In the 1990s, drug users started developing Parkinson's like symptoms. It was found that a contaminant, called MPTP, was in an opioid-like drug. How does MPTP cause Parkinson's like symptoms?

A) MPP⁺ inhibits mitochondrial function in dopaminergic neurons.
B) MPTP inhibits mitochondrial function in dopaminergic neurons.
C) MPTP increases the enzymatic activity of monoamine oxidase with increases the number of free radicals in dopaminergic neurons.
D) MPP⁺ blocks the release in dopamine from dopaminergic neurons, specifically from the substantia nigra.