EFFECT OF RESERPINE ON BODY TEMPERATURE REGULATION OF THE RAT

¹ Department of Physiology, University of Florida, College of Medicine, Gainesville, Florida

Daily intraperitoneal injections of reserpine were found to lower the colonic temperature of rats maintained at room temperature (25°) only if the dose was 1.0 mg/kg or greater. Much smaller doses (0.125 mg/kg) of the drug significantly increased the rate at which these animals cooled when exposed to reduced environmental temperatures (5°C and 14°C). Metabolic studies indicated that decreased heat production rather than increased heat loss was the mechanism whereby reserpine exerted its effect on cooling rate. Physiological doses of thyroxine (50 µg/kg) were found to improve the metabolic response of reserpine-treated rats to cold and to return their cooling rates toward control values. TSH administration to reserpine-treated rats did not improve their response to cold. These observations suggest that reserpine may interfere with the normal response of the thyroid gland to stimulation by TSH, but not to peripheral utilization of thyroid hormone.