Dynamic changes in hypothalamic LH-RH levels associated with the ovarian steroid-induced gonadotrophin surge.
Pro-oestrous-type LH surges were induced by treating ovariectomized rats (day 0) with either oestradiol benzoate (OeB, 40 micrograms/rat) or oestrogen (10 micrograms/rat followed by progesterone (4 mg/rat, day 2, OeBP). To characterize the temporal changes associated with the LH surge on day 2, LH-RH levels in the medial basal hypothalamus (MBH) and the pre-optic area (POA) were analyzed by RIA in rats sacrified at hourly intervals between 10.00--19.00 h. Following these treatments the LH-RH content of POA fluctuated somewhat but no definite pattern was observed. In OeB rats, the MBH LH-RH levels were unchanged through the initial LH surge period (13.00--15.00 h) declining significantly, as in the OeBP group, near the end of the surge period (19:00 h). However, in OeBP rats, the MBH LH-RH contents decreased at 14.00 h and these were followed by markedly elevated levels between 15.00--17.00 h coincident with maximal increments in serum LH. The OeBP group alone showed a surge of serum FSH.
D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis / Q000378:metabolism*; D007031:Hypothalamus / Q000032:analysis / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D011301:Preoptic Area / Q000032:analysis / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology*; D011863:Radioimmunoassay; D051381:Rats; D013997:Time Factors
D004967:Estrogens; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone