Activation of large conductance Ca(2+)-activated K+ channels in N1E-115 neuroblastoma cells by platelet-activating factor.

Using patch-clamp single channel recording techniques, we reported a Platelet-Activating Factor "PAF"-induced activation of large conductance Ca(2+)-activated K+ "BK(Ca)" channels in N1E-115 cells. This activation was only observed in cell-attached configuration and was blocked by the PAF antagonist BN50739 or removal of calcium from the bath. Nanomolar concentration of PAF produced a transient hyperpolarization observed in whole-cell current clamp configuration which was blocked by the bath application of BN50739 or iberiotoxin. Our results suggest that the PAF-induced hyperpolarization is mediated by an activation of BK(Ca) channels coupled to specific PAF receptors. This coupling is not direct and results from the PAF-induced elevation in cytosolic free Ca2+ concentrations that we have previously described in N1E-115 cells (Cell Calcium 1995, 17, 442-452).