Movement of labeled macromolecules to the goldfish optic tectum following intraocular injection of 125I-labeled tetanus toxin

Abstract

This study demonstrates that radioiodinated tetanus toxin, whose retrograde axonal transport has been established, is taken up by the retinal ganglion cell and transported in the anterograde direction. The time course of arrival of labeled macromolecules in the optic tectum following intraocular injection of 125I-labeled toxin is contrasted with the axonal transport of [ 3H]proline-labeled protein and [ 3H]fucose-labeled glycoproteins in this system. The rapid axonal transport of tritium-labeled proteins is complete within 24 hr, whereas the movement of 125I-labeled macromolecules into the optic tectum contralateral to the injected eye is detected after 12 hr and continues for several days. The small amount of toxin-related radioactivity in the optic nerve 5 days after injection indicates that, similar to glycoprotein transport, little, if any, toxin moves at the rate of slowly transported proline-labeled protein. The appearance of 125I-labeled macromolecules in the optic tectum is blocked by exposure of the toxin to antitetanus antibody prior to injection into the eye. The anterograde axonal transport of radioiodinated bovine serum albumin is not detected in this system. The data suggest that following intraocular injection, labeled tetanus toxin is either transported at a variety of rapid and intermediate rates following a brief uptake interval or moves along the optic nerve at a minimum rate of 14 mm/day after its slow and continuous uptake into the retinal ganglion cell.