Noradrenergic Control of GnRH Release from the Ewe Hypothalamus <i>In Vitro</i>: Sensitivity to Oestradiol

Ghuman, S. P. S.; Jones, D Neil; Prabhakar, S.; Smith, Robert F.; Dobson, H.

doi:10.1111/j.1439-0531.2007.00997.x

Cited by 3 publications

(4 citation statements)

References 36 publications

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“…Concerning in vitro GnRH secretion in ewes, oestradiol again has considerable impact via adrenergic and GABA-ergic influence. Basal GnRH increases in the presence of oestradiol ( Ghuman et al., 2006 ) and an adrenergic agonist increases release of GnRH that is prolonged by oestradiol ( Ghuman et al., 2008b ). In contrast, a GABA-A antagonist results in greater GnRH secretion that is higher in the absence of oestradiol ( Ghuman et al., 2008c ) concurring with in vivo studies ( Scott and Clarke, 1993 ).…”

Section: Role Of Neurotransmitters In Ewes Subjected To Transport Inmentioning

confidence: 99%

Understanding the trade-off between the environment and fertility in cows and ewes

2020

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The environment contributes to production diseases that in turn badly affect cow performance, fertility and culling. Oestrus intensity is lower in lame cows, and in all cows 26% potential oestrus events are not expressed (to avoid getting pregnant). To understand these trade-offs, we need to know how animals react to their environment and how the environment influences hypothalamus-pituitary-adrenal axis (HPA) interactions with the hypothalamus-pituitary-ovarian axis (HPO). Neurotransmitters control secretion of GnRH into hypophyseal portal blood. GnRH/LH pulse amplitude and frequency drive oestradiol production, culminating in oestrus behaviour and a precisely-timed GnRH/LH surge, all of which are disrupted by poor environments. Responses to peripheral neuronal agents give clues about mechanisms, but do these drugs alter perception of stimuli, or suppress consequent responses? In vitro studies confirm some neuronal interactions between the HPA and HPO; and immuno-histochemistry clarifies the location and sequence of inter-neurone activity within the brain. In both species, exogenous corticoids, ACTH and/or CRH act at the pituitary (reduce LH release by GnRH), and hypothalamus (lower GnRH pulse frequency and delay surge release). This requires inter-neurones as GnRH cells do not have receptors for HPA compounds. There are two (simultaneous, therefore fail-safe?) pathways for CRH suppression of GnRH release via CRH-Receptors: one being the regulation of kisspeptin/dynorphin and other cell types in the hypothalamus, and the other being the direct contact between CRH and GnRH cell terminals in the median eminence. When we domesticate animals, we must provide the best possible environment otherwise animals trade-off with lower production, less intense oestrus behaviour, and impaired fertility. Avoiding lifetime peri-parturient problems by managing persistent lactations in cows may be a worthy trade-off on both welfare and economic terms-better than the camouflage use of drugs/hormones/feed additives/intricate technologies? In the long term, getting animals and environment in a more harmonious balance is the ultimate strategy.

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Section: Role Of Neurotransmitters In Ewes Subjected To Transport Inmentioning

confidence: 99%

Understanding the trade-off between the environment and fertility in cows and ewes

2020

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“…1991). It is assumed that modulation of AVP secretion must take place elsewhere because a noradrenergic agonist increased both AVP and GnRH release during in vitro perfusions of the ewe hypothalamus (Ghuman et al. 2008a,c).…”

Section: Discussionmentioning

confidence: 99%

“…2003). In vitro perfusion of ewe hypothalamic slices has established that a α 1 ‐adrenoreceptor agonist stimulates (Ghuman et al. 2008a), whereas GABA inhibits AVP release (Ghuman et al.…”

Section: Introductionmentioning

confidence: 99%

Integration Between Different Hypothalamic Nuclei Involved in Stress and GnRH Secretion in the Ewe

Ghuman¹,

Morris²,

Spiller³

et al. 2010

Reprod Domestic Animals

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This study investigated possible integrated links in the neuroanatomical pathways through which the activity of neurones in the paraventricular nucleus and arcuate nucleus may modulate suppression of gonadotrophin-releasing hormone (GnRH) secretion during stressful situations. Double-label immunofluorescence and laser scanning confocal microscopy were used to examine the hypothalamic sections from the follicular phase ewes. Noradrenergic terminals were in close contact with 65.7 ± 6.1% corticotrophin-releasing hormone (CRH) and 84.6 ± 3.2% arginine vasopressin (AVP) cell bodies in the paraventricular nucleus but not with β-endorphin cell bodies in the arcuate nucleus. Furthermore, γ-amino butyric acid (GABA) terminals were close to 80.9 ± 3.5% CRH but no AVP cell bodies in the paraventricular nucleus, as well as 60.8 ± 4.1%β-endorphin cell bodies in the arcuate nucleus. Although CRH, AVP and β-endorphin cell terminals were identified in the medial pre-optic area, no direct contacts with GnRH cell bodies were observed. Within the median eminence, abundant CRH but not AVP terminals were close to GnRH cell terminals in the external zone; whereas, β-endorphin cells and terminals were in the internal zone. In conclusion, neuroanatomical evidence is provided for the ewe supporting the hypothesis that brainstem noradrenergic and hypothalamic GABA neurones are important in modulating the activity of CRH and AVP neurones in the paraventricular nucleus, as well as β-endorphin neurones in the arcuate nucleus. These paraventricular and arcuate neurones may also involve interneurones to influence GnRH cell bodies in medial pre-optic area, whereas the median eminence may provide a major site for direct modulation of GnRH release by CRH terminals.

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“…2009). Furthermore, in the ewe, in vitro evidence exists for the noradrenergic control of AVP neurones (Ghuman et al. 2008).…”

Section: Introductionmentioning

confidence: 99%

Neuronal Responses in the Brainstem and Hypothalamic Nuclei Following Insulin Treatment During the Late Follicular Phase in the Ewe

Ghuman

Morris

Routly

et al. 2011

Reprod Domestic Animals

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The aim of this study was to determine the neuronal responses following insulin administration during the late follicular phase. Intact ewes were given either saline or insulin (5 IU/kg, i.v.) at 35 h after progesterone withdrawal and killed 3 h later. There was a marked increase in the number of Fos-positive noradrenergic neurones in the caudal brainstem of insulin-treated ewes. In the hypothalamic paraventricular nucleus, insulin treatment increased the presence of Fos-positive corticotrophin-releasing hormone neurones (from 2% to 98%) and Fos-positive arginine vasopressin parvocellular neurones (from 2% to 46%). Interestingly, after insulin treatment, despite a general increase in Fos-positive neurones in the arcuate nucleus (ARC), there was a marked reduction (from 47% to 1%) in Fos-positive β-endorphin neurones. Similarly, colocalized Fos and oestradiol receptor (ER) α-positive neurones decreased in the ARC after insulin (from 7% to 3%). Conversely, in the ventromedial nucleus, ERα-positive neurones with Fos increased (from 7% to 22%) alongside a general increase in Fos-positive neurones. Overall, a complex system of neurones in brainstem and hypothalamus is activated following insulin administration during the late follicular phase.

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Noradrenergic Control of GnRH Release from the Ewe Hypothalamus In Vitro: Sensitivity to Oestradiol

Cited by 3 publications

References 36 publications

Understanding the trade-off between the environment and fertility in cows and ewes

Understanding the trade-off between the environment and fertility in cows and ewes

Integration Between Different Hypothalamic Nuclei Involved in Stress and GnRH Secretion in the Ewe

Neuronal Responses in the Brainstem and Hypothalamic Nuclei Following Insulin Treatment During the Late Follicular Phase in the Ewe

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