Fig. 7.

Differences between frog and mouse MCell AZ models in the fraction of vesicle fusion events that included residual bound Ca²⁺ ions. A: in the frog AZ model, the vesicles that fuse during a train of action potentials at 100 Hz have a strongly increasing fraction of Ca²⁺ ions that remain bound from a prior action potential stimulus. B: in the mouse AZ model, there are fewer vesicle fusion events that are partially triggered by residual bound Ca²⁺ ions than observed in the frog model (A).