On the basis of the transport filament model, Ca-Mg ATPase is considered present on the side arms of microtubules, hydrolyzing ATP to supply the energy to move transport filaments carrying the various materials down the axons. The de-sheathed peroneal nerve preparation of the cat was used to show that Ca2 ion plays an essential role in maintaining transport and its relation to Ca regulatory mechanisms in the axon, where a regulated level of Ca2 ion appears to be necessary for calmodulin to activate Ca-Mg ATPase. This model will be tested by procedures which alter the internal levels of ions, which will be studied and ionic interactions assessed. A study will be made of the calmodulin activation of Ca-Mg ATPase associated with tubulin. An assessment of the relationship of the block of transport produced by metabolic blocking agents and vinca alkaloids and maytansine will be made to determine the quantitative relationship between transport block and microtubule density. Location of radioactivity in the axons will be studied to test proposed transport models, in normal fibers and after varying tonicity and producing a maintained stretch to cause beading. The "unitary" hypothesis will be tested using SDS-PAGE to determine if some components characteristic of slow transport also have a fast component. An asymmetry of labeled materials slow transported in dorsal root ganglion neurons will also be looked for on that basis. Dopamine transport will be examined to determine if its rate when turnover is blocked with disulfiram is similar to that of NA and labeled proteins.