Estradiol enables cortisol to act directly upon the pituitary to suppress pituitary responsiveness to GnRH in sheep

Neuroendocrinology
Bree N PierceAlan J Tilbrook

Abstract

We have shown that cortisol infusion reduced the luteinizing hormone (LH) response to fixed hourly GnRH injections in ovariectomized ewes treated with estradiol during the non-breeding season (pituitary-clamp model). In contrast, cortisol did not affect the response to 2 hourly invariant GnRH injections in hypothalamo-pituitary disconnected ovariectomized ewes during the breeding season. To understand the differing results in these animal models and to determine if cortisol can act directly at the pituitary to suppress responsiveness to GnRH, we investigated the importance of the frequency of GnRH stimulus, the presence of estradiol and stage of the circannual breeding season. In experiment 1, during the non-breeding season, ovariectomized ewes were treated with estradiol, and pulsatile LH secretion was restored with i.v. GnRH injections either hourly or 2 hourly in the presence or absence of exogenous cortisol. Experiments 2 and 3 were conducted in hypothalamo-pituitary disconnected ovariectomized ewes in which GnRH was injected i.v. every 2 h. Experiment 2 was conducted during the non-breeding season and saline or cortisol was infused for 30 h in a cross-over design. Experiment 3 was conducted during the non-breeding and bree...Continue Reading

Citations

Dec 6, 2008·Biology of Reproduction·Elizabeth R WagenmakerFred J Karsch
Apr 2, 2011·Tropical Animal Health and Production·Gustavo Guerino MacedoEliane Vianna da Costa e Silva
Feb 3, 2009·Domestic Animal Endocrinology·B N PierceA J Tilbrook
Apr 16, 2016·General and Comparative Endocrinology·Breanna N Harris, James A Carr
Feb 9, 2016·The Journal of Reproduction and Development·Ryutaro MoriyamaYukio Kato
Apr 14, 2016·Reproduction : the Official Journal of the Society for the Study of Fertility·Cameron RalphAlan Tilbrook
Jan 3, 2012·Hormones and Behavior·Marie-France BarretteAndrew F Russell
Aug 3, 2016·Reproduction, Fertility, and Development·Adrienne E CrosierDavid E Wildt
Feb 13, 2019·Human Reproduction·D StockE Schernhammer
Dec 10, 2019·The Journal of Reproduction and Development·Ryutaro MoriyamaYukio Kato
Jan 7, 2020·The Journal of Reproduction and Development·Sho NakamuraRyutaro Moriyama
May 2, 2021·Biochemical and Biophysical Research Communications·Chiaki KashinoFumio Otsuka

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