Effects of ammonia poisoning on cognitive behavior and hippocampal synaptic damage in mice

doi:10.12307/2026.044

Abstract

Abstract: BACKGROUND: Ammonia poisoning is considered to be the main hypothesis for the pathogenesis of hepatic encephalopathy. Ammonia can lead to psychiatric and cognitive behavioral disorders, although the specific pathological molecular mechanisms remain unclear.
OBJECTIVE: To investigate the effects of ammonia poisoning on cognitive behavior and hippocampal neuronal synapses in mice.
METHODS: Thirty-two C57BL/6J mice were randomly divided into a normal control group and an ammonium chloride group, with 16 mice in each group. Normal saline was injected intraperitoneally in the control group, and ammonium chloride (10 mmol/kg) was injected intraperitoneally in the ammonium chloride group to construct a model of ammonia poisoning, once a day. After 7 days of ammonium chloride intervention, blood samples were collected from the hearts of six mice in each group for blood ammonia concentration detection. Behavioral experiments, including the open field test, novel object recognition test, and Y-maze test, were performed to assess mental and cognitive-behavioral changes in mice. Finally, hippocampal tissues were extracted for western blot analysis to detect the expression levels of synaptophysin and postsynaptic density protein-95 in hippocampal neurons.
RESULTS AND CONCLUSION: The blood ammonia concentration was significantly elevated in the ammonium chloride group compared with the control group (P < 0.05). Mice in the ammonium chloride group showed anxiety-like behavior and disinhibition phenomenon, and a significant decrease in recognition memory and working memory ability. Western blot results revealed that the expression of synaptophysin and postsynaptic density protein-95 protein in hippocampal neurons in the ammonium chloride group was lower than that in the control group (P < 0.05). To conclude, ammonia poisoning can induce hippocampal neuronal synaptic damage, leading to psychiatric and cognitive behavioral abnormalities in mice.

Key words: ammonia poisoning, ammonium chloride, hepatic encephalopathy, cognitive behavior, hippocampal neurons, synapses, engineered tissue construction

CLC Number:

Zhang Jiuxuan, Zhang Jinnan, Sui Xiaofan, Pei Xiaxia, Wei Jianhong, Su Qiang, Li Tian. Effects of ammonia poisoning on cognitive behavior and hippocampal synaptic damage in mice[J]. Chinese Journal of Tissue Engineering Research, 2026, 30(5): 1122-1128.

Figures/Tables 3

2.1 实验动物数量分析 32只小鼠全部进入结果分析。 2.2 验证氯化铵诱导氨中毒小鼠模型成功如图1所示，氯化铵组小鼠血氨浓度高于对照组2倍以上(P < 0.01)，表明氨中毒小鼠模型构建成功[16]。 2.3 氨中毒模型小鼠出现焦虑样行为和行为脱抑制旷场实验结果显示，与对照组相比，氯化铵组小鼠总运动距离、在旷场中央区域时间百分比均增加(P < 0.01，P < 0.05)，见图2A，B。图2C展示两组小鼠在旷场中的运动轨迹图。上述结果提示氯化铵组小鼠出现焦虑样行为，同时也表现出行为脱抑制。 2.4 氨中毒模型小鼠识别记忆能力下降行为脱抑制是痴呆症的重要临床表现[17]，上述结果提示氨中毒小鼠模型可能表现出记忆能力缺失。为此，此次研究进行了新物体识别实验(如图3A)，熟悉期时，两组小鼠对相同物体的探索时间无显著差异(P > 0.05)，见图3B；测试期时，氯化铵组小鼠新物体识别指数显著低于对照组(P < 0.05)，见图3C，结果表明氯化铵干预后小鼠出现识别记忆损害，短期记忆能力下降。 2.5 氨中毒模型小鼠工作记忆能力减弱图4A表示自发交替实验示意图。两组小鼠总进臂次数无显著差异(P > 0.05)，见图4B，排除两组小鼠运动能力的差异；但与对照组相比，氯化铵组小鼠自发交替正确率显著降低(P < 0.01)，见图4C。上述结果均表明氯化铵组小鼠工作记忆能力受到了损害。 2.6 氨中毒模型小鼠海马突触素和突触后致密物95蛋白下调突触素是突触小泡是最为丰富的蛋白之一，对维持神经递质传递至关重要，突触素的缺失可导致突触前递质释放受阻、神经递质传传递受损[18-19]；突触后致密物95蛋白棕榈酰化保持在突触处，可控制突触传递和可塑性，突触后致密物95蛋白减少可产生突触抑制[20-21]。如图5所示，与对照组小鼠相比，氯化铵组小鼠海马神经元突触素和突触后致密物95蛋白表达显著降低(P < 0.01)，表明氯化铵组小鼠海马神经元突触结构和功能可能受损，为上述氨中毒小鼠模型发生精神和记忆行为异常提供了可能的分子机制，同时也进一步为氨的神经毒性提供了支持。"

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