Preoptic/anterior hypothalamic neurons: thermosensitivity in rapid eye movement sleep

The thermosensitivity of 15 warm-sensitive neurons (WSNs) and 19 cold-sensitive neurons (CSNs) from the medial preoptic/anterior hypothalamus (POAH) was tested during wakefulness, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep by local POAH warming and cooling in freely moving cats. Thermosensitivity was quantified by three criteria, Q10, impulses per second per degree Celsius, and percent change per degree Celsius. Irrespective of the criterion used, WSNs did not exhibit a significant change in thermosensitivity during REM sleep compared with wakefulness and NREM sleep. In contrast, CSNs exhibited decreased mean thermosensitivity during REM sleep compared with wakefulness. CSNs as a group did not retain significant thermosensitivity in REM sleep. These findings are consistent with evidence that thermoeffector responses to cooling are lost in REM sleep, whereas some responses to warming are preserved.