Ca2+ signaling evoked by activation of Na+ channels and Na+/Ca2+ exchangers is required for GABA-induced NG2 cell migration

NG2 cells originate from various brain regions and migrate to their destinations during early development. These cells express voltage-gated Na+ channels but fail to produce typical action potentials. The physiological role of Na+ channels in these cells is unclear. We found that GABA induces membrane depolarization and Ca2+ elevation in NG2 cells, a process requiring activation of GABA(A) receptors, Na+ channels, and Na+/Ca2+ exchangers (NCXs), but not Ca2+ channels. We have identified a persistent Na+ current in these cells that may underlie the GABA-induced pathway of prolonged Na+ elevation, which in turn triggers Ca2+ influx via NCXs. This unique Ca2+ signaling pathway is further shown to be involved in the migration of NG2 cells. Thus, GABAergic signaling mediated by sequential activation of GABA(A) receptors, noninactivating Na+ channels, and NCXs may play an important role in the development and function of NG2 glial cells in the brain.