Calcium wave propagation in the giant axon of the earthworm

We examined a spatio-temporal pattern of intracellular free Ca²⁺ concentration in the giant axons of the earthworm, Eisenia foetida, with a fluorescent imaging technique using conforcal laser-scanning microscope and calcium indicator, 'Calcium Green 1'. Electrical tetanic stimulation applied to the nerve cord induced calcium waves along the giant axon. The calcium waves propagated both anteriorly and posteriorly with various speeds, and sometimes were split into several waves with different velocities. The results suggest that some types of calcium-releasing mechanisms may be associated with the calcium wave propagation.