Voltage-dependent gating of veratridine-modified RIIA Na+ channel α subunit expressed heterologously in CHO cells

The voltage-dependent kinetics of veratridine-modified RIIA Na+ channel α subunit expressed heterologously in CHO cells were studied using the whole-cell patch-clamp technique. The activation and deactivation kinetics are well described by double exponential functions but poorly by a monoexponential function. Unlike the slow component, the fast time constant and associated amplitude factor depended steeply on the potential. The steady-state activation of veratridine-modified channels is described by a Boltzmann function with a V1/2 of –131.9 mV and a slope of 9.41 mV. A two-state model is proposed for the fast component that explains the kinetics of veratridine’s mechanism of action.