Single transient potassium channels in human neuroblastoma cells induced to differentiate in vitro.

Single channel recordings were obtained from inside-out patches of cultured human neuroblastoma cells (cell line SH-SY5Y) treated with a phorbol ester, 12-o-tetradecanoylphorbol-13-acetate (TPA) to induce differentiation. An outward current reversing near the calculated reversal potential for potassium was detected. This channel is transiently active at membrane potentials between -40 and -70 mV but with preceding hyperpolarizing pulses also at more positive potentials, up to +75 mV. The current seems to consist of two components; a slowly activating component at potentials negative to -40 mV and a fast component, more sensitive to 4-aminopyridine, seen at more positive potentials.