Blockade of Ovulation in Rats by Inhibitory Analogs of Luteinizing Hormone-Releasing Hormone

Abstract
An antagonist of luteinizing hormone-releasing hormone (LH-RH). [D-Phe2-Phe3-D-Phe6]-LH-RH (Phe, phenylalanine), suppressed luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release in male rats in response to LH-RH for at least 4 hours. Three subcutaneous injection of 1 milligram of this antagonist into rats during proestrus completely suppressed ovulation, while a single injection of 1.5 milligrams per rat inhibited 95.3 percent of the preovulatory surge of LH, 84.2 percent of the FSH surge, and suppressed ovulation by 86.4 percent.