Control of action potential propagation by intracellular Ca2+ in cultured rat dorsal root ganglion cells.

1. To assess the role of intracellular Ca2+ in action potential (AP) propagation, whole‐cell recordings of cultured dorsal root ganglion (DRG) cells were carried out while Ca2+ was simultaneously measured with a laser‐scanning confocal microscope. 2. Flash photolytic liberation of a Ca2+ buffer during trains of APs which partly failed to invade the DRG cell body immediately lowered intracellular Ca2+ and restored safe AP propagation. Furthermore, the speed of the propagated AP was reduced considerably when intracellular Ca2+ was increased by flash photolysis of caged Ca2+. 3. Both results suggest that intracellular Ca2+ regulates the safety factor for AP propagation and may thus provide a control mechanism for synaptic integration, which acts pre‐ as well as postsynaptically.