Role of caffeine-sensitive ca²⁺ stores in ca²⁺ signal termination in adult mouse DRG neurones

The role of calcium stores in cytoplasmic calcium signal termination was studied in acutely isolated small and large DRG neurones from mice. Cytoplasmic calcium concentration ([Ca²⁺]_in) was recorded using indo-1 microfluorometry and membrane potential was monitored by ‘perforated’ whole-cell patch-clamp. Depolarization-induced [Ca²⁺]_in transients recovered significantly faster in large neurones than in small neurones. Caffeine was able to release Ca²⁺ from internal stores only in large neurones, while small neurones lacked caffeine-releasable calcium stores. Thapsigargin abolished caffeine-induced Ca²⁺ release and significantly slowed down recovery of depolarization-triggered [Ca²⁺]_in transients in large neurones. We conclude that [Ca²⁺]_in signals recover faster in large DRG neurones, at least in part due to the higher rate of Ca²⁺ sequestration by intracellular stores.