Stochastic fire-diffuse-fire model with realistic cluster dynamics

Abstract

Living organisms use waves that propagate through excitable media totransport information. Ca2+ waves are a paradigmatic example of thistype of processes. A large hierarchy of Ca2+ signals that range fromlocalized release events to global waves has been observed in Xenopus laevisoocytes. In these cells, Ca2+ release occurs troughinositol 1,4,5-trisphosphate receptors (IP3R´s) which are organizedin clusters of channels located on the membrane of the endoplasmicreticulum. In this article we construct a stochastic model for acluster of IP3R´s that replicates the experimental observationsreported in Fraiman et al, Biophys. J. 90, 3897(2006). We then couple this phenomenological cluster model with areaction-diffusion equation, so as to have a discrete stochastic modelfor calcium dynamics. The model we propose describes the transitionregimes between isolated release and steadily propagating waves as theIP3 concentration is increased.