Effects of paradoxical sleep deprivation on thermoregulation in the rat

Rats were subjected to chronic paradoxical sleep deprivation (PSD) by the disk-over-water method to determine if they would develop the sustained increase in core (hypothalamic) temperature (T(hy)); elevated temperature setpoint (Tset); and the attenuation of the normal decline in core temperature during the transition from wake to sleep observed in rats subjected to total sleep deprivation (TSD). PSD rats did not show a significant elevation in T(hy). PSD rats and their yoked controls (PSC) were provided with a continuously available operant by which they could increase ambient temperature (Tamb). Change in Tset was assessed by evaluating operant behavior as a function of hypothalamic and intraperitoneal temperature (T(ip)). Unlike TSD rats, PSD and PSC rats maintained near-baseline Tamb at all T(hy) and T(ip) values throughout the deprivation, indicating no change in Tset. As deprivation progressed, PSD rats displayed an attenuation of the normal fall of T(hy) and T(ip) during the transition from wake to sleep. PSC rats did not. During the final quarter of survival time, T(ip) in PSD rats actually rose above waking values during the transition to NREM. These results indicate that PS loss may alter thermoregulation during sleep. It would appear that selective PSD is sufficient to attenuate the normal decline in T(hy) and T(ip) during NREM sleep, whereas NREM loss is required for elevations in T(hy) and Tset.