Cell permeabilization and inhibition of voltage-gated Ca(2+) and Na(+) channel currents by nanosecond pulsed electric field

Previous studies have found that nanosecond pulsed electric field (nsPEF) exposure causes long-term permeabilization of the cell plasma membrane. In this study, we utilized the whole-cell patch-clamp method to study the nsPEF effect on currents of voltage-gated (VG) Ca(2+) and Na(+) channels (I(Ca) and I(Na)) in cultured GH3 and NG108 cells. We found that a single 300 or 600 ns pulse at or above 1.5-2 kV/cm caused prolonged inhibition of I(Ca) and I(Na). Concurrently, nsPEF increased a non-inactivating "leak" current (I(leak)), presumably due to the formation of nanoelectropores or larger pores in the plasma membrane. The nsPEF effects were similar in cells that were exposed intact and subsequently brought into the whole-cell recording configuration, and in cells that were first brought into the whole-cell configuration and then exposed. Although both I(leak) and the inhibition of VG currents were enhanced at higher E-field levels, these two nsPEF effects showed relatively weak correlation with each other. In some cells, I(leak) increased 10-fold or more while VG currents remained unchanged. At longer time intervals after exposure (5-15 min), I(Ca) and I(Na) could remain inhibited although I(leak) had largely recovered. The causal relation of nsPEF inhibitory effects on VG currents and permeabilization of the plasma membrane is discussed.