AbstractThe nervous system of the pond snail,Helisoma trivolvis, was investigated for its ability to synthesize and accumulate3H‐catecholamines from3H‐tyrosine.3H‐Dopamine, but not3H‐norepinephrine, was synthesized by several ganglia. The highest accumulations were found in the cerebral, pedal, and buccal ganglia. The Falck‐Hillarp and glyoxylic acid fluorescence histochemical techniques were applied to the buccal ganglia to visualize dopamine‐containing cells. Fluorescing cells were found on both dorsal and ventral sides of the ganglion. Peripheral nerves of the buccal ganglia also displayed catecholamine fluorescence and accumulated3H‐dopamine. However, no3H‐dopamine synthesis occurred in the cerebral‐buccal connectives, which connect the buccal ganglia with the rest of the central nervous system. Therefore, we conclude that there is a dopaminergic system intrinsic to the buccal ganglia and their p