Propranolol and pyrogen effects of shivering and nonshivering thermogenesis in rats

Abstract

Injection of bacterial endotoxin (Piromen) into unanesthetized rats elicited increases in shivering and nonshivering thermogenesis as well as in colonic temperature. In animals exposed to 24-25.degree. C, treatment with propranolol (a .beta.-adrenergic antagonist) markedly diminished the pyrogen-induced increases in O2 consumption (heat production) and colonic temperature with little change occurring in shivering activity. In contrast, in rats exposed to mild cold (17-18.degree. C), propranolol did not significantly alter the magnitude of the pyrogen-evoked thermogenesis. In these animals, shivering tended to increase when nonshivering thermogenesis was blocked. These data are interpreted as reflecting differential effects of pyrogen on the pathways controlling the 2 modes of heat production in the rat.