STUDIES OF COLD TOLERANCE

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Abstract
The effects of various hormone preparations and autonomic nerve blocking agents on survival time of mice in a low ambient temperature is studied. The mechanism of acquisition of cold tolerance is studied. Mature mice, acclimatized in a low ambient temperature at -5 [plus or minus] 1[degree]C, were exposed to extreme cold of -30 [image] s -35[degree]C and their survival times were determined. The mice had been treated with preparations of various sorts during acclimatization or immediately before exposure. The results obtained are as follows (1) The time required for acquisition of acclimatization to cold and its disappearance was less than one week. (2) Prednisolone increased the survival time of mice when given just before exposure, whereas it decreased cold tolerance (probably due to adrenal suppression) when given during acclimatization. (3) DOCA was without effect. (4) Thyroxine increased survival time regardless of time of administration, whereas methylmercaptoimidazole decreased survival time if given during acclimatization. (5) Chloropromazine directly increased the tolerance to cold, whereas reserpin had no such effect. (6) Castration appeared to increase tolerance to cold. (7) Survival time of male mice was longer than that of females. (8) Androgen was without effect, whereas estrogen increased tolerance to cold if given during acclimatization of castrated mice of either sex.