Central neurotoxicity induced by the instillation of ZnO and TiO2 nanoparticles through the taste nerve pathway

Aim: To explore whether nanoparticles (NPs) can be transported into the CNS via the taste nerve pathway. Materials & methods: ZnO and TiO2 NPs were tongue-instilled to male Wistar rats. Toxicity was assessed by Zn/Ti biodistribution, histopathological examination, oxidative stress assay, quantitative reverse-transcriptase PCR analysis, learning and memory capabilities. Results: ZnO NPs and TiO2 NPs significantly deposited in the nerves and brain, respectively. The histopathological examination indicated a slight injury in the cerebral cortex and hippocampus. Ultrastructural changes and an imbalanced oxidative stress were observed. The Morris water maze results showed that the learning and memory of rats were impaired. Conclusion: NPs can enter the CNS via the taste nerve translocation pathway and induce a certain adverse effect.