Schematic diagram of the proposed action of caffeine on I_Ca and intracellular stores and the action of store-released calcium on glutamate release,I_Ca, and the release-activated calcium transport. Caffeine was shown to suppressI_Ca moderately via a direct action and more significantly via an indirect one in which intracellular calcium led to a decrease in I_Ca. Caffeine also caused a transient peak in calcium that is attributable to a caffeine-induced release from stores. The depression of [Ca²⁺]_i can be explained by a release-activated uptake into stores and the suppression ofI_Ca.