Figure 2.

Effects of different holding potentials on the IC₅₀ of EPA. I_Na was elicited by 10-ms test pulses from different holding potentials to 30 mV every 10 s. Concentration-dependent inhibitions of I_Na by EPA were fit with a logistical equation at different holding potentials, and IC₅₀ of EPA was calculated by the equation. The data of IC₅₀ were fit with the equation of linear regression for the wild type (○), Y1767K (●), F1760K (▴), and N406K (■) of hH1_α Na⁺ channels. The regression coefficients were similar for the wild type (−0.157 ± 0.008) and Y1767K (−0.124 ± 0.015). However, the regression coefficients were significantly different (P < 0.01) between the wild type and N406K (−0.322 ± 0.018), as well as between the wild type and F1760K (−0.254 ± 0.014).