The effects of 1-methyl-4-phenylpyridinium (MPP+) has been extensively researched due to its selective toxicity to dopaminergic neurons. Mitochondrial dysfunction which is common in the etiology of Parkinson's disease (PD), has been widely implicated in MPP+-induced toxicity. MPP+-induced mitochondrial dysfunction is believed to result in the generation of free radicals. This study was therefore performed to assess the effect of MPP+ on mitochondrial function and the ability of MPP+ to generate superoxide free radicals. Furthermore, we assessed the ability of the non-narcotic analgesics, acetaminophen and acetylsalicylic acid to prevent any diliterious effects of the potent neurotoxin, MPP+, on mitochondrial function and superoxide anion generation, in vivo. Acetylsalicylic acid and acetaminophen prevented the MPP+-induced inhibition of the electron transport chain and complex 1 activity In addition, acetylsalicylic acid and acetaminophen significantly attenuated the MPP+-induced superoxide anion generation. Furthermore the results provide novel data explaining the ability of these agents to prevent MPP+-induced mitochondrial dysfunction and Subsequent reactive oxygen species generation. While these findings suggest the usefulness of non-narcotic analgesics in neuroprotective therapy in neurodegenerative diseases, acetylsalicylic acid appears to be a potential candidate in prophylactic as well as in adjuvant therapy in Parkinson's disease. (c) 2005 Elsevier Inc. All rights reserved.