The turnover of acetylcholine in ligated sciatic nerves of the rat

The accumulation of acetylcholine (ACh) and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities proximal to a crush on rat sciatic nerves was investigated after superfusion of the nerves in situ with or without inhibitors of ACh synthesis and/or AChE. 9 h after crushing of nerves, the ACh-content of the 5 mm segment of nerve immediately proximal to the crush was increased from 37±5 to 80±4 pmol (mean ± SE), while ChAT-activity was increased to 112±10% and AChE-activity to 198±19% over that in non-ligated nerves. Superfusion of the nerves for 8 h with Krebs' bicarbonate medium had no effect on enzyme accumulations, but reduced the ACh content to 59±4 pmol. The presence of hemicholinium 3 (HC-3) (2×10^-5 M) in the superfusion medium reduced the ACh content markedly (to 17±2 pmol), but had no effect on enzyme accumulations at the crush. Adding eserine (10^-5 M) or soman (10^-6 M) to the superfusion medium increased ACh content to 133±8 pmol and 101±8 pmol, respectively, and markedly reduced AChE-activity; ChAT activity was not effected. Superfusion with a combination of HC-3 and eserine caused a marked reduction in ACh content compared with eserine alone; the effect was less with soman. The results are consistent with the view that the ACh which accumulates proximal to crush exists in a protective organelle, but that there is a continuous turnover of ACh due to leakage of ACh from the organelle, both during axonal transport and after accumulation.