Inactivation of the ERG Current in NG108-15 Cells

Abstract

Differentiated NG108-15 neuroblastoma × glioma hybrid cells were whole-cell voltage clamped. The rate of inactivation of ERG (ether-à-go-go related gene) potassium channels was measured with a three-pulse protocol. Contamination with delayed rectifier current at positive potentials was avoided by using the selective ERG channel blocker E-4031. The curve relating time constant of inactivation τ to membrane potential V could be fitted by a Gauss curve. In a bath with 40 mM K+, the curve peaked at V = −36 mV. Lowering [K+]o decreased τ. At V = −20 mV, the average τ was 25.4 ms in 40 mM K+, 20.6 ms in 6.5 mM K+, and 15.0 ms in 0 mM K+. This resembles the relation between τ and [K+]o in ERG channels expressed in Xenopus oocytes.