Abstract
Intracellular Ca^2+^ is an important regulator of many cellular processes. Besides ion channels and transporters in the plasmalemma, changes in [Ca]~i~ can be mediated by uptake and release mechanisms of internal organelles. Theoretical and experimental procedures are developed aiming to reveal the distribution of internal Ca^2+^ pools and their role in generating complicated spatial patterns of [Ca]~i~ gradients. Cultured pyramidal neurons from rat hippocampus were loaded with Ca^2+^βsensitive fluorescent dyes, furaβ2 and fluoβ3. Cell images were partitioned according to pixel amplitude and highlighted pictures were characterized by their intensity, relative area and connectivity. This approach facilitates the localization of the sites of Ca^2+^ release from internal stores induced by application of different agents. After each trial, neurons were stained with dyes, acridine orange or DiOC~6~, which bind preferentially to nucleus and endoplasmic reticulum. A correlation between images confirmed the spatial localization of Ca^2+^ release sites. Application of the partition procedure also gave a clear evidence for the importance of Ca^2+^ influx in the mechanism of [Ca]~i~ oscillations.