1-Methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP)

• thermal breakdown product of a meperidine-like synthetic opioid called 1-methyl-4-phenyl-4-propionoxypiperidine (MPPP) that is used by drug addicts as a heroin substitute and may be accidentally produced during the synthesis of MPPP
• produces severe Parkinsonian symptoms in humans and primates (the humans are often addicts who unwillingly inject themselves with some MPTP-laced MPPP)
• hallucinations and near total immobility ('the frozen addict')
  
• is transformed in the brain to MPP+ (1-methyl-4-phenylpyridinium, in case you were wondering), which selectively destroys dopamine-releasing neurons in the substantia nigra, the area of the brain that is damaged in people with Parkinson's disease
• in 1982, six people in San Jose, California were exposed to MPTP and developed Parkinson's disease - one of the docs who examined them wrote a book about his experiences
  
• is used to generate a model for Parkinson's disease in lab animals, permitting the study of the disease and the development of ways to treat it
  

Singer TP, Salach JI, Castagnoli N Jr, Trevor A. Interactions of the neurotoxic amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine with monoamine oxidases. Biochem J. 1986 May 1;235(3):785-9.
http://en.wikipedia.org/wiki/MPTP