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Sex difference in the effect of cortisol on the LH response of the pituitary to exogenous GnRH in hypothalamo-pituitary disconnected gonadectomised sheep

Stackpole, C. A., Clarke, I. J., Turner, A. I. and Tilbrook, A. J. 2005, Sex difference in the effect of cortisol on the LH response of the pituitary to exogenous GnRH in hypothalamo-pituitary disconnected gonadectomised sheep, in SRB 2005 : The 36th Annual Conference of the Society for Reproductive Biology, CSIRO Publishing, Collingwood, Vic., doi: 10.1071/SRB05Abs276.

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Title Sex difference in the effect of cortisol on the LH response of the pituitary to exogenous GnRH in hypothalamo-pituitary disconnected gonadectomised sheep
Author(s) Stackpole, C. A.
Clarke, I. J.
Turner, A. I.ORCID iD for Turner, A. I. orcid.org/0000-0002-0682-2860
Tilbrook, A. J.
Conference name Conference of the Society for Reproductive Biology (36th : 2005 : Perth, W.A.)
Conference location Perth, W.A.
Conference dates 4-7 Sep. 2005
Title of proceedings SRB 2005 : The 36th Annual Conference of the Society for Reproductive Biology
Publication date 2005
Publisher CSIRO Publishing
Place of publication Collingwood, Vic.
Summary We have used the hypothalamo-pituitary disconnected (HPD) sheep model to investigate direct pituitary actions of cortisol to suppress LH secretion in response to exogenous GnRH. We previously observed that, during the non-breeding season, treatment with cortisol did not suppress the LH response to GnRH in HPD gonadectomised rams or ewes.1 In the present experiment, we tested the effect of cortisol on the LH response to exogenous GnRH in gonadectomised HPD sheep during the breeding season. Using a cross-over design, HPD gonadectomised Romney Marsh rams (n = 6) and ewes (n = 5) received a saline or cortisol (250 μg/kg/h) infusion for 30 h on each of two days, one week apart. All animals were treated with 125 ng i.v. injections of GnRH every 2 h during a 6 h control period preceding the infusion and during the infusion. Jugular blood samples were taken during the control period and the first 6 h and last 6 h of the infusion (over 3 LH pulses). Mean plasma concentrations of LH and LH pulse amplitudes, driven by programmed GnRH injections, were similar in gonadectomised rams and ewes and there were no significant effects of saline infusion between the control periods or the saline infusion in either sex. The amplitude of LH pulses was significantly (P < 0.05) reduced in rams during the first 6 h of the cortisol infusion compared to the control period, but there were no effects of the cortisol infusion in ewes. These data show that, in the absence of sex steroids, there is a sex difference in the mechanism by which cortisol acts at the pituitary to reduce LH secretion in response to exogenous GnRH in HPD gonadectomized sheep during the breeding season. We conclude that the effect of cortisol to reduce secretion of LH involves an action on the pituitary, at least in gonadectomised rams.
Notes The abstract for this paper has been published in : Reproduction, Fertility and Development, v.17(Supplement) p.114–114, 2005.
ISSN 1031-3613
1448-5990
Language eng
DOI 10.1071/SRB05Abs276
Field of Research 119999 Medical and Health Sciences not elsewhere classified
Socio Economic Objective 970111 Expanding Knowledge in the Medical and Health Sciences
HERDC Research category E3.1 Extract of paper
Copyright notice © 2005 CSIRO
Persistent URL http://hdl.handle.net/10536/DRO/DU:30022082

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