Mass Spectrometry Imaging Identifies Abnormally Elevated Brain L-Dopa Levels And Extrastriatal Monoaminergic Dysregulation In L-Dopa-Induced Dyskinesia

L-DOPA treatment for Parkinson's disease frequently leads to dyskinesias, the pathophysiology of which is poorly understood. We used MALDI-MSI to map the distribution of L-DOPA and monoaminergic pathways in brains of dyskinetic and nondyskinetic primates. We report elevated levels of L-DOPA, and its metabolite 3-O-methyldopa, in all measured brain regions of dyskinetic animals and increases in dopamine and metabolites in all regions analyzed except the striatum. In dyskinesia, dopamine levels correlated well with L-DOPA levels in extrastriatal regions, such as hippocampus, amygdala, bed nucleus of the stria terminalis, and cortical areas, but not in the striatum. Our results demonstrate that L-DOPA-induced dyskinesia is linked to a dysregulation of L-DOPA metabolism throughout the brain. The inability of extrastriatal brain areas to regulate the formation of dopamine during L-DOPA treatment introduces the potential of dopamine or even L-DOPA itself to modulate neuronal signaling widely across the brain, resulting in unwanted side effects.