MPP+ iodide, a toxic metabolite of the neurotoxin MPTP, causes symptom of Parkinson's disease in animal models by selectively destroying dopaminergic neurons in substantia nigra. MPP+ iodide is taken up by the dopamine transporter into dopaminergic neurons where it exerts its neurotoxic action on mitochondria by affecting complex I of the respiratory chain. MPP+ iodide is also a high affinity substrate for the serotonin transporter (SERT)