligand-gated ion channels
- Rj Lewis
- Garcia
Lewis RJ, Garcia ML. Therapeutic potential of venom peptides. Nat Rev Drug Discov 2003;2:790–802. [3] Strømgaard K. Natural products as tools for studies of ligand-gated ion channels. Chem Rec 2005;5:229–39.
Parawixia bistriata and Scaptocosa raptoria venoms: inhibition of GABA uptake and convulsant effect
- Mar Cairrão
- A M Ribeiro
- A B Pizzo
Cairrão MAR, Ribeiro AM, Pizzo AB, et al. Parawixia bistriata and Scaptocosa
raptoria venoms: inhibition of GABA uptake and convulsant effect. Pharm Biol
2002;40:472-7.
Anticonvulsant and behavioral effects of the venom of the social wasp Polybia occidentalis in rats
- Mr Mortari
- Aos Cunha
- L Oliveira
- Eb Vieira
- Ea Gelfuso
- Santos
Mortari MR, Cunha AOS, Oliveira L, Vieira EB, Gelfuso EA, Santos WF. Anticonvulsant and behavioral effects of the venom of the social wasp Polybia occidentalis in rats. Basic Clin Pharmacol Toxicol 2005;97:289–95.
Beta-lactam antibiotics offer neuroprotection by increasing glutamate transporter expression.
- Rothstein J.D.
- Patel S.
- Regan M.R.
Rothstein JD, Patel S, Regan MR, et al. Beta-lactam antibiotics offer neuroprotection by increasing glutamate transporter expression. Nature 2005;433:73–7.
- Nc Danbolt
- Glutamate Uptake
Danbolt NC. Glutamate uptake. Prog Neurobiol 2001;65:1–105.
Anticonvulsant and anxiolytic activity of FrPbAII, a novel GABA uptake inhibitor isolated from the venom of the social spider Parawixia bistriata (Araneidae: Araneae)
- J L Liberato
- Aos Cunha
- M R Mortari
Liberato JL, Cunha AOS, Mortari MR, et al. Anticonvulsant and anxiolytic activity of
FrPbAII, a novel GABA uptake inhibitor isolated from the venom of the social
spider Parawixia bistriata (Araneidae: Araneae). Brain Res 2006;1124:19-27.
Anticonvulsant and behavioral effects of the venom of the social wasp Polybia occidentalis in rats
- M R Mortari
- Aos Cunha
- L Oliveira
- E B Vieira
- E A Gelfuso
- W F Santos
Mortari MR, Cunha AOS, Oliveira L, Vieira EB, Gelfuso EA, Santos WF.
Anticonvulsant and behavioral effects of the venom of the social wasp Polybia
occidentalis in rats. Basic Clin Pharmacol Toxicol 2005;97:289-95.
Neurotoxins from invertebrates as anticonvulsants: from basic research to therapeutic application
- M R Mortari
- Aos Cunha
- L B Ferreira
- W F Santos
Mortari MR, Cunha AOS, Ferreira LB, Santos WF. Neurotoxins from invertebrates as
anticonvulsants: from basic research to therapeutic application. Pharmacol Ther
2007;114:171-83.
Beta-lactam antibiotics offer neuroprotection by increasing glutamate transporter expression
- Rothstein