We investigated the inhibitory role of γ-aminobutyric acid A (GABAA) receptors on amylase release and the evidence for functional coupling with central-type benzodiazepine receptors in rat parotid acinar cells. Muscimol and GABA decreased isoprenaline-induced amylase release. This effect was blocked by bicuculline, a GABAA-receptor antagonist, and enhanced by clonazepam, a central-type benzodiazepine-receptor agonist, and diazepam, a central- and peripheral-type benzodiazepine-receptor agonist. Although bicuculline completely blocked the combination effect of GABAA-receptor agonist and clonazepam, it did not completely block the combination effect with diazepam. These results suggest that protein secretion is suppressively regulated by GABAA receptors coupled with central-type benzodiazepine receptors.
