Evidence of environmental influence on the development of thermoregulation in the rat.

Sprague-Dawley rats were raised in an environmentally controlled room at 33 degrees C. Thermoregulatory responses of animals reared in this way were compared with those of control and warm-acclimated rats. Warm-reared animals demonstrated a significantly greater fall in colonic temperature during cold exposure when compared with both warm-acclimated (p less than 0.01) and control (p less than 0.001) animals. Warm-reared animals also show a modified response to central infusion of noradrenaline; they produce a hyperthermia in contrast with the hypothermia observed in control and warm-acclimated rats. These results suggest that the early thermal environment may modify the development of temperature regulation in the Sprague-Dawley rat in a way different from the normal acclimation process.