Figure 4.

Pharmacological effects of formalin, fentanyl, and Yokukansan on TRPA1. Typical traces (left) and current–voltage relationships (right) of formalin-induced TRPA1 currents in HEK293T cells expressing human TRPA1. The concentrations of formalin (For), fentanyl (FEN), and Yokukansan (YKS) were 0.003%, 10 μM, and 1 mg/mL, respectively. YKS (a) or FEN (b), and YKS and FEN (c) were pretreated for 1 min before the concomitant administration of formalin. TRPA1 was not inhibited by both fentanyl and YKS. The holding potential was −60 mV, and ramp pulses (−100 to +100 mV, 300 ms) were applied every 5 s.