Axoplasmic Flow—the Fast Transport System in Mammalian Nerve Fibers

Abstract

In the relatively short time since a review of axoplasmic flow appeared in the first edition of this book (Ochs, 1966), study of the subject has undergone several remarkable shifts in emphasis. Whereas it was previously believed necessary to present evidence in support of the concept that materials synthesized in the neuron somas are continuously transported down inside the axons, a number of studies have since then fully confirmed the phenomenon (e.g., Friede, 1966; Barondes, 1967; Ochs, 1969; Grafstein, 1969; Droz, 1969). Another change was the realization that slow and fast-moving components of axoplasmic flow are present in the fibers. Most of the previous evidence obtained with isotope-labeling techniques had supported a rate of axoplasmic flow of several millimeters per day, a value close to an earlier one arrived at from morphological evidence of damming proximal to a constriction of the nerve trunk (Weiss and Hiscoe, 1948). The increase in the volume of the fibers in the dammed portions above the constriction was interpreted as reflecting a growth of the axoplasmic contents down inside the fibers. However, evidence obtained by Dahlstrom and Haggendal (1966), Karlsson and Sjostrand (1968), Kerkut et al. (1967), Burdwood (1965), Lasek (1967, 1968), Livett et al. (1968), Ochs et al. (1967), Ochs and Johnson (1969), and Sjostrand (1969) indicated the presence of a much faster moving component additional to the slow-moving component.