托福阅读材料(230)：褪黑素有助睡眠的原因

　　托福阅读材料/知识之褪黑素有助睡眠的原因，更多托福阅读背景材料/知识尽在新东方在线托福考试频道！

　　褪黑素与我们的睡眠质量密切相关，下面的新托福考试阅读资料要讨论的就是褪黑素有助睡眠的原因。

　　Melatonin, sometimes called “the hormone of darkness,” plays an important role in regulating our daily sleep patterns. This hormone is produced by our bodies and in most organisms melatonin production is higher during the night than during the day.

　　In addition to their body’s own melatonin, many people take melatonin supplements in an attempt to help them sleep, fight jet lag or balance out seasonal affective disorder.

　　Melatonin And Memories

　　But a study by a group of scientists at the University of Houston suggests that melatonin might have a negative impact on the ability to form new memories.

　　The researchers were interested in how the body’s internal clock affects the formation of new memories. They found that small striped minnows called zebra fish learned very well during the day but very poorly at night, when melatonin levels are higher.

　　They wondered if melatonin played a role in learning and memory.

　　Melatonin And Learning

　　They treated zebra fish with extra melatonin during the day, boosting the hormone levels to night-time amounts.

　　They discovered that high melatonin did not affect learning per se, but dramatically reduced the fishes’ ability to form new memories, or to remember what they’d learned.

　　Then the scientists inhibited melatonin activity in the fish. They did this by blocking melatonin receptors with inhibitory drugs. The fishs’ melatonin levels were unchanged, but the ability of melatonin to affect the brain was blocked.

　　Blocking Melatonin

　　With melatonin activity blocked, the ability of the fish to form new memories was drastically improved, even at night.

　　This research has potential benefits for humans. For example, the use of melatonin receptor blockers could improve performance of night-time cognitive tasks, helping people such as night-shift workers or students cramming for exams.

　　褪黑素，又名黑素细胞凝集素的荷尔蒙，在调节我们日常睡眠规律中扮演重要角色。人体自身分泌褪黑激素，而且大多数生物夜晚比白天分泌得更多。

　　此外，一些人通过体外补充褪黑素改善睡眠，缓解飞机时差感、平衡季节性情绪失调。

　　褪黑素对记忆的影响

　　但是，休斯顿大学的科学家们研究表明：褪黑素阻碍记忆形成。

　　研究人员想弄清楚体内生物钟如何影响新生记忆的形成。研究人员发现斑马鱼白天学习能力很好;夜晚却很差，而夜晚褪黑素分泌旺盛。研究人员怀疑褪黑素影响学习和记忆。

　　褪黑素对学习的影响

　　白天，研究人员喂给斑马鱼褪黑素，促进斑马鱼夜晚褪黑素分泌。

　　研究人员发现大量的褪黑素没有直接影响学习本身，但是却很大程度地使斑马鱼的记忆衰退，斑马鱼不记得学过的东西。

　　接着，科学家们抑制斑马鱼体内的褪黑素的作用：抑制药物阻碍褪黑素受体。斑马鱼褪黑素分泌量没改变，但是褪黑素不能影响不了大脑。

　　阻碍褪黑素

　　褪黑素的作用受阻，斑马鱼新生记忆能力明显改善，夜晚也很好。

　　该项研究带给人类潜在好处。例如，褪黑素受体的阻碍能影响人夜晚的认知能力，那么对于那些夜班工作者和熬夜备考的学生都有所帮助。