Synthesis and Release of 14cacetylch0line in Synaptosomes

Abstract— Synaptosomes took up 14 Ccholine, about half or more of which was converted to I4 Cacetylcholine when incubated in an appropriate medium containing 1 to 5 μ M‐ 14 C choline and neostigmine. The amount of 14 Cacetylcholine synthesized in synaptosomes increased in parallel with the increase of Na + concentration in the incubation medium. The effect of Na + on the uptake of I4 Ccholine into synaptosomes was dependent on the concentration of choline in the incubation medium. About 25 per cent of 14 Cacetylcholine synthesized in synaptosomes was released rapidly into the medium by increasing the K + concentration in the medium from 5 m m to 35 m m . The change of Na + concentration hardly affected the release of 14 Cacetylcholine. The effect of K + on the release of 14 Ccholine was rather small compared to that on 14 C acetylcholine. Ouabain promoted the release of 14 Cacetylcholine.