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.