Figure 9. Effect of the rate of rise of the voltage command.

A, the I–V relations are shown for trials with rates of rise of 9 mV s⁻¹ (thin grey trace), 18 mV s⁻¹ (thick grey trace), 90 mV s⁻¹ (thin black trace), and 180 mV s⁻¹ (thick black trace). A single breakthrough spike (shown truncated) was observed with the trial using a voltage command of 180 mV s⁻¹. B, the traces from A are shown leak- and TTX-subtracted to reveal the effect of rate of rise on Na_P. By increasing the rate of rise of the voltage command, Na_P was markedly increased, suggesting that Na_P does slowly inactivate.