SEROTONIN RECEPTORS EXPRESSED BY MYELINATING SCHWANN-CELLS IN RAT SCIATIC-NERVE

We have previously reported that Schwann cells cultured from rat sciat ic nerves express 5-HT2A receptors. In this study we extend these in v itro observations to Schwann cells in situ. Since the serotonin (5-HT) levels in rat sciatic nerve are elevated following nerve injury, we e xamined Schwann cells in healthy and injured adult rat sciatic nerves, These nerves were double-labeled immunohistochemically with an anti-i diotypic antibody that recognizes 5-HT1B, 5-HT2A, and 5-HT2C receptors and an antibody against S100 beta, a Schwann cell marker. 5-HT recept or labeling was observed in Schwann cells of healthy and regenerating nerves, but not of degenerating nerves, while S100 beta labeling was o bserved in the Schwann cells of all nerves examined. The 5-HT receptor immunolabeling was cytoplasmic, as with the cultured Schwann cells, W hile staining was observed at the nodes of Ranvier, it was not restric ted to these locations. These results suggest that myelinating rat Sch wann cells normally express 5-HT receptors in vivo, and that receptor expression is reduced during times when 5-HT levels are elevated in th e sciatic endoneurium. (C) 1997 Elsevier Science B.V.