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  • Title: Ghrelin regulates the hypothalamic-pituitary-adrenal axis and restricts anxiety after acute stress.
    Author: Spencer SJ, Xu L, Clarke MA, Lemus M, Reichenbach A, Geenen B, Kozicz T, Andrews ZB.
    Journal: Biol Psychiatry; 2012 Sep 15; 72(6):457-65. PubMed ID: 22521145.
    Abstract:
    BACKGROUND: Ghrelin plays important roles in glucose metabolism, appetite, and body weight regulation, and recent evidence suggests ghrelin prevents excessive anxiety under conditions of chronic stress. METHODS: We used ghrelin knockout (ghr-/-) mice to examine the role of endogenous ghrelin in anxious behavior and hypothalamic-pituitary-adrenal axis (HPA) responses to acute stress. RESULTS: Ghr-/- mice are more anxious after acute restraint stress, compared with wild-type (WT) mice, with three independent behavioral tests. Acute restraint stress exacerbated neuronal activation in the hypothalamic paraventricular nucleus and medial nucleus of the amygdala in ghr-/- mice compared with WT, and exogenous ghrelin reversed this effect. Acute stress increased neuronal activation in the centrally projecting Edinger-Westphal nucleus in WT but not ghr-/- mice. Ghr-/- mice exhibited a lower corticosterone response after stress, suggesting dysfunctional glucocorticoid negative feedback in the absence of ghrelin. We found no differences in dexamethasone-induced Fos expression between ghr-/- and WT mice, suggesting central feedback was not impaired. Adrenocorticotropic hormone replacement elevated plasma corticosterone in ghr-/-, compared with WT mice, indicating increased adrenal sensitivity. The adrenocorticotropic hormone response to acute stress was significantly reduced in ghr-/- mice, compared with control subjects. Pro-opiomelanocortin anterior pituitary cells express significant growth hormone secretagogue receptor. CONCLUSIONS: Ghrelin reduces anxiety after acute stress by stimulating the HPA axis at the level of the anterior pituitary. A novel neuronal growth hormone secretagogue receptor circuit involving urocortin 1 neurons in the centrally projecting Edinger-Westphal nucleus promotes an appropriate stress response. Thus, ghrelin regulates acute stress and offers potential therapeutic efficacy in human mood and stress disorders.
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