Simulation of RYR distribution into clusters and release units and their activation during calcium sparks. (A–C) Distribution of the size of release units (in number of RYRs per release unit, nRYR) composed of 1 (A), 3 (B), and 10 (C) random clusters. The number of RYRs in clusters was distributed bi-exponentially according to Baddeley et al. (2009). The average number of RYRs per simulated release unit was 14 ± 18, 43 ± 31, and 145 ± 58 (mean ± sd). (D–F) Average of 100 simulations of the number of open RYRs (nO) in release units formed of 1 (D), 3 (E), and 10 clusters (F), respectively. (Top row) Simulated controls. PO set to approximate the overall shape of the distribution observed by Wang et al. (2004). (Bottom row) Simulated effects of tetracaine (PO = 15% of control). (Left columns) Simulations of the release site model of Xie et al. (2010) with control PO = 0.34 for coupled RYRs. (Right columns) Simulations of the release site model with independent RYRs with control PO = 0.24, 0.06, and 0.002 for D, E, and F, respectively. For details of simulations see Zahradníková et al. (2010).
