Photosensitization and the nervous system in the planarian Dugesia gonocephala. A histochemical, ultrastructural and behavioral investigation.

Photosensitization phenomena may be induced in planarias by eosin and hematoporphyrin, and as a result, dopamine agonistic behavior (“screw-like” hyperkinesia) is set up in the animal. Histochemical, ultrastructural and pharmacological investigations have shown that this hyperkinesia is of postsynaptic origin in eosin photosensitization, and of pre-synaptic origin in hematoporphyrin photosensitization. The authors suggest an hypothesis to explain the different activity of the two photosensitizers, and discuss the validity of the experiment with regard to human porphyria.