Figure 1.

Ulipristal acetate (UPA) inhibits ovulation after the initiation of luteinizing hormone (LH) signaling. A, Schematic diagram depicts the superovulatory protocol used in our experiments. In this paradigm, mice are treated with pregnant mare serum gonadotropin (PMSG) for 48 hours, mimicking follicle-stimulating hormone (FSH), to foster follicular development; subsequent administration of human chorionic gonadotropin (hCG), mimicking the effects of the LH, induces ovulation. Typically, ovulation occurs 11 to 12 hours following hCG treatment. The total number of oocytes is counted 18 hours later to evaluate the ovulatory response. B, Vehicle or UPA was administered intraperitoneally at 2, 6, or 8 hours after hCG injection, and the number of oocytes was counted 18 hours later to evaluate the ovulatory response. The data are represented as mean ± standard error of the mean (SEM).