Opening of ATP-sensitive K+ (KATP) channels enhance hydroxyl radical generation induced by MPP+ in rat striatum

The present study examined whether opening of adenosine triphosphate (ATP) sensitive K+ (KATP) channels can enhance 1-methyl-4-phenylpyridinium (MPP+)-induced hydroxyl radical (OH) generation in rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5 nmol/ml per min) was infused through a microdialysis probe to detect the generation of OH as reflected by the non-enzymatic formation of 2.3-dihydroxybenzoic acid (DHBA) in the striatum. MPP+ (5 mM) enhanced generation of OH with concomitant increased efflux of dopamine (DA). Cromakalim (100 μM), a KATP channel opener, through the microdialysis probe significantly increased both DA efflux and OH formation induced by MPP+. Another KATP channel opener, nicorandil (1 mM), also increased the level DA or DHBA, but these changes were not significant. However, in the presence of glibenclamide (10 μM), a KATP channel antagonist, and the increase of MPP+-induced DA or DHBA were not observed. Cromakalim (10, 50 and 100 μM) increased MPP+-induced DHBA formation in a concentration-dependent manner. However, the effects of cromakalim in the presence of glibenclamide were abolished. These results suggest that opening of KATP channels may cause OH generation by MPP+.