Relative effects of exercise, diet, and female stimulation on sexual aging of male mice.

These experiments examined the effects of several environmental variations on the rate at which sexual activity declines in aging male mice. CF-1 males were reared from 3 to 22 months of age in one of seven experimental conditions: in isolation with or without running wheels and on breeder or low-fat diets, or cohabited throughout this time span with intact or ovariectomized females that were either replaced monthly or not. Monthly replacement of intact females resulted in a pronounced delay in the expected loss of sexual activity of the aging males. Terminal tests of sexual capacity, administered at 23 months of age, however, showed no enduring effect of female replacement. These tests did reveal a larger than expected depression in the sexual activity of isolated males fed the breeder diet. Access to running wheels was totally without on sexual activity. Sexual aging is known to be a highly variable process in male mice. The present results may suggest that much of this variation is ultimately traceable to genetic or early experiential factors, or both.