Orthograde, Retrograde, and Turnaround Axonal Transport of Dopamine‐β‐Hydroxylase: Response to Axonal Injury

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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 2nd ligature was placed proximal to the 1st and turnaround transport measured just distal to the 2nd 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.