Effect of zinc oxide nanoparticles on memory retrieval, hippocampal CA1 pyramidal neurons and some serum oxidative stress factors in male Wistar rats

Due to the fact that nanoscale zinc oxide nanoparticles can pass through the blood brain barrier and have devastating effects on various posts of nervous system, the present study investigated the effects of N-Acetyl cysteine on memory retrieval, hippocampal CA1 pyramidal neurons and some blood serum oxidative stress factors on male Wistar rats treated with zinc oxide nanoparticles.

The study was conducted on 48 male Wister rats in 6 groups: Control, ZnO NPs groups (0.5, 1, 1.25, 2.5 mg/kg) and N-Acetyl cysteine (300 mg/kg) with ZnO NPs (1.25 mg/kg) group. In all groups, saline or ZnO NPs were injected intraperitonealy 30 minutes before the training. In the group of NAC (300mg/kg) with ZnO NPs, the injection of NAC (300mg/kg) was done 5 minutes before injection of nanoparticles. After the memory test animals brain were fixed and the the number of healthy neurons in the CA1 region of the hippocampus were counted. In the groups of control, ZnO NPs (1.25mg/kg) and NAC (300mg/kg) with ZnO NPs (1.25mg/kg), the blood serum were measured for levels of catalase and superoxide dismutase.

Injections of ZnO NPs significantly reduced memory retrieval and the number of healthy neurons in the CA1 region compared to the control group (P<0.001). The use of NAC significantly improved the effects of ZnO NPs on memory deficits, the number of healthy neurons in the CA1 region, and the level of antioxidant enzymes of catalase and superoxide dismutase in serum compared with the ZnO NPs group (P <0.001).

It seems that ZnO NPs decrease the memory retrieval, and cause cell death in the pyramidal neurons of the CA1 region of the hippocampus by increasing the oxidative stress. NAC, as a potent antioxidant by reducing the active oxygen species can prevent the harmful effects of ZnO NPs on memory and neurons of the hippocampal CA1 area