The distribution of acetylcholine in normal and in regenerating nerves.

1. The distribution of acetylcholine (ACh) in various nerves which had been regenerating for different periods after crushing has been compared with that in uncrushed nerves.2. Normal ventral roots from cats contained 78.1 +/- 22.7 (S.D.) mumole ACh/kg (blotted wet wt.); rabbit ventral roots contained 48.0 mumole/kg +/- 19.0 (S.D.) and rabbit sciatic nerves 16.6 +/- 7.3 (S.D.) mumole/kg. In the sciatic nerves the distal cm of 5 cm lengths taken from the thigh contained 30% more ACh than the most central cm portion. Possible explanations for this difference have been discussed.3. After both sciatic nerves and ventral roots had been crushed, there was an initial build-up (4 times control) of ACh central to the lesion and a decline ((1/4) control) distal to the lesion. These changes were maximum around 5 days after crushing. In sciatic nerves in which long periods of regeneration were investigated, the central build-up fell off to 1(1/2) times control by 25 days and the distal decline reversed to 2 times control in about 10 days. It then again decreased towards the control level by 25 days after crushing. These changes have been discussed in relation to the morphological changes which occur in a nerve following crushing.4. A peak of ACh content moved distally along the nerve from the crushed region at a rate of 1.0-1.5 mm/day. This was considered to represent an average rate of regeneration of the bulk of the axons. The amplitude of the peak declined progressively with time in the more distal parts of the nerve, probably because of dispersion as axons regenerated at different rates.