Figure 4.
Nav1.8 currents are enhanced in large-sized DRG neurons from inflamed rats. (A) Immunofluorescence staining of Nav1.8 (green) and NF200 (red) on acutely dissociated primary afferent neurons, 14 days post-CFA. Merge images show dually labeled large-sized sensory neurons (yellow). (B) Isolation of TTX-resistant Nav1.8 currents in large-sized sensory neurons from sham and inflamed rats. Nav1.8 currents are significantly increased post-CFA. Representative I-V curves of currents are determined using the pulse protocol indicated in the inset. (C) I-V curves of Nav1.8 currents obtained from large-soma DRG neurons. The peak maximum current is observed at 0 mV in all groups, with the exception of day 14 (–10 mV). (D) Peak Nav1.8 current densities are significantly increased at days 3, 8, and 14 post-CFA injection (***P <0.001 *P <0.05 vs. sham; $$$P <0.001 vs. day 3; ###P <0.001 vs. day 8; ANOVA followed by Sidak’s MCT; n = 6–13). (E, F) Kinetic properties of Nav1.8 currents in large-sized sensory neurons. CFA treatment induces a leftward shift of the activation (E) and inactivation (F) curves of Nav1.8 current. Half-activation and half-inactivation potentials and slope factors are summarized in Additional file 3: Table S3.