Dopamine activates masculine sexual behavior independent of the estrogen receptor α

Estrogen receptor α (ERα) is believed to be a critical part of the regulatory processes involved in normal reproduction and sexual behavior. However, in this study we show the ERα is not required for display of masculine sexual behavior. Male and female, ERα knock-out (ERαKO) and wild- type mice were gonadectomized and implanted with testosterone. Sexual behavior and social preferences were tested after injection of the dopamine agonist, apomorphine (APO), or vehicle. All wild-type mice showed normal masculine behavior, including mounts and pelvic thrusts in females, and ejaculation in males. In agreement with past reports, ERαKO mice, given vehicle, failed to show mating behavior. Yet, ERαKO males given APO showed masculine copulatory behavior and chemoinvestigatory behavior directed at females. ERαKO females, treated with APO, mounted and thrusted when tested with receptive females. HPLC revealed that wild-type and ERαKO mice had equivalent catecholamine content in brain regions associated with masculine sexual behavior. These data show that the ERα is not essential during development or adulthood for the expression of masculine sexual behavior in mice. Moreover, dopamine can activate sexual behavior via a mechanism that either acts on an ER other than ERα or via an estrogen-independent pathway.