title: Daily variations in GABA receptor function in Syrian hamster cerebral cortex.
abstract: The existence of diurnal changes in postsynaptic expression of gamma-aminobutyric acid (GABA) type A receptors was assessed in cerebral cortex of Syrian hamsters by measuring [3H]GABA binding and the influx of 36Cl- in synaptoneurosomes. A diurnal variation in dissociation constant of [3H]GABA binding to cerebral cortex membranes, and the absence of diurnal differences in maximal number of sites, were found. When the nycthemeral changes in muscimol-stimulated 36Cl- uptake by cortical synaptoneurosomes were assessed, a maximum occurred late at night (i.e. 0400 h). At 1600 h, micromolar concentrations of flunitrazepam potentiated significantly the influx of chloride induced by muscimol, while at 0400 h flunitrazepam did not exert any significant effect on 36Cl- uptake. The results indicate that postsynaptic type A GABAergic activity peaked at nocturnal hours in the cerebral cortex of Syrian hamsters.
authors.affiliation: Departamento de Fisiología, Universidad de Buenos Aires, Argentina.
authors.forename: B I
authors.initials: BI
authors.lastname: Kanterewicz
authors.forename: R E
authors.initials: RE
authors.lastname: Rosenstein
authors.forename: D A
authors.initials: DA
authors.lastname: Golombek
authors.forename: P C
authors.initials: PC
authors.lastname: Yannielli
authors.forename: D P
authors.initials: DP
authors.lastname: Cardinali
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism / Q000502:physiology*; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D005445:Flunitrazepam / Q000494:pharmacology; D018755:GABA Agonists / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008647:Mesocricetus; D009118:Muscimol / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018118:Chloride Channels; D018755:GABA Agonists; D018757:GABA Modulators; D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam