Figure 5.

The effects of various concentrations of methyl eugenol on the recovery from inactivation of Na⁺ channels. The recovery from inactivation was measured with a two-pulse protocol that consisted of a 100-ms conditioning pulse to 0 mV from a −100 mV holding potential, followed by an interpulse interval of varying duration at a −100 mV holding potential, then a test pulse to 0 mV for 10 ms. The amplitude of the current elicited by the test pulses was normalized with respect to the current elicited by the conditioning pulses in each series and were plotted as a function of the recovery interval. (A) Methyl eugenol slowed the recovery rate from inactivation. An interpulse interval of 2.5–100 ms was used to show more clearly the initial slowing effect. The data fit to a double exponential function according to the equation y=1−A exp(t/τ₁)−B exp(t/τ₂), where y is the normalized current, A, B are the amplitudes of the corresponding components, t is the interpulse interval, and τ₁ and τ₂ are time constants for recovery. (B) Methyl eugenol slowed the rate of recovery from inactivation with an interpulse interval of varying duration (2.5–5000 ms), while a higher concentration of methyl eugenol (500 μmol/L) produced an incomplete recovery of inactivated Na_v1.7 channels. (C) The differences between the normalized currents in the presence of various concentrations of methyl eugenol and the corresponding normalized control currents are shown. Data are from (A).