Characterization of elementary Ca2+ release signals in NGF-differentiated PC12 cells and hippocampal neurons

Elementary Ca2+ release signals in nerve growth factor- (NGF-) differentiat ed PC12 cells and hippocampal neurons, functionally analogous to the "Ca2sparks" and "Ca2+ puffs" identified in other cell types, were characterized by confocal microscopy. They either occurred spontaneously or could be act ivated by caffeine and metabotropic agonists. The release events were dissi milar to the sparks and puffs described so far, as many arose from clusters of both ryanodine receptors (RyRs) and inositol 1,4,5-trisphosphate recept ors (InsP(3)Rs). Increasing either the stimulus strength or loading of the intracellular stores enhanced the frequency of and coupling between element ary release sites and evoked global Ca2+ signals. In the PC12 cells, the el ementary Ca2+ release preferentially occurred around the branch points. Spa tio-temporal recruitment of such elementary release events may regulate neu ronal activities.