Extrusion of calcium from a single isolated neuron of the snailHelix pomatia

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Abstract
Simultaneous optical measurements of extra- and intracellular Ca2+ concentrations were carried out on isolated snail neurons injected iontophoretically with Ca2+. The fluorescent indicator Fura-2 was used to measure intracellular concentration of free Ca, and the absorbant indicator Antipyrylazo III to measure changes in extracellular calcium concentration in the microchamber containing the cell. The velocity of Ca2+ extrusion from a single cell has been shown to be in accordance with the level of free Ca in the neuronal cytoplasm. After an increase in intracellular free Ca by iontophoretic injection from a microeletrode to 0.2–0.5 μm, the velocity of Ca2+ extrusion from the neuron was approximately 0.3–4.6 μm/sec per cell volume. During caffeine-induced calcium-dependent calcium release of Ca2+ from intracellular stores a stimulation of calcium extrusion took place, reaching the velocity of 5.0 μm/sec per cell volume.