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

Genetically anovulatory female medaka did not show female receptivity, although they were normally courted by males. Consistently, intact females exhibited sexual behavior only after ovulation. Additionally, the administration of progesterone, which is released during ovulation, partially reinstated the sexual receptivity of anovulatory knockout females. Taken together with our result that progesterone receptor is expressed in brain regions that are considered strong candidates 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 around the time of ovulation.