[The monoamines in molluscs. II. Dopamine and neurotransmission. Cardiac dopaminergic innervation in Helix pomatia (author's transl)].

In the molluscs, dopamine is very probably a chemical transmitter at the level of both the central nervous system and certain peripheral structures. The heart of Helix pomatia does not have any intrinsic innervation, but it receives extrinsic innervation from fibres coming from the visceral nerve. Formaldehyde fluorescence histochemistry localizes the cardiac catecholamines in some of these fibres and in their endings. However, dopamine, which dominates, does not seem to be a transmitter involved in cardioregulation in the same way as 5-hydroxytryptamine. The quantities of active dopamine (stimulants) cannot be compared with those required for a neurotransmitter. This is also true for noradrenaline. Dopamine more certainly plays a role at the metabolic and tropic level by acting within a more or less short period as a regulator of cellular activity and contractility. The Helix heart is a suitable model for future research in this field.