Lack of Influence of Hysterectomy on Meal Size and Meal Number in Fischer-344 Rats

Abstract

Based on our previous observation that, when eating the same amount of food per 100 g b.wt., male rats gain five to seven times more weight than females who have an estrous cycle every 4 to 5 days, we questioned whether lower weight gain seen in female rats could be the result of increased energy cost in preparing endometrium for anticipated fertilization. Because the uterus modulates estrogenic effects on other hormone-dependent behaviors, for example, sexual receptivity and lordosis, we performed this study to determine if estrogen-mediated cyclical changes in food intake and feeding pattern occur after hysterectomy. Fifteen female Fischer 344 rats were randomized during the estrous phase to either hysterectomy with ovarian preservation or sham operation. A rat eater meter was used to continuously measure food intake, meal number, and meal size for two estrous cycles before and four cycles after surgery. Both groups showed the estrous phase linked cycling in meal number, meal size, and food intake. No differences existed between the two groups in these indices either before or after surgery. No differences existed between groups in rate of body weight gain after surgery, 0.95 ± 0.13 g/day in hysterectomized and 0.77 ± 0.1 g/day in sham-operated rats. We conclude that hysterectomy has no effect on rate of weight gain, food intake, and estrus linked cyclical feeding pattern in Fischer 344 rats.