Total calorimetric measurements in the rat: influences of the sleep-wakefulness cycle and of the environmental temperature.

Rates of production as well as dry and evaporative heat loss during the sleep-wakefulness cycle were studied in 11 male, adult albino rats with chronically implanted electrodes and thermocouple re-entrant tubes. Two groups of animals chronically acclimated to 6 or 23 degrees C were acutely studied at 15, 20, 25, 30 and 35 degrees C. Statistical analysis of the data shows that rates of heat production and dry heat loss differ with respect to acclimation and acute environmental temperatures, and show significant differences depending on the states of the sleep-wakefulness cycle. Rate of heat production was highest during wakefulness, intermediate during synchronized sleep and lowest during paradoxical sleep. Rate of dry heat loss of 15 degrees C was maximal during paradoxical sleep. Rate of evaporative heat loss apparently did not change with the states of the sleep-wakefulness cycle. Heat storage estimated from difference in rates of heat production and heat loss was positive during wakefulness, slightly negative during synchronized sleep and markedly negative during paradoxical sleep. The data presented suggest a clear although partial suppression of thermoregulatory mechanisms during paradoxical sleep in the white rat.