The dependence of fast transport in mammalian nerve fibers on metabolism.

Abstract

A fast transport of labelled components in the myelinated fibers of cat sciatic nerve was found after injection of the L7 dorsal root ganglion with 3H-leucine. Fast transport was shown by a crest of activity which moved outward in the nerve at a regular rate of close to 400 ± 35 mm/day without change in its shape. The transport inside the axons is independent of a propulsive force exerted from the soma. After incorporated materials are supplied by the soma to the fiber, the somas can be destroyed without effect on the subsequent movement of material in the fibers. The mechanism of transport was shown thereby to be present all along the length of the fiber. It was also found to be closely dependent on oxidative phosphorylation in studies made in an in vitro system where fast transport is maintained by O2. Fast transport was rapidly blocked with N2 or oxidative blocking agents such as CN or DNP present in the Ringer solution. The energy derived from oxidative phosphorylation is most likely transferred through ATP to a sliding transport filament mechanism involving microtubules and/or neurofilaments which is believed to underly fast axoplasmic transport.