People who find themselves rummaging around in the refrigerator for a snack not long after they’ve eaten a filling meal might have overactive food-seeking neurons, 不是胃口太大.
正规欧洲杯买球网站洛杉矶分校 psychologists have discovered a circuit in the brain of mice that makes them crave food and seek it out, 即使他们不饿. 当刺激, this cluster of cells propels mice to forage vigorously and to prefer fatty and pleasurable foods like chocolate over healthier foods like carrots.
人类拥有相同种类的细胞, 如果在人类身上得到证实, the finding could offer new ways of understanding eating disorders.
该报告发表在该杂志上 自然通讯, is the first to find cells dedicated to food-seeking in a part of the mouse brainstem usually associated with panic, 但不包括喂养.
“This region we’re studying is called the periaqueductal gray (PAG), 它位于脑干, which is very old in evolutionary history and because of that, 人类和老鼠在功能上是相似的,通讯作者说。 Avishek Adhikari, 正规欧洲杯买球网站洛杉矶分校的心理学副教授. “尽管我们的发现令人惊讶, it makes sense that food-seeking would be rooted in such an ancient part of the brain, 因为觅食是所有动物都需要做的事情.”
Adhikari studies how fear and anxiety help animals assess risks and minimize exposure to threats, and his group made the discovery while trying to learn how this particular spot was involved in fear.
“Activation of the entire PAG region causes a dramatic panic response in both mice and humans. But when we selectively stimulated only this specific cluster of PAG neurons called vgat PAG cells, 他们并没有改变恐惧, 反而导致了觅食和进食,阿迪卡里说.
The researchers injected into mouse brains a virus genetically engineered to make the brain cells produce a light-sensitive protein. 当激光通过光纤植入物照射到细胞上时, the new protein translates that light to electrical neural activity in the cells. 微型显微镜, 由正规欧洲杯买球网站洛杉矶分校研发并贴在老鼠头上, 记录细胞的神经活动.
当受到激光刺激时, the vgat PAG cells fired and kicked the mouse into hot pursuit of live crickets and non-prey food, 即使它刚吃了一顿大餐. The stimulation also induced the mouse to follow moving objects that were not food — like ping pong balls, although it did not try to eat them — and it also prompted the mouse to confidently explore everything in its enclosure.
“The results suggest the following behavior is related more to wanting than to hunger,阿迪卡里说. “Hunger is aversive, meaning that mice usually avoid feeling hungry if they can. But they seek out activation of these cells, suggesting that the circuit is not causing hunger. Instead, we think this circuit causes the craving of highly rewarding, high-caloric food. These cells can cause the mouse to eat more high-calorie foods even in the absence of hunger.”
Satiated mice with activated vgat PAG cells craved fatty foods so much, 他们愿意忍受足部的电击来得到它们, 这是吃饱了的老鼠通常不会做的事. 相反, when the researchers injected a virus engineered to produce a protein that dampens the cells’ activity under exposure to light, 老鼠觅食的次数减少了, 即使他们很饿.
“Mice show compulsive eating in the presence of aversive direct consequences when this circuit is active, and don’t search for food even if they’re hungry when it’s not active. This circuit can circumvent the normal hunger pressures of how, 吃什么，什么时候吃,费尔南多·赖斯说, a 正规欧洲杯买球网站洛杉矶分校 postdoctoral researcher who did most of the experiments in the paper and came up with the idea to study compulsive eating. “We’re doing new experiments based on these findings and learning that these cells induce eating of fatty and sugary foods, 但在老鼠体内没有蔬菜, 这表明这种电路可能会增加垃圾食品的摄入量.”
Like mice, humans also possess vgat PAG cells in the brainstem. 如果这个回路在一个人体内过度活跃, they might feel more rewarded by eating or crave food when not hungry. 相反, 如果这个电路不够活跃, 他们与饮食相关的乐趣可能会减少, 可能会导致厌食症. 如果在人类身上发现, the food-seeking circuit could become the treatment target for some kinds of eating disorders.
The research was supported by the National Institute of Mental 健康, the Brain & Behavior 研究 Foundation and the National Science Foundation.
