Attempt to “pharmacologically treat” spark metastability. The black curve shows a histogram (log ordinate) of spark extinction times, assuming RyR gating rates estimated from the lipid bilayer data of Guo et al. (2012) and the JSR refilling rate estimated from spark restitution in rat (Sobie et al., 2005). As shown by the tail extending to long durations, these parameters give unstable sparks. The green curve shows the effect of doubling both the opening and closing rate constants of the RyR, thereby leaving the “calcium sensitivity” defined by p_o unchanged. This substantially shortens the unstable tail, because it accelerates RyR gating relative to the rate of refilling of the JSR. The red curve shows the additional effect of doubling the concentration of Casq, slowing down JSR depletion and refilling by increasing buffering. The peak of the distribution moves to the right, as expected, but the tail is actually shortened because JSR refilling is slower relative to RyR gating, reducing spark metastability.