Peripheral heat as a reward for heart rate response in the curarized rat.

It is generally assumed that the mechanical perception of shivering is necessary for the perception of cold discomfort. Shivering of rats in a cool environment was eliminated by curarization. The rats were kept alive by artificial respiration. Heart rate was proportional to rectal temperature in a group of controls. One group of rats was conditioned to increase heart rate to trigger an infrared lamp; another group was conditioned to decrease heart rate to obtain heat. When compared with the results of the control group without infrared heat reward, the results obtained from the two heart-rate-modifying groups show that shivering is not a necessary signal to determine thermoregulatory behavior in rats and, presumably, cold discomfort in man.