Normalized leak-corrected R666G gating pore currents are not altered by divalent substitution in the bath. Gating pore currents were segregated from the nonspecific oocyte membrane leak as described (see Results) and scaled to the maximal rNaV1.4 gating charge in the corresponding oocyte. The mean I-V relationship of these normalized steady-state currents is shown in A. A nonlinear current component was not detected for WT-expressing oocytes in K⁺-containing bath solutions (n = 5). Inward gating pore current is seen when R666G channels are recorded in K⁺-containing bath solution (n = 6), whereas the gating pore current is abolished by NMDG substitution in the bath (n = 4; symbol key in figure inset). In B, R666G gating pore K⁺ currents were recorded in the presence of different divalent cations in the bath. No difference in the amplitude or voltage-dependent plateau of the R666G gating pore current is seen despite substitution with either 6 mM Ca²⁺ (n = 4), Ba²⁺ (n = 4), or Zn²⁺ (n = 3; symbol legend in the figure inset).