Article date: 1990/7/1
PubMed ID: 1976421
Journal name: Brain research bulletin (ISSN: 0361-9230)
The effects of gamma-aminobutyric acid (GABA), muscimol, baclofen and the anxiolytics; diazepam (DZP), flurazepam (FZP) and zopiclone on single-unit neural activities in the suprachiasmatic nucleus (SCN) were investigated using the rat hypothalamic slice preparation. Exposure of the slice to GABA 10(-4) M produced inhibitory responses in 65% of the 49 SCN neurons examined. The threshold concentration of GABA ranged from 10(-6) to 10(-4) M. Neurons responsive to GABA were not found to be restricted to a subdivision of the SCN, but were diffusely distributed throughout the nucleus. DZP, FZP and zopiclone produced responses similar to those of GABA. The inhibitory effects of GABA (10(-5) M) were potentiated by coadministration of DZP (10(-5) M). Muscimol and baclofen (10(-7) M to 10(-4) M) also inhibited SCN neuronal activity in a dose-dependent manner. Bicuculline (10(-5) M-10(-4) M) scarcely affected the baclofen-induced inhibition (1/6) but strongly antagonized the effects of muscimol (6/6), GABA (6/8) and DZP (4/5). These results suggest that the receptors mediating the inhibitory effects of GABA and anxiolytics within the SCN may be GABAA and/or GABAB or GABA-BDZ receptor complex, respectively.
Author List: Liou S Y, Shibata S, Albers H E, Ueki S
Publication Types: Journal Article
Substances mentioned in the article: Anti-Anxiety Agents; Azabicyclo Compounds; Piperazines; Receptors, GABA-A; zopiclone; Muscimol; gamma-Aminobutyric Acid; Flunitrazepam; Baclofen; Diazepam; Bicuculline;
Mesh terms: Animals; Anti-Anxiety Agents/pharmacology; Azabicyclo Compounds; Baclofen/pharmacology; Bicuculline/pharmacology; Diazepam/pharmacology; Flunitrazepam/pharmacology; Hypothalamus/cytology; In Vitro Techniques; Muscimol/pharmacology; Neurons/drug effects; Piperazines/pharmacology; Rats; Receptors, GABA-A/drug effects; Suprachiasmatic Nucleus/cytology; gamma-Aminobutyric Acid/pharmacology;