Brief Refeeding Restores Reproductive Readiness in Food-Restricted Female Musk Shrews (Suncus murinus)

Abstract

Food deprivation blocks sexual behavior and disrupts estrous cycles in mammals. We asked whether reduced copulatory behavior, produced by limited food intake, could be reversed by brief refeeding intervals in the female musk shrew. In Experiment 1, animals were food restricted to 60% of ad lib (FR), and an additional group of FR females were refed for 90 min prior to testing (RF). Refed and ad lib (AL) fed females were significantly more likely to mate than FR females. To test the hypothesis that food-induced restoration of copulatory behavior is not the result of changes in peripheral steroids, we repeated Experiment 1 using ovariectomized and testosterone-implanted females. The results from Experiment 2 were similar to those found in the first study. Next, a more severe refeeding schedule was employed; females were restricted to 50% of ad lib intake. Females in the RF and FR groups were significantly less likely than the AL animals to mate. In the last experiment, females were food restricted to 50% and longer refeeding intervals were employed. Four and one-half hours of food intake did not reinstate sexual behavior, but females refed for 12 h were as likely to mate as ad lib fed controls. We also did not detect any differences in plasma concentrations of testosterone and cortisol in AL, FR, and RF ovary-intact animals. These results define a nutritional threshold for copulatory behavior in the musk shrew. Since this species is highly sensitive to small alterations in food intake, it is a useful model for studies of interactions between metabolic fuels and behavior.