Fig. 7

Overexpression of Navβ4-WT increases excitability of DRG neurons. DRG neurons co-transfected with Nav1.6r and fluorescent probe tag (control) or Navβ4-WT were examined under current clamp conditions. 500 nM TTX was included in the bath solution to block endogenous TTXS channels and Nav1.8 was knocked-down with shRNA. a Representative traces of spontaneous activity recorded in control (left panel) and Navβ4 (right panel) groups. b Overexpression of Navβ4 (n = 14) increased the percentage of neurons that were spontaneously active (p < 0.05, Fisher’s exact test) compared to control (n = 15). Cells that were not spontaneously active were examined for evoked activity. A series of 1 s depolarizing current steps (0 pA up 1.2 nA in 100 pA increments) were injected into transfected DRG neurons from their resting membrane potentials. c Representative membrane responses to current injections at rheobase in control (left panel) and Navβ4-WT (right panel). d Compared with control, Navβ4-WT overexpression significantly increased the maximum number of evoked action potentials. The maximum number of evoked action potentials was defined as the maximum number of action potentials elicited at a given step depolarization from 0 pA to 1.2 nA for each cell. Data are mean ± SEM. *p < 0.05, Student’s t test