The neurotoxicity of MPTP was hinted at in 1976 after Barry Kidston, a 23-year-old chemistry graduate student in Maryland, US, synthesized MPPP with MPTP as a major impurity, and self-injected the result. Within three days he began exhibiting symptoms of Parkinson's disease. The National Institute of Mental Health found traces of MPTP and other pethidine analogues in his lab. They tested the substances on rats, but due to rodents' tolerance for this type of neurotoxin nothing was observed. Kidston's parkinsonism was successfully treated with levodopa but he died 18 months later from a cocaine overdose. Upon autopsy, destruction of dopaminergic neurons in the substantia nigra was discovered.
In 1982, seven people in Santa Clara County, California, US, were diagnosed with Parkinsonism after having used MPPP contaminated with MPTP. The neurologist J. William Langston in collaboration with NIH tracked down MPTP as the cause, and its effects on primates were researched. The motor symptoms of two of the seven patients were eventually successfully treated at Lund University Hospital in Sweden with neural grafts of fetal tissue.