Non-steroidal anti-inflammatory drug sodium salicylate, but not diclofenac or celecoxib, protects against 1-methyl-4-phenyl pyridinium-induced dopaminergic neurotoxicity in rats.

We evaluated the hydroxyl radical (*OH) scavenging action of nonsteroidal anti-inflammatory drugs (NSAIDs), sodium salicylate (SA), diclofenac and celecoxib in Fenton's reaction and their neuroprotective effects in 1-methyl-4-phenylpyridinium (MPP(+))-induced striatal dopamine (DA) depletion in rats. Salicylate hydroxylation procedure employing HPLC-electrochemistry was used to assay formation of *OH in Fenton's reaction in test tubes. While SA dose- and time-dependently hydroxylated itself and inactivated *OH, celecoxib (up to 10 mM) showed no effect on *OH formation and diclofenac caused a reduction in *OH generation only at high doses (100 microM-10 mM). Administration of the non-selective cyclooxygenase (COX) inhibitor, SA (50, 100 mg/kg, i.p.) significantly attenuated striatal DA depletion caused by intrastriatal infusion of MPP(+) (100 nmol in 4 microl). Treatment with another nonselective, reversible COX inhibitor, diclofenac (5, 10 mg/kg) did not protect against MPP(+)-induced DA depletion. The selective COX-2 inhibitor, celecoxib (2.5-50 mg/kg) treatment exacerbated MPP(+)-induced decrease in DA. Failure of celecoxib or diclofenac to render protection in animals against MPP(+)-induced DA depletion indicates absence of prostaglandin involvement in MPP(+) action. These results also suggest that the neuroprotective ability of SA is independent of prostaglandin mediation. A relationship between inactivation of *OH by SA and its ability to protect DA depletion in the striatum caused by MPP(+) indicates a direct involvement of *OH in the action of this neurotoxin. The present study establishes potent neuroprotective activity of SA and suggests the use of aspirin in adjuvant therapy in Parkinson's disease.