Effects of isolation on mice in relation to age and sex

Isolated-housing conditions (a single mouse in cage) have been reported to induce various changes in physiological and behavioral characters of mice comparing with collective-housing conditions. However, the effect of age and sex has not been studied in detail. In this report, the young (8 or 11 weeks old) and the mature (29 weeks old for male and 32 weeks for female) of both sexes were comparatively studied on the response to isolation. The duration of isolation was 12-13 weeks. Significant differences were seen in body weight, weights of fur and interscapular adipose tissue, and weight of adrenals in male, and the difference in weight of adrenals was more outstanding in the young than in the mature. In female, only weight of ovaries differed significantly between the isolation and the collective groups, and the difference prevailed in the young than in the mature. The heavy body weight with fat deposition and small adrenals in the isolated male is not consistent with the results on the isolated male rat (Hatch et al. 1965). Small ovary in the isolated female is a similar finding to reports on mice (Weltman et al. 1962) and on rats (Hatch et al. 1965).