Effect of Increasing Choline, In Vivo and In Vitro, on the Synthesis of Acetylcholine in a Sympathetic Ganglion

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Abstract
Experiments were designed to test whether increasing choline availability over normal physiological levels increases acetylcholine synthesis in the cat superior cervical ganglion. When ganglia were perfused with Krebs solution, an increase in the medium''s choline concentration over physiological (10-5 M) levels increased tissue choline but did not increase tissue acetylcholine or the release of acetylcholine from stimulated ganglia. Increasing plasma choline in the whole animal increased ganglionic acetylcholine levels. The basis for this difference in the effects on in vivo and in vitro exposure to elevated choline levels on the tissue acetylcholine content involves plasma factor(s), rather than indirect actions of choline, and the acetylcholine content of isolated ganglia was increased when the tissue was perfused with plasma, instead of Krebs solution, containing 10-3 M choline. The extra acetylcholine generated by this procedure was associated with a subsequent transient increase in transmitter release during short intervals of stimulation, but most of the extra acetylcholine was not readily available for release from stimulated ganglia. Increasing choline available to sympathetic ganglia over physiological concentration does not have a sustained effect on the turnover of releasable transmitter under the conditions of these experiments. Implications for the therapeutic use of choline in treating human neurological disorders were discussed.