These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Central regulation of pulsatile gonadotropin-releasing hormone (GnRH) secretion by estradiol during the period leading up to the preovulatory GnRH surge in the ewe.
    Author: Evans NP, Dahl GE, Glover BH, Karsch FJ.
    Journal: Endocrinology; 1994 Apr; 134(4):1806-11. PubMed ID: 8137746.
    Abstract:
    An experiment was conducted to investigate the central regulatory effects of estradiol on GnRH secretion leading up to the preovulatory LH surge in the ewe. Midluteal phase ewes were ovariectomized, treated with steroid implants to maintain luteal phase concentrations of progesterone and estradiol, and fitted with an apparatus for collection of hypophyseal portal blood. After simulated luteolysis (removal of progesterone implants), the ewes were allocated to one of three groups: estradiol withdrawn, estradiol maintained at a luteal phase level, or estradiol raised from a luteal phase level to a peak follicular phase level in two increments. The results demonstrated that during the interval between luteolysis and the preovulatory gonadotropin surge, estradiol exerts a dose-dependent suppression of GnRH secretion from the hypothalamus. This effect reflects a suppression of GnRH pulse size and occurs despite a stimulatory action of estradiol on GnRH pulse frequency. The suppressive effect of estradiol on GnRH secretion, however, was delayed relative to that on LH. We conclude that during the period leading up to the preovulatory surge in the ewe, estradiol acts centrally, reducing GnRH secretion by suppressing GnRH pulse size.
    [Abstract] [Full Text] [Related] [New Search]