Fig. 1.

Capsaicin inhibited I_h in DRG neurons. (A) Representative current responses of DRG neurons to 1-s voltage pulses injected in 10-mV increment under control condition, during application of 1 µM capsaicin (CAP) and after washout (recovery). (B) Current-voltage relationship of I_h. Amplitudes of I_h in the presence were compared with those of control I_h at the same test voltage. (C) Concentration dependence of capsaicin inhibition of I_h. The curve was fitted by Hill equation (IC₅₀=0.68 µM). (D) Effects of capsaicin on the voltage dependence of activation. Normalized tail current was plotted versus various potentials (-60 to -130 mV) and fitted with Boltzmann equation. Estimated V_1/2 was shifted to left by CAP. (E) Voltage dependence of capsaicin inhibition of I_h. Amplitudes of capsaicin inhibition of I_h in the presence of capsaicin were normalized to those in control at the same test voltages.