Changes in hypothalamic FSH-RF and pituitary FSH during the estrous cycle of rats.

Abstract

Hypothalamic FSH-RF content and pituitary FSH concentration were measured in female rats during the estrous cycle. Vaginal smears were take from adult female Holtzman rats daily and only those that showed at least 2 consecutive 4-day cycles were used. The rats were killed by guillotine at 9:00 or 11:00 AM on the days of proestrus, estrus and diestrus, or at 4:30 PM on the day of proestrus. Hypothalamic FSH-RF (assay method of Mittler and Meites) content was high during the morning of diestrus and proestrus, and low on the afternoon of proestrus and morning of estrus. A significant decline in hypothalamic FSH-RF content was observed between 11:00 AM and 4:30 PM on the day of proestrus. Similar changes were observed in pituitary FSH concentration. Ovariectomy early in the morning of proestrus at least partially prevented the PM decline in hypothalamic FSH-RF content. These results suggest that FSH as well as LH are involved in the process of ovulation, and that the CNS may have a common regulatory mechanism...