Evidence for RNA transport in rat optic nerve.

A NUMBER of biochemical and autoradiographic studies have been made on the distribution and movement of labelled substances within the neuron. Proteins labelled after in duo administration of radioactive precursors have been shown to be conveyed from the original site of synthesis down the nerve fibres at an average daily rate of a few millimetres (GRAFSTEIN, 1967; LASEK, 1968; TAYLOR and WEISS, 1965 and WEIS and HOLLAND, 1967). Furthermore, recent studies on the uptake of radioactive amino acids from isolated axons have shown that the nerves can carry on a significant local protein synthesis (EDSTR~M, 1966; GIUDIITA, DETTBARN and BRZIN, 1968 and KOENIG, 1967). The discovery within axons of small amounts of RNA. mainly of the ribosomal type (EDSTROM, EICHNER and EDSTROM, 1962; KOENIG, 1965 and KOEMG, 1967), would indicate the presence of a protein-synthesizing machinery which operates independently from the cell body. At present the origin and form of this RNA are unknown. It may either be synthesized by the axon or by satellite cells, or perhaps be transported down from the neuronal perikaryon. In the present experiments the possibility of axonal flow of RNA from the cell body has been studied by measuring the distribution of radioactivity along the optic nerves at various times after injection into the eyeball of radioactive precursors. EXPERIMENTAL