This project will examine ion channels in neurons of the jellyfish Cyanea capillata and cnidocytes (sting cells) in the sea anemone Anthopleura. Although neurons in this jellyfish function in much the same way as neurons in all higher animals, they have at least one property that may reflect their evolutionary position. The physiology of their sodium-dependent action potentials is essentially the same as that of sodium currents in other animals but the pharmacology of those currents is that of calcium currents. Since these are the most primitive animals to possess a nervous system, and the first to produce sodium-dependent action potentials, this finding suggests that these neurons may be intermediates in sodium channel evolution. The physiology and pharmacology of sodium and other ionic currents in these neurons and in sting cells will be examined with voltage clamp and single channel recording techniques. In addition, information on the structure of the various ion channels will be obtained from studies of the binding characteristics of various ion channel blockers. This project will provide important information about how nervous systems evolved. The physiology and pharmacology of ion channels in the most primitive animals possessing a nervous system will allow comparison with channels in primitive and more advanced animals. The results may provide useful information to neurobiology in general by identifying subtypes of ion channels with equivalents in higher animals.
