Abstract
Estrogens potently suppress food intake. Compelling evidence suggests that estradiol, the primary form of estrogens, reduces food intake by facilitating other anorectic signals. Brain-derived neurotrophic factor (BDNF), like estradiol, appears to suppress food intake by affecting meal size. We hypothesized that estradiol modulates Bdnf expression and the anorectic effect of BDNF. The first goal was to determine whether Bdnf expression was regulated by endogenous estradiol of cycling rats and by cyclic estradiol treatment using ovariectomized rats. Bdnf expression within the ventromedial nucleus of hypothalamus (VMH) was temporally elevated at estrus following the estradiol peak, which coincided with the decline in feeding at this phase of the ovarian cycle. Additionally, food intake and body weight were increased following ovariectomy with a parallel decrease in Bdnf expression in the VMH. All of these alterations were reversed by cyclic estradiol treatment, suggesting that Bdnf expression within the VMH was regulated in an estradiol-dependent manner. The second goal was to determine whether estradiol modulates the anorectic effect of BDNF. Sham-operated estrous rats and ovariectomized rats cyclically treated with estradiol responded to a lower dose of central administration of BDNF to decrease food intake than male rats and oil-treated ovariectomized rats, implying that endogenous estradiol or cyclic estradiol replacement increased the sensitivity to anorectic effect of BDNF. These data indicate that Bdnf expression within the VMH and the anorectic effect of BDNF varied depending on plasma estradiol levels, suggesting that estradiol may regulate BDNF signaling to regulate feeding.