Neuromelanin

[1] Neuromelanin is found in large quantities in catecholaminergic cells of the substantia nigra pars compacta and locus coeruleus, giving a dark color to the structures.

[3] Neuromelanin is directly biosynthesized from L-DOPA, precursor to dopamine, by tyrosine hydroxylase (TH) and aromatic acid decarboxylase (AADC).

[citation needed] Motor symptoms of Parkinson's disease are caused by cell death in the substantia nigra, which may be partly due to oxidative stress.

[citation needed] The death of neuromelanin-containing neurons in the substantia nigra, pars compacta, and locus coeruleus have been linked to Parkinson's disease and also have been visualized in vivo with neuromelanin imaging.

[5] Dark pigments in the substantia nigra were first described in 1838 by Purkyně,[8] and the term neuromelanin was proposed in 1957 by Lillie,[9] though it has been thought to serve no function until recently.

5,6-Dihydroxyindole, the monomer out of which neuromelanin polymers are formed
Photomicrograph of neuromelanin (brown material) in a neuron of the substantia nigra. Hematoxylin and eosin stain. The scale bar is 20 microns (0.02mm) in length.