Article date: 1989/3/7
PubMed ID: 2540998
Journal name: European journal of pharmacology (ISSN: 0014-2999)
Rat cerebral cortex synaptosomes prelabeled with [3H]gamma-aminobutyric acid [( 3H]GABA) were exposed in superfusion to various concentrations of KCl (9-50 mM). The evoked release of [3H]GABA reached a plateau at about 35 mM KCl. The K+-induced release was Ca2+-dependent, particularly at the lowest K+ concentrations. The GABAB agonist (-)-baclofen concentration dependently inhibited the release of [3H]GABA evoked by K+; this effect decreased with increasing K+ concentration and disappeared at 35 mM KCl. The GABAA agonist muscimol (1-100 microM) was totally ineffective to inhibit the release of [3H]GABA. Veratrine (1-30 microM) induced the release of [3H]GABA and the effect was tetrodotoxin-sensitive. (-)-Baclofen, but not muscimol, decreased the veratrine-induced [3H]GABA release; the GABAB agonist was particularly effective in presence of low concentrations of veratrine (1-3 microM) but the effect disappeared when 30 microM of the alkaloid was used. The inhibitory effect of (-)-baclofen on the release of [3H]GABA evoked by 15 mM KCl was dependent on the concentration of Ca2+: the effect increased as the concentration of Ca2+ was raised, reaching a plateau at 0.6 mM Ca2+. Exogenous GABA, in presence of the GABA uptake blocker SK & F 89976A, inhibited the release of [3H]GABA evoked by K+; this effect was antagonized by phaclofen. The data support the idea that terminal GABA autoreceptors in the rat cerebral cortex are of the GABAB type.
Author List: Bonanno G, Pellegrini G, Asaro D, Fontana G, Raiteri M
Publication Types: Journal Article; Research Support, Non-U.S. Gov't
Substances mentioned in the article: Neuromuscular Depolarizing Agents; Receptors, GABA-A; phaclofen; Muscimol; Potassium Chloride; Veratrine; Baclofen; Calcium;
Mesh terms: Animals; Baclofen/analogs & derivatives; Calcium/metabolism; Cerebral Cortex/metabolism; In Vitro Techniques; Male; Muscimol/pharmacology; Neuromuscular Depolarizing Agents/pharmacology; Potassium Chloride/pharmacology; Rats; Rats, Inbred Strains; Receptors, GABA-A/metabolism; Synaptosomes/metabolism; Veratrine/pharmacology;