| Passage 1
Caffeine, the stimulant in coffee, has been called 咖啡因——一种在咖啡中的刺激
n.咖啡因, 茶精(兴奋剂) 物质——被称为“地球上使用最
“the most widely used psychoactive substance on Earth .” 广的神经物质。
adj.作用于精神的,影响(或改变)心理状态的
Synder, Daly and Bruns have recently proposed that Synder, Daly and Bruns最近提出
caffeine affects behavior by countering the activity in 咖啡因对人行为产生的影响与自
(5) the human brain of a naturally occurring chemical called 然产生的被称为腺苷的化学物质
vi.发生, 出现 对人类大脑具有相反的活性。
adenosine. Adenosine normally depresses neuron firing 腺苷通常大脑的许多区域抑制
n.[生化]腺苷 vt.使沮丧,压下, 使萧条v.压下 神经活性。
in many areas of the brain. It apparently does this by 它表现为抑制神经传递素的释放
adv.显然地 ，一种将神经冲动从一个神经元
inhibiting the release of neurotransmitters, chemicals 向另一个神经元传递的化学物质
adj.抑制作用的, 约束的 adj.化学的
n.化学制品, 化学药品
n.化学药品
that carry nerve impulses from one neuron to the next.
n.神经冲动
(10) Like many other agents that affect neuron firing 如同很多其它影响神经细胞活
adenosine must first bind to specific receptors on 性的化学剂那样, 腺苷必须先
订约,约定 n.接受器, 感受器, 受体 和神经细胞膜上的受体结合。
neuronal membranes. There are at least two classes 有至少两类这种受体，被标记为
of these receptors, which have been designated A1 and A1和A2。
A2. Snyder et al propose that caffeine, which is structurally Snyder等人提出咖啡因——与腺
abbr. (Lat) 以及其他人，等人 苷在结构上相似——都能与两种
(15) similar to adenosine, is able to bind to both types 受体结合，然后阻止腺苷接近自己
of receptors, which prevents adenosine from attaching 但是允许神经元比其他情况下更
v.阻止, 妨碍 剧烈的接触。
there and allows the neurons to fire more readily than
adv.乐意地, 欣然, 容易地
they otherwise would.
adv.另外, 否则, 不同地, 别的方式adj.另外的, 其他方面的
For many years, caffeine’s effects have been attributed 多年以来，咖啡因的效果被
v.归因于 归因于它对产生磷酸二酯酶
(20) to its inhibition of the production of phosphodiesterase, 的抑制，这种酶破坏一种被
n.[生化]磷酸二酯酶 称为循环AMP的化学物质。
an enzyme that breaks down the chemical
n.[生化]酶
called cyclic AMP.A number of neurotransmitters exert 大量的神经传递素在目标神经元
their effects by first increasing cyclic AMP concentrations 中，为了首先提高循环AMP的浓
n.集中, 集合, 度而耗尽他们的效力。
专心, 浓缩, 浓度
in target neurons. Therefore, prolonged periods at 因此，也许由磷酸二酯酶抑制剂
(25) the elevated concentrations, as might be brought about 导致的，延长了的高浓度阶段，
adj.提高的, 严肃的, 欢欣的 v.使发生, 致使 可以致使很大程度上的神经活性
by a phosphodiesterase inhibitor, could lead to a greater ，所以造成实质上的刺激。
amount of neuron firing and, consequently, to behavioral
adv.从而, 因此 adj.动作的
stimulation. But Snyder et al point out that the 但是，Snyder等人指出，咖啡因的
abbr. (Lat) 以及其他人，等人 浓度，抑制大脑中磷酸二酯酶产物
caffeine concentrations needed to inhibit the production 必要条件，要高于那些产生刺激作
(30) of phosphodiesterase in the brain are much higher than 用的物质。
those that produce stimulation. Moreover, other compounds 另外，其他阻滞磷酸二酯酶活性的
adv.而且, 此外 化合物不是刺激物。
that block phosphodiesterase’s activity are not
stimulants.
To buttress their case that caffeine acts instead by preventing 支持他们的例子：咖啡因的效果被
n.(建筑)扶壁, 支持物 替代为保护腺苷结合后，Snyder等
vt.支持, (以扶壁)扶住 人比较了一系列的咖啡因派生出的
(35) adenosine binding, Snyder et al compared the 具有在鼠脑中从受体上驱逐腺苷的
n.[生化]腺苷 能力的刺激物的效果。
stimulatory effects of a series of caffeine derivatives with
adj.引出的, 系出的
n.派生的事物, 派生词
their ability to dislodge adenosine from its receptors in
v.驱逐
the brains of mice. “In general,” they reported, “the “通常来讲”，他们报告说，“化合
ability of the compounds to compete at the receptors 物争夺受体的能力与他们在鼠脑中
(40) correlates with their ability to stimulate locomotion in 刺激移动的能力有关。例如，他们
使...与...发生关系， n.运动, 移动 与受体结合的能力越强，他们刺激
把...与...联系起来 , 运动力, 移动力 移动的能力也越强。”
the mouse; i.e., the higher their capacity to bind at the
receptors, the higher their ability to stimulate locomotion.”
Theophylline, a close structural relative of caffeine 茶碱，茶叶中一种结构关系上接近
[化]茶碱 咖啡因的主要刺激物，是在这两方
and the major stimulant in tea, was one of the most 面都非常有效的化合物。
(45) effective compounds in both regards.
There were some apparent exceptions to the general 但是有一些在观察中发现的明显的
adj.显然的, 之例外 腺苷受体结合与刺激物常规关系之
外观上的 外的情况。
correlation observed between adenosine-receptor binding
n.相互关系, 相关(性)
and stimulation. One of these was a compound called 其中的一种化合物被称为IBMX，是
3-isobuty1-1-methylxanthine(IBMX), which bound very 一种活性极好但是实际上减少老鼠
(50) well but actually depressed mouse locomotion. Snyder 运动的物质。
et al suggest that this is not a major stumbling block to 但是Snyder等人认为这不是他们假
n.障碍物, 绊脚石 设中的主要绊脚石。
their hypothesis. The problem is that the compound has 问题是化合物在大脑中常会产生混
n.假设 合作用，这是精神药物经常会出现的
mixed effects in the brain, a not unusual occurrence with 情况。
n.发生, 出现, 事件
发生的事情
psychoactive drugs. Even caffeine, which is generally 即使咖啡因，这种只有刺激作用被众
adj.作用于精神的, 所周知的物质，也显示出这种在非常
影响(或改变)心理状态的 低的浓度下抑制老鼠活动，而在较高
(55) known only for its stimulatory effects, displays this 浓度下刺激的特性。
property, depressing mouse locomotion at very low
concentrations and stimulating it at higher ones.
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