托福考试阅读练习题：Out for the Count

    下面是托福考试阅读练习题，育路教育网特别为您搜集整理，内容如下：

    麻醉，是各种手术中不可缺少的环节。麻醉被广泛应用了很多年，但目前为止，为什么药物能在人体内工作并让人在一段时间内失去知觉仍是神经科学中的未解之谜。

    If you've ever had major surgery， you probably remember lying down and waking up——but nothing in between. Learn about anesthetics on this Moment of Science.

    If you‘ve ever had major surgery， you probably remember lying down and waking up–but nothing in between. Thanks to the anesthesiologist， during the actual surgery you were out of it： immobilized and insensitive to pain. But until recently scientists had little understanding of how anesthetics actually work on the cellular level.

    That‘s changed thanks to recent experiments performed by researchers at the University of Zurich， in Switzerland. They knew that anesthetics caused pain receptors in the brain to turn off by acting like most drugs do： anesthetizing drugs attach to particular sites on nerve cells and turn them off. The question was， where on nerve cells do these drugs attach？

    Nerve cell membranes（细胞膜） have receptors for different kinds of chemicals produced by the brain. Gamma-amino butyric acid（γ-氨基丁酸）， or GABA（伽马氨基丁酸）， for example， is a chemical that shuts down nerve cells. The hypothesis was that general anesthesia works by binding to GABA receptors on a nerve cell， thereby activating the receptor and instructing the cell to shut down. So it made sense for the Zurich researchers to focus on GABA receptors.

    To do this they worked with mice that had been genetically engineered to have nerve cells with GABA receptors that wouldn‘t respond to anesthetics. And sure enough， when such mice were given anesthetic drugs they weren’t nearly as immune to pain as regular mice that had also been given pain-blocking drugs. Clearly， GABA receptor sites on nerve cells are part of what allows anesthetics to do their job.

    While the Zurich experiment fills in only one piece of the puzzle， it is an important step towards learning how these amazing drugs work， and how to make them even better.

    译文：

    如果你曾经动过手术，你可能会记得躺下和醒来这两个动作，但是对中间发生的事情一无所知。多亏了你的麻醉师，在实际的手术过程中你对疼痛全然不知。但直到最近科学家们对麻醉药如何在细胞水平上发挥作用仍然了解甚少。

    归功于瑞士苏黎世大学研究人员的最新研究，这种情况得以改变。他们知道正如许多药物那样，麻醉药让大脑里的疼痛受体处于关闭状态。麻醉药依附在神经细胞里的特定区域，并对它们进行麻醉。问题是，这些药物是依附在神经细胞的的哪个部位呢？

    神经细胞膜针对大脑产生的各种化学物质都有受体。如γ-氨基丁酸或伽马氨基丁酸，都是可以使神经细胞关闭的化学物质。假设全身麻醉与神经细胞上的伽马氨基丁酸受体有关，那么可以激活受体，指示细胞关闭。因此苏黎世大学研究人员认为应该着重研究伽马氨基丁酸受体。

    为了此项研究，研究人员们用经过遗传工程处理后的老鼠做实验，这些老鼠的伽马氨基丁酸受体不会对麻醉药起反应。果然，这些老鼠在注射了麻醉药后并不像正常的老鼠注射了麻醉药那样，对疼痛免疫。显然，在神经细胞上的伽马氨基丁酸受体就是麻醉药发挥作用的地方。

    尽管苏黎世大学的实验只解决了谜团中的一小部分，但是研究麻醉药是怎样工作的以及怎样让它们工作的更好仍是非常重要的。

    Notes：

    （1）Out for the Count 死的， 毁了的

    Count me out for the banana split.

    别指望我同你一起分享香蕉味。