Effects of nanoparticle zinc oxide on spatial cognition and synaptic plasticity in mice with depressive-like behaviors

Background: Nanomaterials, as a new kind of materials, have been greatly applied in different fields due to their special properties. With the industrialization of nanostructured materials and increasing public exposure, the biosafety and potential influences on central nervous system (CNS) have received more attention. Nanosized zinc oxide (nanoZnO) was suggested to up-regulate neuronal excitability and to induce glutamate release in vitro. Therefore, we hypothesized nanoparticles of nanoZnO may lead to changes in balance of neurotransmitter or neuronal excitability of CNS. This study was to investigate if there were effects of nanoZnO on animal model of depression. Methods: Male Swiss mice were given lipopolysaccharides (LPS, 100 mu g/kg, 100 mu g/ml, every other day, 8 times, i.p.) from weaning to induce depressive-like behaviors. NanoZnO (5.6 mg/kg, 5.6 mg/ml, every other day, 8 times, i.p.) was given as the interaction. The mouse model was characterized using the methods of open field test, tail suspension test and forced swim test. Furthermore, the spatial memory was evaluated using Morris water maze (MWM) and the synaptic plasticity was assessed by measuring the long-term potentiation (LTP) in the perforant pathway (PP) to dentate gyrus (DG) in vivo. Results: Results indicated that model mice showed disrupted spatial memory and LTP after LPS injections and the behavioral and electrophysiological improvements after nanoZnO treatment. Conclusion: Data suggested that nanoZnO may play some roles in CNS of mental disorders, which could provide some useful direction on the new drug exploring and clinical researches.