Fig. 6.

Simulating synaptic responses to train stimulations using a sequential SV pool model. (A) Sequential SV model. On their way toward exocytosis, SVs transit sequentially from an infinitely large recycling pool (above, not shown) to an intermediate pool (resting pool size: eight SVs), followed by replacement sites and to docking sites (five sites each per AZ). All pool replenishment rates (downward arrows) are assumed to be calcium dependent (see numerical values in SI Appendix, Figs. S1B and S2B). (B) Recovery kinetics of s_1f, s_2f, and S_5–8 after an 8-AP train. Recovery time constants are similar to experimental values (compare with Fig. 3 P and Q). (C) Fast and slow components of synchronous release during 8-AP trains. The simulation reproduces the leftward shift of the cross-over point between the two curves at short intertrain intervals (compare with experimental data in Fig. 3 M–O). (D) Recovery kinetics of s_1f, s_2f, and S_5–8 after a 40-AP train (compare with Fig. 5 D and E).