Fig. 11.

Simulations of calcium channel activation.A, Simulations showing the effect of the imposed command voltages (top) on the calcium current (middle) and the fraction of open calcium channels (bottom). The waveforms used in this simulation are the same as the one measured in control conditions and two versions of it broadened to correspond to the waveforms seen in 100 μmand 300 μm TEA. The action potentials have been scaled to have an amplitude of 100 mV and a resting potential of −70 mV. The calcium channel kinetics was simulated with a two-state model as described in Materials and Methods. B, Simulation as inA, but with calcium channel kinetics slowed by a factor of 5. Calcium currents in A and B are shown on the same scale. C, Total calcium influx (top), calcium current half-width (middle), and peak calcium current (bottom) plotted as a function of action potential half-width. The symbols show experimental data from Figures 5 and 8, and lines show the results produced by the simulation parameters used in A (solid line) andB (dashed line).