Deakin University
Browse

File(s) not publicly available

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

conference contribution
posted on 2005-01-01, 00:00 authored by C Stackpole, I Clarke, Anne TurnerAnne Turner, A Tilbrook
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.

History

Event

Conference of the Society for Reproductive Biology (36th : 2005 : Perth, W.A.)

Publisher

CSIRO Publishing

Location

Perth, W.A.

Place of publication

Collingwood, Vic.

Start date

2005-09-04

End date

2005-09-07

ISSN

1031-3613

eISSN

1448-5990

Language

eng

Notes

The abstract for this paper has been published in : Reproduction, Fertility and Development, v.17(Supplement) p.114–114, 2005.

Publication classification

E3.1 Extract of paper

Copyright notice

2005 CSIRO

Title of proceedings

SRB 2005 : The 36th Annual Conference of the Society for Reproductive Biology

Usage metrics

    Research Publications

    Categories

    No categories selected

    Keywords

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC