Anxiogenic effects of methyl-beta-carboline-3-carboxylate in a light/dark choice situation.

Doses of benzodiazepine, clorazepate, and also of the inverse agonist of the benzodiazepine receptor, beta-CCM, which failed to present sedative or postictal depressive effects, were at first determined in a free exploratory situation. Then, the effects of clorazepate dosed at 1.0, 2.0 and 4.0 mg/kg and beta-CCM dosed at 1.0 and 2.5 mg/kg were studied in the light/dark box choice procedure. Clorazepate tended to produce an increase of the time spent by mice in the lit box as well as of the number of transitions between the two boxes, whereas the dose of 1.0 mg/kg of beta-CCM had opposite effects. The benzodiazepine antagonist RO 15-1788 completely counteracted the anxiolytic effects of clorazepate dosed at 2.0 mg/kg and the anxiogenic effects of beta-CCM.