Continuing Studies on the Evolution of Ion Channels

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This research project will investigate ion channels in the neurons of the jellyfish and the flatworm. Although neurons in the jellyfish function in much the same way as neurons in higher animals, they have at least one property that may reflect their evolutionary position of being the most primitive animal possessing a nervous system. The physiology of their sodium- dependent action potentials is essentially the same as that of sodium currents of other animals but the pharmacology of those currents is that of calcium currents. Biochemical and electrophysiological techniques will be employed to elucidate the structure of the fast sodium channel in neurons of the jellyfish. Dr. Anderson will also examine the diversity and properties of ion channels in the flatworm. Flatworms are the "first" animals to possess a centralized brain, therefore occupying an significant position in nervous system evolution. These animals are the lowest organism reported of being sensitive to tetrodotoxin, a sodium channel blocker. Furthermore these animals are a major class of parasites and information about the physiology of their excitable cells may lead to the development of new classes of anthelminthic drugs. This study will provide important facts about how nervous systems evolved. The physiology and pharmacology of ion channels in the most primitive animals possessing a nervous system will allow comparisons with channels in primitive and more advanced animals. Results obtained from this study will provide useful information to neurobiology in general by identifying subtypes of ion channels with equivalents in higher animals.