Effects of light physical exercise on sleep regulation in rats

Purpose: Acute physical exercise is known to enhance slow-wave sleep (SWS) and reduce paradoxical sleep CPS) in humans. In this study, we examined the effects of moderate physical exercise on sleep in rats. Method: Young adul t Wistar rats underwent a 4-h baseline electroencephalographic (EEG) record ing session. The following day, they were induced to walk (0.8 m.min(-1)) o r run (4 m.min(-1)) for 45 min in a rota-rod treadmill. Active control rats (ACR) were placed on the locked rota-rod for 45 min, whereas passive contr ol rats (PCR) remained in their home cages. They were then left free to sle ep for 4 h during which EEG activity was recorded. Rectal temperature (T-re ) was monitored before and after exercise in ACR, walking and running rats (WR and RR, respectively) and at 45 min intervals in PCR. Results: WR were able to walk for 45 min consecutively whereas in RR performances differed. Posttraining T-re was unchanged in ACR, PCR, and WR and resulted about 1.8 degreesC above baseline in RR. In both WR and RR after exercise i) length o f SWS and PS, ii) intensity of SWS (spectral power density in 1-4 Hz range) , and iii) propensity for falling asleep were enhanced. Interestingly, ther e was a more conspicuous increment in PS than SWS. In ACR and PCR there wer e no changes in sleep. Conclusions: Due to the complexity of sleep regulati on, the interaction of several factors might underlie the observed incremen t in SWS and PS. Nevertheless, it is interesting that light physical exerci se favors sleep and above all a harmonic enhancement of both sleep phases.