Choline acetyltransferase activity in the sympathetic nerves of the rabbit ear artery

1 No statistically significant difference in the activity of choline acetyltransferase (ChAT) was detected between sympathetically denervated and control rabbit ear artery (REA) tissue. This was interpreted as evidence against the hypothesis that endogenous acetylcholine plays an obligatory role in sympathetic postganglionic neurotransmission. 2 The values obtained for ChAT activity in the extraneuronal REA tissue were very low, but were greater than the boiled blank values. 3 Treatment with a specific inhibitor of ChAT did not reduce the REA values, while it did for rabbit iris. Addition of acetylcholinesterase to the REA assay reduced the activity of the collectable product to a markedly lesser degree than was observed with other tissues. 4 The specificity of the enzyme assay at the very low yield levels observed in the extraneuronal REA tissue was therefore questioned.