Light and Electron microscopic autoradiography of 3H-dopamine uptake in the ganglia of the freshwater mussel, Anodonta cygnea L.

In the central nervous system of the freshwater mussel, Anodonta cygnea, uptake of 3H-dopamine has been investigated by light and electron microscopic autoradiography following in vitro incubation and topical application, respectively. The autoradiographic reaction observed over the ganglia can be taken as a morphological evidence of the existence of a specific uptake mechanism for dopamine. It has been found that labeled dopamine was taken up by the axon profiles and terminals, while perikarya remained free of activity, indicating a basic difference between the perkaryal and axonal membrane in respect of the 3H-dopamine uptake. According to the electron microscopic autoradiography, labeled terminals and axon profiles contained both normal and accentric dense-core vesicles and they proved to be similar to those seen after 3H-serotonin in vitro incubation. Therefore, it seems possible that certain Anodonta central neurons contain both dopamine and serotonin.