Characterization of R-and S-<i>I_Na</i> recorded in zebrafish DRG neurons.

<p><b><i>A</i></b>, The current density versus test potential (<i>I–V</i>) relationship for R- and S-<i>I_Na</i>. <b><i>B</i></b>, Dot plots represent the membrane capacitance of DRG neurons displaying R- (open circles) and S-<i>I_Na</i> (filled circles). Vertical bars represent the median. *** P<0.001, Mann-Whitney <i>U</i>-test. <b><i>C</i></b>, Concentration-response curves for block of the R- and S-<i>I_Na</i> by tetrodotoxin (TTX). Solid lines represent nonlinear regression least-square fits of experimental points to a Hill equation (see under <i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042602#s4" target="_blank">Material and Methods</a></i>). <b><i>D</i></b>, The voltage-dependence of the Na⁺ conductance (<i>G_Na</i>, left panel) and steady-state inactivation (right panel) of R- and S-<i>I_Na</i>. Conductance was calculated from <i>G_Na = I_Na/(V_m−V_rev)</i>, in which <i>I_Na</i> is the peak current, <i>V_m</i> is the potential of the test pulse, and <i>V_rev</i> is the reversal potential for <i>I_Na</i>. The solid line represents a nonlinear regression fit to the Boltzmann function: 1/(1+exp[−(<i>V</i>−<i>V_1/2</i>)/<i>k</i>]), where <i>V</i> is the step membrane potential, <i>V_1/2</i> is the half-activation potential, and <i>k</i> is a slope factor. Voltage-dependence of inactivation was determined using a 200 ms conditioning pulse followed by a test pulse to −10 mV. Test pulse currents were normalized to the maximal value. Solid line is a fit to the Boltzmann equation (<i>k</i> is negative for inactivation curve). Error bars on each symbol represent the mean ± s.e.m. The number of neurons tested is shown in parentheses.