The monoamine carrier of noradrenergic synaptic vesicles was assayed in the rat sciatic nerve by in vitro binding of [3H]dihydrotetrabenazine. The number of binding sites increased with time on both sides of a ligature, indicating fast anterograde and retrograde axoplasmic transports of comparable amplitude. Anterogradely and retrogradely transported binding sites had similar pharmacological properties, which were characteristic of binding to the monoamine carrier embedded within a lipid bilayer. Contrary to the secreted synaptic vesicle matrix constituents, the intrinsic monoamine carrier assayed by [3H]dihydrotetrabenazine binding is a marker adapted to retrograde transport studies.