Effect of Vitamin B1 and Cocarboxylase on Synthesis of Acetylcholine.

1. The synthesis of acetylcholine in vitro in the presence of thiamine chloride and thiamine pyrophosphate was investigated. 2. Both thiamine chloride and thiamine pyrophosphate, in concentrations of 3.10-6 M and 2.10-6 M respectively, slightly increased the synthesis of acetylcholine (average 10%). 3. The thiamine compounds in higher concentrations depressed the synthesis of acetylcholine. Thiamine chloride is a more potent depressor than thiamine pyrophosphate.