Tordoff M G, Ulrich P M, Sandler F
Monell Chemical Senses Center, Philadelphia, PA 19104.
Appetite. 1990 Feb;14(1):29-44. doi: 10.1016/0195-6663(90)90052-a.
Previous work suggests that fuel oxidation in the liver provides an unconditioned stimulus for "calorie-based" flavor preference learning. To investigate this possibility in more detail, we manipulated liver metabolism by taking advantage of the greater specificity to the liver of fructose than glucose. Intact rats preferred flavored food ingested with a drink of 35% fructose solution to flavored food eaten with either no sweet drink (Experiment 1) or an equicaloric drink of glucose (Experiment 2). The effect on food preference did not depend on the taste of the sugar solutions: when given a choice between glucose and fructose solutions, the rats drank the same volume of each. Moreover, a preference for fructose-paired flavored food was obtained when fructose and glucose solutions were given by gavage (Experiment 3). Unlike intact rats, rats with hepatic vagotomy preferred equally flavored food paired with fructose solution and flavored food paired with no sugar solution (Experiment 1). They also avoided flavored food paired with gavage of fructose slightly, relative to flavored food paired with gavage of glucose (Experiment 3). These results suggest that the unconditioned stimulus for calorie-based conditioning is transduced in the liver, and that an intact hepatic vagus nerve is required for conditioning to occur.
先前的研究表明，肝脏中的燃料氧化为“基于卡路里的”风味偏好学习提供了一种无条件刺激。为了更详细地研究这种可能性，我们利用果糖对肝脏的特异性高于葡萄糖这一特性来操纵肝脏代谢。完整的大鼠更喜欢与35%果糖溶液一起饮用时摄入的调味食物，而不是与无糖饮料（实验1）或等热量葡萄糖饮料一起食用的调味食物。对食物偏好的影响并不取决于糖溶液的味道：当在葡萄糖溶液和果糖溶液之间进行选择时，大鼠饮用的每种溶液体积相同。此外，当通过灌胃给予果糖和葡萄糖溶液时，大鼠对与果糖配对的调味食物表现出偏好（实验3）。与完整的大鼠不同，肝迷走神经切断的大鼠对与果糖溶液配对的调味食物和与无糖溶液配对的调味食物同样偏好（实验1）。相对于与葡萄糖灌胃配对的调味食物，它们也略微避免了与果糖灌胃配对的调味食物（实验3）。这些结果表明，基于卡路里条件作用的无条件刺激在肝脏中被传导，并且条件作用的发生需要完整的肝迷走神经。
