43977

The modulation by chlormethiazole of the GABAA-receptor complex in rat brain.

Article date: 1989/9/1

PubMed ID: 43977

Journal name: British journal of pharmacology (ISSN: 0007-1188)

ABSTRACT

1. The interactions of chlormethiazole with gamma-aminobutyric acid (GABA) synthesis and release, and with ligand binding to sites associated with the GABAA-receptor complex and the GABAB-receptor have been studied in the rat. The GABAA-receptor was studied using [3H]-muscimol, [3H]-flunitrazepam was used to label the benzodiazepine modulatory site, and [35S]-butyl-bicyclophosphorothionate ([35S]-TBPS) to label the chloride channel. 2. Chlormethiazole had no effect on GABA synthesis in the cortex, hippocampus and striatum or on GABA release from cortical slices in vitro. Chlormethiazole did not displace [3H]-baclofen binding to the GABAB-receptor. 3. Chlormethiazole (IC50 = 140 microM) and pentobarbitone (IC50 = 95 microM) both inhibited [35S]-TBPS binding by increasing the rate of [35S]-TBPS dissociation. In addition, chlormethiazole caused an apparent decrease in the affinity of [35S]-TBPS binding. 4. Chlormethiazole enhanced the binding of [3H]-muscimol but had no effect on [3H]-flunitrazepam binding. In contrast, the sedative barbiturate pentobarbitone enhanced both [3H]-muscimol and [3H]-flunitrazepam binding. 5. It is concluded that the sedative and anticonvulsant effects of chlormethiazole are probably mediated through an action at the GABAA-receptor. However, chlormethiazole does not interact with the GABAA-receptor complex in an identical manner to the sedative barbiturate pentobarbitone.

Author List: Cross A J, Stirling J M, Robinson T N, Bowen D M, Francis P T, Green A R

Publication Types: Journal Article

Substances mentioned in the article: Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Receptors, GABA-A; Chlormethiazole; Picrotoxin; Muscimol; gamma-Aminobutyric Acid; Flunitrazepam; tert-butylbicyclophosphorothionate; Baclofen;

Mesh terms: Animals; Baclofen/pharmacology; Brain/drug effects; Bridged Bicyclo Compounds/pharmacology; Bridged Bicyclo Compounds, Heterocyclic; Cerebral Cortex/drug effects; Chlormethiazole/pharmacology; Flunitrazepam/pharmacology; In Vitro Techniques; Male; Muscimol/pharmacology; Picrotoxin/pharmacology; Rats; Receptors, GABA-A/drug effects; gamma-Aminobutyric Acid/biosynthesis;

Citations: - Effect of latent iron deficiency on gaba and glutamate neuroreceptors in rat brain.

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