mediates sensory neuron responses to histamine. A. Representative image of dissociated DRG neurons loaded with Fura-2 AM. B. Representative traces of selected cells (corresponding colored circles in A in response to histamine, capsaicin, and KCl. C. Proportion of total histamine responders in WT and KO DRG neurons (WT = 11.1% (126/1137 total WT neurons); KO = 6.7% (47/706 total KO neurons); **p < 0.01, χ2 test). D. Peak calcium increase in response to histamine, defined as % signal increase above baseline. WT 33.6 ± 2.8% change from baseline, n = 126 cells; KO 39.9 ± 6.6% change from baseline, n = 47 cells, unpaired t-test, p = 0.304. E. Percent of histamine-responsive neurons that responded to capsaicin (74/126 WT His + neurons; 19/47 KO His + neurons; p < 0.05, χ2 test). F. Proportion of capsaicin-responsive neurons (117/194 WT neurons, 144/259 KO neurons, p = 0.315, χ2 test). G. Proportion of histamine-responsive neurons in scramble- vs. inhibitor-treated groups (18.5% (75/405) of scramble-treated neurons vs. 13.1% (69/527) of peptide-treated neurons, p < 0.05, χ2 test). H. Peak calcium increase in response to histamine (inhibitor: 33.23 ± 2.7% change from baseline, n = 69 cells; scramble: 41.0 ± 3.7% change from baseline, n = 75 cells, p = 0.095, unpaired t test).