Effects of pinealectomy on baseline sleep and response to sleep deprivation

STUDY OBJECTIVES: We have previously reported that older (24 mo.) Fischer rats manifest a diminished post-sleep deprivation increase in NREM and REM sleep. In order to examine whether this decline reflects an age-related change in pineal function, we are now reporting on baseline and recovery sleep parameters in pinealectomized 3-, 12-, and 24-month old rats following 24 hours of sleep deprivation using the disk-over-water method. DESIGN: Three independent age groups; within each group there were sequential measures of sleep under baseline conditions and during recovery from sleep deprivation. SETTING: The Sleep Research Laboratory at the University of Chicago PARTICIPANTS: 56 male Fisher (F344) rats INTERVENTIONS: 24 hours of total sleep deprivation using the disk-over-water method MEASUREMENTS: Sleep staging of EEG and EMG, and power spectral analysis of the EEG RESULTS: Pinealectomized (pinex) rats did not differ from sham-operated (sham) rats in total sleep, REM sleep, super-modal high-amplitude NREM sleep (HS2), a measure of NREM EEG delta power, or circadian rhythm amplitude. In the pinex rats, there was a modest (2.5%) age-independent increase in NREM sleep (p<0.02). The pinex rats of all ages failed to manifest the increase in NREM sleep during recovery seen in the sham-operated animals (p<0.04). CONCLUSIONS: We found no evidence that altered pineal function is responsible for age-related changes in baseline sleep in the rat. These data also suggest that, independent of age, normal pineal function may be relevant to the ability to generate increased NREM sleep in response to prior sleep deprivation.