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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties of [3H]clonazepam, [3H]diazepam and [3H]zolpidem (N,N,6[trimethyl-2-(4-methyl-phenyl)imidazo[1,2-a]pyridine-3-acetamide hemitratrate) binding to synaptic membranes of cerebellum, cortex, olfactory bulb, striatum and spinal cord of rat were compared to the binding properties of [3H]flunitrazepam, [3H]flumazenil and [3H]midazolam. In the cerebellar, cortical and olfactory bulb membranes, the density of high-affinity binding sites of all these tritiated benzodiazepine (BZ) ligands is almost identical. In contrast, in the striatum, the density of [3H]clonazepam and [3H]zolpidem binding sites is approximately 60 and 30%, respectively, of the density of [3H]diazepam, [3H]flunitrazepam or [3H]flumazenil sites. In spinal cord membranes, the number of high-affinity binding sites of [3H]clonazepam and [3H]zolpidem is less than 20% of the number of binding sites for [3H]diazepam, [3H]flunitrazepam, [3H]flumazenil and [3H]midazolam. Moreover, the displacement of [3H]flunitrazepam from spinal cord membranes by clonazepam and zolpidem was characterized by high IC50 values and Hill slopes significantly less than 1. Because [3H]BZ ligand binding in the spinal cord is enhanced by gamma-aminobutyric acid (GABA), these data suggest that different regions of the rat central nervous system may contain different GABA-BZ receptor subtypes. The different pharmacological properties of clonazepam, diazepam and zolpidem (i.e., regarding their ability to enhance bicuculline seizure threshold, to decrease locomotor activity, to induce ataxia or to elicit anticonflict action) further support the concept that in the rat central nervous system preferential occupancy of heterogeneous GABAA receptors by these drugs can be related to their effects on behavior.
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PMID:gamma-Aminobutyric acidA receptor heterogeneity in rat central nervous system: studies with clonazepam and other benzodiazepine ligands. 184 29

Exposure to monomethylhydrazine (MMH), a common rocket propellant, can cause dose-related central nervous system (CNS) disturbances ranging from tremors to tonic-clonic convulsions to death. MMH inhibits gamma-aminobutyric acid (GABA) synthesis in the CNS. Diazepam (BZ) acts at the GABA receptor site, and it is also here that ivermectin (AVM) is pharmacologically active. Mice were injected with 30 mg/kg MMH. Groups of 12 mice each were then given varying doses of AVM (5, 10 and 15 mg/kg), or AVM + BZ combinations (5 mg/kg AVM with 5 mg/kg BZ, 10 mg/kg AVM with 5 mg/kg BZ). Time to first convulsion and time to death were recorded over the next 7 h and all groups were monitored over the next 7 days. Times to convulsion were not altered with AVM alone, but death was significantly prevented with AVM dosages. A treatment of 10 mg/kg AVM with 5 mg/kg BZ resulted in no seizures or deaths.
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PMID:Modulation of monomethylhydrazine-induced seizures by ivermectin. 185 61

The calcium-dependent gamma-aminobutyric acid (GABA) and glutamate release from rat hippocampal CA1 slices, evoked by a 1-min depolarization with 50 mM K+, was investigated in different stages of kindling epileptogenesis. Kindling was induced by tetanic stimulation of the Schaffer collateral/commissural pathway. In agreement with our previous results, we found a significantly increased calcium-dependent GABA release compared to that of implanted controls, in a group of fully kindled animals 1 day after the last seizure and also 25-36 days after the last seizure. In addition, we found that the increase in GABA release was associated with late phases of kindling epileptogenesis since no significant alterations were found in partly kindled animals that had received only 6 kindling stimulations while a significant increase was apparent in animals that had received 14 tetanic stimuli. When the release protocol was carried out in the presence of SK&F 89776-A, a blocker of the GABA uptake carrier, an additional amount of GABA was found after depolarization. This additional amount of GABA, reflecting the amount of GABA taken up under conditions without blocker, was in kindled animals not different from controls which demonstrates that a reduced GABA uptake does not account for the observed enhanced release in kindled animals. The calcium-dependent release of glutamate evoked by 1 min of high potassium depolarization was not significantly changed in the kindled groups. Only after prolonged depolarization during 4 subsequent minutes a significant increase in animals of the fully kindled group and at long-term after kindling was observed. The threshold K+ concentration for eliciting a calcium-dependent release of GABA and glutamate, was not changed in the kindled animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Development of changes in endogenous GABA release during kindling epileptogenesis in rat hippocampus. 186 54

Anticonvulsant activity, degradation into gamma-aminobutyric acid (GABA), and concentration in brain of 1-dodecanoyl-2-pyrrolidinone (I), a lipophilic derivative of a lactam of GABA, were compared with those of N-dodecanoyl GABA (II) and 1-dodecyl-2-pyrrolidinone (III) to get information about their pharmacological mechanisms. Compounds I and II degraded into GABA in mouse liver homogenate, gradually into GABA in brain homogenate and more slowly in plasma. Compound III had no degradation in the biological media. The derivatives administered intraperitoneally had dose-dependent anticonvulsant activity on picrotoxin-induced seizure in mice. Their anticonvulsant activities were changed by the time intervals between pretreatment of derivatives and administration of picrotoxin. Compounds II and III showed anticonvulsant activity on pentylenetetrazole-induced seizure and a prolonged sleeping time induced by sodium pentobarbital in mice. However, these three derivatives never significantly increased the GABA level in mouse brain after intraperitoneal administration compared to the endogenous GABA level. They were detected as intact derivatives in the brain. In the previous report, we demonstrated the anticonvulsant activity of sodium dodecanoate. These results suggested that the dodecyl chain of derivatives may be important for their anticonvulsant activities and I does not act as GABA via prodrug.
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PMID:Comparative studies on the anticonvulsant activity of lipophilic derivatives of gamma-aminobutyric acid and 2-pyrrolidinone in mice. 186 Dec 36

Domoic acid, in increasing doses (10-300 pmol), was microinjected into the hippocampal CA3 region of rats. All rats consistently exhibited generalized bilateral electrical seizure discharge activity at 100 pmol of domoic acid. Seizure latency varied inversely with the dose of domoic acid in the range tested. Local hippocampal administration of gamma-aminobutyric acid (GABA) resulted in neuronal recovery from domoic acid-induced seizures. The seizure activity of domoic acid might be the result of decreased GABAergic inhibition.
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PMID:Domoic acid induced seizure activity in rats. 188 31

Withdrawal seizure-prone (WSP) mice were genetically selected to express severe handling-induced convulsions (HIC) upon cessation of chronic ethanol vapor inhalation. The HIC is a sensitive measure of CNS excitability, and the current paper compares the effects of eleven convulsant drugs on the HIC in WSP and WSR (withdrawal seizure-resistant) mice, the latter selected for minimal alcohol withdrawal HIC. If WSP and WSR mice were differentially sensitive to a subset of the tested drugs, a common mechanism of action for that subset would imply that genes influencing that mechanism were important in determining ethanol withdrawal severity. All drugs significantly enhanced HIC in WSP mice. The magnitude of enhancement was small for N-methyl-D-aspartate (NMDA), kainic acid, BAY K 8644, Ro 15-4513, and strychnine; greater enhancement in WSP mice was seen after nicotine, and the direct and indirect gamma-aminobutyric acid (GABA) antagonists bicuculline, 3-mercaptopropionic acid, picrotoxin, t-butylcyclophosphorothionate (TBPS), and pentylenetetrazol. Only two drugs, picrotoxin and pentylenetetrazol, had a marked effect on WSR mice: maximal effect of these drugs was equivalent in WSP and WSR mice. However, picrotoxin and pentylenetetrazol were more potent in WSP than in WSR mice. Three other GABA antagonists, bicuculline, 3-mercaptopropionic acid, and TBPS, had a very small effect in WSR mice: these drugs also seemed to be more potent in WSP than in WSR mice. For all other tested drugs, maximal effect in WSP mice was much greater in WSP than in WSR mice.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of convulsants on handling-induced convulsions in mice selected for ethanol withdrawal severity. 188 87

Five patients had apparently drug-induced seizures while simultaneously receiving theophylline and either imipenem (three patients), ciprofloxacin (one patient), or ciprofloxacin and metronidazole (one patient). Seizures ceased upon reduction in dosage or discontinuation of the suspected offending agents. Imaging studies failed to reveal new structural lesions in the central nervous system in any patient, and only one had a history of neurologic disease. Although the exact mechanism for seizure induction cannot be determined from these cases, potential drug interactions exist, because theophylline, imipenem, and ciprofloxacin are all believed to increase excitation of the central nervous system by inhibition of gamma-aminobutyric acid binding to receptors. In addition, ciprofloxacin decreases the clearance of theophylline from the body, predisposing the patient to elevated theophylline levels. Physicians prescribing theophylline with imipenem, ciprofloxacin, or metronidazole should carefully monitor patients for indications for drug therapy, drug dosage, organ impairment affecting drug metabolism, and signs of toxicity. Seizures may accompany oral theophylline therapy, even at "therapeutic" serum theophylline concentrations.
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PMID:Seizures in patients simultaneously receiving theophylline and imipenem or ciprofloxacin or metronidazole. 190 67

Gabapentin exerts anticonvulsant effects in different animal models of seizure states and in epileptic patients with different seizure types, but the mechanism of action of these effects is unknown. In the present study, the gamma-aminobutyric acid (GABA) accumulation induced by aminooxyacetic acid (AOAA) was used as a method to study the effects of gabapentin on regional turnover of GABA in the rat brain. Gabapentin was administered at a dose of 23 mg/kg i.p. (the ED95 against tonic electroconvulsions in rats) 1, 2 and 8 h prior to injection of AOAA, 100 mg/kg, i.p. Gabapentin significantly increased the AOAA-induced GABA accumulation in most of the 12 brain regions examined, but the time course of the increases in GABA accumulation differed from region to region. Regions in which the time course of the increase in GABA accumulation was similar to the anticonvulsant time course of gabapentin included substantia nigra, amygdala and thalamus. The data suggest that an effect of gabapentin on GABA synthesis might be involved in its mechanism of anticonvulsant action.
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PMID:Gabapentin increases aminooxyacetic acid-induced GABA accumulation in several regions of rat brain. 194 36

The substantia nigra (SN) is thought to be involved in the regulation of seizure activity and there is evidence that the nigra might be a site of anticonvulsant drug action, especially in the case of drugs that act by potentiating gamma-aminobutyric acid (GABA)-mediated neurotransmission. The current studies monitored the anticonvulsant effect of four major antiepileptic drugs, i.e. valproic acid, carbamazepine, phenobarbital and diazepam, in fully kindled rats before and after bilateral destruction of the SN. Rats were kindled by stimulation of either the basolateral amygdala or the piriform cortex. The SN was lesioned bilaterally by microinjection of ibotenic acid, and only animals with near-complete, selective destruction of the SN were used for final evaluation of the anticonvulsant drug experiments. The behavioural characteristics and the duration of fully kindled seizures were not altered by bilateral destruction of the SN. Phenobarbital, diazepam and valproate significantly reduced kindled seizures severity and duration before and after the SN lesions. Carbamazepine was the only drug to show a marked decrease in its anticonvulsant effects after SN lesion. Since benzodiazepines, valproate and phenobarbital are though to enhance GABAergic transmission, the lack of effect of SN lesions on the anticonvulsant effects of these drugs argues against the suggestion that the SN is the anatomical site responsible for exerting anticonvulsant effects in response to drug-induced augmentation of GABA transmission.
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PMID:Effect of selective bilateral destruction of the substantia nigra on antiepileptic drug actions in kindled rats. 196 44

Anticonvulsant tests in mice revealed specific, potent actions of remacemide for protection of mice against maximal electroshock seizures (MES). Comparisons of oral efficacy to reference compounds yielded the following ED50 values (expressed as mg/kg): remacemide = 33, phenytoin = 11, phenobarbital = 20, carbamazepine = 13 and valproate = 631. The duration for protection by remacemide was longer than carbamazepine or valproate, but shorter than phenytoin or phenobarbital. In neural impairment tests (inverted screen or rotorod) to determine the oral toxic dose 50 (TD50) the following therapeutic indices (TD50/ED50) were obtained: (1) inverted screen--remacemide = 17.6, phenytoin = 57.4, phenobarbital = 5.1, carbamazepine = 10.2, and valproate = greater than 3; and (2) rotorod--remacemide = 5.6, phenytoin = 9.6, phenobarbital 4.8, and valproate = 1.9. Remacemide was devoid of sedative actions and possessed a favorable 28.1 margin of safety value (median estimated lethal dose/ED50 for MES). An intermediate potency against either audiogenic- or N-methyl-D-aspartate-induced seizures was exhibited by remacemide. Tolerance to MES was not apparent after 5 days of oral daily dosing of remacemide. Remacemide was inactive in vitro against gamma-aminobutyrate or benzodiazepine receptors and adenosine uptake mechanisms. Therapeutic utility for generalized tonic/clonic seizures is predicted for remacemide.
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PMID:Preclinical profile of remacemide: a novel anticonvulsant effective against maximal electroshock seizures in mice. 196 6


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