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. 1999 May;127(1):9–18. doi: 10.1038/sj.bjp.0702488

Figure 4.

Figure 4

Effects of RSD 921 on the use-dependent block of heart, skeletal muscle, neuronal and IFMQ3 Na+ channels in the absence or presence of 10 or 100 μM RSD 921. A series of depolarizing pulses of 20 ms duration to −10 mV were applied from a holding potential of −100 mV at 30 Hz. The peak currents were normalized to the current during the first depolarization, and plotted as a function of pulse number. The peak currents measured in the presence of the drug were normalized to the current during the first depolarization in the presence of the drug. Those currents measured ∼80% for the low RSD 921 concentration and ∼30% for the high RSD 921 concentration compared to current amplitudes in the absence of RSD 921. The normalization emphasizes the amount of use-dependent block that developed independently of the tonic block by RSD 921.