: The effects of hyper- and hypothermic acting compounds on the rectal and skin temperature, oxygen consumption, and heart rate were studied in the decapitated rat. Noradrenaline infusion (2 μg/kg/min.) caused thermogenesis, increased oxygen consumption, tachycardia, and vasoconstriction. 2,4-Dinitrophenol (2 × 2.5 mg/kg intraperitoneally) and sodium salicylate (150 mg/kg intra-peritoneally), which cause an uncoupling of the oxydative phosphorylation, caused thermogenesis and increased oxygen consumption but no significant changes in the skin temperature or heart rate. The effects of noradrenaline but not those of 2,4-dinitrophenol and sodium salicylate could be blocked or reduced by the administration of propranolol and phentolamine. Thus the thermogenesis caused by noradrenaline could be differentiated from that caused by uncouplers of oxydative phosphorylation. The metabolic poison, iodoacetic acid reduced or prevented the noradrenaline induced thermogenesis when given as a pretreatment (30 mg/kg intraperitoneally) 60-75 min. before the noradrenaline infusion. Chlorpromazine (10 mg/kg intraperitoneally) did not influence the noradrenaline induced thermogenesis either when given as a pretreatment or when given during the infusion. It is concluded that the decapitated rat is useful for the study of the mechanism of action of hyper- and hypothermic acting compounds.
Acta pharmacologica et toxicologica