Acclimatization to Cold Air; Hypothermia and Heat Production in the Golden Hamster

Abstract

Adult golden hamsters were artificially cooled while their colonic temps. were being recorded by thermocouples. The lowest body temp. from which half recovered was 3.8[degree]C. Heat production was measured as oxygen consumption, air being drawn through a cylinder containing the animal and through a Pauling oxygen analyser. During sudden cooling, heat production augmented 6-fold, and then diminished progressively as the colonic temp. fell toward 4[degree] C. Breathing frequency and heart-beat frequency were not proportional to heat production during cooling. Heat production did not consistently increase as defense against body cooling below 5[degree] C. Total exchanges of heat were computed during cooling and during rewarming, and were compared with those of rats. Acclimatization to cold air was produced by sojourn in air of 4[degree] to 6[degree] C for 6 days, as shown by significant increase of resting minimal oxygen consumption. It decreased again after 3 weeks of no cooling. Certain other measurements showed no evidences of acclimatization. Spontaneous brief hypothermia and lethargy occurred in some hamsters kept in 5[degree] air. This graded imperceptibly into hibernation which lasted 2-4 days, with spontaneous rewarming of the body thereafter.