Ryanodine-induced intracellular calcium mobilisation in cultured astrocytes.

Changes in intracellular Ca2+ concentration were monitored in cultured cortical astrocytes challenged with ryanodine and ATP. Ryanodine elicited a modest, in comparison to ATP, increase in cytosolic Ca2+ concentration in approximately 60% of the cell fields examined. This effect was evident and, in fact, was augmented when incubations were performed in Ca(2+)-free bathing medium. In addition, ryanodine-evoked changes in intracellular Ca2+ concentration were dose dependent, desensitised rapidly, and could not be mimicked by caffeine. Exposure to ryanodine was without effect on eicosanoid release from these cells nor did it influence Ca2+ mobilisation and eicosanoid release in response to ATP. In contrast, caffeine attenuated part of the ATP-evoked increase in intracellular Ca2+ concentration in the majority of cells tested and abolished its effect on eicosanoid release.