Journal article
Neural Systems Mediating Seasonal Breeding in the Ewe
Journal of neuroendocrinology, Vol.22(7), pp.674-681
07/2010
Handle:
https://hdl.handle.net/2376/104780
PMCID: PMC2908208
PMID: 20456601
Abstract
Seasonal reproduction in ewes is caused by a dramatic increase in response to oestradiol (E
2
) negative feedback during the non-breeding (anoestrous) season. Considerable evidence supports the hypothesis that A15 dopaminergic (DA) neurones in the retrochiasmatic area (RCh) play a key role in these seasonal changes. These A15 neurones are stimulated by E
2
and inhibit GnRH secretion in anoestrus, but not the breeding season. Because A15 neurones do not contain estrogen receptors-α (ERα), it is likely that E
2
-responsive afferents stimulate their activity when circulating E
2
levels increase during anoestrus. Retrograde tract tracing studies identified a limited set of ERα-containing afferents primarily found in four areas (ventromedial preoptic area, RCh, ventromedial and arcuate [ARC] nuclei). Pharmacological and anatomical data are consistent with γ-aminobutyric acid (GABA)- and glutamate-containing afferents controlling A15 activity in anoestrus, with E
2
inhibiting GABA and stimulating glutamate release at this time of year. Tract tracing demonstrated that A15 efferents project posteriorly to the median eminence and the ARC, suggesting possible direct actions on GnRH terminals or indirect actions via kisspeptin neurones in the ARC to inhibit GnRH in anoestrus. Identification of this neural circuitry sets the stage for development of specific hypotheses for morphological or transmitter/receptor expression changes that would account for seasonal breeding in ewes.
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Details
- Title
- Neural Systems Mediating Seasonal Breeding in the Ewe
- Creators
- R. L Goodman - Department of Physiology & Pharmacology, West Virginia University, Morgantown, West Virginia 26506 USAH.T Jansen - Department of Neurobiology & Anatomy, West Virginia University, Morgantown, West Virginia 26506 USAH. J Billings - Department of Veterinary and Comparative Anatomy, Washington State University, Pullman, Washington 99164 USAL.M Coolen - Department of Anatomy & Cell Biology, University of Western Ontario, London, Ontario, N6A 5C1, CanadaM. N Lehman - Department of Anatomy & Cell Biology, University of Western Ontario, London, Ontario, N6A 5C1, Canada
- Publication Details
- Journal of neuroendocrinology, Vol.22(7), pp.674-681
- Academic Unit
- Integrative Physiology and Neuroscience, Department of
- Identifiers
- 99900546520601842
- Language
- English
- Resource Type
- Journal article