Development of running activity in maturing rats: dependence upon prior androgen exposure and ovarian function

Female Sprague-Dawley derived rats were given either 1 mg testosterone propionate or an oil vehicle at 2 days of age. At weaning age half of each group were ovariectomized and at puberty the rats were placed in Wahmann activity wheels. In all groups there was a rise in running activity during the first 10 days after vaginal opening. This rise continued progressively in intact, ovulatory rats but did not continue in either persistent estrous or ovariectomized females. Beginning at 85 days of age running activity began to decline in all groups except the ovulatory females. This regression was protected against to some extent by ovariectomy in the androgen-treated females. It can be concluded that the ovaries are not required for either the initiation of running activity or the later decline seen in mature rats but that the gradually increasing running seen in intact rats is directly related to ovarian function.