Oxidative stress indices in rat hippocampus using the memory deficit model induced by zinc oxide nanoparticles

Some beneficial effects of zinc oxide nanoparticles (nano ZnO) in medicine have been widely considered in the food and pharmaceutical industries. Despite its beneficial effects and the contradictory oxidant and antioxidant properties of these nano ZnO on cognitive and memory processes, a challenge would be on the medicinal application of these nanoparticles. This study aimed to evaluate the parameters of hippocampal oxidative stress in memory deficits induced by nano ZnO. In this study, 28 adult male Wistar rats (200-250g) were allocated into 4 groups (n=7): control (Saline injection) and three experimental groups with different doses of ZnO (1.25, 2.5 and 5 mg/kg). Long-term memory in an inhibitory avoidance paradigm was examined at one day after the treatment and training. The malondialdehyde (MDA) level as an index of lipid peroxidation and the total thiols (- SH) were evaluated using the biochemical analysis of the hippocampus. Nano ZnO at 1.25, 5 and also 2.5 doses resulted in the impairment of memory (P<0.001 and P<0.01, respectively) with no change in the locomotor activity; a decrease in groups received the higher doses of nano ZnO (2.5 and 5 mg/kg) and an increase in the thiols level groups that received the highest dose of nano ZnO (P<0.001). It can be concluded that memory impairment induced by nano ZnO in rats may not be attributed to the effects of oxidative stress in the hippocampus.