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Catecholamine effects upon rat hypothalamic corticotropin-releasing hormone secretion in vitro
A E Calogero1, W T Gallucci, G P Chrousos
1Developmental Endocrinology Branch, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
The Journal of Clinical Investigation
|September 1, 1988
Summary
Norepinephrine and epinephrine directly stimulate hypothalamic corticotropin-releasing hormone (CRH) secretion through alpha 1 and alpha 2 receptors. This catecholaminergic system is excitatory to CRH secretion at the hypothalamic level.
Area of Science:
- Neuroendocrinology
- Neuropharmacology
- Hypothalamic-Pituitary-Adrenal (HPA) Axis Regulation
Background:
- Catecholaminergic systems play a crucial role in regulating the HPA axis.
- Understanding the direct effects of catecholamines on corticotropin-releasing hormone (CRH) secretion is vital for comprehending stress response mechanisms.
Purpose of the Study:
- To investigate the direct influence of various catecholamine agonists and antagonists on hypothalamic CRH secretion.
- To elucidate the specific receptor subtypes involved in catecholamine-mediated CRH release.
Main Methods:
- Utilized an in vitro rat hypothalamic organ culture system.
- Quantified CRH secretion using radioimmunoassay (RIA) for intact rat CRH (IR-rCRH).
- Administered a range of catecholamine agonists and antagonists to assess their effects.
Main Results:
- Norepinephrine (NE) and epinephrine (E) dose-dependently stimulated IR-rCRH secretion via alpha 1 and alpha 2 receptors.
- Alpha-adrenergic agonists (phenylephrine, clonidine) mimicked NE and E effects, while beta-agonists showed minimal impact.
- NE-induced CRH secretion was modulated by GABA but not by serotonin or acetylcholine.
Conclusions:
- Central catecholaminergic systems are directly excitatory to CRH secretion at the hypothalamic level.
- Alpha-adrenergic receptors mediate the stimulatory effects of norepinephrine and epinephrine on CRH release.
- GABAergic neurotransmission plays a modulatory role in catecholamine-induced CRH secretion.
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