PREOPTIC ANTERIOR HYPOTHALAMIC NEURONS - THERMOSENSITIVITY IN WAKEFULNESS AND NON RAPID EYE-MOVEMENT SLEEP/

Thermosensitive neurons of the preoptic/anterior hypothalamic area (PA OH) have been implicated in the regulation of both body temperature an d non rapid eye movement (NREM) sleep. During NREM sleep, a majority o f POAH warm-sensitive neurons (WSN) exhibit increased discharge compar ed to wakefulness. Cold-sensitive neurons (CSN) exhibit reduced discha rge in NREM sleep compared to wakefulness. To further study the mechan ism underlying these processes, the present study compared discharge r ate and thermosensitivity (discharge rate change/degrees C) of WSNs an d CSNs in NREM sleep and wakefulness in freely moving adult cats. The thermosensitivity of 24 WSNs and 31 CSNs from the medial POAH was dete rmined from responses to local POAH warming and cooling. WSNs with inc reased discharge in NREM sleep exhibited increased thermosensitivity d uring NREM sleep compared to wakefulness. CSNs with decreased discharg e during NREM sleep exhibited decreased thermosensitivity in NREM slee p. The charge in thermosensitivity from wakefulness to NREM sleep was correlated with the change in discharge rate in WSNs but not in CSNs. In addition, 9 of 47 neurons that were thermo-insensitive during wakef ulness became warm-sensitive during NREM sleep. Changes in POAH neuron al thermosensitivity could be a component of the mechanism for stabili zation of state after state transition.