英语听力文摘 English Digest 549、中枢痛成因你知多少？

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　　What would it be like if wearing a soft cotton t-shirt felt like your skin was being scrubbed with a Brillo pad? For people who suffer from a condition called central pain, such pain is all too familiar.

 

　　Central Pain on this moment of science.

 

　　No one’s sure why some people suffer agonizing¹ pain at the slightest touch, but the secret may lie in an area of the brain called the thalamus, which acts as a gateway² for all sensory³ messages processed by the brain. Nerve cells known as neurons relay messages to the thalamus, which passes the messages to a set of neurons that carry the messages to other areas of the brain.

 

　　Different sets of neurons bring pain and touch signals into the thalamus, but both types of messages are passed to other areas of the brain by one set of outgoing neurons.

 

　　So how does the brain distinguish between signals of touch and pain? Messages of touch trigger the release of a chemical called GABA, which diminishes the intensity⁴ of the outgoing message. But messages of pain don’t seem to cause GABA to be released, so they come through at full strength.

 

　　GABA might be muting some messages by altering their length. Messages of touch might cause a brief burst of information and then be shut off by GABA, while messages of pain continue to fire, unimpeded by GABA. In people who suffer from central pain, GABA might NOT be released in response to messages of touch. With no GABA to turn the touch signal down, every signal of touch may be read as one of pain.

 

　　中枢痛成因你知多少？

 

　　当你穿上一件棉布T恤，感到皮肤像是被钢丝球来回擦拭时，是什么滋味？对那些患有中枢痛的患者来说，这种感觉太常见了。

 

　　本期的科学一刻就让我们来讨论讨论中枢性疼痛。

 

　　为何某些人仅被稍微触碰就会感到剧痛？没人知道确切原因，但其中奥妙可能存在于大脑中一处名为丘脑的区域，丘脑是所有经大脑处理的感知信息的中转站。被称为“神经元”的神经细胞将信息转播给丘脑，丘脑再将信息传送给一组神经元，最后由它们将信息传播至大脑其他区域。

 

　　不同的神经元将疼痛和触觉信号传送给丘脑，但这两类信号由同一组输出神经元传送到大脑的其他区域。

 

　　那么大脑是如何区分疼痛和触觉信号的？触觉信息会引发一种名为γ-氨基丁酸（GABA）的化学元素释出，该元素减弱所输出信息的强度。但疼痛信息并不能引发GABA的释放，因此它们会完全传播。

 

　　GABA可能通过改变信息长度来更改某些信息。触觉信息可能会引发信息的短簇脉冲，随后GABA将其切断，而疼痛信息不受GABA的阻碍，继续横行。在那 些患有中枢性疼痛的人中，触觉信息不会引发GABA的释出。当没有GABA屏蔽触觉信号时，每一触觉信号都被误读为疼痛。

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