Choline Acetyltransferase in Individual Neurons of Aplysia Californica¹

The activities of choline acetyltransferase in the various ganglia of the nervous system of Aplysia californica and in some of the individually identifiable neurons in these ganglia were measured. At least four of the neurons were characterized by an apparent absence of the enzyme. The neurons containing measurable amounts of the enzyme had reproducible levels from animal to animal. Individual neurons from the same animal were generally characterized by different levels of activity whether expressed on a cell or a protein basis. However, those pairs of neurons previously classified as ‘homologous’ because of their similar appearance, location and/or electrophysiological function, also contained the same total amounts of enzyme activity.