Dose-dependent block of Na_{v}1.7 and Na_{v}1.8 currents by different lidocaine concentrations. Whole-cell Na^{+} currents were evoked every 5 s by 40 ms pulses to −15 mV from a holding potential of −100 mV until current stabilized (Na_{v}1.7). Solid lines represent control currents while dotted lines represent the current amplitude after superfusion with lidocaine to produce a steady-state lidocaine effect. For Na_{v}1.8, whole-cell Na^{+} currents were evoked every 20 s by 40 ms pulses to +20 mV from a holding potential of −100 mV until current stability was obtained. Solid lines represent currents under control conditions while dotted lines represent currents after lidocaine superfusion to produce a steady-state lidocaine effect. (a) 10 *μ*M , 100 *μ*M (b) and 300 *μ*M (c). Na_{v}1.7 (A) and Na_{v} 1.8 (B). (C) Dose–response curves for both Na_{v}1.7 and Na_{v}1.8 channels (*n*=5) were obtained from fits of a four parameters Hill's equation described in the Methods section. The values of the Hill coefficients for Na_{v}1.7 were: *a*=100.79, *b*=1.31, *c*=477.10 and *y*_{0}=1.52. For Na_{v}1.8, the values were: *a*=96.98, *b*=1.06, *c*=118.31 and *y*_{0}=4.78. Filled circles represent Na_{v}1.7 and filled triangles represent Na_{v}1.8. Na_{v}1.8 exhibits greater sensitivity to lidocaine than Na_{v}1.7 (∼4.4-fold), with EC_{50} values of 104 and 450 *μ*M, respectively.

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