Figure 8

Firing frequency is increased in current clamped DRG neurons expressing M1627K mutant channels when stimulus intensities are compared at fold-threshold. For each cell the firing frequency at 2× and 3× threshold was determined and then averaged. Since threshold is lower for M1627K expressing neurons (154 ± 19 pA) compared to hNav1.7r-WT expressing neurons (292 ± 37 pA), the mean stimulus intensity at 2× and 3× was similarly scaled (319 ± 40 pA for M1627K versus 617 ± 68 for WT at 2× threshold; 483 ± 59 pA for M1627K versus 926 ± 101 pA for WT at 3× threshold). The firing frequency was significantly different between M1627K and WT for 3× threshold and peak firing frequency (p < 0.05 and p < 0.01) The lowest stimulus intensity that elicited the peak firing frequency was not significantly different (545 ± 50 pA for M1627K versus 564 ± 60 pA for WT).