Rotenone is a classical inhibitor of complex I of the mitochondrial electron transport chain, inhibiting NADH/DB oxidoreductase and NADH oxidase with IC50 values of 28.8 and 5.1 nM, respectively.¹ In substantia nigra pars compacta neurons, it activates ATP-sensitive potassium channels and increases the production of reactive oxygen species (ROS) in the mitochondria, effects that are decreased by the antioxidant trolox .² In rodents, rotenone induces dopaminergic cell death in the substantia nigra, formation of cytoplasmic inclusions similar to Lewy bodies, oxidative damage to proteins, and parkinsonian symptoms of bradykinesia and rigidity.³ In a rat model of Parkinson’s disease, chronic rotenone administration of 1.5 and 2.5 mg/kg per day for two months reduces tyrosine hydroxylase levels in the posterior striatum and prefrontal cortex, induces catalepsy, and decreases spontaneous locomotion and exploration in the open field test.⁴ Formulations containing rotenone have been used as insecticides and piscicides.⁵