Fig. 5: Intradermal capsaicin rapidly activates a localized subset of excitatory cells which are enriched within Ex1_TACR3/1.

a Schematic of intradermal capsaicin (caps) model of central sensitization. Relative size and location of the primary and secondary sites are shown on the left and duration/intensity of the psychophysical phenomena within each region are shown on the right. b Schematic for capsaicin injection and testing in the ex vivo preparation, the grey grid shows the testing sites for receptive field mapping. c Example ΔF/F Ca²⁺ traces from cells which were responsive to capsaicin injection. d Heat map of ΔF/F Ca²⁺ traces from cells within the same spinal cord which were activated or quiescent after capsaicin injection. e Percent of excitatory cells activated by capsaicin. N = 4 mice, mean ± SEM. f Somatic location in the SDH of SPB neurons (triangles) and interneurons (circles) which were either quiescent (open) or active (red) after capsaicin injection (scale bar, 50 µm). Rostral (R), caudal (C), medial (M), and lateral (L) are indicated on the black cross. g Using the relative distribution of cells along the medio-lateral (ML) axis activated by HT stimulation at different receptive fields (RF) we can infer the position and proximal-distal spread of the capsaicin injection by comparing the distribution of capsaicin responders (red) to the receptive field stimulations. h Percent of cells which responded to capsaicin injection within each excitatory population. A multiple logistic regression model was used to test how predictive each cluster was for being capsaicin responsive **P < .001. Odds ratio (OR) shown for significant results (Ex1_TACR3/1, P = 0.0001, P values are calculated from an F test). Full logistic regression model shown in source data. i Relative frequency of Ex1-7 within all CICADA identified cells responsive to capsaicin. j Radar chart showing the percent of cells in Ex1_TACR3/1 which responded to the indicated cutaneous stimuli. k Cardinal tuning for Ex1_TACR3/1. l Mechanical sub-modality tuning for Ex1_TACR3/1. Dotted circle is 1 unit vector in diameter. As described in methods: all tests were 2 tailed and where multiple post hoc comparisons were indicated by the main effect, 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.