Body temperature regulation in rats during exercise of various intensities at different ambient temperatures.

We examined the relationship between body temperature, tail vasomotor response, and work intensity at different ambient temperatures in rats, using a treadmill and continuously measuring oxygen uptake during exercise. At an ambient temperature (Ta) of 24 degrees C, rectal temperature (Tre) at the beginning of tail vasodilation during exercise increased in proportion to work intensity. After tail vasodilation Tre remained steady, and at the end of 30 min exercise Tre level was proportional to work intensity. At Ta of 14 degrees C, Tre at the end of exercise was slightly higher than at 24 degrees C, and was higher at higher work intensities. At Ta of 4 degrees C, Tre rose slower during exercise than at higher Tas and even dropped at relatively low work intensities. Tail vasodilation did not occur in most cases. At Ta of 34 degrees C, Tre rose continuously during exercise. These data indicate that body temperature of rats during exercise rises in proportion to work intensity, but the extent of body temperature rises differs according to Ta.