Introduction Dietary nitrate lowers blood pressure and improves athletic performance in humans, yet data supporting observations that it may increase cerebral blood flow and improve cognitive performance are mixed. Here we tested the hypothesis that nitrate and nitrite treatment would improve indicators of learning and cognitive performance in a zebrafish ( Danio rerio ) model. We also explored the extent to which nitrate and nitrite treatment affected the brain metabolome in order to understand how nitrate and nitrite supplementation may affect indices of cognitive function. Methods Fish were exposed to sodium nitrate (606.9 mg/L), sodium nitrite (19.5 mg/L), or control water for 2-4 weeks and free swim, startle response, innate predator avoidance, social cohesion, and shuttle box assays were performed. Results Nitrate and nitrite treatment did not change fish weight, length, predator avoidance, or distance and velocity traveled in an unstressed environment. Nitrate- and nitrite-treated fish initially experienced more negative reinforcement and increased time to decision in the shuttle box assay, which is consistent with a decrease in associative learning or executive function however, over multiple trials, all treatment groups demonstrated behaviors associated with learning. Nitrate and nitrite treatment significantly increased anxiety-like behavior but did not alter epinephrine, norepinephrine or dopamine levels. Targeted LC-MS/MS analysis revealed no significant increase in brain nitrate or nitrite concentrations with treatment. An untargeted metabolomics analysis found 47 metabolites whose abundance was significantly altered in the brain with nitrate and nitrite treatment including an 18-19% reduction in the neurotransmitter γ-aminobutyric acid (GABA), and 17-22% reduction in its precursor, glutamine, which may contribute to the increased anxiety-like behavior. Conclusion Nitrate and nitrite treatment did not adversely affect multiple parameters of zebrafish health but was associated with mild anxiety-like behavior, changes in the brain metabolome, and caused a short-term decrease in executive function or associative learning.

中文翻译：

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硝酸盐和亚硝酸盐暴露会增加斑马鱼的焦虑样行为并改变大脑代谢组学特征

简介饮食中的硝酸盐可降低血压并改善人类的运动表现，但支持它可能增加脑血流量和改善认知能力的观察数据混杂在一起。在这里，我们测试了以下假设：硝酸盐和亚硝酸盐处理将改善斑马鱼（Danio rerio）模型中的学习和认知能力指标。我们还探讨了硝酸盐和亚硝酸盐治疗对大脑代谢组的影响程度，以了解补充硝酸盐和亚硝酸盐如何影响认知功能指数。方法将鱼暴露于606.9 mg / L的硝酸钠，19.5 mg / L的亚硝酸钠或对照水中暴露2-4周，并自由游泳，惊吓反应，避免先天捕食，社交凝聚力和穿梭箱检测执行。结果硝酸盐和亚硝酸盐处理不会改变鱼的体重，长度，避免捕食者，也不会改变在无压力环境中的游走距离和速度。硝酸盐和亚硝酸盐处理的鱼最初在穿梭箱测定中经历了更多的负强化作用，并增加了决策时间，这与联想学习或执行功能的降低是一致的，但是，在多项试验中，所有治疗组均表现出与学习相关的行为。硝酸盐和亚硝酸盐治疗显着增加了焦虑样行为，但并未改变肾上腺素，去甲肾上腺素或多巴胺水平。有针对性的LC-MS / MS分析显示，治疗后脑中硝酸盐或亚硝酸盐浓度没有明显增加。一项非目标代谢组学分析发现，使用硝酸盐和亚硝酸盐治疗后，大脑中47种代谢物的丰度发生了显着变化，包括神经递质γ-氨基丁酸（GABA）降低了18-19％，其前体谷氨酰胺降低了17-22％，这可能有助于增加焦虑样行为。结论硝酸盐和亚硝酸盐处理不会对斑马鱼健康的多个参数产生不利影响，但会引起轻度的焦虑样行为，脑代谢组的改变，并导致执行功能或联想学习的短期减少。