Fig. 6: Capsaicin injection increases the frequency of LT responsive neurons and enhances LT tuning.

a Experimental design. b Experimental protocol for testing the effects of capsaicin induced central sensitization. c Field of view in the superficial SDH showing maximum ΔF/F responses during LT stimulation at 3 RFs before and after intradermal injection of capsaicin (scale bar, 50 µm). N = 4 animals. d Left: radar chart showing the percent of excitatory cells responsive to the indicated stimuli before (grey) and after capsaicin (red). Right: change in percent responders. There was a significant main effect of stimulation (F (4, 12) = 41.11), P < 0.0001, and a significant interaction between stimulation and time (F (4,12) = 5.176), P = 0.0117 (2-way RM ANOVA). Post hoc testing was performed comparing post/pre capsaicin for all stimulations. N = 4 mice, *Q < 0.05 e Percent of all excitatory cells responsive to LT stimulation before/after capsaicin. N = 4 animals. *Q < 0.05. Data are presented as mean values ± SEM. f LT RF size of excitatory cells before/after capsaicin. Corrections for both LT and HT were included (HT data shown in Supplementary Fig. 8). There was a significant interaction between stimulation and time (F (1,3) = 13.34), P = 0.0354 (2-way RM ANOVA). Post hoc testing was performed comparing RF size before/after capsaicin. N = 4 mice, *Q < 0.05. Data are presented as mean values ± SEM. g, Mechanical sub-modality tuning for excitatory cells before/after capsaicin. Mean value shown as thick arrows and individual animals shown as light, thin lines. Dotted circle is 1 unit vector in diameter. *P > 0.05 (two-tailed paired t test, P = 0.0281). h Percent responders to LT stimuli before (left) and after (right) capsaicin for each CICADA population. The change in % responders (Δ) is indicated with a black tick mark. There was a significant main effect of capsaicin (F (1, 3) = 11.02), P = 0.0451 (Mixed-effects restricted maximum likelihood model). Post hoc testing was performed comparing post/pre capsaicin for all populations. N = 4 mice, *Q < 0.05. Ex2, Q = 0.0161; Ex5 Q = 0.0157; Ex6, Q = 0.0155. As described in methods: all tests were 2 tailed and where multiple post hoc comparisons were indicated, a correction for multiple comparisons was implemented using a False Discovery Rate of 0.05 via the two-stage step-up method of Benjamini, Krieger and Yekutieli. Reported Q-values are the FDR corrected P-values.