The Temporal Pattern of LH, FSH, and Ovulatory Responsiveness To Luteinizing Hormone Releasing Hormone in the Cyclic Hamster (40195)

LH, and FSH were measured by radioimmunoassays in hamsters injected SC with LHRH on each day of the estrous cycle. The ovulatory dose of LHRH required to reverse the phenobarbital-block in proestrous (Day 4) hamsters was 100 ng as a single injection or 50 ng as two injections 2 hr apart while a tenfold greater dose was required in Day 3 animals. Hamsters injected on Day 1 or 2 could not be induced to ovulate with up to a total of 4 μg LHRH. LHRH generally resulted in significant increases in LH and FSH on all days of the cycle including larger pre- to posttreatment rises on Days 2 and 3 than on Day 1 and, with smaller LHRH doses, potentiation of LH and FSH release on Days 3 and 4.