How does alcohol make you drunk? - Judy Grisel

譯者: Lilian Chiu 審譯者: Carol Wang

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

乙醇：

其分子僅由幾個碳原子組成，

is responsible for drunkenness.

醉意就是它造成的。

Often simply referred to as alcohol,

乙醇通常被稱為酒精，

ethanol is the active ingredient in alcoholic beverages.

是酒精性飲料中活性成份。

Its simplicity helps it sneak across membranes

其簡單結構有助於它溜過薄膜，

and nestle into a many different nooks,

躲在許多不同的隱蔽處，

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

產生出的影響會比其他 更笨重的分子多出許多。

So how exactly does it cause drunkenness,

那麼酒精是如何造成醉意，

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

它對不同人的影響 為什麼有這麼大的不同？

To answer these questions,

要回答這些問題，

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

我們就需要跟著酒精 走一趟體內之旅。

Alcohol lands in the stomach and is absorbed into the blood

酒精會進入胃，透過消化道，

through the digestive tract, especially the small intestine.

特別是小腸，被吸收到血液中。

The contents of the stomach impact alcohol’s ability

胃裡面的東西會影響到 酒精進入血液的能力，

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

因為在吃過東西後，

which separates the stomach from the small intestine, closes.

將胃和小腸分開的 幽門括約肌會關閉。

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

所以，在吃過大餐之後， 進入到血液中的酒精量

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

可能只有空腹情況的四分之一。

From the blood, alcohol goes to the organs,

酒精會從血液到達器官，

especially those that get the most blood flow:

特別是血液流入最多的器官：

the liver and the brain.

肝臟和大腦。

It hits the liver first, and enzymes in the liver

酒精會先抵達肝臟，

肝臟中的酵素 分兩步將酒精分子分解。

break down the alcohol molecule in two steps.

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

第一步，叫做抗利尿激素的酵素

會將酒精轉為有毒的乙醛。

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

接著，叫做醛脫氫酶的酵素

會將有毒的乙醛 轉換為無毒的乙酸鹽。

As the blood circulates, the liver eliminates alcohol continuously—

伴隨著血液循環， 肝臟會持續將酒精清除——

but this first pass of elimination determines how much alcohol

這個消除酒精的第一關 就決定了有多少酒精

reaches the brain and other organs.

能到達大腦及其他器官。

Brain sensitivity is responsible for the emotional, cognitive,

酒精會產生哪些情緒、 認知、行為上的影響——

and behavioral effects of alcohol— otherwise known as drunkenness.

也就是所謂的醉態， 則由大腦敏感度來決定。

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

酒精增加大腦的主控物質， 即神經傳遞質 γ-氨基丁酸，

and turns down its primary gas, the neurotransmitter glutamate.

並減少大腦的主要汽油， 即神經傳遞質麩胺酸，

This makes neurons much less communicative,

這會讓神經元的溝通大大減少，

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

適量酒精會讓飲酒者放鬆，

更高劑量則令飲酒者睡著，

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

若高到會中毒的劑量， 則能阻礙生存必需的大腦活動。

Alcohol also stimulates a small group of neurons

酒精也會刺激

從中腦延伸到依核的一小群神經元，

that extends from the midbrain to the nucleus accumbens,

a region important for motivation.

這個區域和動機息息相關。

Like all addictive drugs,

和所有成癮性藥物一樣，

it prompts a squirt of dopamine in the nucleus accumbens

它也會促進將多巴胺注入依核中，

which gives users a surge of pleasure.

讓飲用者感到一股愉悅感。

Alcohol also causes some neurons to synthesize and release endorphins.

酒精也會造成一些神經元 合成及釋放腦內啡，

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

腦內啡能讓我們面對壓力 或危險時能冷靜下來。

Elevated levels of endorphins contribute to the euphoria

腦內啡水平的提升，

帶來與服用酒精相關的 陶醉感和放鬆感。

and relaxation associated with alcohol consumption.

Finally,

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

最後，如果肝臟分解酒精的速度 比大腦吸收的速度快，

drunkenness fades away.

醉意就會消失。

Individual differences at any point in this journey

每個人在這趟旅程中 任何一處有所不同，

can cause people to act more or less drunk.

就可能會影響到酒醉的程度。

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

比如，體重相同的一男一女，

在吃一樣的餐點時， 喝了等量的酒精，

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

血液中的酒精濃度 （BAC）仍然會不同。

or BACs.

This is because women tend to have less blood—

這是因為，女性的 血液通常比較少——

women generally have a higher percentage of fat,

一般來說女性的脂肪比例較高，

which requires less blood than muscle.

比起肌肉，需要的血液比較少。

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

如果比較少的血液量 要運載同等量的酒精，

means the concentration will be higher for women.

那就表示女性的 酒精濃度會比較高。

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

肝臟中處理酒精的酵素 若有基因差異也會影響 BAC。

And regular drinking can increase production of these enzymes,

經常喝酒可能會增加 這些酵素的生產量，

contributing to tolerance.

從而改變酒精的耐受度。

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

另一方面，長期飲酒過量的人

may develop liver damage, which has the opposite effect.

肝臟可能會受損， 那就會有反效果。

Meanwhile, genetic differences in dopamine, GABA,

同時，多巴胺、γ-氨基丁酸、 及腦內啡傳遞在基因上的差異，

and endorphin transmission may contribute to risk

可能造成酒精使用疾患的風險。

for developing an alcohol use disorder.

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

天生腦內啡或多巴胺比較低的人，

可以透過飲酒來自我治療。

through drinking.

Some people have a higher risk for excessive drinking

有些人比較可能會飲酒過量，

due to a sensitive endorphin response that increases the pleasurable effects

是因為有敏感的腦內啡反應， 會增加酒精的愉悅效果。

of alcohol.

Others have a variation in GABA transmission

其他人因為在 γ-氨基丁酸的 傳遞方面有所不同，

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

導致他們對於酒精的 鎮靜效果特別敏感，

which decreases their risk of developing disordered drinking.

這會降低其發展為 飲酒失調的可能性。

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

同時，大腦會減少 γ-氨基丁酸、 多巴胺、腦內啡的傳遞，

dopamine, and endorphin transmission, and enhancing glutamate activity.

並增強谷氨酸活動， 以適應長期飲酒。

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

即有飲酒習慣的人 更可能會焦慮、難入睡，

and experience less pleasure.

且不容易感受到愉悅。

These structural and functional changes can lead to disordered use

當飲酒感覺很正常、 不飲酒反而不舒適時，

when drinking feels normal, but not drinking is uncomfortable,

這些結構和功能上的改變 都可能會導致酒精濫用，

establishing a vicious cycle.

因而形成惡性循環。

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

所以，人對酒精的感受 會受基因和過去經驗的影響——

which means that some people are more prone

那就表示有些人比其他人 更容易出現某些飲酒模式，

to certain patterns of drinking than others,

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

且飲酒史會導致 神經和行為的改變。