Hypotensive drugs, sodium nitroprusside and prazosin inhibit the metabolic rate in rabbits.

1. Thermoregulatory responses (metabolic rate, rectal and ear skin temperatures, respiratory rate) were measured after treatment with two antihypertensive drugs, i.e. when sodium nitroprusside (6 mg/kg/2 hr) or prazosin (0.75 mg/kg/3 hr) were applied to normothermic or febrile rabbits under thermoneutral conditions (19 +/- 1 degree C). 2. Both drugs significantly decreased blood pressure and metabolic rate. 3. These changes were accompanied by antipyresis. 4. In the case of normothermic rabbits only sodium nitroprusside produced prominent falls in body temperature. 5. The relationship between changes in blood pressure and the intensity of metabolic rate is discussed.