Effects of pontine tegmental lesions that induce paradoxical sleep without atonia on thermoregulation in cats during wakefulness.

The characteristics of thermoregulation during wakefulness of cats with pontine tegmental lesions that induced paradoxical sleep (PS) without atonia have been studied. Thresholds for shivering and for panting, brain temperature and body posture at different ambient temperatures were noted and compared with those in intact animals. Intact cats began to shiver, piloerect and curl their bodies at ambient temperatures (Ta) of 8-10 degrees C, whereas after the lesions these responses began at Ta of 15-17 degrees C. Body temperature (Tb) did not change. Cats with lesions panted and extended their bodies much earlier at high Ta than did normal cats, and Tb began rising at a lower Ta and reached a higher value. Therefore, the cats with lesions were more susceptible to thermal loads; the thresholds for shivering (heat-gain) and panting (heat-loss) were both lowered. These results obtained in wakefulness suggest that the absence of shivering previously shown in cats during PS without atonia cannot simply be the result of an overall increased threshold for heat-gain responses but, rather, are in keeping with the observation that thermoregulation is suppressed in PS.