Effects of sleep deprivation in neonatal rats.

This investigation represents the first systematic study of sleep homeostasis in developing mammals that spans the preweaning and postweaning periods. Neonatal rats from 12 to 24 days of postnatal life (P12-P24) were anesthetized with Metofane (methoxyflurane) and implanted with miniaturized electroencephalographic (EEG) and electromyographic electrodes. After 48 h of recovery, neonatal rats were sleep deprived for 3 h by either gentle handling or forced locomotion. We find that 3-h sleep deprivation produces dramatically different compensatory responses at different stages of postnatal development. In striking contrast to adult rats, sleep deprivation does not increase slow-wave sleep EEG delta (0.5-4.0 Hz) activity in rats younger than P24. However, P12-P20 rats do show evidence of sleep regulation because they show compensatory increases in sleep time and sleep continuity during recovery. In P12 rats, approximately 90% of total slow wave sleep time lost during the sleep-deprivation period was recovered during subsequent sleep. A similar recovery of active sleep time was observed in P20-P24 rats. These findings suggest not only that sleep is regulated in neonatal rats but that the accumulation and/or discharge of sleep need changes dramatically between the third and fourth postnatal weeks.