Effects of angiotensin II on metabolic, respiratory and vasomotor activities as well as body temperatures in the rabbit.

The effects of intraventricular administration of angiotensin II (10 to 50 micrograms, third cerebral ventricle) on thermoregulatory responses of conscious rabbits to different ambient temperatures (Ta) of 2, 22 and 32 degrees C were assessed. Angiotensin II administration produced dose-dependent hypothermia in rabbits at both 2 and 22 degrees C Ta. The hypothermia in response to angiotensin II was due to decreased metabolic heat production and increased heat losses. The increase in heat loss was shown by an increase in both skin blood flow and respiratory evaporative heat loss. However, at 32 degrees C Ta, angiotensin II produced no change in rectal temperature or other thermoregulatory responses. The data indicate that angiotensin II decreases heat production and increases heat loss mechanisms in the rabbit brain which leads to hypothermia.