Antagonism by propyl-beta-carboline-3-carboxylate of passive avoidance impairment induced by diazepam.

We investigated the effects of propyl-beta-carboline-3-carboxylate (beta-CCP) on learning and memory tasks in a passive avoidance test in mice to clarify whether beta-CCP is an agonist or antagonist at benzodiazepine (BZP) receptors. At doses up to 10 mg/kg i.v., beta-CCP had no effect on mice in the passive avoidance test. Diazepam impaired passive avoidance behavior and methyl-beta-carboline-3-carboxylate(beta-CCM) enhanced it. beta-CCP blocked these effects of diazepam and beta-CCM in a dose-dependent manner similar to the effect of Ro15-1788. These effects of beta-CCP, which are thought to be mediated by BZP receptors, indicate that beta-CCP is an antagonist in the passive avoidance test.