The aversive and hypophagic effects of estradiol

Estradiol is known to reduce food intake in many species. Recent studies have also shown that estradiol can function as an unconditioned stimulus in taste aversion paradigms, suggesting that it induces nausea and malaise in rats and mice. The experiments reported here compared the hypophagic and aversive effects of estradiol. Using mice as subjects, the first investigation examined the taste aversion properties of the estradiol receptor antagonist MER-25, which is estrogenic with respect to feeding. MER-25 induced a strong taste aversion, contrary to a previous report. Second, progesterone, which counteracts the hypophagic effects of estradiol, did not disrupt the taste aversion induced by estradiol in mice. The third investigation used the Mongolian gerbil, a species in which estradiol increases food intake, in contrast to other species. Despite increasing food intake, estradiol induced a conditioned taste aversion in the gerbil similar to that seen in rats and mice. Taken together, these results indicate that the feeding and aversive effects of estrogen are mediated by different mechanisms.