Is dopamine a transmitter in the periphery?

There is now substantial experimental evidence supporting the hypothesis that a dopaminergic neuronal system is present in peripheral tissues. This evidence includes identified and characterized dopaminergic receptors, the presence of relatively large concentrations of dopamine and DOPAC in some neurons and organ systems, and the differential loss of norepinephrine or dopamine following treatment with catecholaminergic neurotoxins. There are still many studies that remain to be completed, however, existing evidence is consistent with a peripheral dopaminergic neuronal system.