How do drugs affect the brain? - Sara Garofalo

譯者: Ann Chen 審譯者: Marssi Draw

大多數人在一生中會吃藥丸

Most people will take a pill,

receive an injection,

接受注射

or otherwise take some kind of medicine during their lives,

或用不同方式使用某些藥物

but most of us don't know anything about how these substances actually work.

但我們大多不知道這些物質 是如何真正產生作用

How can various compounds impact the way we physically feel,

各種化合物是如何影響身體的感覺

think,

思考

and even behave?

甚至行為？

For the most part, this depends on how a drug alters the communication

多數情況下 這取決於藥物如何改變

between cells in the brain.

大腦細胞間的溝通

There are a number of different ways that can happen.

可能發生的方式有很多種

But before it gets into the brain,

但在進入大腦之前

any drug must first reach the bloodstream

藥物仍須先花數秒至數小時 才能抵達血液

on a journey that can take anywhere from seconds to hours,

depending on factors like how it's administered.

所需時間依給藥的方式而定

The slowest method is to take a drug orally

最慢的方法是口服藥物

because it must be absorbed by our digestive system

因為藥物必須經消化系統吸收

before it takes effect.

才能發揮作用

Inhaling a drug gets it into the bloodstream faster.

吸入型藥物能較快進入血液

And injecting a drug intravenously works quickly too

而靜脈注射藥物的作用最快

because it pumps the chemicals directly into the blood.

因為是將化學製劑直接注入血液

Once there, the drug quickly reaches the gates of its destination, the brain.

一旦進入血液，藥物很快抵達 其目的地──大腦──的入口

The entrance to this organ is guarded by the blood-brain barrier,

此器官的入口受「血腦障壁」所保護

which separates blood from the nervous system

它將血液與神經系統分隔開來

to keep potentially dangerous substances out.

可將有害物質擋在外面

So all drugs must have a specific chemical composition

因此藥物必須具有特殊的化學成分

which gives them the key to unlock this barrier and pass through.

才能讓它們開啟血腦障壁並通過

Once inside, drugs start to interfere with the brain's normal functioning

一旦入內

藥物開始影響大腦的正常機能

by targeting its web of neurons and synapses.

作用於神經元及突觸的網絡

Neurons are brain cells that have a nucleus, dendrites, and an axon.

神經元是具有細胞核 樹突和軸突的腦細胞

Synapses are structures placed along the dendrites or the axon

突觸是沿著樹突或軸突的一種構造

which allow the exchange of electrochemical signals between neurons.

能讓神經元之間 進行電化學訊號的交換

Those signals take the form of chemicals called neurotransmitters.

那些以化學物質形式呈現的訊號 稱為「神經遞質」

Each neurotransmitter plays different roles in regulating our behaviors,

每個神經遞質各司其職 以調節我們的行為

emotions,

情緒

and cognition.

和認知

But they all work in one of two ways.

但它們運作的方式只有兩種

They can either inhibit the receiving neuron,

一種是抑制接收神經元

limiting its activity,

以限制其傳導功能

or excite it,

或是興奮它

creating a new electrochemical signal that spreads throughout the network.

即產生能傳遍整個網絡的 新電化學訊號

Any leftover neurotransmitter usually gets degraded

任何殘餘的神經遞質通常會被分解掉

or reabsorbed into the transmitting neuron.

或被重新吸收，再進入傳遞神經元

A drug's effectiveness stems from its ability

藥物的效能是基於

to manipulate these synaptic transmissions at different phases of the process.

它在過程中的不同階段 控制突觸遞質的能力

That results in an increase or a decrease

其結果會造成增加或減少

in the amount of neurotransmitters being spread.

被傳送的神經遞質的數量

For instance, common antidepressants, like SSRIs,

例如常用的抗憂鬱藥物 如「選擇性血清素抑制劑 SSRIs 」

stop the reabsorption of serotonin,

能阻止調節情緒的神經遞質 ──血清素──再吸收

a neurotransmitter that modulates our moods.

This effectively pushes more of it into the neural network.

這能有效地促使更多的血清素 進入神經網絡

Meanwhile, painkillers, like morphine,

另外，如嗎啡等止痛藥

raise levels of serotonin and noradrenaline,

提升血清素與去甲基腎上腺素的濃度

which regulate energy,

它們能調節活力

arousal,

覺醒

alertness,

機敏

and pleasure.

和愉悅

Those same neurotransmitters also affect endorphin receptors,

這兩個神經遞質也會影響 腦內啡接受體

reducing pain perception.

從而降低疼痛的感覺

And tranquilizers works by increasing the production of GABA

鎮靜劑是增加 γ-胺基丁酸（GABA）的製造

to inhibit neural activity

以抑制神經活動

putting the person in a relaxed or sedated state.

讓人處在放鬆或鎮靜的狀態

What about illegal or elicit drugs?

那毒品或禁藥又如何呢？

These have powerful impacts on the brain that we're still trying to understand.

這些藥物對大腦有極大的影響 我們仍嘗試了解中

Crystal meth, an amphetamine,

甲基苯丙胺，這種安非他命

induces a long-lasting release of dopamine,

會導致持續釋放多巴胺

a neurotransmitter linked with the perception of reward and pleasure.

它是一種連結 犒賞和愉悅感知的神經遞質

It also activates noradrenaline receptors,

甲基苯丙胺也會活化 去甲基腎上腺素接受體

which increases the heart rate,

因而增加心跳速率

dilates pupils,

擴張瞳孔

and triggers the body's fight or flight response.

並且觸發身體的應急反應

Cocaine blocks the reuptake of dopamine and serotonin,

古柯鹼會阻斷 多巴胺和血清素的再吸收

pushing more into the network

迫使進入網絡的量更多

where they boost energy,

進而提高活力

create feelings of euphoria,

產生欣快感

and suppress appetites.

以及抑制胃口

And hallucinogenic drugs have some of the most puzzling effects.

而迷幻藥則具有一些 最令人困惑的作用

Substances like LSD,

如麥角二乙醘胺（LSD）

mescaline,

麥斯卡林

and DMT

和二甲基色胺（DMT）等物質

all block the release of serotonin,

都會阻斷調節情緒 與衝動性的血清素之釋放

which regulates mood and impulsivity.

They also have an impact on the neural circuits

它們也會影響感知 學習與行為調節的神經迴路

involved in perception, learning, and behavioral regulation,

which may explain why these drugs have such powerful impacts.

這可以說明為什麼這些藥物 會有如此強烈的影響力

Even if some of these effects sound exciting,

就算是有些作用聽起來很棒

there are reasons why some of these drugs are highly controlled and often illegal.

這些藥物被嚴格管制 且視為違法也有其因

Drugs have the power to alter the brain's chemistry,

藥物有改變大腦化學作用的能力

and repeated use can permanently rewire the neural networks

而且反覆使用會永久改變

協助我們思考

that support our ability to think,

make decisions,

作決定

learn,

學習

and remember things.

和記憶能力的神經網絡

There's a lot we still don't know about drugs and their effects,

有關藥物及其作用仍有許多未明

both the good and the bad.

不管是好或壞的方面

But those we do know about are the ones we've studied closely,

但我們已經仔細研究過的

and turned into effective medicines.

就製作成有效的醫用藥品

As our knowledge grows about drugs and the brain,

隨著我們對於藥物和大腦的知識增長

the possibilities will also increase

治療現在令研究人員困擾的疾病 可能性也會增加

for treating the many medical problems that puzzle researchers today.