On the central antiserotonin action of trazodone

Trazodone, an antidepressant drug with an unknown mechanism of action, has been examined in order to demonstrate its central antiserotonin action. Trazodone antagonizes the head twitch response induced by 5-hydroxytryptophan in rats and mice, or by-5-methoxytryptamine in rats (the ED50 values are 9.3, 5.2, and 10.8 mg/kg respectively). It counteracts convulsions induced by tryptamine in rats (ED50=3.75 mg/kg). Trazodone abolishes hyperthermia induced by serotoninomimetics (LSD, quipazine, fenfluramine) in rabbits. It does not affect ptosis induced by reserpine, and diminishes stimulation of the locomotor activity induced by amphetamine. Our findings demonstrate that trazodone has a central antiserotonin action, similarly as three other antidepressant drugs: mianserin, danitracen and doxepin, whose central antiserotonin action has been found previously.