Sexual receptivity increases in synchrony with the ovulatory cycle in female medaka

Successful reproduction requires coordinated regulation of gonadal function and sexual behavior. However, the mechanisms of such a regulation remain elusive. Here, we used a teleost medaka to find out possible involvement of ovulation in the control of female sexual behaviors by analyzing the sexual behaviors of the female gene-knockout medaka that do not ovulate and found that ovulation is essential for the facilitation of female sexual receptivity. Behavioral recordings and anatomical examinations showed that the sexual behavior of medaka occurs only after the ovulation. Furthermore, progesterone administration partially reinstated the sexual receptivity of the anovulatory knockout females. Taken together with the result that progesterone receptor is expressed in the brain regions that are considered strong candidate for regulation of sexual behavior, we propose that female sexual receptivity is facilitated in synchrony with the ovulatory cycle via progesterone receptor signaling in specific brain regions that occurs around the timing of ovulation.