The role of axonal transport in the development of structural changes of axons can be examined using experimental models. Two different compounds, 2,5-hexanedione (2,5-HD) and carbon disulfide (CS2), cause axonopathies characterized by the formation of neurofilaments (NF) containing enlargements in preterminal regions of central and peripheral axons. These axonopathies are excellent experimental models of the giant axonal neuropathies, a group of acquired and inherited human diseases of the central and peripheral nervous system. We previously reported that following administration of 2,5-HD, transport of NF is accelerated while number of NF and cross-sectional area are decreased in regions of the axon proximal to the enlargements. We proposed that acceleration of NF transport leads to a 'longitudinal' redistribution of NF which are decreased proximally and increased distally where they form the NF containing axonal enlargements. We have now carried out morphometric, transport and immunocytochemical studies in primary visual axons of rats exposed to CS2. NF-containing axonal enlargements were observed in optic tract and superior colliculus and they increased in number in a proximodistal direction. There was no detectable axonal degeneration and the cross-sectional area of axons proximal to the enlargements was decreased. Transport of NF was markedly accelerated. Immunostaining showed that all 3 NF subunits and phosphorylated epitopes of the 200-kDa NF subunit were present in the NF-containing axonal enlargements. All these findings were similar to those previously observed in the 2,5-HD axonopathy.(ABSTRACT TRUNCATED AT 250 WORDS)