[Thermoregulation in rats in a helium-oxygen environment]

Effects of 21% O2 + 79% He mixture at the normal pressure on temperature of different body areas, blood temperature, heat emission, heat production, and the muscle electrical activity were studied at ambient temperature 21-22 degrees C. Action of the mixture during 60 min increased the heat emission by 21%, heat production by 17%, muscle activity by 37%. In spite of this, the temperature decreased in hypothalamus, cerebral cortex, rectum, muscles, and under the skin, as well as the blood temperature in the aortic arch and in the v. cava anterior. The occurring increase in the heat production is insufficient for preventing the drop of the body temperature. The disturbance of thermoregulation in the helium-oxygen atmosphere seems to occur mainly because of the excessive increase in the heat emission.