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

Veratridine causes deplorization of excitable cells and produces marked elevation of adenosine 3',5'-monophosphate (cyclic AMP) and guanosine 3',5'-monophosphate (cyclic GMP) levels in incubated slices of mouse cerebral cortex. Phenytoin, carbamazepine, phenobarbital, primidone, phensuximide, methsuximide, alpha-methyl-alpha-phenylsuccinimide, and high concentrations of clonazepam are anticonvulsant drugs that preferentially prevent maximal electroshock seizures (MES) and generalized tonic-clonic convulsions; all these agents inhibit veratridine-induced accumulation of both cyclic AMP and cyclic GMP. In contrast, ethosuximide, trimethadione, valproic acid, and low concentrations of clonazepam are anticonvulsant drugs that act predominantly against Metrazol and absence seizures; these agents are ineffective or inhibit accumulation of only cyclic GMP. The results suggest that inhibition of cyclic AMP and cyclic GMP accumulation in depolarized brain tissue is a molecular neuropharmacological action characteristic of anticonvulsant drugs that have direct effects on cellular membrane function and prevent MES. Anticonvulsant drugs that do not inhibit accumulation of both cyclic AMP and cyclic GMP in depolarized brain tissue preferentially prevent Metrazol and absence seizures and probably exert their effects by altering neurotransmission mechanisms.
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PMID:Inhibitory effects of anticonvulsant drugs on cyclic nucleotide accumulation in brain. 3 36

Local blood flow, ECoG and single cortical neurone activity were recorded simultaneously from single microelectrodes in 17 cats. Seizures were induced by repeated intravenous injections of pentylenetetrazol (PTZ, 10-20 mg/kg) or by local application of 1 M Na-penicillin. Seven to 20 sec after appearance of burst activity in cortical neurones and ECoG, focal flow increased up to 300% of control. The extent of this flow increase was significantly correlated with the change in firing rate of the neurones. With cessation of seizure activity the flow returned to or below control values. Forty to 70 mg/kg PTZ caused status epilepticus with high voltage rhythmic discharges lasting 30 min-2 h. In 3 cats with status, the flow decreased below control despite persisting seizures, indicative of uncoupling between activity and flow. The delayed coupling between activity and flow during drug-induced seizures indicates a metabolic mediator. Uncoupling observed in cases with long lasting seizures may be due to brain oedema following increased permeability of the blood-brain barrier.
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PMID:Coupling between neuronal activity and focal blood flow in experimental seizures. 8 43

Nonspecific cortical, thalamic, mesencephalic, and pontine multiple unit activities (MUA) and changes in EEG and MUS of the sciatic nerve after threshold pentylenetetrazol activation were studied in three groups of animals in which neuronal connections were interrupted at three different levels of the central nervous system: spinal, mesencephalic, and prethalamic. Maximal increments of nonspecific MUA and maximal increments and maximal decrements of sciatic MUA after pentylenetetrazol from each group of lesioned animals were statistically compared with tose observed in intact animals. 1. Pentylenetetrazol threshold for producing cortical tonic-clonic EEG discharges was increased in animals with nesencephaic and prethalamic lesions but was not modified in animals with spinal transection. 2. Cortical MUA maximal increment was significantly decreased in mesencephalic and prethalamic lesioned animals, whereas thalamic MUA maximal increment was significantly decreased in mesencephalic and significantly increased in prethalamic lesioned animals. Pontine MUA maximal increment was significantly increased in spinal, mesencephalic, and prethalamic lesioned animals, and mesencephalic M-A maximal increment was not significantly modified in either prethalamic lesioned or in spinal transected animals. 3. Sciatic MUA maximal increment and maximal decrement were significatly decreased in spinal transected animals, whereas only maximal increment was significantly decreased in mesencephalic and only maximal decrement was significantly decreased in prethalamic lesioned animals. These results based on lesion experiments permit us to infer than under normal cinditions the development of generalized seizures induced by threshold pentylenetetrazol injection is highly dependent upon the neuronal interactions between nonspecific structures at different levels of the central nervous system. The possible nature of these neuronal interactions in the intact animals is discussed.
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PMID:Specific and nonspecific multiple unit activities during the onset of pentylenetetrazol seizures. II. Acute lesions interrupting nonspecific system connections. 18 24

Severe depletion of brain noradrenaline and separately of brain dopamine was induced in rats by intracerebral injection of the selective neurotoxin 6-hydroxydopamine, and the susceptibility of the treated animals to various seizure-inducing manipulations was examined. A significant potentiation of the seizures induced both by Metrazol and by electroconvulsive shock was found in animals depleted of brain noradrenaline, but no alteration was seen after depletion of brain dopamine on either measure. The catecholaminergic drug cocaine also induced seizures, but these were found not to depend on either brain noradrenaline or dopamine as they continued to occur in the virtual absence of either catecholamine. It is concluded that cocaine induces seizures by a non-specific toxic mechanism and that noradrenaline, but not dopamine, is involved in reducing the suceptibility of the central nervous system to the several distinct forms of seizure induction examined.
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PMID:Catecholamines and convulsions. 46 25

The hypothesis that the seizure susceptibility of chronically denervated cortex is due to interruption of recurrent inhibitory pathways was tested by examining the release of 3H-labeled gamma-aminobutyric acid ([3H]GABA) from chronic slabs and normal cortex of cats. Seizure activity was maintained throughout the test periods in both normal and chronically isolated cortex. When methacholine was used to evoke seizure activity, [3H]GABA release was depressed in both normal and epileptic cortex, suggesting that the mechanism of seizure genesis by cholinomimetics involves suppression of inhibitory neuron activity. Pentylenetetrazol-induced seizures evoked a small, equal increase in [3H]GABA efflux from epileptic and normal cortex. Continuous electrical stimulation evoked a large, and again equal increase in [3H]GABA release. Preseizure efflux of [3H]GABA was the same from chronic slabs and normal cortex in all experiments. Since the interruption of recurrent inhibitory pathways by chronic denervation would result in a decreased resting and seizure-evoked release of [3H]GABA, results obtained do not support the above-mentioned hypothesis.
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PMID:Release of exogenous gamma-[3H]aminobutyric acid during seizure activity in chronically denervated and normal cat cortex. 49 93

A series of newly synthesized N-phenyl-substituted derivatives of succinimide were screened for anticonvulsant activity. Addition of a sulfonamide group in the p-position was of great consequence for the anticonvulsant effect. Substitution of a halogen in the m- or o-position improved activity against electroshock induced seizures. Pentylenetetrazole convulsions could only be prevented by few of these substances in smaller than 200 mg/kg oral doses. Activity could be further enhanced by adding more aliphatic or aromatic groups to the succinimide ring. The lethal doses of most of the active succinimides were higher than 5000 mg/kg p.o. With sublethal doses mice sometimes become drowsy and had myoclonic seizures and/or diarrhoea. At therapeutic dose levels kinetic disturbances, potentiation of pentobarbitone hypnosis or analgesia were rarely observed.
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PMID:[Anticovulsant activity of N-(p-sulfamoyl-phenyl)-succinimide derivatives (author's transl)]. 57 5

Thiabendazole was found to be specifically effective against maximal electroshock seizures in albino rats. It produced a significant dose-dependent decrease in the duration of the tonic extensor phase of hind legs. The ED50 was similar for oral or s.c. administration. PTZ-induced convulsions were unaffected by lower doses but aggravated by the higher dose studied.
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PMID:Anticonvulsant action of thiabendazole. 59 Mar 46

The mechanism of action of hypoxia on cerebral blood vessels and its role in the regulation of the cerebral circulation were investigated in anesthetized cats. Arterial hypoxia produced marked cerebral arteriolar vasodilation, which was partially reversed by perfusing the space under the cranial window with artificial cerebrospinal fluid (CSF) containing 6-94% oxygen. More marked increase in the local supply of oxygen, via perfusion of the space under the cranial window with fluorocarbon FC-80 equilibrated with 100% oxygen, completely eliminated the vasodilation induced by arterial hypoxia. Fluorocarbon equilibrated with 100% N2 had no effect on the vasodilation. The vasodilation associated with hypotension was completely reversed by perfusion with fluorocarbon equilibrated with 100% oxygen and was unaffected by perfusion with fluorocarbon or CSF equilibrated with gas not containing oxygen. The vasodilation associated with Metrazole-induced seizures was partially reversed by perfusion with fluorocarbon containing oxygen. The results show that hypoxia dilated cerebral blood vessels entirely via a local mechanism, that hypoxia is the dominant mechanism involved in the vasodilation associated with hypotension, and that it is, at least partially, responsible for the vasodilation associated with seizures.
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PMID:Role of tissue hypoxia in local regulation of cerebral microcirculation. 64 24

Fifteen children, aged 0.3 to 10.5 years (mean 3.8 years) after repair of coarctation of the aorta, underwent cerebral arteriography as part of postoperative catheterization. Four manifested central nervous system symptoms postoperative catheterization. Four manifested central nervous system symptoms postoperatively: Two had persistent headaches, one had exercise-induced hemianopsia and one had major motor seizures. All four had greater blood pressure in the right arm than in the left and evidence of subclavian steal, with retrograde filling of the left vertebral and left subclavian arteries on selective right vertebral arteriography. Ligation of the left vertebral artery in three patients and left subclavian graft arterioplasty in one resulted in disappearance of symptoms. None of the 11 asymptomatic patients manifested cerebrovascular anomalies, and no patient in the series had berry aneurysm. This study suggests that patients with central nervous system symptoms and a disparity of blood pressure in the arms after surgery for coarctation of the aorta should be evaluated carefully to exclude subclavian steal as the cause of the symptoms.
Am J Cardiol 1978 Jul
PMID:Cerebrovascular abnormalities in postoperative coarctation of aorta. Four cases demonstrating left subclavian steal on aortography. 67 42

The (+)-amphetamine (2.5 mg/kg) increase in pentylenetetrazol seizure was abolished by pretreatment with reserpine, alpha-methyltyrosine methyl ester (alpha-MT), FLA-63 or 6-hydroxydopa. All treatments except reserpine antagonized the increase in seizure threshold produced by (-)-amphetamine (4 mg/kg). Only reserpine +alpha-MT antagonized the decrease in seizure threshold produced by (+)-amphetamine (15 mg/kg). These results indicate that amphetamine alterations in PTZ seizure susceptibility are mediated indirectly via the release of newly synthetized and/or granular stores of catecholamines.
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PMID:Catecholaminergic involvement in the effects of amphetamine isomers on seizure susceptibility. 83 77


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