Polystyrene microplastics affect learning and memory in mice by inducing oxidative stress and decreasing the level of acetylcholine

Microplastics pollution has become a growing environmental concern, but its potential neurotoxic effects remain unknown. In this study, we determined the effects of exposure to polystyrene microplastics (micro-PS) on learning and memory, and explored the underlying mechanisms. Kunming mice were orally exposed to 0.01, 0.1, 1 mg/d micro-PS or saline for four weeks. Employing the Morris water maze test, we observed that exposure to micro-PS affected the learning and exploration abilities of mice, and impaired their learning and memory functions. After exposure to micro-PS, the nerve cells in the hippocampus became loose and disordered, and the number of Nissl bodies decreased. Increases in the levels of ROS and MDA, and a decrease in levels of glutathione were found in the brain tissue of the mice exposed to micro-PS. Exposure to micro-PS also induced a reduction in the level of acetylcholine, and inhibited the CREB/BDNF pathway. Importantly, after treatment with the antioxidant, Vitamin E, the learning and memory abilities of the mice were restored, and the release of neurotransmitters rebounded. These results show that micro-PS exposure can affect the learning and memory functions through inducing oxidative stress and decreasing the levels of acetylcholine.