Responses of cold-acclimatized men to infused norepinephrine

Abstract

Nine healthy males were infused with norepinephrine (o. μg/kg min) for 20 min before and after five 40-hr weeks of seminude exposure to 5 C. All infusions were given in the basal state, in a quiet room at 27 C, after a 30-min period of control measurements. Rectal temperatures and respiratory rates were unchanged either by the drug or the intervening cold exposure. The drug increased respiratory minute volumes and tidal volumes and decreased heart rates, but equally so in both experiments. Mean skin temperatures were unaffected by the drug but were significantly (P < .025) higher after cold exposure (mean 1 C). Both basal and drug-induced increase above basal of systolic and diastolic blood pressures was significantly lower (P < .025) after cold exposure. Oxygen consumption was the same in both basal periods and was unaffected by the drug before cold exposure. After cold exposure, norepinephrine produced a significant (P < .025) increase in oxygen consumption (mean 18 cc/min m2). These results show a changed sensitivity to norepinephrine in cold-exposed men, with a decrease in vasopressor response and the development of a calorigenic response. The data suggest that in men, norepinephrine may be a mediator of a nonshivering thermogenesis occurring with cold acclimatization. Note: (With the Assistance of Joseph C. Matone, Gerald W. Newcomb, and Wendell C. Bradford) cold exposure; catecholamines; norepinephrine calorigenesis; nonshivering thermogenesis Submitted on May 2, 1963