ABSTRACT
The effects of a variety of ions and ionic conditions on fast axonal transport have been studied in order to elucidate the mechanism behind the fast axonal transport-machinery and the possible connection between fast axonal transport and neuronal activity. At the axonal level Na+-deprivation does not affect fast axonal transport in sheathed frog and cat sciatic nerves. Increased levels of axonal Na+ can be obtained by various means including electrical stimulation, the exposure of nerves to batrachotoxin, ouabain, or Na+-ionophores. Batrachotoxin, which increases the Na+ permeability of the nerve, is the most potent fast axonal transport-inhibitor reported so far and inhibits transport in the nanomolar range. Ouabain is an effective inhibitor of fast axonal transport in the sheathed and desheathed frog and cat sciatic nerves and also in the cat hypogastric nerve. Calmodulin is axonally transported and has been shown to activate a Ca2+-Mg2+-ATPase in mammalian nerve at relevant axonal Ca2+ levels.
