THE ACCUMULATION OF RADIOACTIVE ACETYLCHOLINE BY A SYMPATHETIC GANGLION AND BY BRAIN: FAILURE TO LABEL ENDOGENOUS STORES

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Abstract
Abstract— The accumulation of radioactively labelled acetylcholine (ACh) by perfused superior cervical ganglia of cats and by incubated brain slices from rats was studied in the presence of diisopropylphosphorofluoridate. Ganglia accumulated more labelled ACh than an extracellular marker (inulin), but the amount of ACh accumulated did not increase when ACh turnover was increased by preganglionic nerve stimulation. The ACh that accumulated in ganglia was not released when the preganglionic nerve was subsequently stimulated. Sliced cerebral cortex also accumulated labelled ACh but this was not released when the tissue was subsequently exposed to a high K+ medium. Thus accumulated ACh does not appear to mix with releasable transmitter stores. Chronically (7 days) decentralized ganglia lost most of their transmitter store but retained their ability to accumulate labelled ACh. Uptake of ACh by sliced cerebellum was not less than uptake of ACh by sliced cerebral cortex and the amount of ACh accumulated by synaptosomes isolated from cerebellum was similar to the amount of ACh accumulated by synaptosomes isolated from cerebral cortex. It is concluded that ACh uptake is not specifically into cholinergic nerve endings. Hexamethonium reduced ACh uptake by cerebral cortex slices but did not increase the amount of ACh collected from slices stimulated by raised K+.