Coscina D V, Lacombe S, Chambers J W, Dixon L, Nobrega J N
Section of Biopsychology, Clarke Institute of Psychiatry, Toronto, Ontario, Canada.
Appetite. 1989 Aug;13(1):15-24. doi: 10.1016/0195-6663(89)90023-8.
Rats with medial hypothalamic lesions are known to prefer greasy diets. Past research has suggested that this is based on the oily texture rather than caloric content of these foods. We have re-examined this appetite in rats with bilateral parasagittal knife-cuts between the medial and lateral hypothalamus. Following knife cuts vs. sham surgery, the body weight and food consumption of adult female rats were monitored during four experimental phases. During the first month post-surgery rats were fed powdered Chow (3.61 kcal/g) and showed the usual hyperphagia and obesity. Each group was then subdivided and fed either a high-fat diet (5.5 kcal/g) or a similarly greasy mineral-oil diet (3.61 kcal/g) for a second month. The knife-cut group fed high-fat showed significantly higher intake than both sham-cut controls and knife-cut rats fed the mineral-oil diet. The latter group showed only a non-significant feeding increase over controls. Following a third month when all groups again received Chow, animals were given the opposite greasy diet for a final month. Knife-cut rats previously fed the high-fat diet showed significant overeating of the mineral-oil diet and defended their obesity, while those fed the mineral-oil free diet first now showed significant hyperphagia and obesity on the high-fat diet. Across both target phases (months 2 and 4) knife-cut rats always ate significantly more of the high-fat diet than of the mineral-oil diet. The latter only elicited hyperphagia in animals that had been previously exposed to the high-fat diet. These findings suggest that the hyperphagic response to greasy foods relatively low in calories and digestible fats by rats with hypothalamic injury is a function of prior experience with the sensory and/or metabolic consequences of having first eaten highly caloric fatty foods. If that is true, it may be that such animals are capable of learning positive food-associated cues in addition to negative ones (i.e. enhanced taste aversions) documented earlier by other investigators.
已知患有下丘脑内侧损伤的大鼠偏爱油腻食物。过去的研究表明，这是基于这些食物的油性质地而非热量含量。我们重新研究了在内侧和外侧下丘脑之间进行双侧矢状旁切口的大鼠的这种食欲。与假手术相比，在四个实验阶段监测成年雌性大鼠在进行切口手术后的体重和食物消耗量。在手术后的第一个月，给大鼠喂食粉末状的普通饲料（3.61千卡/克），它们出现了常见的食欲亢进和肥胖。然后将每组再细分，在第二个月给它们喂食高脂肪饮食（5.5千卡/克）或类似油腻的矿物油饮食（3.61千卡/克）。喂食高脂肪饮食的切口组的摄入量明显高于假切口对照组和喂食矿物油饮食的切口组大鼠。后一组与对照组相比，喂食量仅略有增加但不显著。在第三个月所有组再次喂食普通饲料后，在最后一个月给动物喂食相反的油腻饮食。先前喂食高脂肪饮食的切口组大鼠在食用矿物油饮食时出现明显的暴饮暴食，并维持肥胖状态，而那些首先喂食无矿物油饮食的大鼠现在在高脂肪饮食上出现明显的食欲亢进和肥胖。在两个目标阶段（第2个月和第4个月），切口组大鼠食用高脂肪饮食的量总是明显多于矿物油饮食。后者仅在先前接触过高脂肪饮食的动物中引起食欲亢进。这些发现表明，下丘脑损伤的大鼠对热量和可消化脂肪含量相对较低的油腻食物的食欲亢进反应是先前食用高热量脂肪食物的感觉和/或代谢后果的经验作用。如果这是真的，那么这些动物可能除了能够学习其他研究者先前记录的负面食物相关线索（即增强的味觉厌恶）之外，还能够学习正面的食物相关线索。
