In this study, we treated PC12 cells with 0-20 μM amyloid-β peptide (25-35) for 24 hours to induce cytotoxicity, and found that 5-20 μM amyloid-β peptide (25-35) decreased PC12 cell viability, but adenosine triphosphate-sensitive potassium channel activator diazoxide suppressed the decrease in PC12 cell viability induced by amyloid-β peptide (25-35). Diazoxide protected PC12 cells against amyloid-β peptide (25-35)-induced increases in mitochondrial membrane potential and intracellular reactive oxygen species levels. These protective effects were reversed by the selective mitochondrial adenosine triphosphate-sensitive potassium channel blocker 5-hydroxydecanoate. An inducible nitric oxide synthase inhibitor, Nω-nitro-L-arginine, also protected PC12 cells from amyloid-β peptide (25-35)-induced increases in both mitochondrial membrane potential and intracellular reactive oxygen species levels. However, the H2O2-degrading enzyme catalase could not reverse the amyloid-β peptide (25-35)-induced increase in intracellular reactive oxygen species. A 24-hour exposure to amyloid-β peptide (25-35) did not result in apoptosis or necrosis, suggesting that the increases in both mitochondrial membrane potential and reactive oxygen species levels preceded cell death. The data suggest that amyloid-β peptide (25-35) cytotoxicity is associated with adenosine triphosphate-sensitive potassium channels and nitric oxide. Regulation of adenosine triphosphate-sensitive potassium channels suppresses PC12 cell cytotoxicity induced by amyloid-β peptide (25-35). In this study, we treated PC12 cells with 0-20 μM amyloid-β peptide (25-35) for 24 hours to induce cytotoxicity, and found that 5-20 μM amyloid-β peptide (25-35) decreased PC12 cell viability, but adenosine triphosphate-sensitive potassium channel activator diazoxide suppressed the decrease in PC12 cell viability induced by amyloid-beta peptide (25-35). Diazoxide protected PC12 cells against amyloid-beta peptide (25-35) -induced increases in mitochondrial membrane potential and These protective effects were characterized by the fact that they were protected by PC12 cells from amyloid-beta peptide (25-35) -induced increases in both mitochondrial membrane potential and intracellular reactive oxygen species levels. However, the H2O2-degrading enzyme catalase could not reverse the amyloid-beta peptide (25 -35) -induced increase in intracellular reactive oxygen species. A 24-hour exposure to amyloid-beta peptide (25-35) did not result in apoptosis or necrosis, suggesting that the increases in both mitochondrial membrane potential and reactive oxygen species levels preceded cell death. The data suggest that amyloid-β peptide (25-35) cytotoxicity is associated with adenosine triphosphate-sensitive potassium channels and nitric oxide. Regulation of adenosine triphosphate-sensitive potassium channels suppresses PC12 cell cytotoxicity induced by amyloid-β peptide (25 -35).