Involvement of hypothalamic luteinizing hormone-releasing hormone in the regulation of the estrous follicle-stimulating hormone surge in the female golden hamster.

Hypothalami collected from female hamsters during proestrus and estrus were assessed for LHRH content by bioassay and RIA. During estrus, as serum FSH levels rose, a depletion of hypothalamic LHRH was observed. The pattern of hypothalamic LHRH accumulation and depletion during proestrus and estrus as well as changes in serum and pituitary FSH concentrations were altered as a result of phenobarbital administration at 1200 h on proestrus. The effects of phenobarbital upon hypothalamic LHRH content as well as serum and pituitary FSH concentrations were overridden by the injection of purified FSH into the third ventricle of the hypothalamus at 1500 h during proestrus. The results of the present study suggest that the estrous FSH surge in hamsters is mediated, at least in part, by a concurrent discharge of hypothalamic LHRH. Further, intraventricular injection of FSH elicits a selective increase in serum FSH during estrus by influencing this LHRH-dependent system.