Fig. 5.

Reduction of refractory period by VX-548. (A) Action potentials were evoked by a pair of 0.5-ms current injections with a variable time between them, with magnitude of both at 1.5-times the threshold current determined in control. The time between the two current injections was varied from longer to shorter to determine the refractory period with this stimulus. The figure shows superimposed sweeps from 8 different sets of times in control (black) and with 10 nM VX-548 (red). In control, the second stimulus evoked an action potential with a spacing (start to start) of 42 ms but not with 35 ms, while after VX-548, a spacing of 21 ms evoked an action potential using the same stimuli. Note faster decay of afterhyperpolarization in VX-548. (B) Collected results in 14 neurons, plotting the maximum spacing between the stimuli (with magnitude set at 1.5-times the threshold in control) in which the second stimulus failed to evoke a spike.