Abstract

The metabolism and subcellular distribution of a novel choline analog, N-amino-N,N-dimethylaminoethanol (N-aminodeanol) in rat striatal synaptosomes was studied using combined gas chromatography mass spectrometry for simultaneous estimation of N-aminodeanol, choline, tracer choline and their acetate esters. The enzymes choline acetyltransferase, acetylcholinesterase and choline kinase were assayed in kinetic studies using N-aminodeanol or acetyl-N-aminodeanol as substrates. The results demonstrate that [2H4]N-aminodeanol is transported and acetylated in synaptosomes at rates approximately 30% of those measured for [2H4]choline. Of the [2H4]N-aminodeanol that was transported by the high affinity choline uptake system, the proportion acetylated was similar to that measured for [2H4]choline. [2H4]Acetyl-N-aminodeanol replaced endogenous acetylcholine stores and was released. The combined release of endogenous and false transmitters from synaptosomes in the presence of [2H4]N-aminodeanol was reduced compared to controls in the presence of [2H4]choline, although combined tissue stores did not change significantly. After coincubation with [2H4]N-aminodeanol and [2H4]choline, the molar ratios of true and false transmitter in the tissue appeared to reflect the kinetic parameters for high affinity transport of the precursors. Subcellular fractionation experiments indicated that [2H4]acetyl-N-aminodeanol was incorporated into vesicles more slowly than [2H4]acetylcholine. These results indicate that the reduced rate of turnover in the presence of false precursor is not due to its rate of acetylation or to the rate of release of previously formed false transmitter, but rather to the slower membrane transport of N-aminodeanol by the high affinity uptake system. The replacement of endogenous acetylcholine in synaptosomes by acetyl-N-aminodeanol, which has 4% the potency of acetylcholine at muscarinic receptors, suggests that N-aminodeanol may be useful in studying the in vivo effects of a false cholinergic transmitter.