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Neural control of adrenocortical secretion
S Feldman1, J Weidenfeld, D Saphier
1Department of Neurology, Hadassah University Hospital, Jerusalem, Israel.
Summary
Neural stimuli increase ACTH and corticosterone secretion via CRF-41, involving diverse pathways and norepinephrine. Hypothalamic norepinephrine depletion blocks these responses, highlighting its crucial role in the hypothalamo-pituitary-adrenocortical axis.
Area of Science:
- Neuroendocrinology
- Physiology
Background:
- Neural and extrahypothalamic stimuli can elevate ACTH and corticosterone (CS) secretion.
- This response is partly mediated by corticotropin-releasing factor (CRF)-41.
Purpose of the Study:
- To investigate the neural pathways and neurochemical mechanisms regulating ACTH and CS secretion.
- To elucidate the role of norepinephrine (NE) in the hypothalamo-pituitary-adrenocortical (HPA) axis activation.
Main Methods:
- Utilized stimulation techniques, brain lesions, and hypothalamic deafferentations.
- Examined the effects of hypothalamic norepinephrine depletion on CS secretion.
- Assessed changes in CRF-41 and ACTH levels following adrenalectomy.
Main Results:
- HPA axis activation involves multiple pathways, including anterior hypothalamic, medial forebrain bundle, and medial posterior hypothalamic inputs.
- Hypothalamic NE depletion significantly inhibits the rise in serum CS induced by both peripheral and central neural stimuli.
- NE acts via alpha 1 and alpha 2 adrenoceptors, with its role in beta receptors being uncertain.
- NE influences early and late alterations in median eminence CRF-41 and serum ACTH post-adrenalectomy.
Conclusions:
- The regulation of ACTH and CS secretion is complex, involving distinct neural pathways for different stimuli.
- Norepinephrine plays a critical facilitatory role in HPA axis activation, primarily through alpha-adrenergic mechanisms.
- Understanding these pathways is crucial for comprehending stress responses and neuroendocrine regulation.