Kotaro Oka

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.

Glutamate-induced deporalization in earthworm ventral nerve cord

We investigated glutamate-induced neuron response in the ventral nerve cord of the earthworm (Eisenia foetida) using a voltage-sensitive dye-imaging technique. Isolated earthworm ganglia were stained by fluorescence voltage-sensitive dye, RH414, and voltage image was acquired by a conventional charge-coupled device (CCD) technique or a confocal laser scanning microscope. The fluorescence images before and during the glutamate stimulation was acquired and the relative fluorescence change was imaged as pseudo-color. Bath-applied glutamate (1 mM) depolarized many neurons on the ventral side, and in the three giant fibers on the dorsal side.