Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ability of steroids to influence brain excitability is well documented. Certain 3 alpha-hydroxylated pregnanes are known to possess anticonvulsant and sedative-hypnotic/anesthetic properties. It has been observed that the seizure susceptibility in menstruating women with catamenial epilepsy appears to be correlated with changes in ovarian steroid levels. However, the underlying mechanism of these steroid influences on brain activity has only been recently revealed by pharmacological studies. These studies have provided compelling evidence for the presence of a novel steroid recognition site on the GABAA-benzodiazepine receptor complex (GBRC). Steroids may interact with this site with high affinity and stereospecificity to enhance chloride channel conductance in a manner similar to that produced by benzodiazepines (BZs) or barbiturates. The existence of such a steroid site on the GBRC is further supported by recent experiments involving the transfection of GABAA receptor cDNAs into a human embryonic kidney cell line. Based on the knowledge of the structure-activity requirements for the interaction of steroids with this novel recognition site, it is conceivable that the development of new anticonvulsant steroids with high therapeutic indices can be achieved.
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PMID:Anticonvulsant steroids and the GABA/benzodiazepine receptor-chloride ionophore complex. 217 79

Gamma-hexachlorocyclohexane (gamma-HCH), the active ingredient of the insecticide lindane, has been shown to decrease seizure threshold to pentylenetrazol (PTZ) 3 h after exposure to gamma-HCH and conversely increase threshold to PTZ-induced seizures 24 h after exposure to gamma-HCH (Vohland et al. 1981). In this study, the severity of response to other seizure-inducing agents was tested in mice 1 and 24 h after intraperitoneal administration of 80 mg/kg gamma-HCH. One hour after the administration of gamma-HCH, the activity of seizure-inducing agents was increased, regardless of their mechanism, while 24 h after gamma-HCH a differential response was observed. Seizure activity due to PTZ and picrotoxin (PTX) was significantly decreased; however, seizure activity due to 3-mercaptopropionic acid (MPA), bicuculline (BCC), methyl 6,7-dimethoxy-4-ethyl-B-carboline-3-carboxylate (DMCM), or strychnine (STR) was not different from control. In vitro, gamma-HCH, pentylenetetrazol and picrotoxin were shown to inhibit 3H-TBOB binding in mouse whole brain, with IC50 values of 4.6, 404 and 9.4 microM, respectively. MPA, BCC, DMCM, and STR showed no inhibition of 3H-TBOB (t-butyl bicyclo-orthobenzoate) binding at concentrations of 100 micron. The pharmacological challenge data suggest that tolerance may occur to seizure activity induced by PTZ and PTX 24 h after gamma-HCH, since the response to only these two seizure-inducing agents is decreased. The in vitro data suggest that the site responsible for the decrease in seizure activity 24 h after gamma-HCH may be the GABA-A receptor-linked chloride channel.
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PMID:Differential effects of gamma-hexachlorocyclohexane (lindane) on pharmacologically-induced seizures. 244 Apr 13

Several different types of chemical compounds are useful as antiepileptic drugs. Their mechanisms of action, as well as their physical structures, differ. Compounds such as carbamazepine, phenytoin, and probably valproate act by modifying ionic conductances, particularly sodium and calcium, in excitable membranes, thus limiting sustained high-frequency neuronal discharges. In contrast, barbiturates and benzodiazepines tend to affect gamma-aminobutyric acid (GABA) mediation of the chloride channel opening. Knowledge of drug mechanisms is important for choosing the proper drug for various seizures types. In addition, an understanding of antiepileptic drug pharmacokinetics, nontherapeutic effects, and interactions is essential for optimal therapy. The lack of uniform pharmacokinetics among patients and among different formulations of a drug can make it difficult to arrive at uniform criteria for both seizure control and determinations of toxicity. both pharmacokinetic and pharmacodynamic interactions can occur between antiepileptic medications and other drugs. Three major types of side effects with anticonvulsants can be identified: dose-related alterations of neurologic function, idiosyncratic reactions, and nonidiosyncratic function, idiosyncratic reactions, and nonidiosyncratic direct actions on other organ systems. These effects often compromise treatment.
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PMID:Pharmacology of antiepileptic drugs. 244 60

gamma-Hexachlorocyclohexane (gamma-HCH), the active ingredient of the insecticide lindane, has been shown to be a seizure-inducing agent in mammals. gamma-HCH and two non-convulsant isomers of HCH (alpha and delta) were compared as to their CNS-related pharmacological and biochemical effects. gamma-HCH was a potent seizure-inducing agent in mice while the alpha or the delta isomer significantly decreased mouse motor activity. Acute administration of gamma-HCH increased the severity of seizure activity of either pentylenetetrazol (PTZ) or picrotoxin (PIC). However, acute exposure to alpha- or delta-HCH inhibited the seizure activity due to PTZ but increased that of PIC. gamma-, alpha-, and delta-HCH inhibited the binding of 3H-TBOB (a ligand for the GABA-A receptor linked chloride channel) to mouse whole brain membranes with IC50 values of 4.6, 20.0, and 31.8 microM, respectively. All three isomers were weak inhibitors of GABA-stimulated uptake of 36Cl into mouse brain neurosynaptosome preparations in vitro, being much less potent than PIC, an agent known to act at the chloride channel. At concentrations producing no effect by itself, gamma-HCH increased the effect of PIC on GABA-stimulated chloride uptake. In combination with PTZ, the delta and alpha isomers decreased the effect of PTZ in vitro while the gamma isomer increased the effects of PTZ. These effects correspond to observations made on seizure activity. The results show that the non-seizure-inducing isomers of HCH have biochemical and pharmacological effects in the CNS which differ from those of the insecticidally relevant gamma isomer. The actions of the HCH isomers in the CNS appear to be mediated, at least in part, through GABA-A receptor linked chloride channel sites.
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PMID:CNS biochemical and pharmacological effects of the isomers of hexachlorocyclohexane (lindane) in the mouse. 245 20

Convulsive seizures are a potential side effect of antidepressant drug treatment and can be produced by all classes of antidepressants. It is also known that some convulsant and anticonvulsant drug actions are mediated by the GABA-receptor chloride-ionophore complex. Drugs acting at this complex appear to induce convulsions by inhibiting chloride conductance through the associated chloride channel. Using the method of GABA-stimulated 36Cl-uptake by rat cerebral cortical vesicles, we show that some antidepressant drugs (imipramine, amitryptyline, and mianserine) can inhibit the GABA-receptor chloride uptake, and that the degree of chloride channel inhibition by these drugs correlates with the frequency of convulsive seizures induced by them.
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PMID:Antidepressants and seizure-interactions at the GABA-receptor chloride-ionophore complex. 245 40

The GABA/benzodiazepine (BZ) receptor chloride channel complex was investigated during repeated episodes of ethanol intoxication and withdrawal in the rat; the intragastric intoxication technique was applied and the severity of intoxication, withdrawal and number of seizures were recorded. The following groups were studied after decapitation during withdrawal 10-16 h after the last ethanol feeding: A) isocalorically fed controls not receiving ethanol; B) isocalorical controls subjected to a single ethanol intoxication period; C) animals subjected to 15 intoxication-withdrawal episodes (spontaneous seizures); D) same as C, but without developing seizures. A radio receptor technique was applied in the characterization of the receptor complex comprising specific binding to the BZ-receptor, the chloride channel and the GABA receptor by 3H-diazepam, 35S-TBPS and 3H-muscimol, respectively. The allosteric couplings among the components of the receptor complex were studied by 3H-diazepam and 35S-TBPS binding enhancement tests involving muscimol, ZK 93423 and DMCM. Cortex, hippocampus and cerebellum were the brain regions studied. Except for a reduced specific binding of 3H-diazepam in cerebellum, there were no indications of changes in specific binding to any part of the receptor complex. The allosteric coupling of BZ and GABA receptors as well as chloride channel-BZ receptors were unchanged in all groups. It is notable that no changes at all could be related to number of intoxication-withdrawal episodes or to the development of seizures. Thus, the present study gave no indication that the GABA/benzodiazepine receptor chloride channel complex is directly involved in the augmentation of cerebral nervous system excitability (seizures) during repeated episodes of physical ethanol dependence.
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PMID:The GABA/benzodiazepine receptor chloride channel complex during repeated episodes of physical ethanol dependence in the rat. 246 1

The repeated administration of N-methyl-beta-carboline-3-carboxamide (FG 7142) to mice leads to 'chemical kindling', i.e. the development of seizures in response to doses which were initially insufficient to produce convulsive activity. To determine if chemical kindling produced changes in the GABAA receptor/chloride channel complex, we measured the binding of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to the convulsant site of the complex by quantitative autoradiography. As a measure of chloride channel function, we studied muscimol-stimulated uptake of 36Cl- by isolated brain synaptosomes. Kindling decreased the Bmax of [35S]TBPS binding in cortex but not in cerebellum or hippocampus. Kindling did not alter binding affinities in any of these brain regions. Some mice injected with FG 7142 did not kindle despite receiving the same treatment as kindled mice. These 'injected but not kindled' mice did not display decreased receptor binding in any of these brain areas. Muscimol-stimulated 36Cl- uptake into cortical synaptosomes was also diminished by chemical kindling. These findings suggest that a decrease in functioning GABA-regulated chloride channels may be responsible for chemical kindling with FG 7142.
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PMID:Chemical kindling decreases GABA-activated chloride channels of mouse brain. 246 90

Because hypothermia and anorexia were previously found to be more sensitive indices of the effects of lindane than were convulsions, these endpoints were used to quantify the ability of benzodiazepines (BDs) and phenytoin either to ameliorate or exacerbate the toxicity of lindane in the rat. After administration of lindane (40 or 50 mg/kg) in oil per os, toxicity was counteracted by phenytoin and the "central" BD agonists diazepam and clonazepam, but was worsened by Ro 5-4864 a "peripheral" BD agonist. Clonazepam and diazepam were each more effective in counteracting lindane-induced anorexia than in stimulating food intake, presumably because the animals had been fasted and probably even controls ate maximally when food was presented. Diazepam alone (3 injections in 1 day) produced withdrawal-induced decreased food intake the following day. Clonazepam and diazepam alone each transiently decreased colonic temperature, yet effectively blocked the more severe hypothermia produced by lindane. Ro 5-4864 by itself did not produce any measurable effects, yet exacerbated all of the effects, including lethal effects, of lindane. The present findings are compatible with other evidence that lindane and Ro 5-4864 act at the picrotoxinin receptor of the GABAA-activated chloride channel and that systemic administration of agents acting at this site may produce a constellation of effects, including seizures, hypothermia and anorexia.
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PMID:"Central" and "peripheral" benzodiazepines and kinetics of lindane-induced toxicity. 247 Dec 14

Chronic treatment with benzodiazepine receptor agonists increases sensitivity to the convulsant action of FG 7142, an inverse agonist. We investigated whether or not changes in the number and function of GABA-gated chloride channels accompanies this increased sensitivity. Diazepam, 5 mg.kg-1, was administered to mice daily for five days, and mice were then tested with a single injection of FG 7142, 40 mg.kg-1, at several intervals thereafter. At 24 hours after the last diazepam dose, 10 of 15 mice had clonic seizures following FG 7142 and four of the remaining five had myoclonic jerks. At 48 hours, only one of six mice developed a clonic seizure, and none were observed in mice tested at 96 or 144 hours. Muscimol-stimulated chloride flux was reduced in cortical synaptosomes from diazepam-treated mice at 24 hours but not at 48 or 96 hours. However, the binding of [35S]TBPS, a ligand closely associated with the chloride channel, was unchanged at 24 hours. These results suggest that a transient diminution in GABA-gated chloride channel function; unaccompanied by a reduction in channel number, may underlie the sensitization to the convulsant action of FG 7142 observed after withdrawal from chronic diazepam treatment.
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PMID:Diazepam sensitizes mice to FG 7142 and reduces muscimol-stimulated 36Cl- flux. 247 37

Lindane-induced dose- and time-related changes in regional 2-14C-deoxyglucose (2-DG) uptake were examined in 59 discrete rat brain structures using the 2-DG autoradiographic technique. At different times (0.5-144 hr) after administration of a seizure-inducing single dose of lindane (60 mg/kg), 2-DG uptake was significantly increased in 18 cortical and subcortical regions mainly related to the limbic system (e.g., Ammon's horn, dentate gyrus, septal nuclei, nucleus accumbens, olfactory cortex) and extrapyramidal and sensory-motor areas (e.g., cerebellar cortex, red nucleus, medial vestibular nucleus). There was also a significant increase in superior colliculus layer II. In addition, significant decreases occurred in a group of 6 regions (e.g., auditory and motor cortices). Non-convulsing animals treated with the same dose of lindane showed a regional pattern of 2-DG uptake less modified than the convulsant group. A non-convulsant single dose of lindane (30 mg/kg) also modified significantly the 2-DG uptake (0.5-24 hr) in some brain areas. Although the various single doses of lindane tested produced different altered patterns of brain 2-DG uptake, some structures showed a similar trend in their modification (e.g., superior colliculi and accumbens, raphe and red nuclei). Repeated non-convulsant doses of lindane produced defined and long-lasting significant elevations of 2-DG uptake in some subcortical structures (e.g., dorsal cochlear nucleus, dentate gyrus). Considering the treated groups all together, 2-DG uptake increased significantly in 26 of the 59 regions examined but only decreased significantly in 9 of them during the course of lindane effects. This fact can be related to the stimulant action described for this neurotoxic agent. The observed pattern provides a descriptive approach to the functional alterations occurring in vivo during the course of lindane intoxication. These results may be linked to the proposed mechanism of lindane neurotoxicity postulating an initial action on the GABAA receptor-chloride channel sites.
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PMID:Regional changes in brain 2-14C-deoxyglucose uptake induced by convulsant and non-convulsant doses of lindane. 248 96


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