**3. Oxidative stress, mitochondrial dysfunction and excitotoxicity**

An impairment in multiple steps of the mitochondrial respiratory chain has been demonstrated in Parkinson's disease (Schapira et al 1998). The importance of this pathogenetic mechanism mainly depends on its role of main source of reactive oxygen species. At the same time, the loss of mitochondrial function and the consequent energetic deficit interfere with glutamate uptake and increase neuronal vulnerability to glutamate excitotoxicity.
