Polygraphic study of anterior hypothalamic-preoptic neuron thermosensitivity during sleep.

Thermal responsiveness of anterior hypothalamic-preoptic (AH-PO) neurons was studied in unanesthetized sleeping cats carrying chronically implanted electrodes and thermistors for recording EEG, EMG and AH-PO temperature. Activity of AH-PO neurons was recorded using tungsten microelectrodes during atraumatic stereotaxic head restraint in a sound-attenuated chamber at 22-25 degrees C. Direct cooling or warning of the AH-PO region was accomplished with bilaterally positioned water-perfused thermodes. 110 thermosensitive neurons (77% cold-sensitive and 23% warm-sensitive) were sampled during wakefulness and synchronized sleep. In contrast, the changes in spontaneous firing rate shown by AH-PO neurons during desynchronized sleep were often associated with a strong depression or outright suppression of their responsiveness to AH-PO thermal stimulation.