HYPOXIA SIMILARLY IMPAIRS METABOLIC RESPONSES TO CUTANEOUS AND CORE COLD STIMULI IN CONSCIOUS RATS

Cold exposure elicits several thermoregulatory responses, including an increased metabolic heat production from shivering and nonshivering t hermogenesis. The increased metabolism can be in response to body core and/or body cutaneous cooling. Hypoxic hypoxia has been shown to atte nuate the metabolic response to cutaneous cooling. We measured metabol ic heat production in adult conscious rats during independent cutaneou s and core cooling, during normoxia and hypoxia, to I) test the hypoth esis that hypoxia suppresses the metabolic response to independent cor e cooling and 2) determine whether hypoxia acts preferentially on the response to cutaneous or core cooling. The animals were studied in a t emperature-controlled metabolic chamber, and body core temperature was controlled by an abdominal heat exchange coil. Ambient temperature wa s varied (10, 19, and 28 degrees C) while core temperature was clamped at 37 degrees C or core temperature was varied (33, 35, and 37 degree s C) at a stable ambient temperature of 28 degrees C. Our data indicat e that although the sensitivity of the metabolic response to core cool ing is about five to six times that to cutaneous cooling, hypoxia simi larly attenuates thermoregulatory responses to both stimuli.