Amino Acid Nutrition and Brain Function

色氨酸和酪氨酸是构建蛋白质块的氨基酸，存在于大多数食物中。大脑的组成和功能可以被色氨酸和酪氨酸改变，因为它们是神经递质的前体：神经递质是神经元或神经中枢放电时释放的物质。神经递质通过突触将神经冲动传递给另一个神经元、肌肉细胞或秘书细胞。色氨酸在某些神经元末梢转化为神经递质血清素。酪氨酸是多巴胺、去甲肾上腺素和肾上腺素的前体，它们统称为儿茶酚胺递质。神经递质的合成和释放可以调节一些重要的行为机制（如疼痛、食欲、睡眠、情绪和表现的控制）。因此，在低蛋白饮食中补充氨基酸引起的神经化学变化与亮度辨别学习测试之间的关系被进一步研究。饲粮中添加0.1%的色氨酸显著提高了玉米脑色氨酸、血清素和5-羟吲哚乙酸（5HIAA）的浓度，提高了玉米的学习能力。特别是R-（错误反应）的频率降低。在10%大豆分离蛋白的基础上添加蛋氨酸和苏氨酸（添加量满足每种氨基酸需求量的两倍），大鼠脑色氨酸、血清素和5HIAA浓度急剧下降。在亮度辨别学习测试中，氨基酸添加组大鼠的总反应（R^+；正确+ R^-；错误）较未添加基础饲料组大鼠有所提高。初级学习测试的正确反应率没有变化，但在逆向学习测试中，氨基酸添加饲料的大鼠的反应率增加。因此，可以认为血清素能神经元的活性（如5-羟基吲哚的浓度，或神经递质的合成和释放）和一些行为活动（如记忆学习）与坚果营养阶段有关，因此这些神经化学和神经药理学参数可以被认为是评价饮食营养和安全性的可能指标。少

Tryptophan and tyrosine are the amino acids to build blocks of protein, and are present in most foods. The composition and function of the brain can be altered by tryptophan and tyrosine because they are the precursors of neurotransmitters: substances that are released from a neuron, or nerve cen, when it fires. The neurotransmitter thereby conveys the nerve impulse across a synapse to either another neuron, a muscle cell or secretary cell. Tryptophan is converted in the terminals of certain neurons into the neurotransmitter serotonin. Tyrosine serves as the precursor of dopamine, norepinephrine and epinephrine, which are collectively called the catecholamine transmitters. The synthesis and release of neurotransmitters may regulate some important behavioral mechanisms (such as the control of pain, appetite, sleep, mood and performance). So, relationships between neurochemical changes caused by amino acid supplementation to low protein diet and a brightness-discrimination learning test … More were investigated.1. The concentrations of brain tryptophan, serotonin and 5-hydroxyindole acetic acid(5HIAA) significantly increased by the addition of 0.1% of tryptophan to corn diet, then the learning ability was improved. Especially the frequency of R-(incorrect response) decreased.2. When rats were fed a 10% soy protein isolate diet supplemented with methionine and threonine(supplemented levels fulfill two-fold of each amino acid requirement), the concentrations of brain tryptophan, serotonin and 5HIAA sharply decreased. By the brightness-discrimination learning test, the total response(R^+; correct + R^-; incorrect) of rats fed amino acid supplemented group increased as compared with those of rats fed non-supplemented basal diet. Correct response ratios of primary learning test did not change, but in reverse learning test, its response ratios of rats fed amino acid supplemented diet increased. Therefore, it may be considered that the activities of serotoninergic neurons(such as the concentrations of 5-hydroxyindoles, or the synthesis and release of neurotransmitters) and some behavioral activities(such as memory-learning) are correlated with the nut ritional stages, so these neurochemical and neuropharmacological parameters may be considered as possible measures for the nutritional and safety evaluation of diets. Less