Description: We investigated the influence of 7-nitroindazole (7-NI), a selective neuronal nitric oxide synthase (nNOS) inhibitor in vivo, on nitrite concentration, superoxide production and superoxide dismutase activity in AlCl3-treated Wistar rats. The observed biochemical changes in neuronal tissues showed that aluminium served as pro-oxidant, while 7-NI had antioxidant effects in AlCl3-treated animals. The protective effects of 7-NI against the cellular damage caused by AlCl3-induced oxidative stress, together with its low toxicity, make 7-NI worthy of investigation as a potential supplement in the treatment of neurological disorders in which the oxidative stress effects have to be minimized