Figure 7.
Local anesthestic and A-fiber selective blockade abolishes light-evoked paw withdrawal. A, Intraplantar ropivacaine (0.5%, 20 μl) blocked light-evoked paw withdrawal in 8/9 mice (n = 9) in the ipsilateral (left) paw, but all mice (9/9) responsed to stimulation of the uninjected, contralateral paw. B, Light-evoked response frequency was strongly attenuated in the ipsilateral paw of Vglut1-ChR2 mice that received A-fiber blockade with QX-314/flagellin (60 mm/1 μg, 20 μl, intraplantar, ipl) but not vehicle control (PBS, 20 μl, ipl) (treatment: F(1,12) = 13.58, p = 0.0031, paw: F(1,54) = 8.00, p = 0.0066, treatment × paw: F(1,54) = 20.3, p < 0.0001). C, Number of light-evoked responses was also strongly attenuated by QX-314/flagellin (treatment: F(1,12) = 12.88, p = 0.0037, paw: F(1,54) = 1.05, p = 0.31, treatment × paw: F(1,54) = 9.97, p = 0.0026). For B and C, in both treatment groups, the contralateral uninjected paw was stimulated after ipsilateral stimulation to demonstrate the localized nature of A-fiber blockade and to confirm the responsiveness of each subject (n = 7/group, stimulation: 5 mW/mm2, 10 Hz). Statistical analysis: two-factor linear mixed effects (LME) model, Tukey's post hoc test. B and C are shown as means ± SEM. Post hoc test: **p < 0.01, ***p < 0.001.