Migration of axonal protein: Absence of a protein concentration gradient and effect of inhibition of protein synthesis

Summary Two experiments have been performed to gain insight into the mechanisms of axoplasmic protein migration. In the first the concentration of protein along cat optic nerves was measured to determine if a concentration gradient was present which might drive protein in a proximo-distal direction. None was found. In the second experiment we endeavored to determine if axonal protein migration would continue despite cycloheximide-induced inhibition of protein synthesis in the cell body. It did continue to migrate and with no significant change in rate (0.8–1.0 mm/day). It is concluded that these experiments rule out diffusion down a proximo-distal concentration gradient as a mechanism for axonal protein migration.Supported by USPHS Grant NB-05038 and USPHS 5T56M 1604-10.