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If you've ever been bitten by a mosquito, a bed bug, or a spider, you probably know the sensation of an itch really well.
大家都知道被蚊子、床虱或蜘蛛咬过后会很痒。
Your immediate reaction is probably to scratch the area and hope the itch goes away. And for a second, it does.
被咬过后，你的当即反应可能就去挠痒痒，并希望以此消除痒痒的感觉。确实有那么几秒钟的效果。
There's that sweet, sweet feeling of relief and satisfaction. Then, the itch comes back with a vengeance.
有一种甜蜜的缓解和满足感。不过一会，又变的更痒了。
So you scratch harder, and then it gets itchy again, and… you get the idea. Creatively, scientists call this the itch-scratch cycle.
所以你更用力的挠，不过一会又痒起来了...懂了吧。科学家给这种循环起了一个创造性的名字—瘙痒-搔抓循环。
And to understand it, it helps to know how scratching and itching work in the first place.
了解这种循环，首先要知道瘙痒和搔抓如何产生。
For a while, researchers thought that an itch was just a mild kind of pain caused by irritated skin cells, but that's not true.
研究人员曾经认为痒只是一种由发炎的皮肤细胞引起的疼痛，但是事实并非如此。
Today, we actually know of a few itch-specific receptors that make sure itch signals and only itch signals get sent to the brain.
现在我们只知道几个针对瘙痒的受容器，它们确保瘙痒信号且只有瘙痒信号可以发送至大脑。
For example, there's an important one in mice called GRPR.
例如，老鼠体内有一种被称为GRPR的重要受容器。
But even if the two sensations aren't the same thing, there is considerable overlap in the nerve pathways that transmit them.
虽然这两种机能并不是一回事，但是在传输信号的神经通道中还是有一些重叠的部分。
And this is why scratching an itch is just so satisfying.
所以挠痒才会如此让人满足。
The sharp sensation of your nails on your skin stimulates certain pain receptors,
指甲作用在皮肤上的尖锐信号刺激了某种皮肤受容器，
and that sends pain signals to your brain that overwhelm the itch ones. Essentially, scratching distracts your brain for a second.
将疼痛信号传输至你的大脑，疼痛感淹没瘙痒感。搔氧暂时分散了大脑的注意力。
But the story doesn't stop there. See, once those pain signals come in,
但是故事到这还没完。你看，一旦那些疼痛信号进入，
your brain responds by releasing the neurotransmitter serotonin to dull them. But that also has a downside.
你的大脑就会做出反应释放神经递质血清素缓和疼痛。但是这样也有缺点。
Serotonin is probably best known as a happiness-related chemical, but it actually does various things throughout the body.
血清素可能是最知名的快乐释放化学物质，但是在身体中它还有其他工作。
And unfortunately, when it comes to your skin, it can end up intensifying an itch.
不幸的是，对皮肤而言，血清素最终会加剧瘙痒感。
In mice, this happens because serotonin overactivates those itch-specific GRPR neurons.
在老鼠体内，如果血清素过度激活那些针对瘙痒的GRPR神经元，就会发生这种情况。
And since these neurons play such a big role in making mice feel itchy in the first place, that increases the intensity of the sensation.
由于这些神经元在引起瘙痒上起了这么大的作用，因此增加了这种瘙痒的感觉。
Many researchers are pretty confident this is at least part of how things work in humans, too.
很多研究人员非常确信这也部分适用于人类。
So if you scratch that itch again, it ultimately just triggers your brain to release more serotonin, which keeps the cycle going.
所以如果你又抓痒的话，只会触发大脑释放更多血清素，造成不断地循环。
Scientists speculate this could happen because GRPR and serotonin receptors are spatially close to each other.
科学家猜测这种情况的发生是因为GRPR和血清素受容器在空间上彼此接近。
And that may cause them to interfere with each other's functions.
这或许会让它们出现功能上的相互干涉。
But even though the reason for serotonin's role is unclear right now,
但是虽然血清素起作用的原因尚不明确，
researchers have shown that disrupting this "conversation" between serotonin and GRPR can stop the itching almost entirely.
但研究人员表示阻断血清素和GRPR之间的这种“对话”基本上可以完全阻止瘙痒。
And if we can do that safely, it could be a really valuable treatment option for people who suffer from chronic itch conditions.
并且如果这么做安全的话，对那些慢性瘙痒患者真的是个有价值的治疗方法。
Of course, like a lot of things in science, there is a chance that there's even more going on,
当然，和科学中的大部分事情一样，还需要进一步的研究，
because there are other proteins and receptors involved in itching, too.
因为其中还有其他蛋白质和受容器参与其中。
For now, though, scientists will just have to keep researching.
目前，科学家只能继续研究。
And while they do, you might want to try resisting the urge to scratch…no matter how relieving it is in the short-term.
在科学家进行研究时，大家或许会想要抵御挠痒的欲望，不论挠痒能给你带来怎样的暂时解脱。
Thanks for watching this episode of SciShow, and special thanks to Tim and Karen Ford and Marcus, who all asked this question!
感谢收看本期《科学秀》，特别感谢三位提问人。
If you want to submit a question to be answered or vote on the one we answer next, you can go to patreon.com/scishow.
如果你们想提问或是对问题进行投票，请登录patreon.com/scishow。
