Comparison the Effect of Zinc Oxide and Magnesium Oxide Nano Particles on Long Term Memory in Adult Male Mice

Background Magnesium (Mg) and zinc (Zn) are two essential elemnts for normal performance of central nervous system. So that the learning and memory are influenced by these ions that antagonized NMDA (N methyl-D-aspartate) receptor. Objectives This study was conducted to evaluate the effect of nanoparticles of zinc oxide (ZnO) and magnesium oxide (MgO) on passive avoidance memory in mice. Methods In this experimental study adult male NMRI mice weighing 25 ± 3g were used. ZnO and MgO nano particles (1, 2.5 and 5 mg/kg, intrapretoneally (i.p.) were injected pre-training in model of passive avoidance learning. Memory was evaluated at 1, 3 and 7 days after training. Delay time in coming down from the safe platform in step down apparatus was evaluated as an index of memory. Open field test was used for evaluation the locomotor activity. Results Nano MgO 2.5 and 5 mg/kg increased delay time in coming down from plateform at one day after training (P < 0.05) in dose dependent manner. Nano ZnO 2.5 and 5 mg/kg reduced delay time in coming down from the platform 1, 3 and 7 day after training (P < 0.05) and just 3 days after training (P < 0.05) respectivley. Locomotor activity did not change in presence of MgO and/or ZnO nano particles. Conclusions It seems that various effects of nano ZnO and MgO on long term memeory is related to the different effects of Zn and Mg ions on receptors (such as NMDA) involved in memory process. Toxicity and/ or preservation of nanoparticle in body are another possible reasons.