The role of ultradian rhythms in post-deprivation rebounds and diurnal rhythms of sleep and wakefulness in rats

Abstract

AbstractThe temporal organization of ultradian rhythms in sleep and wakefulness during post-sleep deprivation (TSD) rebound were investigated in 15 rats under contant bright light (LL). Following baseline recordings, rats were subjected to TSD using gentle manual stimulation. Post-TSD rebounds in cumulative wakefulness (WAKE), rapid eye movement sleep (REM) and non-REM sleep (NREM) were analyzed in WAKE-dominant (υw) and sleep-dominant (υs) ultradian phases. Rebounds in WAKE and NREM were present only when data were analyzed on a full ultradian cycle basis, and were absent in υsand υwphases alone. These rebounds were approximately 50% complete and not proportional to TSD excess/deficit. Rebounds in REM were present in full ultradian cycles and partially expressed in υsbut absent in υw. REM rebounds fully compensated for REM deficit. Rebounds were mediated mainly by a reduction in the duration of the υwultradian phase, and by decreased probability of arousal in the υsultradian phase. These mechanisms were also found to partially mediate diurnal rhythms in 10 rats under a 12:12 h LD cycle.This study implicates an ultradian timing mechanism in the control of post-TSD rebounds and suggests that rebounds in all three states are mainly mediated by post-TSD adjustments in WAKE-promoting mechanisms. Ultradian rhythms should be taken into account to avoid errors in data analysis.HighlightsSleep-wake state exhibits circadian rhythms and ultradian rhythms.These rhythms interact with rebounds after sleep deprivation.Circadian amplitude and sleep rebound are partially mediated by ultradian timing.Arousal-related processes control these sleep-wake patterns in both states.Measuring ultradian rhythms is necessary for accurate analysis of data.