Evidence that the mediobasal hypothalamus is the primary site of action of estradiol in inducing the preovulatory gonadotropin releasing hormone surge in the ewe

Endocrinology
A CaratyA Herbison

Abstract

Although a neural site of action for estradiol in inducing a LH surge via a surge of GnRH is now well established in sheep, the precise target(s) for estrogen within the brain is unknown. To address this issue, two experiments were conducted during the breeding season using an artificial model of the follicular phase. In the first experiment, bilateral 17beta-estradiol microimplants were positioned in either the medial preoptic area (MPOA) or the mediobasal hypothalamus (MBH), and LH secretion was monitored. An initial negative feedback inhibition of LH secretion was observed in ewes that had estradiol microimplants located in the MPOA (6 of 6 ewes) or caudal MBH in the vicinity of the arcuate nucleus (4 of 4). In contrast, a normal LH surge was only found in animals bearing estradiol microimplants in the MBH (5 of 10). Detailed analysis of estradiol microimplant location with respect to the estrogen receptor-alpha-immunoreactive cells of the hypothalamus revealed that 4 of the 5 ewes exhibiting a LH surge had microimplants located bilaterally within or adjacent to the area of estrogen receptor-expressing cells of the ventromedial nucleus. Two of these ewes exhibited a LH surge without showing any form of estrogen negative feed...Continue Reading

Citations

May 13, 2010·Reproductive Biology and Endocrinology : RB&E·J Alejandro Arreguin-ArevaloTerry M Nett
Sep 20, 2012·Endocrinology·Robert L Goodman, Michael N Lehman
Sep 23, 2009·Endocrine Reviews·Amy E OakleyRobert A Steiner
Mar 20, 2010·Endocrine Reviews·Catherine A Christian, Suzanne M Moenter
May 31, 2014·Physiology & Behavior·Joanna H SliwowskaMichael N Lehman
Mar 6, 2007·Reviews in Endocrine & Metabolic Disorders·J T Smith, I J Clarke
May 21, 2016·Nature Reviews. Endocrinology·Allan E Herbison
Aug 2, 2003·Biology of Reproduction·Sandra L PetersenClifford D Carpenter
May 20, 2008·Reproduction in Domestic Animals = Zuchthygiene·S P S GhumanH Dobson
Feb 12, 2009·Journal of Neuroendocrinology·J Clarkson, A E Herbison
Aug 15, 2009·Journal of Neuroendocrinology·S OhkuraH Okamura
Jul 17, 2010·Annals of the New York Academy of Sciences·Hiroko TsukamuraKei-ichiro Maeda
Nov 8, 2018·The Journal of Endocrinology·Christopher J ScottBriony M McGrath
Apr 11, 2014·Reproduction in Domestic Animals = Zuchthygiene·C FerganiH Dobson

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