Basic properties of Nav current in mouse CCs are similar to those in rat CCs. (A) Example currents illustrating basic voltage-dependent activation in a mouse CC in a slice. (B) Plot of Nav current density (mean ± SD) from 18 mouse CCs. Red line corresponds to current density from rat CCs. (C) Points show normalized peak current amplitude for mouse CCs compared with rat CCs (red line). (D) Mouse (and rat) peak currents were converted to conductances assuming a reversal potential of +66 mV. For the G-V from mouse CCs, V_0.5 = −22.3 ± 0.3 mV with z = 5.3 ± 0.3e, while, for rat, V_0.5 = −27.4 ± 0.2 mV with z = 5.4 ± 0.2e.(E) Inactivation time constants (mean ± SD) as a function of command potential are plotted for 18 mouse CCs and compared with values from rat (red line). (F) Steady-state inactivation curves following 25-, 100-, 250-, and 1,000-ms conditioning steps at voltages from −110 to 0 mV for mouse. For 25 ms, V_0.5 = −35.5 ± 0.3 mV, z = 4.8 ± 0.3e; for 100 ms, V_0.5 = −42.6 ± 0.3 mV, z = 4.7 ± 0.2e; for 250 ms, V_0.5 = −46.7 ± 0.2 mV, 5.0 ± 0.2e; and for 1,000 ms, V_0.5 = −49.2 ± 0.3 mV, z = 4.8 ± 0.2e. (G) Comparison of mouse and rat (red) steady-state inactivation curves following 25-ms and 1,000-ms conditioning steps. At 25 ms for rat cells, V_0.5 = −37.8 ± 1.3 mV and, at 1,000 ms, V_0.5 = −57.7 ± 0.6 mV. (H) Comparison of V_0.5 of fractional availability following conditioning steps of differing durations for mouse and rat (red).