Cold-defense function of brown adipose tissue during sleep.

Rats with chronically implanted electroencephalograph scalp electrodes and thermistors were exposed to 24 and 4 degrees C ambient temperatures during the light hours before and after acclimation to 4 degrees C ambient temperature for 9 days. During synchronized sleep, deep interscapular temperature was higher at 4 degrees C than at 24 degrees C both before and after acclimation to cold. After ablation of brown adipose tissue, deep interscapular temperature was lower at 4 degrees C than at 24 degrees C during synchronized sleep. In the presence of brown adipose tissue, deep interscapular temperature decreased sharply during desynchronized sleep at 4 degrees C both before and after acclimation to cold. This decrease was subsequent to and correlated with an increase in the temperature of the nasal mucosa. The decrease in deep interscapular temperature during desynchronized sleep at 4 degrees C ambient temperature was markedly reduced by ablation of the interscapular brown adipose tissue.