Figure 4.

ET-1 sensitizes TRPA1 in cultured mouse DRG neurons. (a) Pseudo color images from Fura-2 ratiometric imaging showing Ca²⁺ responses in mouse DRG neurons in response to MO (5 µM) with or without pretreatment of ET-1 (100 nM). Capsaicin (10 nM) was applied after MO application for comparison. KCl (40 mM) was applied at the end of recording to determine all live DRG neurons. (b) Averaged Ca²⁺ responses from experiments shown in panel (a). Red and black lines show conditions with or without ET-1 pretreatment, respectively. n > 20 cells/group. (c) Averaged Ca²⁺ responses of DRG neurons obtained from Trpa1^–/– mice. n > 20 cells/group. (d) Pharmacological studies of ET-1-induced TRPA1 sensitization in mouse DRG neurons. Cells were preincubated with ET_AR antagonist BQ-123 (10 µM), PKA antagonist H89 (10 µM), PLC antagonist edelfosine (10 µM), or corresponding vehicle (0.1% DMSO) for 5 min and then coapplied with ET-1. n > 20 cells/group. (e) Percentages of mouse DRG neurons responding to MO or Cap in control condition (no ET-1 added) and conditions of ET-1 with vehicle, BQ-123, H89, edelfosine, and TRPA1^–/–. n = 5–6 tests/group, each group contains 150–200 neurons from 3 mice. (f) Summarized Δ increase in ratio of 340/380 of MO or Cap-induced Ca²⁺ responses in mouse DRG neurons as recorded in (e). **p < 0.01 versus control group, ^##p < 0.01 versus ET-1+Veh group.

TRPA1: transient receptor potential cation channel, subfamily A, member 1; ET-1: endothelin-1; MO: mustard oil.