Slow axonal transport of neurofilament protein in cultured neurons

We have investigated the axonal transport of neurofilament protein in cultured neurons by constrict-ing single axons with fine glass fibers. We observed a rapid accumulation of anterogradely and retrogradely transported membranous organelles on both sides of the constrictions and a more gradual accumulation of neurofilament protein proximal to the constrictions. Neurofilament protein accumulation was dependent on the presence of metabolic substrates and was blocked by iodoacetate, which is an inhibitor of glycolysis. These data indicate that neurofilament protein moves anterogradely in these axons by a mechanism that is di-rectly or indirectly dependent on nucleoside triphos-phates. The average transport rate was estimated to be at least 130