Nanomolar concentrations of propranolol inhibit GABA-stimulated benzodiazepine binding to rat cerebral cortex

Abstract

The influence of propranolol on GABA-stimulated [3H]diazepam binding in the rat cerebral cortex was investigated. Maximum potentiation of GABA-stimulated binding (20.6 +/- 4.5%, P less than 0.05) was observed at 100 microM propranolol, whilst maximum inhibition (32.5 +/- 2.5%, P less than 0.01) was observed at 1 nM propranolol. Low concentrations (1 nM) of (+)-propranolol were observed to be equipotent with (+/-)-propranolol in shifting the dose-response curve of GABA-stimulated [3H]diazepam binding by approximately 1/2 log unit. The phenomenon does not therefore show the stereospecificity observed towards either beta-adrenergic receptors or 5-hydroxytryptamine receptors.