Changes in the colonic temperature and metabolism during immobilization stress in repetitively immobilized or cold-acclimated rats.

Effect of immobilization stress on the rat colonic temperature and metabolism was studied in a warm environment of 25 degrees C. Immobilization for 3 hr caused hyperthermia accompanied by increased oxygen consumption (VO2) in the warm controls. The hyperthermic effect of immobilization was accelerated after 1 week repetition of daily immobilization and it was lessened after 2 to 4 week repetition of daily immobilization. The magnitude of VO2 increase was the same throughout the experimental period of 4 weeks during the immobilization. Hypothermia was never observed during immobilization. Immobilization-induced hyperthermia was significantly potentiated in the cold-acclimated rats, while VO2 increase did not differ between cold-acclimated rats and warm controls. These results suggest that immobilization stress causes the changes in body temperature through thermogenic and heat-loss mechanisms.