Study of the 5-HT 2 antagonist ritanserin on sleep-waking cycle in the rat

Abstract

Ritanserin, a 5-HT 2 receptor antagonist, was injected intraperitoneally to rats at light onset. It was found that 0.63 mg/kg decreased waking, increased the slow waves characteristic of the first stage of sleep, and decreased paradoxical sleep (PS) during the first four hours. Active waking was further decreased and slow wave stage increased during the following four hours. The number of synchronized and paradoxical sleep phases decreased whereas their duration increased during the first four hours. Ritanserin at 2.5 mg/kg decreased active waking and PS, whereas quiet waking and slow wave stage were increased during the first four hours. Quiet waking was increased during the following four hours. It is concluded that serotonin acting on 5 HT 2 receptors is actively involved in sleep-waking regulation.