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)

Muscimol, 0.25-1.0 mg/kg, i.v., was administered acutely to 4 adolescent baboons, Papio papio, that show photically induced epilepsy. On the EEG, slowing of background rhythms was associated with the appearance of spikes, polyspikes, and recurring symmetrical spike-wave complexes. These changes were maximal 0.5-2 hr after muscimol injection. Regular testing with intermittent light stimulation showed either no change from control responses or a more severe epileptiform EEG 0.1-3 hr after muscimol. Photically induced myoclonus was not modified by muscimol. Despite its GABA-abonist properties, muscimol is not an effective anticonvulsant.
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PMID:Electroencephalographic and behavioral effects of a GABA agonist (muscimol) on photosensitive epilepsy in the baboon, papio papio. 11 8

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

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