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  3. Pain, unfortunately, is a horrible necessity of life. It protects people by alerting them to things that might injure them. But

Pain, unfortunately, is a horrible necessity of life. It protects people by alerting them to things that might injure them. But

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问题    Pain, unfortunately, is a horrible necessity of life. It protects people by alerting them to things that might injure them. But some long-term pain has nothing to do with any obvious injury. One estimate suggests that one in six adults suffer from a "chronic pain" condition. Steve McMahon, a pain researcher at King’s College, London, says that if skin is damaged, for instance with a hot iron, an area of sensitivity develops around the outside of the burn where although untouched and undamaged by the iron the behaviour of the nerve fibres is disrupted. As a result, heightened sensitivity and abnormal pain sensations occur in the surrounding skin. Chronic pain, he says, may similarly be caused not by damage to the body, but because weak pain signals become amplified.
   This would also help explain why chronic pains such as lower-back pain and arthritis fail to respond well to traditional pain therapies. But now an entirely new kind of drug, called Tanezumab, has been developed. It is an antibody for a protein called nerve growth factor (NGF), which is vital for new nerve growth during development. NGF, it turns out, is also crucial in the regulation of the sensitisation of pain in chronic conditions. After an injury which involves tissue damage and inflammation, levels of NGF increase dramatically. NGF seems to be involved in transmitting the pain signal. As a consequence, blocking NGF reduces chronic pain.
   Tanezumab must still complete the final stages of clinical trials before it can become a weapon for reducing human suffering. But unexpected pains do not always come from the body. According to Irene Tracey, a pain researcher at the University of Oxford, how pain is experienced also depends upon a person’s state of mind. If successive patients suffer the same burn, the extent to which it hurts will depend on whether one is anxious, depressed, happy or distracted.
   Such ideas are being explored with brain scans which suggest that even if a low level of pain is being sent to the brain, the signal can be turned up by the "mind" itself. Indeed, patients can even be tricked into feeling pain. People can feel pain simply because it is expected. They can fail to feel pain for exactly the same reasons, for example when they are given placebos (a substance containing no medication and given to reinforce a patient’s expectation to get well) or are distracted. But although pain may be subjective, that does not mean the final experience is controlled solely by the mind.
   A recent paper in Proceedings of the National Academy of Sciences has shown that genes play a role in determining sensitivity to pain. One gene, known as SCN9A, codes for a protein that allows the channels along which nerve signals are transmitted to remain active for longer and thus transmit more pain signals. It seems likely that this protein will attract a great deal more analgesic research. Variations in SCN9A may also explain why some patients prefer different classes of painkillers.
   Although pain may be a horrible necessity, there is no doubt that humanity could cope with far less of the chronic sort. Understanding how the mind, the body and people’s genes interact to cause pain should bring more relief.
   [A] has got a new finding about gene’s effect on our sensitivity to pain.
   [B] holds that heightened sensitivity to pain may lead to chronic pain.
   [C] showed how people controlled their sense of pain by the mind.
   [D] is involved in the forming of a protein that can make us feel more pain.
   [E] suggests that people are usually cheated by abnormal signals when injured.
   [F] can alleviate chronic pain by blocking the transmission of pain signals.
   [G] indicates that state of mind has an influence on the feeling of pain.
SCN9A
选项
答案D
解析 SCN9A出现在倒数第二段。该段说到，有一种蛋白质能让神经信号的传导通道更长时间地保持活性，从而会传递更多的痛觉信号。而形成该种蛋白质的遗传密码是一种名为SCN9A的基因。D中的involved in the forming of a protein是文中codes for a protein的转述，feel more pain对应原文的transmit more pain signals，故确定D为本题答案。
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