ACTION POTENTIAL-GENERATING CELLS IN HUMAN GLIOBLASTOMAS

We studied the electrophysiological properties of cells from human gli oblastomas obtained after surgery. The membrane currents were compared in cells of acute tissue slices and primary cultures using the whole cell mode of the patch-clamp technique. Very strikingly, in about a th ird of the tumor cells in situ and in vitro, depolarizing voltage step s elicited large, tetrodotoxin-sensitive inward currents with a thresh old of about -30 mV, indicating the presence of voltage-gated sodium c hannels. In addition, three types of potassium currents, a delayed rec tifying, an A-type, and an inward rectifying, were observed. Such a se t of voltage-gated channels is characteristic for neurons. Indeed, in these glioblastoma cells, depolarizing current pulses in the current c lamp mode were able to generate action potentials with properties simi lar to those observed in neurons. We interpret this finding as the abi lity of glioblastoma cells to acquire neuronlike properties but retain some glial features, since they still express markers typical for ast rocytes and their precursors. The role of sodium channels in glioblast oma cells is unclear at this moment and needs further investigation. O ur findings, however, imply that the tumor tissue can be intrinsically excitable and that neoplastic glial cells themselves may be an etiolo gic factor for epileptic seizures.