Orthograde and retrograde axonal transport in the regenerating frog sciatic nerve show different sensitivities to vanadate.

The outgrowth region of the regenerating frog sciatic nerve shows an increased permeability for various drugs. The present experiments indicate that this is also true for vanadate, a substance of special interest in relation to axonal transport. Six days after a bilateral crush lesion, the sciatic nerves, including the spinal ganglia, were incubated in a compartmented chamber. Orthograde transport was assessed from the distribution and the accumulation of [3H]leucine-labelled proteins in the nerve growth region. Retrograde transport was examined by allowing orthogradely transported labelled materials to reverse at the regenerating region and then to accumulate at a ligature during a second incubation period. Vanadate at 0.5 mM and higher concentrations was found to inhibit orthograde and retrograde transport in the outgrowth region (6 mm long at 6 d after crush), whereas 0.2 mM vanadate inhibited transport only in the retrograde direction. The observations lend further support to the idea that the mechanisms of transport in the two directions are different.