ETHANOL-INDUCED CHANGES IN B-ENDORPHIN AND CRF BINDING TO PERIPHERAL TISSUE

点击翻译按钮获取中文摘要

Although ethanol is commonly regarded as an anxiolytic, its administration mimics many actions of stress that involve activation of the hypothalamic-pituitary-adrenal axis (HPAA). An understanding of the effect of ethanol on this axis requires an appreciation of the central and peripheral regulatory factors and their interactions, which constitute the HPAA. Intimately involved in the homeostasis of the HPAA are several neuropeptides of brain origin (vasopressin and corticotropin-releasing factor [CRF]) and pituitary origin (beta-endorphin [BE] and adrenocorticotropin). The long-term goal of these studies is to understand the effect of ethanol at each level of the HPAA, with special emphasis on neuropeptide-dependent events. Before evaluating ethanol-induced perturbations of CRF and BE, it was necessary to validate the existence of specific BE and CRF binding sites in peripheral tissues, and to determine if occupancy of these receptors altered any of the known second-messenger systems. We have (1) identified, using 125-I-rCRF, specific binding sites for CRF in various rat peripheral tissues and bovine chromaffin cells in culture and (2) established that occupancy of the CRF binding sites, at least in rat adrenal membranes and bovine chromaffin cells, activates the adenylate cyclase/cAMP system. Furthermore, we have (1) identified, using 125-I-human BE, specific binding sites for BE in various rat peripheral tissues and (2) established that occupancy of the BE binding sites, at least in rat hepatic membranes, activates the adenylate cyclase/cAMP system. Exposure of rats to ethanol vapor for 14 days lowered immunoreactive plasma BE levels and reduced CRF and BE binding to a variety of peripheral tissues. In addition, chronic exposure of rats to ethanol vapors lowered pituitary CRF binding, basal and CRF-stimulated adenylate cyclase activity, and pro-opiomelanocortin messenger RNA levels.