Axonal Transport of Glycoproteins and Glycolipids in the Goldfish Optic System

The goldfish retino-tectal pathway is a convenient experimental system for studying axonal transport. Radioactive precursors are injected into the eye, and radioactivity which is transported in the axons of the retinal ganglion cells can be studied as it moves in the optic nerve and optic tract to the optic tectum, where the optic fibers terminate. For instance, when labeled amino acids are injected into the goldfish eye, labeled proteins synthesized in the retinal ganglion cells are axonally transported in the optic fibers. Two main waves of protein are transported: most of the labeled protein moves slowly at a rate of about 0.4 mm/day, and much of this slowly transported protein is solubles A smaller fraction of the transported protein moves much faster, at a rate of about 70-100 mm/day, and most of this rapidly transported protein is particulate. Free amino acids are not transported