The role of the NT-3 has been implicated in the survival of progenitor oligodendrocytes in culture. The object of this study was to investigate the expression of the TrkC receptor and its responsiveness in glial cells. We report the expression of two TrW receptor isoforms in rat primary oligodendrocyle cultures, a glial progenitor cell line, CG-4, and in C6 glioma cells. The reverse transcription-polymerase chain reaction-aided amplification of glial trkC with specific primers from the kinase domain, followed by its cloning and sequencing, shows the presence of two trkC transcripts. The sequence of one of the transcripts is homologous to a previously identified trkC isoform which encodes a functional receptor. The other transcript contains a 42-bp insert in the kinase domain. A Western blot of CG-4 and C6 probed with antibody to a TrkC revealed the presence of gpl45-kDa protein band. The investigations revealed a rapid autophosphorylation of gpl45TrkC in CG-4 and C6 cells in the presence of its specific ligand, NT-3. Furthermore, K252a, a neurotrophin-specific inhibitor, abolishes the NT-%mediated receptor autophosphorylation. We also examined other NT-Mependent phosphorylation of cellular substrates in oligodendroglial cells. Interestingly, we observed phosphorylation of phospholipase Cy-1 in CG-4 and C6 cells, and phosphorylation of phosphatidylinositol 3-kinase in C6 cells in the presence of NT-3. Both the NT-mediated phosphorylation of phospholipase Cy-1 and phosphorylation of phosphatidylinositol 3-kinase are blocked in the presence of K252a. The detection of the N T -S mediated early signal transduction events demonstrates that TrkC receptor exhibits NT-%mediated intracellular response in oligodendroglial cells.