The lack of antidepressant properties and a potent central antiserotonin activity of Org 8282.

A potential antidepressant activity and an antiserotonin action of Org 8282, delta (13b, 4a), 4a-carba-mianserin, was studied in mice and rats. Org 8282 did not affect the reserpine-induced hypothermia, hypoactivity and ptosis, did not modify the apomorphine-induced hypothermia and the TRH-induced hyperthermia in mice, did not change the motor stimulation and stereotypy produced by amphetamine. It was inactive in the behavioral despair test in rats and mice. On the other hand, Org 8282 inhibited the head twitch reaction after 5-HTP in mice, the tryptamine-induced clonic convulsions of forepaws in rats, the hyperthermia produced by fenfluramine and m-CPP in rats kept at a high ambient temperature, and the quipazine-induced stimulation of the flexor reflex activity in the spinal rat. These results indicate that Org 8282 is inactive in tests commonly applied for assessment of antidepressant action but--like mianserin--it exerts an antiserotonin activity.