Peters J C, Harper A E
Am J Physiol. 1987 May;252(5 Pt 2):R902-14. doi: 10.1152/ajpregu.1987.252.5.R902.
Male rats (100 g) previously adapted to a 20% casein diet were fed diets containing from 0 to 55% of casein and were killed after 20, 60, 150, 240, or 330 min. Food intake of rats fed a protein-free diet or a diet containing greater than 35% of casein was depressed within 20 min and remained depressed for up to 5.5 h. Depressed food intake of rats fed protein-free diets was accompanied by a rapid reduction in plasma and brain total concentrations of free indispensable amino acids (IAA). Food intake depression among groups fed diets containing in excess of 35% casein was associated with elevated plasma and brain total IAA concentrations, compared with those of animals fed diets containing 15-20% of casein. No consistent relationships were observed between food or protein intakes and whole-brain concentrations of 5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, or their sum. Our results suggest that in animals fed a single diet, food intake is depressed if the total concentration of free IAA in brain either falls below a certain critical minimum or exceeds some maximum tolerable level.
先前适应了含20%酪蛋白饮食的雄性大鼠（体重100克）被喂食酪蛋白含量从0%到55%的饮食，并在20、60、150、240或330分钟后处死。喂食无蛋白饮食或酪蛋白含量高于35%饮食的大鼠，其食物摄入量在20分钟内就会下降，并持续下降长达5.5小时。喂食无蛋白饮食的大鼠食物摄入量下降的同时，血浆和大脑中游离必需氨基酸（IAA）的总浓度迅速降低。与喂食含15 - 20%酪蛋白饮食的动物相比，喂食酪蛋白含量超过35%饮食的组中，食物摄入量下降与血浆和大脑中IAA总浓度升高有关。在食物或蛋白质摄入量与全脑5 - 羟色胺、5 - 羟吲哚 - 3 - 乙酸或它们的总和浓度之间未观察到一致的关系。我们的结果表明，在喂食单一饮食的动物中，如果大脑中游离IAA的总浓度降至某个临界最小值以下或超过某个最大耐受水平，食物摄入量就会下降。
