Estrogen regulates the expression of female sexual behavior by acting through estrogen receptor (ER) α and β. Both types of receptors are widely distributed in various brain regions in social behavioral network. For the facilitation of female sexual behavior during the estrus phase, ERα in the ventromedial hypothalamic nucleus is known to be crucial (Musatov et al., PNAS, 2006). In contrast, neuroendocrine mechanism to suppress sexual receptivity in non-estrous females, particularly on the day after the behavior estrus (BE), still remains unclear. Our previous studies have shown that the ERβ knockout (βERKO) female mice maintained high levels of lordosis expression on the day after BE (Ogawa et al., PNAS, 1999). Therefore, it is hypothesized that ERβ may be involved in the inhibitory regulation of lordosis behavior, but responsible brain sites have not been identified. In the preset study, we site-specifically knocked down the ERβ expression (βERKD) in the dorsal raphe nucleus (DRN) with adeno-associated virus vector expressing a small hairpin (sh)RNA targeting ERβ. We examined the expression of sexual behavior in ovariectomized mice with steroid priming which mimicked the hormonal conditions of the day of BE (Day 1) and the day after BD (Day 2). βERKD mice showed the same levels of lordosis quotient (LQ, number of lordosis / number of mounts and intromissions) and receptivity (average of 15 lordosis scores measured as 0-3) on Day 1 as mice injected with control vectors. However, βERKD mice continuously showed high levels of LQ and receptivity on Day 2, when control mice showed a great reduction in both measurements compared to Day 1. These results suggest that the expression of ERβ in the DRN is involved in the inhibitory regulation of female sexual behavior.