Fig. 8.
The number of VGCCs that open in frog and mouse AZ MCell models. Although both frog and mouse AZ models have VGCCs with a Po during an action potential of ~0.2, since the frog AZ has 26 VGCCs, the average number of VGCCs that open during an action potential in the frog AZ model (A) is much greater than in the mouse AZ model (B). Within one AZ in the mouse model, more than 40% of action potentials do not open any VGCCs (black bar; B), and most action potentials open only one VGCC. Within the frog AZ model, most action potential stimuli open 3–7 VGCCs, and failures (black bar; A) are rare.