Ovarian influences on the meal patterns of female rats

Abstract

A series of experiments examined the effects of estrous cycles, ovariectomy, and estradiol-replacement on free-feeding meal patterns of female rats maintained on a liquid diet. The proestrous decrease in food intake was accomplished by a decrease in meal size and a less than fully compensatory increase in meal frequency. The hyperphagia induced by ovariectomy was reflected in an increase in meal size and a decrease in meal frequency. When food intake returned to preoperative levels, meal size remained elevated while frequency decreased further. Estradiol benzoate (2 μg/day) permanently decreased meal size in long-term ovariectomized rats. The subsequent return to food intake levels of controls was due primarily to an increase in meal frequency. These results suggest that the transient changes in food intake caused by estradiol withdrawal and replacement are accomplished by permanent changes in meal size followed by compensatory changes in the number of meals consumed per day. They suggest that the decrease in meal size at proestrus is due to a direct effect of estradiol on the mechanisms that terminate short-term food intake and are not secondary to changes in the level of total daily food intake.