Orthograde, retrograde, and turnaround axonal transport of dopamine-beta-hydroxylase: response to axonal injury

Abstract

Reversal of the direction (turnaround) of orthograde axonal transport of dopamine-beta-hydroxylase (DBH) activity was studied at a ligature placed on rat sciatic nerve. DBH was allowed to accumulate at a ligature in vivo for selected intervals, at which time a second ligature was placed proximal to the first and turnaround transport measured just distal to the second tie after incubation in vivo or in vitro. Orthograde accumulation of DBH activity proximal to a ligature peaked at 2 days, and then rapidly decreased as a result of turnaround transport and injury-induced reduction of orthograde transport. Destruction of postganglionic sympathetic axon terminals in vivo with 6 hydroxydopamine resulted in a decrease in orthograde transport similar to that seen after axotomy and turnaround at or proximal to the site of chemical injury. Turnaround transport of DBH in vitro was blocked by incubation in the cold and in the presence of NaCN and vinblastine. Orthograde transport of DBH appeared to reverse direction within a few millimeters of a ligature.