Cessation of thermoregulation during REM sleep in the pocket mouse

Electrophysiological sleep patterns, respiration frequency, brain temperature (Tbr), and ear temperature (Tear) were recorded from five pocket mice (Perognathus longimembris) exposed to ambient temperatures (Ta) of 22.5, 27.5, 32.5, and 35.0 degrees C. Thermoregulation was curtailed during rapid-eye-movement (REM) sleep, since Tbr declined following REM onsets at Ta's below thermoneutrality and increased at Ta's above thermoneutrality. Tbr subsequently returned to pre-REM levels following the termination of each REM episode. Respiratory frequency was inversely related to Ta but not as strongly during REM sleep as during slow-wave sleep (SWS). These results confirm previous reports of loss of thermoregulatory ability during REM sleep. Mean duration and proportions of wakefulness, SWS, and REM sleep were unaffected by Ta, consistent with earlier findings on ground squirrels, but differing from reports of decreased REM sleep in nonhibernators. Hibernators may have lower peripheral thermosensitivities than nonhibernators, facilitating sleep at low ambient temperatures and during entrance into hibernation.