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Seasonal differences in the effect of isolation and restraint stress on the luteinizing hormone response to gonadotropin-releasing hormone in hypothalamopituitary disconnected, gonadectomized rams and ewes

Stackpole, C. A., Turner, A. I., Clarke, I. J., Lambert, G. W. and Tilbrook, A. J. 2003, Seasonal differences in the effect of isolation and restraint stress on the luteinizing hormone response to gonadotropin-releasing hormone in hypothalamopituitary disconnected, gonadectomized rams and ewes, Biology of reproduction, vol. 69, no. 4, pp. 1158-1164, doi: 10.1095/biolreprod.103.016428.

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Title Seasonal differences in the effect of isolation and restraint stress on the luteinizing hormone response to gonadotropin-releasing hormone in hypothalamopituitary disconnected, gonadectomized rams and ewes
Author(s) Stackpole, C. A.
Turner, A. I.ORCID iD for Turner, A. I. orcid.org/0000-0002-0682-2860
Clarke, I. J.
Lambert, G. W.
Tilbrook, A. J.
Journal name Biology of reproduction
Volume number 69
Issue number 4
Start page 1158
End page 1164
Publisher Madison, Wis.
Place of publication Society for the Study of Reproduction
Publication date 2003
ISSN 0006-3363
1529-7268
Summary Stress responses are thought to act within the hypothalamopituitary unit to impair the reproductive system, and the sites of action may differ between sexes. The effect of isolation and restraint stress on pituitary responsiveness to GnRH in sheep was investigated, with emphasis on possible sex differences. Experiments were conducted during the breeding season and the nonbreeding season. In both experiments, 125 ng of GnRH was injected i.v. every 2 h into hypothalamopituitary disconnected, gonadectomized rams and ewes on 3 experimental days, with each day divided into two periods. During the second period on Day 2, isolation and restraint stress was imposed for 5.5 h. Plasma concentrations of LH and cortisol were measured in samples of blood collected from the jugular vein. In the second experiment (nonbreeding season), plasma concentrations of epinephrine, norepinephrine, 3,4-dihydroxyphenylalanine, and 3,4-dihydroxyphenylglycol were also measured. In both experiments, there was no effect of isolation and restraint stress on plasma concentrations of cortisol in either sex. During the breeding season, there was no effect of isolation and restraint stress on plasma concentrations of LH in either sex. During the nonbreeding season, the amplitude of the first LH pulse after the commencement of stress was significantly reduced (P < 0.05) in rams and ewes. In the second experiment, during stress there was a significant increase (P < 0.05) in plasma concentrations of epinephrine in rams and ewes and significantly higher (P < 0.05) basal concentrations of norepinephrine in ewes than in rams. These results suggest that in sheep stress reduces responsiveness of the pituitary gland to exogenous GnRH during the nonbreeding season but not during the breeding season, possibly because of mediators of the stress response other than those of the hypothalamus-pituitary-adrenal gland axis.
Language eng
DOI 10.1095/biolreprod.103.016428
Field of Research 070206 Animal Reproduction
Socio Economic Objective 970107 Expanding Knowledge in the Agricultural and Veterinary Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2003, Society for the Study of Reproduction, Inc.
Persistent URL http://hdl.handle.net/10536/DRO/DU:30022083

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