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There is now a considerable amount of data to support the hypothesis that cholinergic transmission occurs at certain synapses in the central nervous system (Feldberg, '45, '50, '51; Koelle and Gilman, '49). One line of evidence is based upon the parallelism found between known cholinergic neurons of the peripheral nervous system and certain regions of the central nervous system with respect to their high concentrations of acetylcholine ( ACh), choline acetylase and specific (true, aceto-, or acetyl-) cholinesterase (ChE). Burgen and Chipman ( '51) recently demonstrated for various regions of the dog's brain relatively close correlations between their own figures for specific ChE activity and those of Feldberg and Vogt ('48) for choline acetylase and of MacIntosh ('41) for ACh. It has been pointed out frequently that conventional determinations of ChE activity employing homogenates, while providing quantitative results, leave much to be desired as far as details of localization are concerned. Thus, when a region of the brain is found to have high activity it.is impossible to be certain whether it is attributable to enzyme associated with the entering axons, with neurons originating in

No abstract