Narrator: Methamphetamine is among the most addictive substances in the world.
旁白：甲基苯丙胺几乎是世界上最容易上瘾的物质之一。
Despite the horrors of exploding meth labs, many burn patients still return to meth abuse.
尽管被冰毒实验室的爆炸所威慑，许多烧伤患者仍然回返至滥用冰毒。
Leading Neuro-pharmacologist, Dr. Edythe London, has spent her entire career trying to figure out why users are so addicted to this drug.
首席神经药理学家，埃德斯·伦敦博士的整个职业生涯都用于试图找出吸毒者如此沉迷于这种毒品的原因。
Doctor London: Neuro-pharmacologists are interested in understanding how drugs work, and particularly how medications might work and interact with brain function.
伦敦博士：神经药理学家的关注点在于毒品是如何发挥作用的，尤其是其药物机制如何，以及其与脑功能的相互作用。

Narrator: Maggie Lavalle is a member of Dr. London's meth study.
旁白：玛吉·拉瓦列是伦敦博士冰毒研究的一员。
Maggie: Well a typical week if I'm a full and flourished meth addict, I can go anywhere from, I can smoke anywhere from $200 worth of meth to $400 worth of meth. Out of my mind.
玛吉：嗯，我是一个彻底的、活跃的冰毒瘾君子，这就是典型的一周，我可以去任何地方，我可以在任何地方吸食冰毒，从200美元到400元不等。我疯掉了。
Doctor London: Go and close your eyes for me for a second.
伦敦博士：进去闭一会眼睛。
Narrator: The volunteers undergo a series of PET scans that produce images that allow Dr London to look inside the brain and analyse the drug's effects.
旁白：志愿者接受了一系列PET扫描，伦敦博士通过产生的影像来透视大脑并借此分析毒品的作用。
Methamphetamine causes the brain to release chemical messengers called 'neurotransmitters' that make us think, feel and behave in a particular way.
甲基苯丙胺致使大脑释放化学信使，即“神经递质”让我们以特定的方式来思考、感知和行为。
Dr London: One of the neurotransmitters that's primarily affected by methamphetamine is dopamine.
伦敦博士：受甲基苯丙胺影响的主要神经递质之一是多巴胺。
Now we think of dopamine as the pleasure transmitter.
现在，我们认为多巴胺是愉悦感递质。
Narrator: Many narcotics stimulate a flow of dopamine to the brain.
旁白：许多麻醉药刺激多巴胺流向大脑。
But methamphetamine floods the brain up to 1200% more than normal.
但是，流入大脑的甲基苯丙胺比正常高至1200%。
Dr. London: There is a huge release of dopamine and that produces a feeling of intense euphoria.
伦敦博士：多巴胺的巨量释放产生了强烈的愉悦感。
It also produces feelings of competence.
它也产生了胜任感。
Narrator: But the areas receiving these chemical messages, the dopamine receptors, are damaged by toxins in the methamphetamine.
旁白：但是接收这些化学信使的区域，多巴胺受体，被甲基苯丙胺中的毒素所损伤。
Over long term use, the receptors begin to fail.
经过长期的使用，受体开始衰竭。
Meth addicts may have up to 16% fewer dopamine receptors than a normal brain.
冰毒瘾君子大脑中的多巴胺受体数量比正常人少至16%。
Doctor London: We've recently shown that the level of dopamine activity in the brain is highly correlated with impulsivity.
伦敦博士：我们最近的研究显示大脑中多巴胺活动的水平与冲动行为高度相关。
The fewer dopamine receptors the more impulsive a person is.
多巴胺受体数量越少，人就越冲动。
So dopamine in the methamphetamine abuser is very much linked to self-control.
所以，甲基安非他明滥用者脑中的多巴胺与自我控制密切相关。