A fundamental role for the nitric oxide-G-kinase signaling pathway in mediating intercellular Ca2+ waves in glia

In this study, we highlight a role for the nitric oxide-cGMP-dependent prot ein kinase (NO-G-kinase) signaling pathway in glial intercellular Ca2+ wave initiation and propagation. Addition of the NO donor molsidomine (100-500 mu M) or puffing aqueous NO onto primary glial cell cultures evoked an incr ease in [Ca2+](i) in individual cells and also local intercellular Ca2+ wav es, which persisted after removal of extracellular Ca2+. High concentration s of ryanodine (100-200 mu M) and antagonists of the NO-G-kinase signaling pathway essentially abrogated the NO-induced increase in [Ca2+](i), indicat ing that NO mobilizes Ca2+ from a ryanodine receptor-linked store, via the NO-G-kinase signaling pathway. Addition of 10 mu M nicardipine to cells res ulted in a slowing of the molsidomine-induced rise in [Ca2+](i), and inhibi tion of Mn2+ quench of cytosolic fura-2 fluorescence mediated by a bolus ap plication of 2 mu M aqueous NO to cells, indicating that NO also induces Ca 2+ influx in glia. Mechanical stress of individual glial cells resulted in an increase in intracellular NO in target and neighboring cells and interce llular Ca2+ waves, which were NO, cGMP, and G-kinase dependent, because inc ubating cells with nitric oxide synthase, guanylate cyclase, and G-kinase i nhibitors, or NO scavengers, reduced Delta[Ca2+](i) and the rate of Ca2+ wa ve propagation in these cultures. Results from this study suggest that NO-G -kinase signaling is coupled to Ca2+ mobilization and influx in glial cells and that this pathway plays a fundamental role in the generation and propa gation of intercellular Ca2+ waves in glia.