Multiple effects of drugs acting on benzodiazepine receptors.

The actions on [3H]noradrenaline release of chlordiazepoxide and FG 7142 were investigated in rat hippocampal synaptosomes. The release evoked by GABA, an action mediated by GABAA receptors, was enhanced by chlordiazepoxide and depressed by FG 7142. K+-evoked release, however, was depressed by both chlordiazepoxide and FG 7142 and occurred in the absence of GABA. The actions on both GABA-evoked and K+-evoked release were blocked by Ro 15-1788. The results suggest that the distinction between agonist and inverse agonist applies to the GABA-dependent but not to the GABA-independent action of benzodiazepines.