Article date: 1988/12/13
PubMed ID: 2855312
Journal name: European journal of pharmacology (ISSN: 0014-2999)
The laminar distribution of gamma-aminobutyric acid (GABA) in the superior colliculus of the guinea pig was analyzed. The superficial gray layer, especially the upper half, was found to contain the highest amount, 37.4 +/- 1.1 mmol/kg dry. To investigate the role of GABA in the superficial gray layer, the effect of GABA on neurotransmission in the superficial gray layer was studied in superior colliculus slices in a perfusion system. Bath-applied GABA, 100 microM-1 mM, enhanced the amplitude of the postsynaptic field potential (PSP) in the superficial gray layer dose dependently and at concentrations above 1 mM it depressed the PSP dose dependently. A similar response pattern was obtained with muscimol (0.1-10 microM, enhancement; greater than 10 microM, depression). However, (-)-baclofen only inhibited the PSP dose dependently (0.1-1 microM). The excitatory effect of GABA was enhanced at concentrations of nipecotic acid less than 0.5 mM. Bicuculline 1 microM shifted the dose-response curve of GABA to the right and the excitatory effect was also enhanced. These results indicate that GABA has a dual action on neurotransmission in the superficial gray layer: an excitatory effect, possibly mediated by GABAA receptors and an inhibitory effect mediated by both GABAA and GABAB receptors.
Author List: Arakawa T, Okada Y
Publication Types: Journal Article
Substances mentioned in the article: GABA Antagonists; Nipecotic Acids; Receptors, GABA-A; nipecotic acid; Muscimol; gamma-Aminobutyric Acid; Proline; homoproline; Baclofen; bicuculline methochloride; Bicuculline;
Mesh terms: Animals; Baclofen/pharmacology; Bicuculline/analogs & derivatives; Dose-Response Relationship, Drug; Evoked Potentials/drug effects; GABA Antagonists; Guinea Pigs; In Vitro Techniques; Muscimol/pharmacology; Nipecotic Acids/pharmacology; Perfusion; Proline/analogs & derivatives; Receptors, GABA-A/drug effects; Superior Colliculi/drug effects; Synaptic Membranes/metabolism; Synaptic Transmission/drug effects; gamma-Aminobutyric Acid/pharmacology;