Dopamine and its metabolites in human peripheral nerves: Is there a widely distributed system of peripheral dopaminergic nerves?

Norepinephrine (NE), dopamine (DA) and its metabolites homovanillic acid (HVA) and 3, 4-dihydroxyphenylacetic acid (DOPAC) were analyzed in human ventral spinal nerve roots and peripheral nerves by gas chromatography-mass spectrometry. High concentrations of DA and HVA were found in almost all tissues analyzed. The concentration of DA and HVA was usually higher than in blood. In vagus nerve and in some spinal nerve roots, the concentration of DA was higher than that of NE, while in other nerves (splanchnic nerve and genitofemoral nerve) DA represented 20 or more percent of NE. The concentration of HVA was usually higher than the concentration of DA indicating that a large portion of DA in peripheral nerves is catabolized and not converted to NE. High concentrations of DA and HVA in human peripheral nerves indicate that a wide distribution of peripheral DA-containing nerves might exist. The distribution of DA in different nerves suggests an association of potential DA-containing nerves with the autonomic nervous system.