Gonadal hormones and body temperature in rats: effects of estrous cycles, castration and steroid replacement.

The effects of estrous cycles, castration, subcutaneous steroid replacement, and intracranial steroid implants on the colonic temperatures were examined in 3 experiments. In Experiment 1 a rise in colonic temperature was observed at proestrus in intact females, and castration lowered the colonic temperatures of both males and females 1–2 hr before lights out. In Experiment 2 we tested the effects of 3 doses of progesterone and estradiol benzoate on the colonic temperatures of ovariectomized rats. Both hormones raised colonic temperature. The rise in colonic temperature was directly related to the progesterone dose, but it was inversely related to the dose of estradiol benzoate. In Experiment 3, progesterone and estradiol benzoate were implanted in the preoptic area of ovariectomized rats. Although estradiol benzoate in this site had no effect on colonic temperature, there was some suggestion that progesterone may increase colonic temperature when implanted in the preoptic area.