饥饿激素（ghrelin）或会增强大脑的记忆功能

　　近日，在荷兰举办的摄食行为研究学会年会上，来自南加州大学的神经科学研究人员通过研究鉴别出了饥饿激素（ghrelin）所扮演的新角色，此前研究人员认为，饥饿激素在从肠道向大脑发送饥饿信号的过程中扮演着特殊的角色，这项研究中，研究人员发现，饥饿激素或许对于大脑记忆的控制与非常重要。

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　　饥饿激素在胃部产生，其会因个体期待进食而分泌，同时其在增加机体饥饿感上扮演着非常关键的角色，研究者Elizabeth Davis表示，比如，如果我们身处餐馆之中，机体饥饿激素的水平就会上升，同时我们也期待着一顿即将上桌的美味；一旦饥饿激素被分泌，其就会与迷走神经中的特殊受体相结合，迷走神经是一种能将多种信号从肠道传递到大脑中的神经。除了能够影响进食期间食物的摄入量外，迷走神经还会影响大脑的记忆功能，研究者推测，饥饿激素或许是帮助迷走神经促进大脑记忆的关键分子。

　　利用RNA干扰技术来减少饥饿激素受体的水平，研究人员对实验室大鼠进行研究，阻断了其机体中迷走神经的饥饿激素信号，当给予一系列记忆任务时，迷走神经饥饿激素信号降低的大鼠就会在情境记忆测试中出现障碍，情境记忆是一种包括记住事情发生的时间、地点和内容的记忆，比如回忆起我们上学的第一天，而对于大鼠而言，只需要记住特定位置的特定物体。

　　随后研究人员调查了是否迷走神经饥饿激素信号会影响大鼠的摄食行为，他们发现，当迷走神经无法接受饥饿激素信号时，大鼠就会摄食很频繁，而且每餐会少吃一点，这些研究结果或许与情境记忆问题直接相关，决定吃或者不吃会受到大鼠此前摄食的记忆所影响，饥饿激素传递给迷走神经的信号或许是一种特殊的共享分子联系，其能将大鼠记住上一顿饭的信息与期待下一顿饭所产生的饥饿信号相联系起来。

　　相关研究结果或能帮助研究人员理解机体情境记忆产生的分子机制，同时也能帮助理解记忆和摄食行为之间的关联，未来研究人员或有望开发出一种新型策略，通过操控肠道-大脑中的饥饿激素信号来改善人类的记忆功能。

　　原始出处：

　　'Hunger hormone' enhances memory

　　A team of neuroscience researchers at the University of Southern California have identified a surprising new role for the "hunger hormone" ghrelin. Ghrelin has previously been recognized for its unique role in sending hunger signals from the gut to the brain, but, as presented this week at the annual meeting of the Society for the Study of Ingestive Behavior, these new findings suggest that it may also be important for memory control.

　　Ghrelin is produced in the stomach and secreted in anticipation of eating, and is known for its role to increase hunger. "For example, ghrelin levels would be high if you were at a restaurant, looking forward to a delicious dinner that was going to be served shortly," said Dr. Elizabeth Davis, lead author on the study. Once it is secreted, ghrelin binds to specialized receptors on the vagus nerve—a nerve that communicates a variety of signals from the gut to the brain. "We recently discovered that in addition to influencing the amount of food consumed during a meal, the vagus nerve also influences memory function," said Dr. Scott Kanoski, senior author of the study. The team hypothesized that ghrelin is a key molecule that helps the vagus nerve promote memory.......