RELAXATION AND SLEEP INDUCED BY WARMING OF PREOPTIC REGION AND ANTERIOR HYPOTHALAMUS IN CATS

Diathermic warming of the preoptic and anterior hypothalamic thermoreceptor zone in cats induced relaxation and sleep consisting of lying on the side, resting the head on the floor, closure of eyelids and nictitating membrane, pupil constriction, and delta waves in the EEG. At higher warming levels, panting and stretching out appeared. Termination of warming was followed in 15-150 sec by awakening. Grooming and increased water consumption reported in other species were not obtained. Food deprivation raised the threshold and latencies for relaxation and shortened the postwarming recovery time. Since the diathermy failed to elicit any of the varied nonthermoregulatory responses evoked by 60-Hz electrical stimulation of the same electrodes, it was probably acting selectively on thermoreceptors. It was concluded that PO AH thermoreceptors are an important source of input to the preoptic sleep mechanism, and may contribute to the initiation or maintenance of restorative sleep as well as thermoregulatory sleep. © 1969.