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The display of copulatory behaviors usually requires the presence of a mate and is, therefore, preceded by a search for and approach to a potential partner. The intensity of approach behaviors is determined by a process labeled sexual incentive motivation. Although it is known that female sexual motivation depends on estrogens, their site of action within the brain is unknown. In the present experiment, we obtained data relevant to this issue. An shRNA encoded within an adeno-associated viral (AAV) vector directed against the estrogen receptor α (ERα) gene (or containing a nonsense base sequence as a control treatment) was injected bilaterally into the ventromedial nucleus of the hypothalamus (VMN) or the posterodorsal amygdala (MePDA) of female rats. After an 80% reduction of the number of ERα in the VMN, sexual incentive motivation was absent after treatment with estradiol and progesterone. Proceptivity and receptivity were also much reduced, while the number of rejections was enhanced. Suppression of the ERα in the MePDA lacked these effects. Likewise, the inactive control AAV vector failed to modify any behavior. Thus, the ERα in the VMN, but not in the MePDA, is important for proceptivity and receptivity as well as for sexual incentive motivation. These results show that ERα in the VMN is crucial for the entire sequence of behavioral events from the processes leading to the establishment of sexual contact until the accomplishment of copulatory behaviors.

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