Adinazolam , a triazolobenzodiazepine , has been reported to be an effective antidepressant treatment in major depression. In the present study, a 14-day (but not a five-day) treatment with adinazolam enhanced the responsiveness of rat hippocampal pyramidal neurons to microiontophoretically applied 5-HT but not to NE. A 14-day treatment with diazepam failed to induce sensitization to either 5-HT or NE. Acute intravenous administration of adinazolam did not modify dorsal raphe 5-HT neuron firing rate. It is proposed that the antidepressant activity of adinazolam might be mediated by a heightened 5-HT neurotransmission.