Figure 2. Electrophysiological characteristics of Nav1.8 channel haplotypes.

A) Four haplotype Nav1.8 whole-cell sodium currents recorded from N2a cells in the presence of 150 nM tetrodotoxin. Currents were elicited from a holding potential of −100 mV with depolarizing steps between −70 and +60mV in 10mV increments. B) Current density (pA/pF) versus voltage for WT, PT, VA, and IV+VA+LP constructs. C) Conductance versus voltage for WT, PT, VA, and IV+VA+LP, fit with a Boltzmann function (see Supplemental Methods). V_1/2 for PT was shifted rightward, and VA and IV+VA+LP were both shifted leftward compared to WT. Slope factors (k) were not significantly different. D) Voltage-dependent inactivation as normalized current versus voltage. The V_1/2 and k for the haplotype variants were not significantly different from WT. E) Normalized I_Na,L of PT, WT, and IV+VA+LP, measured from a holding current of −100mV with pulse to +20mV for 475ms. PT shows a smaller and VA+LP+IV a greater I_Na,L compared to WT, respectively. F) Percent I_Na,L versus PR interval. The percent I_Na,L decreases moving from haplotypes with short to long PR intervals. The data were significantly correlated by the fitted line (r²=0.83, P=0.01). *: statistically different from WT (P>0.05).