Co-operative effect between gamma-aminobutyric acid A receptors and central-type benzodiazepine receptors on amylase release in rat parotid acinar cells.

We investigated the inhibitory role of gamma-aminobutyric acid A (GABA(A)) 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 GABA(A)-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 GABA(A)-receptor agonist and clonazepam, it did not completely block the combination effect with diazepam. These results suggest that protein secretion is suppressively regulated by GABA(A) receptors coupled with central-type benzodiazepine receptors.