CHOLINE ACETYLTRANSFERASE, ACETYLCHOLINESTERASE AND AROMATIC l-AMINO ACID DECARBOXYLASE IN SINGLE IDENTIFIED NERVE CELL BODIES FROM SNAIL HELIX ASPERSA

—The distribution of choline acetyltransferase, aromatic l -amino acid decarboxylase and acetylcholinesterase in the nervous system of Helix aspersa has been studied using homogenates of whole ganglia, microdissection from freeze-dried sections and dissection of single neurons from fresh tissue. Choline acetyltransferase was found in both the cell body and neuropil layers of all the Helix ganglia. The enzyme was not specifically localized to any ganglion or region of ganglion. Between 10 and 30 per cent of the isolated single cell bodies contained the enzyme. The enzymic activity corresponded to 50–200 mmol ACh/1 cell bodies/h. Choline acetyltransferase is probably a specific marker for cholinergic cells in this species. Aromatic l -amino acid decarboxylase was more selectivity localized and its distribution corresponded well with that of monoamine containing cells as visualized by the fluorescence histochemical technique. A large proportion of cell bodies were localized in the boundary between the visceral and right parietal ganglia and in the pedal ganglion. The other ganglia contained few such cells. The activity of aromatic l -amino acid decarboxylase corresponded 10–50 mmol dopamine/1 cell bodies/h. A method was developed to measure the enzyme activity towards 5-hydroxytryptophan and DOPA in single cells simultaneously. The ratio between the activity towards both substrates did not vary significantly for the different cells. The enzyme is probably a specific marker for monoamine cells, but cannot be used to differentiate between the different monoamine cells. Acetylcholinesterase was uniformly distributed in the ganglia and was probably present in all nerve cells.