Figure 6. Use-dependent reduction of Na⁺ conductance during pulsing in various ${\text{K }}_{\text{o}}^{+}$.

A-E, after a 1 min dialysis period, the cell was pulsed to +60 mV for 400 ms at 0.05 Hz in 130 mM ${\text{N }}_{\text{i}}^{+}$/5 mM ${\text{N }}_{\text{o}}^{+}$ plus various concentrations of ${\text{K }}_{\text{o}}^{+}$ as indicated. The first current trace and the trace after a steady state was reached (2-3 pulses) are shown. Dotted lines denote zero current. Calibration values in C apply also to A, B, D and E. F, normalized relationship of steady current conductance to peak (first pulse) conductance (g_steady/g_peak) as a function of ${\text{K }}_{\text{o}}^{+}$ concentration. Plotted points are from means of 3–22 observations. The line was fitted through data using a Hill equation: f = 1/(1 + (K_d/[K⁺])^n_H), where f is the fractional conductance ratio, K_d represents the K⁺ concentration which produced 50 % of the maximum response and n_H is the Hill coefficient. For added ${\text{K }}_{\text{o}}^{+}$, the K_d was 230 μM and n_H was 1.55.