Opposite Effects of Gentle Handling on Body Temperature and Body Weight in Rats

Abstract

The aim of this study was to measure the body weight set point when rats are being handled gently and thus experience emotional rise in body temperature. Wistar male rats were used in this experiment, and each rat was its own control. Body weight set point was estimated from the rat's food hoarding behavior. The set point is the intersection of the regression line for hoarding with the X axis. During hoarding sessions the experimenter handled the rat and took its colonic temperature six to eight times, an action sufficient to arouse emotional fever. On alternate days the rats were not handled. Thus, body weight set point was obtained for each rat without handling and with handling. In sessions with handling, rats raised their body temperature, ate less, and defecated more than in control sessions. When handled, the body weight set point declined from 388 ± 44 g to 366 ± 47 g ( p = 0.048, t = 2,39). The decline in the set point induced by gentle handling is believed to result from an elevation of the hypothalamic CRH.