5-hydroxytryptamine-evoked [Ca]i oscillations in rat C6 glioma cells

We have investigated the modulation of the intracellular calcium concentration (Ca²⁺]_i) in rat C6 glioma cells following their activation by the agonists 5-hydroxytryptamine·HCl (5-HT) and bradykinin, using single cell imaging of Ca²⁺]_i with the calcium-sensitive dye Fura-2. The majority of the signals observed involved release of calcium from intracellular stores, and after prolonged application of 5-HT, but not bradykinin, the cells exhibited oscillations in Ca²⁺]_i levels. These calcium oscillations were dependent on the presence of extracellular calcium, and were unaffected by the calcium channel antagonists nifedipine and verapamil. Caffeine, which in other cell types is able to release calcium from inositol trisphosphate-insentive stores, had very little effect on Ca²⁺]_i levels in C6 cells. On the other hand, bradykinin, although able to elevate Ca²⁺]_i probably by acting via the B₂-receptor subtype, was unable to induce any calcium oscillations in these cells.