LH Release by LH-Releasing Hormone in Golden Hamsters at Various Stages of Estrous Cycle

Stimulation of LH release by administration of natural or synthetic luteinizing hormone-releasing hormone (LH-RH) was studied at different stages of the estrous cycle in the golden hamster. The animals were pretreated with phenobarbital to prevent a spontaneous preovulatory surge of LH. In these animals serum LH levels after saline injection remained low throughout the estrous cycle. Intravenous injection of 0.1 or 0.4 μg LH-RH significantly increased serum LH levels compared to appropriate controls. The greatest response to LH-RH was observed during proestrus. The smallest response was observed on the day 1 of diestrus, and in most of the animals, at estrus. The pituitary response to LH-RH on day 2 of diestrus was smaller than during proestrus, and greater than that observed during day 1 of diestrus and estrus. The results indicate that pituitary responsiveness to LH-RH varies at different stages of estrus cycle in the golden hamster.