Effects of food deprivation on daily changes in body temperature and behavioral thermoregulation in rats

Homeothermic animals regulate body temperature (Tb) by using both autonomic and behavioral mechanisms. In the latter process, animals seek out cooler or warmer places when they are exposed to excessively hot or cold environme nts. Thermoregulation is affected by the state of energy reserves in the bo dy. In the present study, we examine the effects of 4-day food deprivation on circadian changes in Tb and on cold-escape and heat-escape behaviors in rats. Continuous measurement of Tb during food deprivation indicated that t he peak Tb amplitude was not different from baseline values, but the trough amplitude continuously decreased after the onset of food deprivation. Cold -escape behavior was facilitated by food deprivation, whereas heat-escape b ehavior was unchanged. After the termination of food deprivation, the lower ed Tb returned to normal on the first day. However, cold-escape behavior wa s still facilitated on the third day after food reintroduction. Autonomic a nd behavioral thermoregulatory effecters are modulated in the face of food shortage so as to maintain optimal performance during the active period, wh ereas increasing energy conservation occurs during the quiescent phase.