Metabolism of Putative Transmitters in Individual Neurons of Aplysia Californica

The activities of acetylcholinesterase (acetylcholine acetyl‐hydrolase; EC 3.1.1.7) and catechol‐ O ‐methyl transferase ( S ‐adenosylmethionine: catechol‐ O ‐methyl transferase; EC 2.1.1 .a) were measured in the various ganglia of the nervous system of Aplysia californica and in some of the individually identifiable neurons in these ganglia. All of the neurons studied had measurable levels of activity for both enzymes. Since different individual neurons exhibited approximately the same level of activity we concluded that neither of these enzymes could be used to classify neurons as ‘cholinergic’ vs. ‘aminergic’ or ‘cholinoceptive’ vs. ‘aminoceptive'. The ubiquitous distribution of either or both of these enzymes in different single neurons may be related to glial contamination.