The turnover of acetylcholine in ligated sciatic nerves of the rat

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Abstract
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. 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) 9 h after crushing of the nerves, while ChAT-activity was increased to 112 .+-. 10% and AChE-activity to 198 .+-. 19% over that in nonligated nerves. Superfusion of the nerves for 8 h with Kreb''s 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 .times. 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.