The participation of shivering and nonshivering thermogenesis in warm and cold-acclimated rats

1. Both shivering and nonshivering thermogenesis are ways of increasing oxygen consumption in the rat. The participation of nonshivering thermogenesis after cold acclimation is well established, but there is little evidence of the relative importance of each kind of thermogenesis in acclimated and nonacclimated rats. 2. Oxygen consumption and rectal temperature were measured in warm and cold-acclimated rats exposed both to cold (10 degrees C) and warm (30 degree C) environments. 3. Shivering was blocked by mephenesin (10 mg/100 g body wt) and nonshivering thermogenesis was blocked by propranolol (0.5 mg/100 g body wt). 4. Control animals were injected with saline (0.5 ml/100 g body wt). 5. The results showed that shivering is not effective in maintaining a constant rectal temperature and that nonshivering thermogenesis does not contribute to the increase in oxygen consumption of warm-acclimated rats exposed to cold.