KB-R7943 Inhibits Store-Operated Ca2+ Entry in Cultured Neurons and Astrocytes

We have studied cyclopiazonic acid (CPA)-sensitive store-operated Ca2+ entry (SOCE) in cultured neurons and astrocytes and examined the effect of 2-[2-[4-(4-nitrobenzyloxy)phenyl]]isothiourea (KB-R7943), which is often used as a selective inhibitor of the Na+–Ca2+ exchanger (NCX), on the SOCE. CPA increased transiently intracellular Ca2+ concentration ([Ca2+]i) followed by a sustained increase in [Ca2+]i in neurons and astrocytes. The sustained increase in [Ca2+]i depended on the presence of extracellular Ca2+ and inhibited by SOCE inhibitors, but not by a Ca2+ channel inhibitor. CPA also caused quenching of fura-2 fluorescence when the cells were incubated in Mn2+-containing medium. KB-R7943 at 10 μM inhibited significantly CPA-induced sustained increase in [Ca2+]i in neurons and astrocytes. KB-R7943 also inhibited CPA-induced quenching of fura-2 fluorescence in the presence of extracellular Mn2+. These results indicate that cultured neurons and astrocytes possess SOCE and that KB-R7943 inhibits not only NCX but also SOCE.