Effects of beta-phenylethylamine on the hypothalamo-pituitary-adrenal axisin the male rat

beta -Phenylethylamine (PEA) is a trace neuroactive amine implicated in the regulation of the hypothalamic-pituitary-adrenal (HPA) response to stress. To test this hypothesis, effects of subchronic levels of PEA (50 mg/kg/day treatment for 10 days) on the corticotroph function were studied. PEA trea tment induces: (i) a significant increase of corticotrophin releasing hormo ne (CRH) immunoreactivity in the median eminence (ME), as measured by semi- quantitative immunofluorescence labeling techniques, (ii) a significant inc rease in CRH mRNA levels in paraventricular nuclei, as detected by in situ hybridization, and (iii) an increase in plasma adreno-corticotrophin hormon e (ACTH) and corticosterone levels in responses to stress. PEA treatment ha s no effect on the number of binding sites and on the dissociation constant of the glucocorticoid receptors in any structure studied. Results of the d examethasone suppression test were similar in PEA- and saline-treated rats. Taken together, these results suggest that PEA treatment stimulated the HP A axis activity levels directly via the CRH hypothalamic neurons, without a ltering the negative feed back control exerted by the glucocorticoids. (C) 2000 Elsevier Science Inc. All rights reserved.