Paracrinology of endometrial neuropeptides: Corticotropin-releasing hormone and opioids

Human endometrium possesses remarkable secretory properties and the charact eristics of a neuroendocrine organ. Epithelial cells of human endometrium e xpress the corticotropin-releasing hormone (CRH) and opioid peptide precurs ors genes (i.e., proopiomelanocortin, proenkephalin, and prodynorphin) and their end products. Endometrial neuropeptides are under the control of ovar ian steroid hormones and locally produced prostanoids and cytokines. Additi onally, neuropeptides participate in local paracrine regulatory loops,facil itating communication between endometrial epithelial and stromal cells as w ell as the interaction between endometrial and myometrial cells. In view of the proinflammatory cytokine properties of CRH, we postulate that endometr ial CRH may participate in intrauterine inflammatory and vascular processes associated with stromal cell decidualization and blastocyst implantation. Additionally, given the myorelaxant actions of opioids these endometrial ne uropeptides may participate in the control of myometrial contractility.