Homeostatic sleep and body temperature responses to acute sleep deprivation are preserved following chronic sleep restriction in rats

Chronic sleep insufficiency is common in our society and has negative cognitive and health impacts. It can also alter sleep regulation, yet whether it affects subsequent homeostatic responses to acute sleep loss is unclear. We assessed sleep and thermoregulatory responses to acute sleep deprivation before and after a '3/1' chronic sleep restriction protocol in adult male Wistar rats. The 3/1 protocol consisted of continuous cycles of wheel rotations (3 h on/1 h off) for 4 days. Sleep latency in a 2-h multiple sleep latency test starting 26 h post-3/1 was unchanged, whereas non-rapid eye movement sleep (NREMS) and associated electroencephalogram delta power (a measure of sleep need) over a 24-h period beginning 54 h post-3/1 were reduced, compared to respective pre-3/1 baseline levels. However, in response to acute sleep deprivation (6 h by 'gentle handling') starting 78 h post-3/1, the compensatory rebounds in NREMS and rapid eye movement sleep (REMS) amounts and NREMS delta power were unaltered. Body temperature increased progressively across the 3/1 protocol and returned to baseline levels on the second day post-3/1. The acute sleep deprivation also increased body temperature, followed by a decline below baseline levels, with no difference between before and after 3/1 sleep restriction. Non-sleep-restricted control rats showed responses to acute sleep deprivation similar to those observed in the sleep-restricted animals. These results suggest that the process of sleep homeostasis is altered on the third recovery day after a 4-day 3/1 sleep restriction protocol, whereas subsequent homeostatic sleep and temperature responses to brief sleep deprivation are not affected.