Effect of restraint on drug-induced changes in skin and core temperature in biotelemetered rats

Temperature homeostasis is modulated by a number of neuroendocrine control systems. Both angiotensin II and isoproterenol have been shown to increase skin temperature. Withdrawal from opioid dependence using naloxone also results in an increased skin temperature and a decreased body core temperature. The effects of restraint stress on these tail skin temperature responses is unknown. We tested the effect of restraint or free movement on tail skin and core temperature responses to three thermoregulatory substances: isoproterenol and angiotensin II in naive rats and naloxone in morphine-dependent rats. In each case restrained rats had significantly lower baseline tail skin temperatures than free moving rats. Baseline core temperatures were not different between restrained and free moving animals. Each agent produced significant acute increases in tail skin temperatures. Restraint did not affect these responses. Both angiotensin II and naloxone also produced significant decreases in core temperatures that were not altered by restraint. This study is the first to show that radiotelemetry can be used to measure tail skin temperatures in rats. The results of this study show that when using three different thermoregulatory agents restraint failed to affect either baseline temperatures or maximal responsiveness to the agents in a detrimental manner. The lack of impairment of temperature changes due to restraint in these studies also validate previous studies that had used restraint in measuring core and tail skin temperatures in rodents.