Effects of GABA and anxiolytics on the single unit discharge of suprachiasmatic neurons in rat hypothalamic slices.
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.
Liou
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Department of Biology, Georgia State University, Atlanta 30303.
Shibata
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Albers
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HE
Ueki
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D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D053961:Azabicyclo Compounds; D001418:Baclofen / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology; D005445:Flunitrazepam / Q000494:pharmacology; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D014151:Anti-Anxiety Agents; D053961:Azabicyclo Compounds; D010879:Piperazines; D011963:Receptors, GABA-A; C515050:zopiclone; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam; D001418:Baclofen; D003975:Diazepam; D001640:Bicuculline