Possible involvement of nitric oxide in the modulation of photolytic flash-induced intercellular calcium waves in cultured astrocytes

Waves of elevated intracellular free calcium that propagate between neighboring astrocytes are important for the intercellular communication between astrocytes as well as between neurons and astrocytes. In this study, intercellular calcium waves were evoked by focal photolysis of a caged calcium ionophore in cultured astrocytes. The focal photolysis of the caged compound resulted in an increase of intracellular calcium in the flashed cells, and this increase then propagated to neighboring astrocytes. The evoked calcium increase was inhibited by incubating cells with an inhibitor of nitric oxide synthase as well as with a scavenger of nitric oxide (NO). In addition, treatment of cultures with an NO donor resulted in the marked enhancement of the photolytic flash-induced calcium rise in astrocytes. This enhancement was reversed by treatment with inhibitors of soluble guanylyl cyclase as well as of protein kinase G.