Mechanism of intracellular Ca2+ oscillations and interspike interval distributions

The dynamics of cytosolic Ca(2+) concentration exhibits oscillations with a wide range of periods. It was suggested in recent years by several modelling studies that these oscillations do not result from an oscillatory local dynamics but that fluctuations drive the formation of spatial and temporal structures in a non-oscillatory dynamic regime. Fluctuations arise from the random opening and closing of release channels on the membrane of the endoplasmic reticulum. Consequently, the interspike interval (ISI) has not a sharp value as with regular oscillations but distributions of ISI arise. We present these distributions and relate them to underlying processes. Oscillations with long average ISI can be comprehended as repetitive wave triggering. The standard deviation of the ISI approximates the. inverse of the triggering rate. Oscillations with short average ISI are often complex oscillations consisting of base line oscillations and intermittent oscillations on an elevated cytosolic Ca(2+) level.