Sleep-wakefulness patterns in the helpless rat.

Sleep-wakefulness patterns were analyzed during a 15-day period in the rat, in relation to induction of helplessness. After a session of inescapable electric footshocks, rats did exhibit escape deficits in avoidance conditioning as classically described, and their spontaneous sleep-wakefulness patterns were not different from those of controls. However, reduced PS latency and increased PS amounts were observed in the helpless group after shuttle-box sessions, especially during the initial period after the induction of helplessness. Such modifications of PS latency and PS amounts are evocative of the sleep impairments classically observed in endogenous depression.