High affinity transport of choline was investigated kinetically and pharmacologically in primary neuronal cultures and synaptosomes of the brain of the rat. Both preparations took up and acetylated [3H]choline in a similar high affinity, sodium-dependent manner. However, monoethylcholine mustard aziridinium ion (AF64A) (an irreversible inhibitor and potential neurotoxin) and hemicholinium-3 (a reversible inhibitor) were much less potent in the neuronal cultures than in synaptosomes. Antibodies, highly selective for ubiquitin, and able to block synaptosomal synthesis of acetylcholine, coupled to high affinity transport of choline had no effect of the synthesis of acetylcholine in intact cultured neurons, suggesting differential post-translational modification of the transporters in these two preparations.
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