Ontogeny of REM rebound in postnatal rats

Study Objectives: The aim of this study was to determine developmental changes (ontogeny) of REM rebound in postnatal rats. Design: Different groups of 2, 3, and 4-week-old experimental rats were instrumentally REM sleep deprived (RSD rats) for 33-48 hours and their sleep was monitored polysomnographically for 48 hours after the REM sleep deprivation (RSD). Age-matched control (RSC) rats also had polysomnographic recordings. Settings: N/A Participants: Subjects were 18 male Long-Evans RSD rats (5 age 2 weeks, 5 age 3 weeks, and 8 age 4 weeks); and 17 age-matched male Long Evans RSC rats (5 age 2 weeks, 5 age 3 weeks, and 7 age 4 weeks). Interventions: Implants for the polysomnographic recordings of the RSD and RSC rats were made by the soft head plug method which permitted continuous, 24 hour/day records during the REM deprivation and post deprivation periods. RSD rats had instrumental RSD by the shaking platform method. RSC rats remained in stationary cages. Measurements and Results: At age 2 weeks, compared with age-matched RSC rats, RSD rats had no REM rebound. At age 3 weeks, compared with age-matched RSC rats, RSD rats had a small but significant REM rebound limited to the first 6 hours after RSD. At age 4 weeks, compared with RSC rats, RSD rats had a larger REM rebound that extended for 18 hours after RSD. The size and duration of REM rebound at the different ages was significantly different. Total sleep lost during the RSD process at each age was made up. Conclusions: The findings possibly indicate that in rats a REM sleep homeostatic process develops between ages 2 and 4 weeks and that a total sleep homeostatic process is already developed by age 2 weeks.