Amphetamine and thermoregulation: Studies in the unrestrained and curarized rat

We investigated the effect of (+)-amphetamine on body temperature in the unrestrained and curarized rat. In the unrestrained animal kept at an ambient temperature of 30°C amphetamine had a dose-dependent hyperthermic action, whereas in animals kept at 7°C it decreased body temperature. An increase in body temperature was evident also in the curarized rat; after spinal cord transection at the level of C1; and in the pithed rat. Pretreatment with the alpha-adrenergic blocking agent azapetine attenuated amphetamine-hyperthermia in the curarized rat, but enhanced the hyperthermic response in the unrestrained rat. Pretreatment with the beta-adrenergic blocking agent propranolol abolished amphetamine-hyperthermia in the curarized rat, but did not affect the response in the unrestrained animal. In the hypophysectomized animal amphetamine had a hypothermic effect even at high ambient temperatures. It is concluded that the action of amphetamine on peripheral beta-receptors has a hyperthermic effect, but that additional mechanisms are involved in the thermal response of the freely moving animal.