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Repeated sleep restriction in adolescent rats altered sleep patterns and impaired spatial learning/memory ability.

STUDY OBJECTIVES
To investigate possible differences in the effect of repeated sleep restriction (RSR) during adolescence and adulthood on sleep homeostasis and spatial learning and memory ability.


DESIGN
The authors examined electroencephalograms of rats as they were subjected to 4-h daily sleep deprivation that continued for 7 consecutive days and assessed the spatial learning and memory by Morris water maze test (WMT).


PARTICIPANTS
Adolescent and adult rats.


MEASUREMENTS AND RESULTS
Adolescent rats exhibited a similar amount of rapid eye movement (REM) and nonrapid eye movement (NREM) sleep with higher slow wave activity (SWA, 0.5-4 Hz) and fewer episodes and conversions with prolonged durations, indicating they have better sleep quality than adult rats. After RSR, adult rats showed strong rebound of REM sleep by 31% on sleep deprivation day 1; this value was 37% on sleep deprivation day 7 in adolescents compared with 20-h baseline level. On sleep deprivation day 7, SWA in adult and adolescent rats increased by 47% and 33%, and such elevation lasted for 5 h and 7 h, respectively. Furthermore, the authors investigated the effects of 4-h daily sleep deprivation immediately after the water maze training sessions on spatial cognitive performance. Adolescent rats sleep-restricted for 7 days traveled a longer distance to find the hidden platform during the acquisition training and had fewer numbers of platform crossings in the probe trial than those in the control group, something that did not occur in the sleep-deprived adult rats.


CONCLUSIONS
Repeated sleep restriction (RSR) altered sleep profiles and mildly impaired spatial learning and memory capability in adolescent rats.