Cytotoxic Lesions of the Pontine Tegmentum Alter the Sleep of Cats in a Cold Environment

The pontine tegmentum of the cat was lesioned by microinjection of a cytotoxin (ibotenic acid) into the brainstem. The sleep-waking cycle of intact cats and cats with the cytotoxic lesions of the pontine tegmentum was studied as a function of ambient temperature. In a cold environment lesioned cats showed a reduction in sleep that was significantly greater than the reduction shown by the intact animals. In a warm environment cats with the tegmental lesions show changes in the sleep-waking cycle similar to intact animals. It is shown that in wakefulness the cytotoxically pontine lesioned cats are more sensitive to cold, but not to heat, than intact animals. The results of these experiments are consistent with the hypothesis that the decreased sleep shown by lesioned animals is due to an alteration in thermoregulation such that the damaged brain interprets ambient temperature to be colder than it is.