Electron microscopic distribution of axoplasmic transport

Abstract

Abstract Light and electron microscopic radioautography have been used to localize the rapid and slow components of axoplasmic flow within the monkey lateral geniculate nucleus (LGN). Three days after an intravitreal injection of H 3 leucine, 53% of the silver grains found in the LGN were localized to retinal synaptic terminals and 27% were over retinal axons. By 30 days post‐injection, 66% of the grains were localized to retinal axons while retinal synaptic terminals now contained 21% of the grains. At both 3 and 30 days LGN neurons postsynaptic to the radioactive retinal axons showed higher levels of labeling than LGN neurons in the layers not receiving afferents from the injected eye. These data indicate that the rapid phase is mainly confined to the synaptic terminal while the slow phase is mainly localized in the axon. This differing distribution of radioactivity may now be utilized as the basis of a neuroanatomical tracing method.