TEMPERATURE-DEPENDENT EFFECTS OF EPHEDRINE IN THE COLD

This experiment examined the effects of intraperitoneal ephedrine (5-2 5 mg/kg) on operant thermoregulatory behavior of rats in the cold (-8 degrees C), and of 10 mg/kg on metabolic rate at a thermoneutral (22 d egrees C) ambient temperature (Ta) and in the cold (5 degrees C). Post test colonic temperature (Tc) decreased dose-dependently in the behavi oral tests, yet the demand for heat varied Little with respect to sali ne except for a significant reduction at the lowest dose tested (i.e., there was no compensation for the reduced Tc induced by ephedrine). E phedrine had a potent thermogenic effect at a Ta of 22 degrees C, incr easing both metabolic rate and Tc. In the cold, ephedrine reduced Tc, but this effect could not be accounted for by a reduction in metabolis m, which was not significantly different from saline.