Tackman J M, Tews J K, Harper A E
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
J Nutr. 1990 May;120(5):521-33. doi: 10.1093/jn/120.5.521.
Food intake, growth, plasma and brain amino acid, and brain serotonin and 5-hydroxyindole-3-acetic acid (5-HIAA) concentrations were measured in rats fed low protein diets containing disproportionate amounts of large neutral amino acids (LNAA) devoid of tryptophan or histidine (tryptophan or histidine imbalance). Five-day food intakes and weight gains of rats fed the imbalanced diets were depressed. The concentration of the limiting amino acid was low in brains of rats fed diets containing LNAA that compete with either tryptophan or histidine for entry into brain. Correlations were observed between the brain concentrations of most individual LNAA and either the ratios of the plasma concentration of that LNAA to the sum of the other LNAA, or the predicted rates of influx of that LNAA. Cumulative food intakes were correlated with brain concentrations of the limiting amino acid, tryptophan or histidine. Food intakes were not consistently correlated with concentrations of serotonin and 5-HIAA because these compounds were altered only in brains of rats in the tryptophan study. Competition among amino acids for uptake into brain appears to be involved in the feeding response of the rat to dietary disproportions of amino acids, but this response is not directly related to changes in brain concentrations of serotonin and 5-HIAA.
在喂食低蛋白饮食的大鼠中测量食物摄入量、生长情况、血浆和脑氨基酸以及脑血清素和5-羟吲哚-3-乙酸（5-HIAA）浓度，这些低蛋白饮食含有不成比例的大量缺乏色氨酸或组氨酸的中性氨基酸（色氨酸或组氨酸失衡）。喂食不平衡饮食的大鼠的五日食物摄入量和体重增加受到抑制。在喂食含有与色氨酸或组氨酸竞争进入大脑的中性氨基酸的饮食的大鼠大脑中，限制性氨基酸的浓度较低。观察到大多数单个中性氨基酸的脑浓度与该中性氨基酸的血浆浓度与其他中性氨基酸总和的比率或该中性氨基酸的预测流入速率之间存在相关性。累积食物摄入量与限制性氨基酸色氨酸或组氨酸的脑浓度相关。食物摄入量与血清素和5-HIAA的浓度并非始终相关，因为这些化合物仅在色氨酸研究中的大鼠大脑中发生了变化。氨基酸之间竞争进入大脑似乎参与了大鼠对饮食中氨基酸比例失调的进食反应，但这种反应与脑血清素和5-HIAA浓度的变化没有直接关系。
