How does alcohol make you drunk? - Judy Grisel

翻译人员: Huihong Bai 校对人员: Yanyan Hong

Ethanol: this molecule, made of little more than a few carbon atoms,

乙醇：其分子是由碳原子组成，

is responsible for drunkenness.

能够让人产生醉意。

Often simply referred to as alcohol,

乙醇通常被简称为酒精，

ethanol is the active ingredient in alcoholic beverages.

是含酒精饮料中的活性成分。

Its simplicity helps it sneak across membranes

简单的分子结构使它能透过细胞膜，

and nestle into a many different nooks,

并停留在许多不同位置，

producing a wide range of effects compared to other, clunkier molecules.

从而比其他较重的分子 产生更多的影响。

So how exactly does it cause drunkenness,

那么乙醇是怎样让人产生醉意的？

and why does it have dramatically different effects on different people?

为什么它对不同人的影响 会有天壤之别？

To answer these questions,

要回答这些问题，

we’ll need to follow alcohol on its journey through the body.

我们就要跟着酒精 去看看它在人体内的旅程。

Alcohol lands in the stomach and is absorbed into the blood

酒精首先进入胃部，

through the digestive tract, especially the small intestine.

通过消化道，尤其是小肠，被血液吸收。

The contents of the stomach impact alcohol’s ability

胃里的东西会影响 酒精进入血液的能力，

to get into the blood because after eating, the pyloric sphincter,

因为进食之后幽门括约肌闭合，

which separates the stomach from the small intestine, closes.

而幽门括约肌是分隔 胃部和小肠的部分。

So the level of alcohol that reaches the blood after a big meal

所以在一顿大餐过后， 酒精进入血液的能力

might only be a quarter that from the same drink on an empty stomach.

可能只有空腹时的四分之一。

From the blood, alcohol goes to the organs,

酒精从血液进入身体器官，

especially those that get the most blood flow:

尤其是血液流动较多的器官：

the liver and the brain.

肝脏和大脑。

It hits the liver first, and enzymes in the liver

酒精首先到达肝脏，

肝脏中的酶类物质分两步分解酒精。

break down the alcohol molecule in two steps.

First, an enzyme called ADH turns alcohol into acetaldehyde, which is toxic.

首先，乙醇脱氢酶 (ADH) 将酒精转化为有毒的乙醛。

Then, an enzyme called ALDH converts the toxic acetaldehyde to non-toxic acetate.

接着，乙醛脱氢酶(ALDH) 将有毒的乙醛转化为无毒的醋酸盐。

As the blood circulates, the liver eliminates alcohol continuously—

随着血液的循环，肝脏持续分解酒精，

but this first pass of elimination determines how much alcohol

而分解乙醇的第一步

决定了有多少酒精 会到达大脑和其他器官。

reaches the brain and other organs.

Brain sensitivity is responsible for the emotional, cognitive,

酒精对情绪、 认知和行为的影响——

and behavioral effects of alcohol— otherwise known as drunkenness.

也就是我们常说的醉态—— 都是由大脑敏感程度决定。

Alcohol turns up the brain’s primary brake, the neurotransmitter GABA,

酒精会给大脑踩刹车， 即提升氨基丁酸水平，使大脑更镇静；

and turns down its primary gas, the neurotransmitter glutamate.

同时给大脑松油门， 即降低谷氨酸水平，减弱兴奋度。

This makes neurons much less communicative,

这会让神经细胞活跃度降低。

and users feel relaxed at moderate doses, fall asleep at higher doses,

适量摄入酒精使人感觉放松， 大量摄入则会陷入睡眠，

and can impede the brain activity necessary for survival at toxic doses.

而过量摄入可能抑制 大脑生存所必须的活动。

Alcohol also stimulates a small group of neurons

酒精也会对一小部分 神经细胞有激活效果，

that extends from the midbrain to the nucleus accumbens,

并从中脑持续到伏隔核区域，

而伏隔核在奖赏和快乐等 感官体验中具有重要作用。

a region important for motivation.

Like all addictive drugs,

和所有成瘾性药物一样，

it prompts a squirt of dopamine in the nucleus accumbens

酒精可以提升伏隔核中的多巴胺含量，

which gives users a surge of pleasure.

使饮用者产生愉悦感。

Alcohol also causes some neurons to synthesize and release endorphins.

酒精还能使部分 神经细胞合成并释放内啡肽。

Endorphins help us to calm down in response to stress or danger.

内啡肽可以帮助我们在 面对压力和危险时保持镇定。

Elevated levels of endorphins contribute to the euphoria

摄入酒精后的愉悦与放松感

and relaxation associated with alcohol consumption.

正是由于内啡肽水平的上升。

Finally,

as the liver’s breakdown of alcohol outpaces the brain’s absorption,

最后，

当肝脏分解酒精的速度 超过了大脑吸收的速度，

drunkenness fades away.

醉意就逐渐散去了。

Individual differences at any point in this journey

整个过程中不同个体间的任何差异

can cause people to act more or less drunk.

都会造成每个人醉酒程度的不同。

For example, a man and a woman who weigh the same and drink the same amount

比如，体重相同的一男一女

在进食情况相同的情况下 摄入等量酒精，

during an identical meal will still have different blood alcohol concentrations,

最终血液中的酒精浓度 (BAC) 仍然会有差异。

or BACs.

This is because women tend to have less blood—

这是因为女性体内血液含量较少——

women generally have a higher percentage of fat,

一般而言女性脂肪含量高于男性，

which requires less blood than muscle.

而脂肪所需血液少于肌肉。

A smaller blood volume, carrying the same amount of alcohol,

等量的酒精和较少的血液，

means the concentration will be higher for women.

意味着女性血液中的酒精浓度会更高。

Genetic differences in the liver’s alcohol processing enzymes also influence BAC.

肝脏中分解酒精的酶类与遗传有关， 这也会影响血液酒精浓度。

And regular drinking can increase production of these enzymes,

定期饮酒可以提高这类酶的产生水平，

contributing to tolerance.

对分解能力有所帮助。

On the other hand, those who drink excessively for a long time

另外，长期过度饮酒的人，

may develop liver damage, which has the opposite effect.

肝脏可能会受损， 从而产生反效果。

Meanwhile, genetic differences in dopamine, GABA,

同时，多巴胺、氨基丁酸、 内啡肽传导的遗传性差异

and endorphin transmission may contribute to risk

可能会增加

for developing an alcohol use disorder.

酗酒的风险。

Those with naturally low endorphin or dopamine levels may self-medicate

先天内啡肽或多巴胺水平较低的人，

through drinking.

可以通过饮酒进行自我治疗。

Some people have a higher risk for excessive drinking

也有人可能由于 对内啡肽的敏感度较高，

due to a sensitive endorphin response that increases the pleasurable effects

提升了酒精带来的愉悦感，

从而导致过量饮酒的风险升高。

of alcohol.

Others have a variation in GABA transmission

还有人会因为氨基丁酸传导的变异，

that makes them especially sensitive to the sedative effects of alcohol,

导致对酒精的镇静作用非常灵敏，

which decreases their risk of developing disordered drinking.

而这会降低他们酗酒的可能性。

Meanwhile, the brain adapts to chronic alcohol consumption by reducing GABA,

同时，大脑为了适应长期的酒精摄入，

会降低氨基丁酸、多巴胺及内啡肽的 传递水平，同时提升谷氨酸盐的活动。

dopamine, and endorphin transmission, and enhancing glutamate activity.

This means regular drinkers tend to be anxious, have trouble sleeping,

这意味着经常喝酒会让人 变得焦虑、产生睡眠障碍，

and experience less pleasure.

且较难产生愉悦感。

These structural and functional changes can lead to disordered use

当喝酒感觉很正常， 不喝酒反而不舒服时，

when drinking feels normal, but not drinking is uncomfortable,

这种结构性和功能性的变化 可能导致酒精滥用，

establishing a vicious cycle.

因此陷入恶性循环。

So both genetics and previous experience impact how a person experiences alcohol—

总而言之，遗传因素和过往经验 都会影响个体对酒精的反应——

which means that some people are more prone

也就是说有一些人在喝酒后

to certain patterns of drinking than others,

会比其他人有更明显的反应，

and a history of consumption leads to neural and behavioral changes.

而长期酒精摄入会导致 神经系统和行为发生变化。