1-Methyl-4-phenylpyridinium ion (MPP+): identification of a metabolite of MPTP, a toxin selective to the substantia nigra.

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a newly described neurotoxin which selectively destroys cells in the substantia nigra when administered systemically to primates. Because the substance creates a condition in humans which is virtually indistinguishable from Parkinson's disease, interest has focused on its mechanism of action. We now report that MPTP appears to be rapidly metabolized after systemic administration in toxic amounts, and identify 1-methyl-4-phenylpyridinium ion (MPP+) as a probable major metabolite.