Vinblastine-induced blockage of orthograde and retrograde axonal transport of protein in retinal ganglion cells

The right eyes of adult, albino rats were injected intravitreally with 0.1–30 μg of vinblastine sulfate, and the left eyes were similarly injected with saline. Twenty-four hours later, both eyes were injected with H³-proline and both superior colliculi with horseradish peroxidase. After 24 hr, the animals were killed and brains and retinae processed both for radioautography and the demonstration of peroxidase. Doses of 0.5 μg or more of vinblastine produced blockage of rapid orthograde transport of radioactively labeled protein within optic nerve axons without causing a significant decrease in protein synthesis in ganglion cells of the retina. A higher dose of vinblastine (10 μg or more) was required to block retrograde axonal transport of peroxidase from the superior colliculus to the ganglion cell somata. This suggests vinblastine-sensitive mechanisms for both orthograde and retrograde axonal transport of protein which may involve microtubules or free tubulin within the axoplasm, since vinblastine in low concentration binds specifically to tubulin.