A growing number of individuals are now exposed to neodymium (Nd) owing to its extensive applications. However, the biological effects of Nd on humans, especially on learning and memory, remain elusive. To investigate whether Nd exposure affects learning and memory, in this study female ICR mice were exposed to nano Nd₂O₃ via intranasal instillation at doses of 50, 100, and 150 mg/kg body weight, daily for 45 days. According to Morris water maze data, learning and memory parameters were significantly reduced in the 150 mg/kg nano-Nd₂O₃ group than the sham control. Furthermore, inductively coupled plasma–mass spectroscopy analysis revealed that Nd levels were significantly higher in the hippo campus of the 100 and 150 mg/kg exposed group than the sham control; however, no significant differences were observed in the hippocampal histopathology between these groups. Furthermore, reactive oxygen species were elevated in hippocampal tissues of experimental groups than the sham control, 447.3 in high dose group and 360.0 in control group; however, malondialdehyde levels were significantly increased and superoxide dismutase activities were decreased only in mice exposed to 100 and 150 mg/kg Nd₂O₃. High-performance liquid chromatography data demonstrated that levels of glutamic acid, glycine, and gamma-aminobutyric acid were higher in the hippocampus of mice exposed to 150 mg/kg Nd₂O₃ than the sham control. Our findings indicated that the neuronal injury was induced by disruption of the oxidation–antioxidation homeostasis and altered amino acid neurotransmitter levels in the hippocampus, which could result in the poor cognitive performance demonstrated by exposed mice.

中文翻译：

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纳米氧化钕致小鼠学习记忆障碍及可能机制

由于其广泛的应用，越来越多的人现在接触到钕 (Nd)。然而，Nd 对人类的生物学影响，特别是对学习和记忆的影响，仍然难以捉摸。为了研究 Nd 暴露是否影响学习和记忆，在这项研究中，雌性 ICR 小鼠通过鼻内滴注以 50、100 和 150 毫克/千克体重的剂量暴露于纳米 Nd ₂ O _{3 中}，每天持续 45 天。根据Morris水迷宫数据，150 mg/kg纳米Nd ₂ O _{3 的}学习和记忆参数显着降低组比假对照。此外，电感耦合等离子体质谱分析显示，100 和 150 mg/kg 暴露组的河马区的 Nd 水平显着高于假对照组；然而，这些组之间的海马组织病理学没有观察到显着差异。此外，实验组海马组织中活性氧含量高于假手术组，高剂量组为447.3，对照组为360.0；然而，仅在暴露于 100 和 150 mg/kg Nd ₂ O _{3 的}小鼠中，丙二醛水平显着增加，超氧化物歧化酶活性降低. 高效液相色谱数据表明，暴露于 150 mg/kg Nd ₂ O ₃的小鼠海马中谷氨酸、甘氨酸和 γ-氨基丁酸的水平高于假对照。我们的研究结果表明，神经元损伤是由氧化-抗氧化稳态的破坏和海马中氨基酸神经递质水平的改变引起的，这可能导致暴露小鼠的认知能力较差。