Effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on ultrastructure of nigral neuromelanin in Macaca fascicularis.

In neurons of the substantia nigra (SN) of Macaca fascicularis the administration of parkinsongenic doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused morphological changes of the neuromelanic granules. Under light microscopy, the granules appeared more dispersed and larger. Electron microscopy revealed coalescence of granules in large masses with loss of the electrodense component. Phagocytosis of neuromelanin by glial cells was also observed. In several neurons the neuromelanic changes were evident in the presence of morphologically intact mitochondria. These data suggest an interaction between MPTP and neuromelanin that may have relevance to the nigrotropic toxicity of MPTP and are in agreement with observations on neuromelanin in parkinsonian patients.