The axonal transport of slowly migrating [ 3H]leucine labelled proteins and the regeraration rate in regenerating hypoglossal and vagus nerves of the rabbit

Abstract

The axonal transport of slowly migrating [ 3H]leucine labelled proteins was studied in regenerating hypoglossal and vagus nerves of the rabbit 1–4 weeks after a nerve crush. In normal nerves, as well as in the nerves contralateral to nerve crush, a transport rate of 4–5 mm/day for the hypoglossal nerve and 20–25 mm/day for the vagus nerve was calculated. The axonal transport of slowly migrating labelled proteins was increased in the regenerating hypoglossal nerve as compared to the contralateral 1 week after a nerve crush; this was mainly due to an increased transport rate. In contrast, the axonal transport of slowly migrating labelled proteins was decreased in the regenerating vagus nerve as compared to the contralateral nerve 1 week after a nerve crush. The results indicate a decreased transport rate and a decreased amount of material transported on the regenerating side. Changes in axonal transport in both hypoglossal and vagus nerves were less pronounced after 4 weeks of regeneration. Rapidly migrating [ 3H]leucine labelled proteins were transported into regenerating hypoglossal and vagus nerves distal to the crush zone, indicating axonal transport in the growing axons. The regeneration rate was estimated to be about 3 mm/day in the vagus nerve after 2–4 weeks of regeneration and about 4 mm/day in the hypoglossal nerve after 1 week of regeneration. The levels of acetyl-CoA: choline O-acetyltransferase (ChAc, E.C. 2.3.1.6) and acetylcholinesterase (AChE, E.C. 3.1.1.7) activity were decreased in regenerating vagus nerve the first week after a nerve crush.