Rapidly exchanging Ca(2+) stores: ubiquitous partners of surface channels in neurons.

Neuronal rapidly exchanging Ca(2+) stores coincide with the endoplasmic reticulum and possess ample, nonrandom distribution, dual receptor channels, IP(3) and ryanodine receptors, and heterogeneous membranes. Because of these properties, the stores are able to reinforce and expand the Ca(2+) signals generated at the surface, working as partners of voltage- and receptor-gated channels.