Effects of chronic oestrogen replacement on stress-induced activation of hypothalamic-pituitary-adrenal axis control pathways

Dayas, CV, Xu, Y, Buller, KM and Day, TA (2000) Effects of chronic oestrogen replacement on stress-induced activation of hypothalamic-pituitary-adrenal axis control pathways. Journal of Neuroendocrinology, 12 8: 784-794. doi:10.1046/j.1365-2826.2000.00527.x

Author Dayas, CV
Xu, Y
Buller, KM
Day, TA
Title Effects of chronic oestrogen replacement on stress-induced activation of hypothalamic-pituitary-adrenal axis control pathways
Journal name Journal of Neuroendocrinology   Check publisher's open access policy
ISSN 0953-8194
Publication date 2000-01-01
Sub-type Article (original research)
DOI 10.1046/j.1365-2826.2000.00527.x
Open Access Status
Volume 12
Issue 8
Start page 784
End page 794
Total pages 11
Place of publication Oxford, UK
Publisher Blackwell Science Ltd
Language eng
Subject C1
320702 Central Nervous System
730104 Nervous system and disorders
Abstract Oestrogen replacement therapy reportedly suppresses hypothalamic-pituitary-adrenal (HPA) axis responses to an emotional stressor in postmenopausal women. However, most studies in the rat suggest a facilitatory role for oestrogen in the control of HPA axis function. One explanation for this difference may be the regimen of oestrogen replacement: during oestrogen replacement therapy, oestrogen levels are low and constant whereas most animal studies examined the HPA axis response when oestrogen levels are rising. In the present study, we assessed HPA axis stress responses in mature ovariectomized rats after plasma oestrogen levels had been maintained at physiological levels for a prolonged period (25 or 100 pg/ml for 7 days). In the case of both an emotional stressor (noise) and a physical stressor (immune challenge by systemic interleukin-1 beta administration), oestrogen replacement suppressed stress-related Fos-like immunolabelling, in hypothalamic neuroendocrine cells and plasma adrenocorticotropin hormone responses. From the present data, and past reports, it appears unlikely that these effects of oestrogen are due to a direct action on corticotropin-releasing factor or oxytocin cells. Therefore, to obtain some indication of oestrogen's possible site(s) of action, Fos-like immunolabelling was mapped in the amygdala and in brainstem catecholamine groups, which are neuronal populations demonstrating substantial evidence of involvement in the generation of HPA axis stress responses. In the amygdala, oestrogen replacement suppressed central nucleus responses to immune challenge, but not to noise. Amongst catecholamine cells, oestrogen replacement was more effective against responses to noise than immune challenge, suppressing A1 and A2 (noradrenergic) and C2 (adrenergic) responses to noise, but only A1 responses to immune challenge. These data suggest that, as in postmenopausal women on oestrogen replacement therapy, chronic low-level oestrogen replacement can suppress HPA axis stress responses in the rat. Moreover, oestrogen appears to exert effects at multiple sites within putative HPA axis control pathways, even though most of the relevant neuronal populations do not contain genomic receptors for this gonadal steroid and the pattern of oestrogen action differs for an emotional vs a physical stressor.
Keyword Endocrinology & Metabolism
Immune Challenge
Catecholamine Cells
Medulla Catecholamine Cells
Paraventricular Nucleus
Postmenopausal Women
Rat Hypothalamus
Female Rat
Systemic Interleukin-1-beta
Neuroendocrine Responses
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 73 times in Thomson Reuters Web of Science Article | Citations
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Created: Tue, 10 Jun 2008, 21:32:33 EST