SYNTHESIS AND RELEASE OF [14C]ACETYLCH0LINE IN SYNAPTOSOMES

Abstract— Synaptosomes took up ¹⁴C]choline, about half or more of which was converted to ^I4C]acetylcholine when incubated in an appropriate medium containing 1 to 5 μ M-¹⁴C] choline and neostigmine. The amount of ¹⁴C]acetylcholine synthesized in synaptosomes increased in parallel with the increase of Na⁺ concentration in the incubation medium. The effect of Na⁺ on the uptake of ^I4C]choline into synaptosomes was dependent on the concentration of choline in the incubation medium.
About 25 per cent of ¹⁴C]acetylcholine 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 ¹⁴C]acetylcholine. The effect of K⁺ on the release of ¹⁴C]choline was rather small compared to that on ¹⁴C] acetylcholine. Ouabain promoted the release of ¹⁴C]acetylcholine.