Lidocaine activates human TRPA1. A. Representative inward currents in HEK293t cells expressing hTRPA1 activated by 3, 10, 30 and 100 mM lidocaine. Cells were held at -60 mV and only one concentration was applied on each cell. B. Concentration-dependent activation of hTRPV1 by lidocaine. The Hill-equation was applied to calculate the EC50 value. Transmembrane domain 5 is a determinant for species different activation of TRPA1 by lidocaine C. Representative inward currents evoked by 30 mM lidocaine on mTRPA1-WT, and the chimeras mTRPA1-hTM5/6 and hTRPA1-mTM5/6. Note the lack of a resurging current for mTRPA1-hTM5/6. D. Typical experiments for lidocaine-induced block of MO-evoked inward currents on hTRPA1-WT, mTRPA1-hTM5/6, mTRPA1-WT and hTRPA1-mTM5/6. Lidocaine was co-applied with MO during the steady-state phase of MO-evoked currents and experiments were performed in a Ca2+-free extracellular solution to minimize desensitization. Note the slow onset of lidocaine-induced block for hTRPA1-WT and mTRPA1-hTM5/6 as compared to mTRPA1-WT and hTRPA1-mTM5/6. Cells were held at -60 mV.