Neuromelanin in manganese-exposed primates.

Monkeys developed muscular weakness and rigidity of the lower limbs after 18 months exposure to manganese. These are neurological signs typical of chronic manganese intoxication. Marked neuronal degeneration with depigmentation was noticed in the region of substantia nigra. Significance of depigmentation in relation to the depletion in the contents of brain dopamine in chronic manganese intoxication has been discussed.