[Effect of selection for behavior on the seasonal characteristics of the reproductive function in brown rats].

Artificial selection of grey rats by the domestic type of behaviour resulted in the decrease of the dependence of reproductive function on the effect of photoperiod. Domesticated animals exhibited a significantly lower decrease of the intensity of reproduction in autumn and winter as compared to aggressive ones. One of the causes of this difference is probably the observed shift in the seasonal changes in the level of sex steroids in the blood.