Expression of galanin in human placenta.

The neuropeptide galanin was originally implicated in the regulation of feeding behaviour. Today, galanin is implicated in several physiological functions including reproduction and feeding. Many hypothalamic neurohormones of the hypothalamo--pituitary axis (HPA) are also expressed in the placenta where the specialized topological compartments of the HPA are missing and where paracrine and autocrine regulatory mechanisms consequently prevail. Since galanin influences gonadotrophin-releasing hormone secretion in the HPA, we argued that a similar regulatory role for galanin might exist in human placenta. Since the presence of galanin in human placenta had not been previously reported, we analysed galanin expression in the human placenta by immunohistochemistry and quantitative polymerase chain reaction (PCR) throughout gestation. We found that the peptide hormone localizes to the syncytio- and cytotrophoblast layers; its RNA could be detected. By quantitative PCR we observed that throughout gestation, there is a loss of galanin mRNA which parallels the fall in signal intensity from immunohistochemical detection of the galanin oligopeptide. Furthermore, we detected secretion of galanin from isolated trophoblastic cells. We conclude that galanin may be an important and novel regulator of placental function.