Neurobehavioral and biochemical modulation following administration of MgO and ZnO nanoparticles in the presence and absence of acute stress.

In this work, the effects of MgO and ZnO nanoparticles were investigated on some behavioral, hormonal and biochemical changes following acute stress. Wistar male rats were divided into groups of control, different times of restraint stress (90, 180 and 360 min), nano-MgO or nano-ZnO alone and with acute restraint stress. Anxiety-like behaviors and pain perception were evaluated by elevated plus maze and hot plate apparatus respectively. Levels of corticosterone hormone, malondialdehyde (MDA) and catalase activity, Mg, Zn, Fe and Ca were evaluated in the serum and hippocampus. The results showed that nano-MgO and nano-ZnO improved anxiety induced by restraint stress and reduced locomotor activity significantly at high doses, while at low doses could induce analgesia in the non-restraint group. Corticosterone level increased temporarily in the presence of 360 min stress while it was reduced in the stress of 90 min just 2 h after stress induction. The highest dose of nano-MgO increased the corticosterone level in non-restraint animals while nano-ZnO reduced it in all the groups. The 90 min stress was increased MDA level and nanoparticles decreased catalase activity in the hippocampus significantly. Influences of both nanoparticles on levels of Mg, Zn, Fe and Ca in the serum and hippocampus seem to be more visible than the other measured biochemical factors. Accordingly, in acute stress conditions, low doses of nano-MgO and nano-ZnO had suitable effects on behavioral responses. It seems that these effects were mostly through the central and peripheral changes of mentioned element's content and acute stress could increase nanoparticles toxicity.