Figure 7. Reduced Na+ current density and available current in KNa1 DKO SGNs. (A) Whole-cell inward Na+ currents were elicited using depolarizing steps from -70 mV to 35 mV (ΔV = 2.5 mV). The currents normalized to individual membrane capacitance (Cm), were recorded from 1-mo-old mice using basal SGNs from WT (shown with black traces) and DKO (shown with grey traces). Data were generated from 15 SGNs of each experimental group. (B) Consistent differences were noted in the peak Na+ current (I)- voltage (V) relation among WT (●) apical and DKO (●) SGNs. (C) In WT ~20% of the Na+ current is sustained, and in the DKO, ~10% persisted. Voltage-dependent activation and inactivation curves fitted with Boltzmann functions. Half-inactivation potentials (V1/2) were measured by fitting plots to them. The V1/2 of the steady-state inactivation for WT was -69.5 ± 3.1 mV and the slope factor k, was, 5.1 ± 0.9 mV (n = 9) and DKO was -66.3 ± 2.7 mV and the slope factor k, was 7.3 ± 0.7 mV (n = 11). The activation curves for Na+ currents from WT and DKO were fitted with the Boltzmann function. The V1/2 for activation WT SGN was -45.1 ± 2.8 mV, and the slope factor k, was 3.1 ± 0.8 mV (n = 9) and DKO was -43.8 ± 2.6 mV, and the slope factor k, was 2.7 ± 0.5 mV (n = 11).