Radioautographic evidence for both orthograde and retrograde axonal transport of labeled compounds after intraocular injection of [3H]proline in the lamprey (Lampetra fluviatilis).

[3H] Proline injected intraocularly in lampreys has been shown to be bidirectionally transported: 24--96 h after the injection, retinofugal fibers and terminals as well as nerve cell bodies at the origin of the retinopetal system were intensely labeled. These results are at variance with the generally held belief that [3H]proline is taken up only by cell bodies and transported by the anterograde flow. The significance of the retrograde axonal transport of [3H]proline in the lamprey retinopetal system is discussed.