INFLUENCE OF EXTRACELLULAR-MATRIX PROTEINS ON MEMBRANE-POTENTIALS ANDEXCITABILITY IN NG108-15 CELLS

Previous studies have demonstrated that components of the extracellula r matrix can induce neurite extension and cell adhesion in the neurobl astoma x glioma hybrid cell line, NG108-15. Using standard intracellul ar recording techniques, we examined the resting membrane potential (R MP) and membrane excitability of NG108-15 cells differentiated under s erum-free media with representative extracellular matrix (ECM) protein components as the substrate. Surfaces coated with collagen IV and a l aminin-l synthetic peptide induced a significantly (P < 0.05) more hyp erpolarized RMP than control polystyrene surfaces. For example, after greater than or equal to 8 days in culture NG108-15 cells plated on po lystyrene exhibited a RMP of -33.2 +/- 0.8 mV (mean +/- SEM, n = 158 c ells) whereas cells cultured on the laminin-l peptide C16 and collagen IV showed a RMP of -37.6 +/- 0.7 mV (n = 157) and -37.5 +/- 1.5 mV (n = 68), respectively. Furthermore, the proportions of cells on ECM sub strates showing membrane excitability, i.e. evoked action potentials ( APs) and the capability for regular firing, were significantly greater compared to those cells cultured on polystyrene. Among excitable cell s cultured on the different substrates, characteristics of the action potentials, such as AP duration, amplitude, and the maximum rate of ri se, dV/dt(MAX), were examined in detail. While little or no difference s were observed between polystyrene and the laminin-l peptide groups, significant differences in the AP parameters were apparent for collage n IV. For example, dV/dt(MAX) for polystyrene and the laminin-l peptid e C16 were only 71.7 +/- 24.5 V/s (n = 11) and 59.0 +/- 8.9 V/s (n = 9 ), respectively, whereas cells cultured on collagen IV surfaces exhibi ted a dV/dt(MAX) reaching 156.1 +/- 22.0 V/s (n = 7). These data suppo rt a role for ECM components in the maintenance of the RMP and membran e excitability in NG108-15 cells. (C) 1998 Elsevier Science Ireland Lt d.