Abstract
Selective deprivation of paradoxical (or rapid eye movements) sleep (REMS) in protein malnourished young male rats, results in circadian and homeostatic alterations. By means of electrocorticographic recordings, we have examined the sleep-wake cycle as a functional maturity index, and its circadian and homeostatic mechanisms in prenatal (PM) and chronically (CM) protein malnourished young male rats. The effects of rapid eye movements sleep-deprivation (REMS-D), by the platform technique in a "conflict experiment" (i.e. recovery from REMS-D begun during the circadian phase of activity), revealed that in PM animals, wake (WAK) was increased significantly during recovery days 1 and 2 (RD1, RD2); and slow wave sleep (SWS) was reduced significantly during these days. Prenatal protein-malnutrition altered the phase of WAK and REMS rhythms, and the amplitude of SWS rhythm was decreased. The REMS compensatory increase after REMS-D (REMS rebound) was confined to the first 4-h block of the activity phase in all experimental groups and 24 h later another REMS rebound was displayed in PM animals. The paradoxical sleep-rebound in CM animals was significantly higher than control and PM rats and it was only shown at the first 4-h block after REMS-D. Before and after REMS-D the circadian distribution of both sleep states, and the electrocortical frequency bands showed different circadian phases at the same day-time in control, PM and CM rats. The aforementioned indicates that protein malnutrition exerts important effects on the circadian and homeostatic mechanisms driving sleep. Therefore, the temporal structure of the malnourished rats may not allow proper synchronization of some sleep parameters, particularly REMS, to the environmental time cues.