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Peripartum plasticity within the hypothalamo-pituitary-adrenal axis
S L Lightman1, R J Windle, S A Wood
1University Research Centre for Neuroendocrinology, Dorothy Crowfoot Hodgkin Laboratories, University of Bristol, Bristol Royal Infirmary, Bristol BS2 8HW, UK.
Progress in Brain Research
|October 9, 2001
Summary
During lactation, the hypothalamo-pituitary-adrenal (HPA) axis shows reduced stress responses. This adaptation, possibly mediated by hormones and oxytocin, supports a stable environment for offspring development.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Stress Physiology
Background:
- The hypothalamo-pituitary-adrenal (HPA) axis regulates physiological adaptations during pregnancy and lactation.
- Lactation alters the HPA axis's diurnal rhythm and stress responsiveness.
Purpose of the Study:
- To investigate the changes in HPA axis activity during lactation.
- To understand the mechanisms underlying stress hyporesponsiveness in lactating animals.
Main Methods:
- Monitoring HPA axis activity and stress responses in lactating vs. non-lactating states.
- Investigating the role of steroid hormones and central nervous system pathways (PVN, c-fos, CRH mRNAs).
- Assessing the impact of offspring removal and the influence of oxytocin.
Main Results:
- Lactation abolishes the diurnal rhythm of HPA axis pulse amplitude and attenuates stress-induced activity.
- Stress hyporesponsiveness is linked to luteolysis and steroid hormone changes (estrogen, progesterone).
- Central mechanisms, including reduced PVN neuronal activation, contribute to down-regulated stress response.
Conclusions:
- The HPA axis undergoes significant adaptation during lactation, leading to stress hyporesponsiveness.
- This adaptation is crucial for maintaining a stable endocrine environment for offspring development.
- Hormonal changes and neural plasticity, potentially involving oxytocin, underlie these adaptations.