Projections to the Preoptic Area from the Paraventricular Nucleus, Arcuate Nucleus and the Bed Nucleus of the Stria Terminalis Are Unlikely to Be Involved in Stress-Induced Suppression of GnRH Secretion in Sheep

Rivalland, Elizabeth Therese Astrid; Tilbrook, Alan John; Turner, Anne I.; Iqbal, Javed; Pompolo, Sueli; Clarke, I. J.

doi:10.1159/000096372

Cited by 15 publications

(22 citation statements)

References 116 publications

(78 reference statements)

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“…One study (4), which included gonadectomized and gonad intact sheep (luteal phase females), found that females had a greater cortisol response than males, and in three other studies (13)(14)(15) in gonadectomized sheep, we found no sex differences. The reasons for these differences between studies are not clear.…”

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confidence: 48%

“…Isolation/restraint stress is a wellcharacterized stressor that we have used often in our laboratory (4,7,8,(13)(14)(15)20). Isolation/restraint stress involves moving the animal from a pen adjacent to a familiar sheep to an unfamiliar pen that has no sheep housed in adjacent pens, securing the animal to the side of the pen with a harness, and enclosing the pen using opaque materials (13).…”

Section: Experiments 2: Plasma Concentrations Of Cortisol In Response mentioning

confidence: 99%

“…In each case, females had a significantly greater cortisol response compared with males, although in some of the studies using isolation/restraint stress (13)(14)(15), there were no differences between the sexes. Although it is tempting to make generalizations about sex differences in reactive and anticipatory responses to stress, it is not that straightforward because females also had a significantly higher cortisol response to tail docking (6), a stimulus that involves pain that was categorized by Herman et al (31) as reactive rather than anticipatory.…”

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Stressor Specificity of Sex Differences in Hypothalamo-Pituitary-Adrenal Axis Activity: Cortisol Responses to Exercise, Endotoxin, Wetting, and Isolation/Restraint Stress in Gonadectomized Male and Female Sheep

et al. 2010

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Sex differences in the stress-induced activity of the hypothalamo-pituitary-adrenal axis in sheep appear to be dependent on the stressor encountered and occur irrespective of the presence of gonadal steroids. We tested the hypotheses that cortisol responses to exercise, endotoxin, wetting (experiment 1), and isolation/restraint (experiment 2) stress differ between gonadectomized male and female sheep. At weekly intervals (in experiment 1), we subjected gonadectomized rams and ewes (n ϭ 6/group) to control conditions, to exercise stress, to iv injection of endotoxin, and to wetting stress. In a second experiment (experiment 2), we subjected gonadectomized rams and ewes (n ϭ 5/group) to control conditions or to isolation/restraint stress. In both experiments, we measured plasma concentrations of cortisol before, during, and after stress at a frequency of at least 15 min with samples collected (from an indwelling jugular catheter) at a greater frequency around the time of the stressor. Cortisol responses to wetting (experiment 1) and isolation/restraint (experiment 2) stress were significantly higher in females compared with males but in response to exercise (experiment 1) and endotoxin (experiment 1) stress, there were no differences between the sexes. For some stressors, there are sex differences in sheep in the stress-induced activity of the hypothalamo-pituitary-adrenal axis that are independent of the presence of the sex steroids, but the existence of these sex differences and the direction of these sex differences differs, depending on the stressor imposed. (Endocrinology 151: 4324 -4331, 2010) S ustained or repeated stress can lead to a range of chronic disease states such as obesity, metabolic syndrome, hypertension, autoimmunity, allergy, insomnia, depression, pain syndromes, and fatigue syndromes (1). Stress can be defined as a complex physiological state that embodies a range of integrative physiological and behavioral processes that occur when there is a real or perceived threat to homeostasis (2). A common response to stress is the activation of the hypothalamopituitary-adrenal axis, which results in the sequential secretion of CRH and arginine vasopressin from the hypothalamus, ACTH from the anterior pituitary, and glucocorticoids such as cortisol from the adrenal cortex. Together with other pathways, activation of the hypothalamo-pituitary-adrenal axis returns the organism to a state of homeostasis, but pathologies can develop when the activation of these pathways is severe and/or prolonged. Cortisol is thought to be responsible for many of the longer term effects of stress.There is an increasing amount of evidence to show that different physiological characteristics of an individual can influence cortisol responses to stress (3). For example, cortisol responses to stress can be influenced by the sex of an individual (4 -6), the amount of visceral adipose tissue an individual is carrying (7), and whether an individual is lactating (8). There also appear to be individuals who are naturally more or les...

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confidence: 48%

Section: Experiments 2: Plasma Concentrations Of Cortisol In Response mentioning

confidence: 99%

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confidence: 94%

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Stressor Specificity of Sex Differences in Hypothalamo-Pituitary-Adrenal Axis Activity: Cortisol Responses to Exercise, Endotoxin, Wetting, and Isolation/Restraint Stress in Gonadectomized Male and Female Sheep

et al. 2010

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“…The regional discrepancy in immunoactive GnRH may be largely explained by the fact that the Arc that is the key area of the steroid hormone feedback regulation on GnRH (Yeo & Herbison 2014). In immunized male rats, the fairly low level of testosterone negatively feedback regulates the production of GnRH neurons in the Arc instead of the Pa and MPN, which contain many GnRH cell bodies to regulate other hypophysiotropic hormone releasing hormones besides GnRH (Van Vugt et al 1997, Rivalland et al 2006. Likewise, the release of GnRH was significantly suppressed via reduction in the conveyance of GnRH to its nerve terminals in the ME of immunized rats (Glanowska & Moenter 2015).…”

Section: Figurementioning

confidence: 99%

Effects of GnRH immunization on the reproductive axis and thymulin

Su¹,

Sun²,

Zhou³

et al. 2015

Journal of Endocrinology

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The bidirectional regulation of thymulin in the reproductive-endocrine function of the hypothalamic-pituitary-gonadal (HPG) axis of rats immunized against GnRH remains largely unclear. We explored the alterations in hormones in the HPG axis in immunized rats to dissect the repressive effect of immunization on thymulin, and to clarify the interrelation of reproductive hormones and thymulin in vivo. The results showed that, in the first 2 weeks of booster immunization, thymulin was repressed when reproductive hormones were severely reduced. The self-feedback regulation of thymulin was then stimulated in later immune stages: the rising circulating thymulin upregulated LH and FSH, including GnRH in the hypothalamus, although the levels of those hormones were still significantly lower than in the control groups. In astrocytes, thymulin produced a feedback effect in regulated GnRH neurons. However, in the arcuate nucleus (Arc) and the median eminence (ME), the mediator of astrocytes and other glial cells were also directly affected by reproductive hormones. Thus, in immunized rats, the expression of glial fibrillary acidic protein was distinctly stimulated in the Arc and ME. This study demonstrated that thymulin was downregulated by immunization against GnRH in early stage. Subsequently, the self-feedback regulation was provoked by low circulating thymulin. Thereafter, rising thymulin levels promoted pituitary gonadotropins levels, while acting directly on GnRH neurons, which was mediated by astrocytes in a region-dependent manner in the hypothalamus.

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“…in pigs, Kanitz et al 2003, Loijens et al 2002, Piekarzewska et al 1999, Piekarzewska et al 2000, Zanella et al 1996 have demonstrated the involvement of neuropeptides such as CRF and enkephalins in different brain areas including the hypothalamus, brainstem and cortices. While neuroanatomical methods have been used to describe the immunoreactive content of brain areas (in sheep: Tillet 1995; in pigs: Kineman et al 1989, Leshin et al 1996, Niblock et al 2005, Rowniak et al 2008; in large mammals: Tillet & Kitahama, 1998), and neuronaltracing methods have been used to describe the interconnections between some of these brain areas (sheep: Qi et al 2008, Rivalland et al 2006, Tillet et al 1993pigs: Chaillou et al 2009), no dynamic functional information is available about the functional interactions among these different factors. The use of MRI techniques could be an interesting way of gaining a better understanding of the neuronal circuits of animal emotion and other functions.…”

Section: Emotional Reactionmentioning

confidence: 99%