‘Quantal’ Ca2+ release reassessed – a clue to oscillation and synchronization

Ca2+ release from intracellular Ca2+ stores, a pivotal event in Ca2+ signaling, is a ‘quantal’ process; it terminates after a rapid release of a fraction of stored Ca2+. To explain the ‘quantal’ nature, ‘all-or-none’ model and ‘steady-state’ model were proposed. This article shortly reviews these hypotheses and considers a recently proposed mechanism, ‘luminal potential’ model, in which the membrane potential of Ca2+ store regulates Ca2+ efflux. By reassessing the ‘quantal’ nature, other important features of Ca2+ signaling, oscillation and synchronization, are highlighted. The mechanism for ‘quantal’ Ca2+ release may underlie the temporal and spatial control of Ca2+ signaling.