老G阅读-1998-1求助

vinci_gohUID: 3469516

Much of the research on hallucinogenic drugs such as LSD has focused on the neurotransmitter serotonin, a chemical that when released from a presynaptic serotonin-secreting neuron causes the transmission of a nerve impulse across a synapse to an adjacent postsynaptic, or target, neuron. There are two major reasons for this emphasis. First, it was discovered early on that many of the major hallucinogens have a molecular structure similar to that of serotonin. In addition, animal studies of brain neurochemistry following administration of hallucinogens invariably reported changes in serotonin levels.

Early investigators correctly reasoned that the structural similarity to the serotonin molecule might imply that LSD’s effects are brought about by an action on the neurotransmission of serotonin in the brain. Unfortunately, the level of technical expertise in the field of brain research was such that this hypothesis had to be tested on peripheral tissue (tissue outside the brain). Two different groups of scientists reported that LSD powerfully blockaded serotonin’s action. Their conclusions were quickly challenged, however. We now know that the action of a drug at one site in the body does not necessarily correspond to the drug’s action at another site, especially when one site is in the brain and the other is not.

By the 1960’s, technical advances permitted the direct testing of the hypothesis that LSD and related hallucinogens act by directly suppressing the activity of serotonin-secreting neurons themselves—the so- called presynaptic hypothesis. Researchers reasoned that if the hllucinogenic drugs act by suppressing the activity of serotonin-secreting neurons, then drugs administered after these neurons had been destroyed should have no effect on behavior, because the system would already be maximally suppressed. Contrary to their expectations, neuron destruction enhanced the effect of LSD and related hallucinogens on behavior. Thus, hallucinogenic drugs apparently do not act directly on serotonin-secreting neurons.

However, these and other available data do support an alternative hypothesis, that LSD and related drugs act directly at receptor sites on serotonin target neurons (the postsynaptic hypothesis). The fact that LSD elicits “serotonin syndrome” —that is, causes the same kinds of behaviors as does the adminis- tration of serotonin—in animals whose brains are depleted of serotonin indicates that LSD acts directly n serotonin receptors, rather than indirectly through the release of stores of serotonin. The enhanced effect of LSD reported after serotonin depletion could be due to a proliferation of serotonin receptor sites on serotonin target neurons. This phenomenon often follows neuron destruction or neurotransmitter depletion; the increase in the number of receptor sites appears to be a compensatory response to decreased input. Significantly, this hypothesis is supported by data from a number of different laboratories.

According to the passage, which of the following is one of the primary factors that led researchers studying hallucinogenic drugs to focus on serotonin?

    A
    The suppression of the activity of serotonin- secreting neurons by the administration of hallucinogens
    B
    The observed similarities in the chemical structures of serotonin and hallucinogens
    C
    The effects the administration of hallucinogens has on serotonin production in the human brain
    D
    Serotonin-induced changes in the effects of hallucinogens on behavior
    E
    Hallucinogen-induced changes in the effects of serotonin on behavior

答案是B选项，但是
“it was discovered early on that many of the major hallucinogens have a molecular structure similar to that of serotonin”很明显这里是molecular structure
B选项是chemical structure，我觉得应该选E吧？？属于前面两个理由的第二个

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wfxmfwjwUID: 3582171

选B答案就是，你标出的这句话，化学结构应该就是分子结构吧。

vinci_gohUID: 3469516

wfxmfwjw 发表于 2015-8-16 17:37
选B答案就是，你标出的这句话，化学结构应该就是分子结构吧。

后来想一下，E也确实不对，文章说的是，reported，并没有指出他们之间的联系。
我纠结molecular 和chemical 是应该之前No题做过一篇讲人体功能材料的，我记得里面说目前对于人体材料和组织之间的研究只达到化学反应的层次，需要进一步达到分子层次，不知道有没有记错。第一反应就把B选项排除掉了，认为它偷换概念。
但后来想想，初中化学告诉我们，化学反应就是在分子层次的反应