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Vertebrate reproductive science and technology
RESEARCH ARTICLE

Patterns of preoptic–hypothalamic neuronal activation and LH secretion in female sheep following the introduction and withdrawal of novel males

Penny A. R. Hawken A , Jeremy T. Smith https://orcid.org/0000-0002-3450-9505 B , Trina Jorre de St Jorre https://orcid.org/0000-0001-7848-0305 A , Tammi Esmaili C , Christopher J. Scott https://orcid.org/0000-0002-2630-6177 D , Jennifer Rodger https://orcid.org/0000-0003-3413-4229 E F , Dominique Blache https://orcid.org/0000-0003-3476-3068 A and Graeme B. Martin https://orcid.org/0000-0002-1905-7934 A G
+ Author Affiliations
- Author Affiliations

A School of Agriculture and Environment, The University of Western Australia, Crawley, WA 6009, Australia.

B School of Human Sciences, The University of Western Australia, Crawley, WA 6009, Australia.

C La Trobe University, Cnr Plenty Road and Kingsbury Drive, Melbourne, Vic. 3086, Australia.

D School of Biomedical Sciences, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.

E School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia.

F Perron Institute for Neurological and Translational Science, Nedlands, WA 6009, Australia.

G Corresponding author. Email: graeme.martin@uwa.edu.au

Reproduction, Fertility and Development 31(11) 1674-1681 https://doi.org/10.1071/RD19079
Submitted: 28 February 2019  Accepted: 14 June 2019   Published: 12 September 2019

Abstract

The neuroendocrine response of female sheep to a novel male involves neural activation in the hypothalamus. However, if males are removed, the gonadotrophic signal declines, so the neural activity is likely to change. We examined Fos-immunoreactive (IR) cells in hypothalamic tissues from seasonally anovulatory female sheep exposed to males for 2 or 6 h, or for 2 h followed by 4 h isolation from males. Control females were killed in the absence of male exposure. Male introduction increased LH secretion in all females; male removal was associated with a reduction only in mean and basal LH concentrations. Females exposed to males for 2 h had more Fos-IR cells in the arcuate nucleus (ARC), ventromedial nucleus of the hypothalamus (VMH) and organum vasculosum of the lamina terminalis (OVLT) than control females. Fos-IR cells in the preoptic area (POA) were only greater than in control females after 6 h exposure to a male. Removal of males decreased the number of Fos-IR cells in the ARC, VMH and OVLT, but not in the POA. Thus, hypothalamic neural activation and LH secretion in female sheep are stimulated by males and decline after male removal. However, activation in the POA persists after removal and may explain the incomplete decline in the LH response.

Additional keywords: fertility, hypothalamus, neuroendocrinology, pheromone, reproduction.


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