Mapping of IP3-mediated Ca2+ signals in single human neuroblastoma SH-SY5Ycells: Cell volume shaping the Ca2+ signal

Mapping of IP3-mediated Ca2+ signals in single human neuroblastoma SH-SY5Y cells: cell volume shaping the Ca2+ signal. J. Neurophysiol. 83: 1052-1057, 2000. Fast confocal laser-scanning microscopy was used to study spatiotemp oral properties of IP3-mediated Ca2+ release signals in human SH-SY5Y neuro blastoma cells. [Ca2+](i) increases were not affected by ryanodine (30 mu M ) or caffeine (10 nM) and largely insensitive to removal of external Ca2+, indicating predominance of IP3-induced Ca2+ release. Ca2+ signals evoked by high concentration (10 mu M) of the muscarinic agonist carbachol appeared as self-propagating waves initiating in cell processes. At low carbachol co ncentrations (500 nM) Ca2+ changes in most cells displayed striking spatiot emporal heterogeneity. The Ca2+ response in the cell body was delayed and h ad a smaller amplitude and a slower rise time than that in processes. Ca2changes in processes either occurred in a homogeneous manner throughout the whole process or were sometimes confined to hot spots. Regional difference s in surface-to-volume ratio appear to be critical clues that determine the spatiotemporal pattern of intracellular Ca2+ release signals.