[Mechanisms of chemical thermoregulation in mature and immature-born animals at an early postnatal age].

The energy contribution of motor activity and gray fat to the total heat production was studied in 3-4-day old mice Acomys cochirinus and Wistar rats at ambient temperatures 37 degrees C, 34 degrees C and 30 degrees C. At lower ambient temperature, the motor activity and the total heat production were found to increase. A significant positive correlation was found among the motor activity, total heat production and temperature of the gray fat tissue. The latter exceeded the rectal temperature by 0.6-1.0 degrees C in all animals in all conditions. The 3-4-day old animals produce more heat per unit of motor activity than the 8-10-day old animals.