Effect of chronic pentobarbital treatment on the sleep patterns of squirrel monkeys.

Following a 30-day baseline, 60 days of sodium pentobarbital treatment (5 mg/kg) were given to squirrel monkeys 2 h prior to the start of a 12-h recording of EEG and EOG. Following the drug-treatment phase, an additional 30-day period was used to determine the rate of recovery. Repeated pentobarbital treatment significantly reduced awake time and slow wave sleep while it elevated the time spent in drowsy and light sleep. The recovery phase indicated a brief recovery of rapid eye movement sleep while the other stages failed to return to baseline levels. The cyclical nature of the changes observed with chronic pentobarbital suggest the importance of circadian fluctuations in the study of chronic drug treatment and the sleep-wakefulness process.