TOLERANCE TO COLD AND ANOXIA IN INFANT RATS

Abstract

Infant rats of known ages up to 27 days were cooled rapidly and were kept at known colonic temps. (indwelling thermocouples) for diverse periods of time, and then they were re-warmed. Survivors could be reared. Survival did not depend upon rate of cooling, nor upon immersion to the shoulders in water, or non-immersion. All signs including heart beat might be absent during severe hypothermia but survival might result. In atmospheres free of 02, newborn rats survived for 2 hrs. at 10[degree]C, for 0.3 hrs. at 1[degree]C and at 37[degree] C. Presence of air enhanced survival above 5[degree]C, and O2 prolonged it for hrs. at temps. up to 12[degree] C. With increasing age the tolerance to anoxia was progressively lost in about 12 days; the tolerance to cold persisted up to about 20 days. These 2 tolerances were therefore partially independent of each other.