Changes in ambient temperature at the onset of thermoregulatory responses in exercise-trained rats.

Spontaneous running in a wheel has emerged as a useful method of exercise in rodents. We investigated how exercise training with a running wheel affects ambient temperatures (T(a)) at the onset of thermoregulatory responses in rats. Female rats were allowed to run freely in the wheel for 6 months. Sedentary control rats did not exercise during the same period. After the exercise training period, they were loosely restrained and T(a) values at the onset of tail skin vasodilation and cold-induced thermogenesis were determined by raising or lowering T(a). Resting levels of core temperature and heat production of the exercise-trained rats were significantly higher than those of the controls. T(a) values at the onset of tail skin vasodilation and cold-induced thermogenesis of the exercise-trained rats were higher than those of the controls. The results suggest that, in rats, exercise training with a running wheel elevates ambient temperatures for heat loss and heat production, which may then contribute to maintaining the core temperature at a high level.