Fig. 4
Effect of TCE on the inactivation of TTX-R Na+ channels. (A) A schematic illustration of the two-pulse protocol for determining inactivation kinetics. The TTX-R INa was induced by initial conditioning pulses (P1: − 10 mV depolarization, 2 to 5000 ms duration), which were followed by test pulses (P2: − 10 mV depolarization, 50 ms duration). The second TTX-R INa was recovered with an interpulse interval of 20 ms at − 80 mV potential. (B) Typical traces of TTX-R INa elicited by test pulses (P2) in the two-pulse protocol in the absence (left) and presence (right) of 3 mM TCE. The dotted lines represent the amplitude elicited by the initial conditioning pulses (P1). (C) The P2/P1 ratio of TTX-R INa against the duration of conditioning pulses in the absence (black circles) and presence (red circles) of 3 mM TCE. Continuous lines represent the best fit of the double exponential function. Each point represents the mean and SEM from seven experiments. (D) TCE (3 mM)-induced changes in kinetic parameters [a: fast time constant (τfast), b: slow time constant (τslow), c: amplitude fraction of fast time constant (Afast), d: amplitude fraction of slow time constant (Aslow). Each column represents the mean and SEM from seven experiments. **; p < 0.01, n.s; not significant. (E) TCE (1 mM, 3 mM, and 10 mM)-induced changes in weighted time constant (τweighted) of the P2/P1 ratio of TTX-R INa. The τweighted was normalized to the respective control (dotted line). Each column represents the mean and SEM from seven experiments for 1, 3, and 10 mM TCE. *; p < 0.05, **; p < 0.01, n.s; not significant