Frequency of elemental events of intracellular Ca(2+) dynamics.

The dynamics of intracellular Ca(2+) is driven by random events called Ca(2+) puffs, in which Ca(2+) is liberated from intracellular stores. We show that the emergence of Ca(2+) puffs can be mapped to an escape process. The mean first passage times that correspond to the stochastic fraction of puff periods are computed from a novel master equation and two Fokker-Planck equations. Our results demonstrate that the mathematical modeling of Ca(2+) puffs has to account for the discrete character of the Ca(2+) release sites and does not permit a continuous description of the number of open channels.