Changes in pituitary responsiveness to LH-RH during puberty in the female rat: initiation of the priming effect

Castro-Vazquez, A.; Ojeda, S.R.

Neuroendocrinology 23(2): 88-98


ISSN/ISBN: 0028-3835
PMID: 331133
DOI: 10.1159/000122657
Accession: 068526422

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Pituitary responsiveness was evaluated after a single or 2 consecutive i.v. injections of LH-RH , the LH response to a 2nd injection of LH-RH administered 60 min after the initial injection was enhanced only during LP. When the 2nd injection of the neurohormone was given after the proestrous gonadotropin surge had started, the response was markedly enhanced. Uterine weight, used as an index of estrogen secretion, was low in A, increased significantly during EP and became maximum at LP, declining thereafter during estrus and diestrus. Ovulation usually occurred in the night prior to the day of vaginal opening. In spite of elevated estrogen levels, the pituitary LH response to LH-RH only increases around the time of puberty when endogenous release of the neurohormone presumably occurs to elevate plasma LH. This increase in LH-RH release, possibly brought about by the rising estrogen titers, can subsequently exert a priming effect on the gland, which enhances the LH response to a further exposure to the neurohormone.