Axonal transport of the molecular forms of acetylcholinesterase in developing and regenerating peripheral nerve

In chick sciatic nerve, acetylcholinesterase (AChE) occurs in four main molecular forms characterized by their sedimentation coefficients in sucrose gradients, referred to as G1 (5S), G2 (7.5S), G4 (11S), and A12 (20S). Under normal conditions, we previously showed by accumulation technique that the G4 and A12 forms are rapidly transported along the axons, whereas G1 and G2 are carried much more slowly. Here, we used to the same technique to study the anterograde axonal transport of these different AChE forms during normal axonal growth and experimental regeneration. During the first 2 months after hatching, G4 and A12 transport virtually doubled, whereas G1 + G2 transport increased only slightly. After nerve cutting, crushing, or freezing, the flow rates of G1 + G2 and G4 in the regenerating proximal stump decreased by 75% at 4 to 7 days compared with control values and that of A12, by 90 to 95%. In crushed and frozen nerves the transport of all four AChE forms slowly recovered thereafter, but failed to attain control values even after 7 weeks. In cut nerves, on the contrary, no significant recovery of G1 + G2, or G4 transport occurred, but A12 transport began to recover by day 7. Taken together, our results show that axonal transport of G1 + G2, G4, and A12 is selectively regulated in chick sciatic nerve, and suggest that the A12 form of AChE might have a special role and/or destination in regenerating axons.