![Basic properties of Nav current and steady-state inactivation in rat CCs.(A) Nav current was activated with the indicated stimulus protocol in a rat adrenal CC in a slice. (B) The averaged peak-current density for inward current is plotted (mean ± SD) for a set of 18 rat CCs. The steady-state current (at end of 5-ms step) for the same set of cells is shown in red. (C) Currents from the set of patches in B were used to generate a G/V curve (mean ± SD), assuming ENa= 66 mV. For each cell, extrapolation of currents activated at +50 and +55 mV yielded ENa = 64.4 ± 2.9 mV (mean ± SD), while ENa calculated from nominal intracellular and extracellular solutions was 67 mV. The fitted voltage of half activation was −27.4 ± 0.2 mV with z = 5.4 ± 0.2e. (D) The rates (mean ± SD; n = 12 cells) of onset of inactivation measured from single exponential fits to the decay phase of the Nav currents are plotted as a function of the inactivation voltages. (E) Fractional availability (mean ± SD) is plotted as a function of conditioning potential over a range of conditioning potential durations (10, 25, 50, 100, 250, 500, and 1,000 ms). Inset shows example voltage protocol, where conditioning potential ranged from −110 to −10 mV (5-mV increments), with a test potential of 0 mV, following an initial holding potential of −80 mV. Numbers of patches tested for each recovery voltage were, from 10 to 1,000 ms, 8, 4, 6, 9, 6, 7, and 13. V0.5 and z for single Boltzman fits were, for 10 ms, −35.6 ± 0.3 mV, z = 5.9 ± 0.3e; for 25 ms, V0.5 = −39.2 ± 0.4 mV, z = 5.7 ± 0.4e; for 50 ms, V0.5 = −44.8 ± 0.4 mV, z = 5.1 ± 0.4e; for 100 ms, V0.5 = −48.7 ± 0.5 mV, z = 4.5 ± 0.3e; for 250 ms, V0.5 = −53.2 ± 0.4 mV, z = 4.1 ± 0.2e; for 500 ms, V0.5 = −56.5 ± 0.3 mV, z = 4.4 ± 0.2; and for 1,000 ms, V0.5 = −57.7 ± 0.2 mV, z = 4.3 ± 0.1e. (F) The mean V0.5 of fractional availability obtained from single Boltzman fits to the curves from each individual cell used for the averages in E is plotted (±SD; n = 4–13 cells, as indicated) as a function of conditioning potential duration. The line simply connects the dots. Red symbols correspond to measurements of voltage of half availability in previous papers with different conditioning step durations (circle: bovine CCs, Fenwick et al. [1982]; diamond: rat CCs, Hollins and Ikeda [1996]; square, rat CCs, Lou et al. [2003]).](https://cdn.rupress.org/rup/content_public/journal/jgp/153/4/10.1085_jgp.202012784/3/jgp_202012784_fig1.png?Expires=1767662463&Signature=J1zzkJM5WRhnVlAZeXQnBjHjeEOlpSV6cyz5URL69WFGmcVX-4qn5qYrNWCdlxUyOqCtwd~F5r6dH8ydRYpQ4UZPmawdPp0ExxepzFPR~~ClVyKXoIHF0VR8WUHlynQEKFxc0LHJf1b5d6D~CIftq-tVt0xTNL~M~g11dSXUzlHHTdiu9pLdbOmbSV7FAgpk8M9kkXvhq-aXmxgUtrnm0I1ylH0TWGlFmqJ6bkGTlJ1ntyHKckxaWODulXfez2CyUpqjEcE2GqtDmPLCD5at3N5Xko0g~XnptFIv~WOVOLEI1sDylYsxT9fGeMLVnqk9puFhVpfjvPNuOokqzKftVg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Basic properties of Nav current and steady-state inactivation in rat CCs. (A) Nav current was activated with the indicated stimulus protocol in a rat adrenal CC in a slice. (B) The averaged peak-current density for inward current is plotted (mean ± SD) for a set of 18 rat CCs. The steady-state current (at end of 5-ms step) for the same set of cells is shown in red. (C) Currents from the set of patches in B were used to generate a G/V curve (mean ± SD), assuming ENa= 66 mV. For each cell, extrapolation of currents activated at +50 and +55 mV yielded ENa = 64.4 ± 2.9 mV (mean ± SD), while ENa calculated from nominal intracellular and extracellular solutions was 67 mV. The fitted voltage of half activation was −27.4 ± 0.2 mV with z = 5.4 ± 0.2e. (D) The rates (mean ± SD; n = 12 cells) of onset of inactivation measured from single exponential fits to the decay phase of the Nav currents are plotted as a function of the inactivation voltages. (E) Fractional availability (mean ± SD) is plotted as a function of conditioning potential over a range of conditioning potential durations (10, 25, 50, 100, 250, 500, and 1,000 ms). Inset shows example voltage protocol, where conditioning potential ranged from −110 to −10 mV (5-mV increments), with a test potential of 0 mV, following an initial holding potential of −80 mV. Numbers of patches tested for each recovery voltage were, from 10 to 1,000 ms, 8, 4, 6, 9, 6, 7, and 13. V0.5 and z for single Boltzman fits were, for 10 ms, −35.6 ± 0.3 mV, z = 5.9 ± 0.3e; for 25 ms, V0.5 = −39.2 ± 0.4 mV, z = 5.7 ± 0.4e; for 50 ms, V0.5 = −44.8 ± 0.4 mV, z = 5.1 ± 0.4e; for 100 ms, V0.5 = −48.7 ± 0.5 mV, z = 4.5 ± 0.3e; for 250 ms, V0.5 = −53.2 ± 0.4 mV, z = 4.1 ± 0.2e; for 500 ms, V0.5 = −56.5 ± 0.3 mV, z = 4.4 ± 0.2; and for 1,000 ms, V0.5 = −57.7 ± 0.2 mV, z = 4.3 ± 0.1e. (F) The mean V0.5 of fractional availability obtained from single Boltzman fits to the curves from each individual cell used for the averages in E is plotted (±SD; n = 4–13 cells, as indicated) as a function of conditioning potential duration. The line simply connects the dots. Red symbols correspond to measurements of voltage of half availability in previous papers with different conditioning step durations (circle: bovine CCs, Fenwick et al. [1982]; diamond: rat CCs, Hollins and Ikeda [1996]; square, rat CCs, Lou et al. [2003]).