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Chronic stress--the key to parturition?
I C McMillen1, I D Phillips, J T Ross
1Department of Physiology, University of Adelaide, Australia.
Reproduction, Fertility, and Development
|January 1, 1995
Summary
The central neural control of parturition timing is explored, focusing on fetal adrenocorticotrophic hormone (ACTH) regulation. This review examines proopiomelanocortin (POMC) processing and cortisol feedback in late gestation.
Area of Science:
- Reproductive Endocrinology
- Neuroendocrinology
- Fetal Physiology
Background:
- Parturition timing relies on fetal hypothalamo-pituitary-adrenal (HPA) axis endocrine signals.
- The central neural mechanisms stimulating ACTH synthesis and secretion in late gestation remain unclear.
Purpose of the Study:
- To review changes in ACTH precursor (POMC) processing in the fetal pituitary.
- To examine the consequences for fetal adrenal corticosteroidogenic enzyme expression.
- To discuss corticotroph cell heterogeneity and maturational changes in the fetal sheep pituitary.
Main Methods:
- Review of existing literature on fetal sheep endocrinology.
- Analysis of proopiomelanocortin (POMC) synthesis and processing.
- Discussion of cortisol negative feedback mechanisms.
Main Results:
- Changes in POMC processing occur in the fetal anterior pituitary before birth.
- Functional heterogeneity and maturational changes in fetal sheep pituitary corticotroph cells are evident.
- Development of cortisol negative feedback in the late gestation fetal HPA axis is observed.
Conclusions:
- The central neural regulation of ACTH secretion is critical for parturition timing.
- Maturational changes in the fetal pituitary and the development of negative feedback are key factors.
- Chronic stress may influence parturition timing through the HPA axis.