Orexins (hypocretins) and adrenal function.
The recently discovered neuropeptides orexin A and B regulate feeding behavior, neuroendocrine and autonomic functions, and sleep-wakefulness by central mechanisms. The expression of orexins and orexin receptors in various peripheral organs and the presence of orexin A in blood indicate the existence of a peripheral orexin system. In rat and human adrenal glands, both OX (1) and OX (2) receptor subtypes have been described with a predominant expression of OX (2) receptors in the adrenal cortex. In male rats, adrenocortical OX (2) receptors are much higher expressed than in female rats. Various experimental data demonstrate a stimulatory effect of orexins on the secretion of adrenocortical steroids, mainly on glucocorticoids. Some results also suggest the regulation of catecholamine synthesis and release by orexins. Whether the gender-dependent expression of adrenocortical OX (2) receptors has functional correlates awaits future clarification. As plasma orexin appears to rise during hunger and hypoglycemia, orexins may link adrenal functions with energy homeostasis.
Jöhren
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O
Institute of Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany. joehren@uni-luebeck.de
Brüggemann
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N
Dominiak
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P
D000311:Adrenal Glands / Q000502:physiology*; D002395:Catecholamines / Q000096:biosynthesis; D005247:Feeding Behavior / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D005938:Glucocorticoids / Q000378:metabolism*; D006801:Humans; D006815:Hunger / Q000502:physiology; D007003:Hypoglycemia / Q000503:physiopathology; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology*; D009479:Neuropeptides / Q000502:physiology*; D009490:Neurosecretory Systems / Q000502:physiology; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide / Q000378:metabolism*; D012737:Sex Factors; D012890:Sleep / Q000502:physiology
D002395:Catecholamines; D005938:Glucocorticoids; C000596229:HCRT protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide