Transport of choline acetyltransferase and acetylcholinesterase in the central stump and isolated segments of a peripheral nerve

Abstract

Axonal transport of choline acetyltransferase (ChAc, E.E.:2.3.1.6) and acetyl cholinesterase (AChE, E.C.:3.1.1.7) was studied in the peroneal fascicles of rabbit sciatic nerves. The accumulation of ChAc in the central nerve stump proceeded 5 times more slowly than that of AChE and occurred at a distanct of 2-4 mm proximally from the end, whereas AChE accumulated in the last 2 mm of the stump. In double-ligated segments of the nerve in situ the activity of ChAc decreased at the proximal and increased at the distal end; the activity of AChE rose at both ends, The increase of ChAc activity did not cease until 22 h, whereas that of AChE stopped before 10 h. The intensity of ChAc transport is considerably diminished in the part of axon separated from the nerve cell body. Differences between the behavior of ChAc and AChE are interpreted by the assumption that the axonal transport of ChAc is slow, unidirectional, concerns all of the enzyme in the nerve, and that most of the transported enzyme is not associated with intraaxonal organelles. In contrast to ChAc, the transport of AChE is fast, bidirectional, and concerns a minor proportion of enzyme in the nerve; the transported enzyme is associated with organelles. The rate of proximodistal transport of ChAc is estimated at 4 mm/day (based on the assumption that 100% of the enzyme moves proximo-distally) and that of AChE at 480 mm/day (based on the extimate that 5% of enzyme moved proximo-distally in the present experiments).