RESPONSES OF EXTRAHYPOTHALAMIC NEURONS TO SHORT TEMPERATURE TRANSIENTS DURING THE ULTRADIAN WAKE-SLEEP CYCLE

The thermosensitivity of neurons in thalamo-striate-limbic structures located dorsally to the classical thermosensitive anterior hypothalami c-preoptic region was studied in cats during the natural ultradian wak e-sleep cycle. Direct cooling or warming of the brain tissue by means of water-perfused thermodes was combined with tonic cooling or warming of the abdominal wall using a water-perfused heat exchanger on which the animal was lying. Out of 482 neurons, 116 (24.1%) were thermosensi tive. They were located in the nuclei reticularis and ventralis anteri or of the thalamus, the fundus of the caudate nucleus, the bed nucleus of the stria terminalis, the bed nucleus of the inferior thalamic ped uncle, and the nucleus of the anterior commissure. Abdominal warming i ncreased the effect of direct brain warming and decreased the effect o f direct brain cooling; opposite effects were obtained by abdominal co oling. Thermosensitivity was present during wakefulness and synchroniz ed sleep, but depressed or altered during desynchronized sleep.