Effect of melatonin on the oxidative stress in N1E-115 cells is not mediated by mt1 receptors.

To explore if protective effect of melatonin on oxidative stress induced by okadaic acid, an inhibitor of protein phosphatases PP1 and PP2A, is mediated by membrane receptors subtype mt1, we used an in vitro model with N1E-115 neuroblastoma cells. We demonstrated that exposure of cells to 50 nM okadaic acid for 2 h induces a reduction in the activity of antioxidative enzymes, and an increase of lipid peroxidation products, while melatonin prevents the effect of okadaic acid. On the other hand, the presence of luzindole, 20 min before adding melatonin, did not cause changes on the effect of the melatonin on oxidative stress. These results seem to indicate that protective effect of melatonin is not mediated by mt1 receptors.