(单词翻译:单击)
Is marijuana now the most widely used psychoactive substance? Nope. And it's not alcohol or nicotine, either. It's actually caffeine, that little gem lurking in your morning cup of coffee. Caffeine is known to be a stimulant; people use it most often to get a little boost of energy. But exactly what is happening in your body when you consume caffeine, either in coffee, tea, or energy drinks, or in foods like chocolate, hasn't been totally figured out yet.
现在大麻是不是被普遍用作精神刺激物质呢？答案是否定的。酒精和尼古丁也不是。实际上，答案是咖啡因，那个潜伏在清晨咖啡中的小精华。众所周知，咖啡因是一种兴奋剂；人们喝咖啡经常是为了让自己更精神。但当你摄入咖啡因（不管是在咖啡、茶、能量饮料还是在巧克力等食物中）时，人们还未完全明白当时你的身体究竟在发生什么。
Researchers currently think that the caffeine buzz has something to do with the inhibitory neurotransmitter adenosine. When adenosine receptors are normally activated, they tend to cause sedative effects, such as reducing your heart rate and suppressing the release of other neurotransmitters (including glutamate and dopamine).
目前，研究员们认为咖啡因陶醉感与抑制性神经递质腺苷有关。当腺苷受体被正常激活时，它们往往会引起镇静作用，比如降低心率和抑制其它神经递质（包括谷氨酸和多巴胺）的释放。
But caffeine may work by binding to (and blocking) adenosine receptors in your brain and throughout your body. And once those adenosine receptors are blocked, the other neurotransmitters excite your system. Caffeine messes with our daily rhythms in other ways, too.
但咖啡因可以通过与大脑和整个身体内的腺苷受体结合而起作用。一旦腺苷受体被阻，其它的神经递质就会使人体系统兴奋。咖啡因也会以其它的方式打乱我们的日常节奏。
For one, it affects the way our bodies release cortisol, commonly known as the "stress hormone." Caffeine actually causes a pretty solid increase in cortisol levels in those who aren't normally coffee-drinkers. But in those who enjoy their daily caffeinated beverages - and have thus built up at least a partial tolerance to the chemical - the effects are a little less clear.
一方面，咖啡因影响着身体释放俗称为"应激激素"的皮质醇的方式。实际上，对于那些不经常喝咖啡的人来说，咖啡因会导致他们的皮质醇水平显著升高。但对于那些每天都喜欢来点含咖啡因饮料的人说--因此他们对这种物质至少已经有了一定的耐受性--咖啡因的影响就不那么清楚了。
But we do know they last for a long time. Even cutting off your caffeine six hours before bedtime may not be enough to ensure you doze off easily. And that's important because those aforementioned adenosine receptors also play a role in keeping our circadian rhythms humming along. So, if you're a regular coffee-drinker, you might want to be extra careful about sticking to your routine. An ill-timed coffee break or - even worse - a skipped one, could make it hard to get back into your normal sleep-wake cycle.
但我们清楚咖啡因会持续很长一段时间。即使在睡前六小时不喝咖啡也不能确保你能快速入睡。因为上述的腺苷受体也在保持我们的昼夜作息正常方面起着一定的作用，因此这一点是很重要的。所以，如果你经常喝咖啡，那在坚持自己的日常习惯方面，你要额外注意哦。在不合时宜的时间喝咖啡--或更糟--直接不喝，都会让你在重回正常的睡眠周期方面变得困难。
On top of all that, we know that different people react to coffee (and its caffeine) differently. While it is pretty much a requirement for some, others complain that it makes them far too jittery to get anything done. And researchers are now learning that difference may depend at least partly on your genes.
除此之外，我们知道不同人对咖啡（和其咖啡因）的反应不同。虽然，对于有些人来说，咖啡是必备的，但有些人却抱怨咖啡使他们过度紧张，搞得什么事都做不成。研究员们目前得知这个差异可能取决于人们的基因。
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