Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027066 (myoclonus)
 4,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inherited congenital myoclonus (ICM) of Poll Hereford cattle is a neurological disease in which there are severe alterations in spinal cord glycine-mediated neurotransmission. There is a specific and marked decrease, or defect, in glycine receptors and a significant increase in neuronal (synaptosomal) glycine uptake. Here we have examined the characteristics of the cerebral gamma-aminobutyric acid (GABA) receptor complex, and demonstrate that the malfunction of the spinal cord inhibitory system is accompanied by a change in the major inhibitory system in the cerebral cortex. In synaptic membrane preparations from ICM calves, both high-and low-affinity binding sites for the GABA agonist [3H]muscimol were found (KD = 9.3 +/- 1.5 and 227 +/- 41 nM, respectively), whereas only the high-affinity site was detectable in controls (KD = 14.0 +/- 3.1 nM). The density and affinity of benzodiazepine agonist binding sites labelled by [3H]diazepam were unchanged, but there was an increase in GABA-stimulated benzodiazepine binding. The affinity for t-[3H]butylbicyclo-o-benzoate, a ligand that binds to the GABA-activated chloride channel, was significantly increased in ICM brain membranes (KD = 148 +/- 14 nM) compared with controls (KD = 245 +/- 33 nM). Muscimol-stimulated 36Cl- uptake was 12% greater in microsacs prepared from ICM calf cerebral cortex, and the uptake was more sensitive to block by the GABA antagonist picrotoxin. The results show that the characteristics of the GABA receptor complex in ICM calf cortex differ from those in cortex from unaffected calves, a difference that is particularly apparent for the low-affinity, physiologically relevant GABA receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Increased gamma-aminobutyric acid receptor function in the cerebral cortex of myoclonic calves with an hereditary deficit in glycine/strychnine receptors. 216 65

It has been hypothesized that the Long-Sleep and Short-Sleep mouse lines were bidirectionally selected for high and low brain excitability, and further, that these differences are mediated by the benzodiazepine/gamma-aminobutyric acid (GABA) receptor-chloride channel complex. Hence, mice from both lines were administered seven convulsants (bicuculline, pentylenetetrazol, 3-carbomethoxy-beta-carboline, picrotoxin, caffeine, flurothyl and strychnine) and myoclonic and clonic seizure latencies recorded. Supporting the original hypothesis, the results show that the two lines were differentiated by all of the convulsants and that in response to the drugs, three distinct convulsive patterns were found. Nevertheless, a simple genetic model accounting for these results was not evident. To further clarify these susceptibility patterns, a convulsant representing each of these patterns (bicuculline, pentylenetetrazol or caffeine) was administered in conjunction with the anticonvulsant-barbiturate phenobarbital or the benzodiazepine antagonist Ro 15-1788. Irrespective of the convulsant given, phenobarbital attenuated both myoclonus and clonus subsequent to all convulsants, while Ro 15-1788 had a more discrete anticonvulsant profile.
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PMID:Patterns of convulsive susceptibility in the long-sleep and short-sleep selected mouse lines. 250 42

Sodium valproate, nipecotic acid, diaminobutyric acid (DABA) and beta-alanine are drugs which enhance transmission mediated by gamma-aminobutyric acid (GABA) by a variety of mechanisms. They were used to study the role of GABA in the high pressure neurological syndrome (HPNS) in the rat. Sodium valproate, nipecotic acid and DABA reduced the increase in slow waves seen in the electroencephalogram (EEG) of control rats at pressures above 10-20 ATA; however, only sodium valproate had a beneficial effect on the behavioural signs of the high pressure neurological syndrome (tremor, myoclonus and convulsions). Sodium valproate is also thought to decrease neurotransmission produced by excitatory amino acids; thus, these results suggest that GABA is not one of the major neurotransmitters involved in all aspects of the high pressure neurological syndrome and that changes in excitatory neurotransmission may affect the behavioural signs.
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PMID:Gamma-aminobutyric acid and the high pressure neurological syndrome. 309 Apr 69

Experiments are described in which the gamma-aminobutyric acid (GABA) antagonist bicuculline was injected into the lentiform complex of conscious monkeys. Injections into either the lateral segment of the globus pallidus, or the medial part of the putamen, gave rise to chorea of the contralateral limbs and/or orofacial region. Control injections of vehicle alone were without effect. Injections of bicuculline into the lateral part of the putamen gave rise to contralateral myoclonus. The chorea produced by lateral pallidal or medial putaminal injections was virtually indistinguishable from the dyskinesia (chorea/ballism) which has been shown, in previous studies, to be induced by injection of GABA antagonists into the subthalamic nucleus. It is proposed that the primary site of action of the GABA antagonist in producing chorea, in the present studies, was the lateral segment of the globus pallidus. The mode of action is suggested to be interruption of GABAergic transmission from the striatum to the lateral pallidal segment. Since this also occurs in Huntington's disease, it is proposed that experimental chorea induced by this method in the monkey may be a useful model of the dyskinesia seen in Huntington's disease in man. Loss of influence of inhibitory striatopallidal fibres would lead to abnormally increased activity of lateral pallidal neurons. These in turn project to the subthalamic nucleus, upon which they have an inhibitory action. Dyskinesia is thus produced by physiological inhibition of the subthalamic nucleus, whose destruction, both in man and the monkey, is known to produce ballism. It is proposed that ballism and chorea share common neural mechanisms, both involving the loss of influence of the subthalamic nucleus on the medial segment of the globus pallidus.
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PMID:Chorea and myoclonus in the monkey induced by gamma-aminobutyric acid antagonism in the lentiform complex. The site of drug action and a hypothesis for the neural mechanisms of chorea. 317 91

The central effects of carboxyethyl-gamma-aminobutyric acid (CEGABA) have been studied both in rabbits and in the guinea pig myoclonus model. This drug caused EEG synchronization and behavioural sedation both after intravenous (i.v.) and intracerebroventricular (i.c.v.) administration in a dose-dependent manner, in rabbits. CEGABA showed a protective action against myoclonus induced by means of L-5-HTP in young guinea pigs. These data substantiate the hypothesis that CEGABA is a drug active on the central nervous system and probably exerts its action by strengthening cortical inhibition and/or directly acting on lower brainstem.
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PMID:Experimental study on central effects of carboxyethyl-gamma-aminobutyric acid (CEGABA). 326 35

Bicuculline methiodide (0.5-3 nmol) and picrotoxin (0.5-4 nmol) were injected uni- or bilaterally into the rat amygdala and the resulting behavioural, electroencephalographic and morphological alterations were studied. In rats treated unilaterally with lowest doses of either bicuculline or picrotoxin (0.5 and 1 nmol) increase in the locomotor activity, occasional myoclonus of the hindlimbs and wet dog shakes were observed. At doses of 2-3 nmol, both gamma-aminobutyrate antagonists produced a sequence of repetitively occurring behavioural alterations including limbic gustatory automatisms, tremor and myoclonus of the forelimbs, head nodding and rearing, that developed over 15-30 min and built up progressively into the recurrent motor limbic seizures lasting for 1-6 h. In animals injected bilaterally with either bicuculline (0.5-3 nmol) or picrotoxin (0.5-3 nmol) motor limbic seizures rapidly developed into the status epilepticus lasting for several hours. Bicuculline and picrotoxin produced both ictal and interictal epileptiform activity in the electroencephalogram. A spectrum of electroencephalographic changes consisted of high voltage fast activity, slow and fast voltage spiking, paraoxysmal bursts and periods of postictal depression. The earliest electrographic alterations appeared in the amygdala and then rapidly spread to cortical areas. Electrographic seizures started 1-10 min after unilateral injections of large doses of bicuculline and pictrotoxin (2-4 nmol). Ictal periods lasted for 1-2 min, recurred every 5-10 min and were followed by periods of depression of the electrographic activity. Bilateral injections of large doses of both gamma-aminobutyrate antagonists (2-3 nmol) resulted in the status epilepticus. Morphological examination of frontal forebrain sections with light microscopy revealed a widespread damage to the amygdala, olfactory cortex, substantia nigra, thalamus, hippocampus and neocortex. Pretreatment of animals with diazepam prevented the build-up of convulsive activity and brain damage produced by bicuculline or picrotoxin. Muscimol retarded the appearance and shortened the duration of convulsive activity, but did not alter the sequence and intensity of seizures. The results indicate that gamma-aminobutyrate antagonists, bicuculline and picrotoxin when directly applied to the amygdala can elicit in rats motor limbic seizures, epileptic changes in the electroencephalogram indicative of repetitive limbic seizures, and status epilepticus accompanied by seizure-related brain damage.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Injections of picrotoxin and bicuculline into the amygdaloid complex of the rat: an electroencephalographic, behavioural and morphological analysis. 397 84

1 The effect of catechol on uptake and K+-stimulated release of gamma-aminobutyric acid (GABA), D-aspartate, noradrenaline and acetylcholine has been studied in slices of cerebral cortex and thalamus. 2 Low concentrations of catechol did not influence the uptake of any of the neurotransmitters in either brain area. 3 Noradrenaline release was unaffected by catechol. 4 Acetylcholine release from both cortical and thalamic slices was inhibited by high concentrations of catechol. This phenomenon is unlikely to be related to catechol-induced convulsions. 5 Catechol (100 microM) inhibited GABA release from cortical slices by 28%. However, at a concentration of 10 microM catechol enhanced the release of D-aspartate from thalamic slices by over 100%. 6 Potentiated release of excitatory amino acid transmitters may contribute to the enhanced excitability of thalamic cells which occurs during sensory myoclonus induced by low doses of catechol.
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PMID:The effect of the convulsant agent, catechol, on neurotransmitter uptake and release in rat brain slices. 611 45

Progressive myoclonus epilepsy without Lafora's bodies (PME) is a rare inherited disease found predominantly in Finland, where the incidence is one case per 20,000 to 30,000 children. This fatal disease is characterized by normal early development, progressive stimulus-sensitive myoclonus, ataxia, dysarthria, occasional grand mal seizures, and loss of cerebellar Purkinje cells. Concentrations of gamma-aminobutyric acid in the CSF averaged 89 +/- 10 pmole/mL (mean +/- SE) in eight patients with PME, compared with 135 +/- 18 pmole/mL in ten control patients. The concentrations of adenosine (16 pmole/mL v 17 pmole/mL), inosine (560 pmole/mL v 570 pmole/mL) and hypoxanthine (6.2 nmole/mL v 6.1 nmole/mL) were the same in patients with PME and in controls.
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PMID:Concentrations of gamma-aminobutyric acid and adenosine in the CSF in progressive myoclonus epilepsy without Lafora's bodies. 641 68

We studied Sprague-Dawley rats with spike activity and myoclonus after intraperitoneal injections of penicillin. Twenty minutes after penicillin injection, one group received a random crossover treatment by intraperitoneal GABA (gamma-aminobutyric acid) or liposome-entrapped GABA (LEG) or phosphatidylserine alone. The other group received GABA, LEG, or phosphatidylserine followed 15 minutes later by the injection of penicillin. LEG decreased or prevented the epileptic activity, whereas no significant changes were seen with either GABA or phosphatidylserine given alone. LEG may enhance penetration of GABA across the blood-brain barrier because of the carrier action of the liposomes.
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PMID:Liposome-entrapped GABA modifies behavioral and electrographic changes of penicillin-induced epileptic activity. 689 Jan 56

We review the neurochemical and behavioral profile of the selective gamma-aminobutyric acid (GABA) uptake inhibitor, (R)-N-(4,4-di-(3-methylthien-2-yl)but-3-enyl) nipecotic acid hydrochloride [tiagabine (TGB), previously termed NNC 05-0328, NO 05-0328, and NO-328], which is currently in phase III clinical trials for epilepsy. TGB is a potent, and specific GABA uptake inhibitor. TGB lacks significant affinity for other neurotransmitter receptor binding sites and/or uptake sites. In electrophysiological experiments in hippocampal slices in culture, TGB prolonged the inhibitory postsynaptic potentials (IPSP) and inhibitory postsynaptic currents (IPSC) in the CA1 and CA3 produced by the addition of exogenous GABA. In vivo microdialysis shows that TGB also increases extracellular GABA overflow in a dose-dependent manner. Together these biochemical data suggest that the in vitro and in vivo mechanism of action of TGB is to inhibit GABA uptake specifically, resulting in an increase in GABAergic mediated inhibition in the brain. TGB is a potent anticonvulsant agent against methyl-6,7-dimethyoxy-4-ethyl-B-carboline-3-carboxylate (DMCM)-induced clonic convulsions (mice), subcutaneous pentylenetetrazol (PTZ)-induced tonic convulsions (mice and rats), sound-induced convulsions in DBA/2 mice and genetically epilepsy-prone rats (GEPR), and electrically induced convulsions in kindled rats. TGB is partially efficacious, against subcutaneous PTZ-induced clonic convulsions, and photically induced myoclonus in Papio papio. TGB is weakly efficacious in the intravenous PTZ seizure threshold test and the maximal electroshock seizure (MES) test and produces only partial protection against bicuculline (BIC)-induced convulsions in rats. The overall biochemical and anticonvulsant profile of TGB suggests potential utility in the treatment of chronic seizure disorders such as generalized clonic-tonic epilepsy (GTCS), photomyoclonic seizures, myoclonic petit mal epilepsy, and complex partial epilepsy.
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PMID:A review of the preclinical pharmacology of tiagabine: a potent and selective anticonvulsant GABA uptake inhibitor. 755 76


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