Angiotensin II inhibits both heat production and heat loss mechanisms in the rat

Abstract

The effects of intracerebroventricular injections of angiotensin II on thermoregulatory responses of conscious rats to ambient temperatures (Ta) of 8, 22, and 30 degrees C were assessed. Administration of angiotensin II produced dose-dependent hypothermia in rats at both Ta 8 and 22 degrees C. The hypothermia in response to angiotensin II was due to decreased metabolic heat production. In addition, angiotensin II produced cutaneous vasoconstriction at Ta 8-22 degrees C. However, at Ta 30 degrees C angiotensin II produced no change in rectal temperature or other thermoregulatory responses. Furthermore, the hypothermia induced by angiotension II was antagonized by pretreatment with 6-hydroxytryptamine (a selective catecholamine neurotoxin) and propranolol (a selective beta-adrenergic antagonist) but not either 5,6-dihydroxytryptamine (a selective serotonin neurotoxin), atropine (a cholinergic antagonist), or phentolamine (a selective alpha-adrenergic antagonist). The data indicate that angiotension II inhibits both heat production and heat loss mechanisms which lead to an alteration in body temperature, probably via the activation of central adrenergic receptors.