阳光在体内制造令人快乐的化学物质内啡肽

Sunlight makes pleasure chemical in the body

 

在紫外线照射后，老鼠会产生感觉良好的化学物质，而当治疗结束时，它们就会失去这种感觉。

 

来自太阳的紫外线可能会引起大脑内部的良好感觉，也可能导致晒黑或晒伤。

 

太阳的紫外线可以导致晒黑或晒伤。事实上，一项新的研究发现，它们对大脑的影响远不止于皮肤。研究表明，暴露在紫外线下会使老鼠产生一种感觉良好的化学物质 内啡肽（Endorphin)。这种化学物质也许能解释为什么那么多人觉得有必要晒黑。

　

　

　

史蒂文·费尔德曼在接受《科学新闻》采访时表示，这项研究也有助于解释为什么人们会涌向海滩和海滩放松。他在北卡罗来纳州温斯顿塞勒姆的维克森林大学医学院研究公共健康和皮肤病。

 

“你知道为什么人们去海滩度假吗?”为什么他们把迪斯尼乐园放在佛罗里达，而不是在明尼苏达州，那里比较凉快?为什么洞穴不像旅游胜地那么受欢迎呢?费尔德曼说，这都是因为这些人在他们的新研究中所研究的内容。他没有参与这项新研究。

　

 

高能量、紫外线来自太阳和用于晒黑的特殊灯光。即使人们知道紫外线辐射可能是危险的，但他们仍然有晒黑的危险。皮肤癌的发病率一直在上升。David Fisher想知道原因。他是一位肿瘤学家——一位在波士顿麻省总医院治疗癌症患者的医生。

 

“我们知道紫外线是很危险的，”Fisher说，但是很多人选择不去保护自己。

 

费雪和他的同事们将老鼠暴露在适量的紫外线下，每周5天，持续6周。科学家们把老鼠剃光，这样光线就会到达他们的皮肤。这些动物受到紫外线照射，就像一个皮肤白皙的人在佛罗里达太阳20或30分钟后得到的一样。

 

在进行了一周的紫外线治疗后，老鼠体内的一种叫做-内啡肽的分子水平比未接触到这种辐射的老鼠高。与海洛因和鸦片等药物类似，内啡肽能激活大脑中的感觉良好的过程。之前的研究已经发现了内啡肽在皮肤中的作用。这项新的研究表明，这种分子也会在血液中结束。

 

然而，紫外线并不能长期促进内啡肽的产生。在紫外线治疗停止后一周，水平恢复正常。而老鼠似乎并没有想要这些治疗结束。事实上，他们表现出了对这种光线上瘾的迹象。

 

Fisher的研究小组将一种叫做纳洛酮(Naa-LOX-ohn)的药物注射给了紫外线治疗的小鼠。医生给滥用海洛因的人开这种药。它阻断了大脑中海洛因触发感觉良好反应的地方。但是，当一个海洛因成瘾者接受了纳克索酮，这种药物可以在几分钟内引发戒断症状。

 

在接受紫外线照射的小鼠中，这种药物似乎阻断了紫外线照射的良好效果。它还导致了牙齿打颤和动物的摇晃。这些症状与人们在吸食海洛因时的症状相似。

Bryon Adinoff告诉《科学新闻》，新数据“令人着迷”。这名精神科医生在退伍军人管理局北德州医疗系统和位于达拉斯的德克萨斯大学西南医学中心，在这项新研究中没有任何作用。

 

其他研究表明，紫外线能让人感觉良好，Adinoff注意到。

 

“有很多人晒黑了，不管是在沙滩上还是在室内美容院。许多人报告的症状与上瘾一致。而且，他和他的同事们已经证明，紫外线能刺激人大脑中与成瘾有关的部分活动。

 

不过，他认为，这项新的研究并没有证明老鼠已经对紫外线上瘾了。“上瘾意味着渴望，失去控制和容忍，”他解释道。而这项新的研究“没有研究这些东西。”

　

 

参考文献

Sunlight makes pleasure chemical in the body

 

Mice made feel-good chemical after exposure to ultraviolet light — and missed that light when the treatments ended

 

Ultraviolet light from the sun may cause good feelings inside the brain, as well as a tan or burn.

The sun’s ultraviolet rays can cause more than a tan or burn. Indeed, their influence goes more than skin deep — to the brain, a new study finds. It showed that exposure to ultraviolet (UV) light causes mice to make a feel-good chemical. And that chemical may explain why so many people feel compelled to get a tan.

 

The study also may help explain why people flock to beaches and coasts for relaxation, Steven Feldman told Science News. He studies public health and skin diseases at the Wake Forest University School of Medicine in Winston-Salem, N.C.

 

“Do you know why people go to the beach on vacation? Why they put [Disney World] in Florida and not in Minnesota, where it’s cooler? Why caves are not more popular as a tourist destination? It’s all because of what these guys studied” in their new research, Feldman says. He did not work on the new study.

 

High-energy, UV rays come from the sun and the special lights used in tanning booths. Even though people know UV radiation can be dangerous, they continue to risk sunburns for a tan. Rates of skin cancer have been going up. David Fisher wanted to know why. He's an oncologist — a doctor who treats people with cancer — at Massachusetts General Hospital in Boston.

 

“We know [UV light is] dangerous,” Fisher says, but many people choose not to protect themselves.

 

Fisher and his colleagues exposed mice to a moderate amount of UV light five days a week, for six weeks. The scientists shaved the mice so the light would reach their skin. The animals received an exposure to UV light that was similar to what a fair-skinned person gets after 20 or 30 minutes in the Florida sun.

 

After just a week of the UV treatment, mice had higher levels of a molecule in their blood called beta-endorphin than did mice not exposed to this radiation. Similar to drugs such as heroin and opium, beta-endorphin activates feel-good processes in the brain. Previous studies had found beta-endorphin in the skin. This new study showed the molecule also ends up in the blood.

 

UV light didn’t boost beta-endorphin for very long, though. Levels returned to normal a week after the UV treatments stopped. And the mice didn’t seem to have wanted those treatments to end. In fact, they showed signs of an addiction to this light.

 

Fisher’s group gave a drug, called naloxone (Naa-LOX-ohn), to the UV-treated mice. Doctors prescribe this drug to people who have been abusing heroin. It blocks the places in the brain where heroin triggers the feel-good response. But when a heroin addict receives naxolone, the drug can set off withdrawal symptoms within minutes.

 

In the UV-treated mice, the drug seemed to block the feel-good effects of UV exposure. It also caused chattering teeth and shaking in the animals.  Those symptoms looked similar to what people go through when they are suffering from withdrawal from heroin.

 

The new data are “fascinating,” Bryon Adinoff told Science News. This psychiatrist at the Veterans Administration North Texas Health Care System and the University of Texas Southwestern Medical Center in Dallas, had no role in the new study.

 

Other studies with people have shown that UV rays make people feel good, Adinoff notes.

 

“There are a lot of people out there who tan, either on the beach or in indoor salon tanners. And many of these folks report symptoms that are consistent with addiction,” he notes. What's more, UV light boosts activity in parts of the human brain associated with addiction, he and his colleagues have shown.

 

Still, he argues, the new study falls short of proving the mice had become addicted to UV light. “Addiction means craving, loss of control and tolerance,” he explains. And the new study “didn’t look at any of those things.”

 

Sunlight makes pleasure chemical in the body | Science News for Students  https://www.sciencenewsforstudents.org/article/sunlight-makes-pleasure-chemical-body