The effect of agonists at the GABA-benzodiazepine receptor complex on the duration of immobility of mice in the forced swimming test.

In the present study, we examined the effect of various agents which affect in a different manner the GABA-benzodiazepine receptor-chloride ionophore complex system in relation to the immobile behavior of mice in the forced swimming test. The benzodiazepines diazepam and flurazepam, the barbiturates pentobarbital and phenobarbital, zopiclone and beta-CCP (propyl-beta-carboline-3-carboxylate) enhanced the immobile behavior in a dose-dependent manner. In the doses used here, these agents produced almost no muscle relaxant action. Ro15-1788 and beta-CCM (methyl-beta-carboline-3-carboxylate) themselves had no effect on the duration of immobility. However, Ro15-1788 and beta-CCM reversed the enhancing effect produced by all 6 drugs. These results indicate that the enhancement of the duration of immobility of mice may be somehow correlated to the anxiolytic action but not to the muscle relaxant action. The effect may be mainly mediated by the benzodiazepine receptor, which forms a part of the GABA-benzodiazepine receptor-chloride ionophore complex. Furthermore it is suggested that there were behavioral similarities in the effects of beta-CCP and benzodiazepines.