托福閱讀資料之人體腦白金

　　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，又名黑素細(xì)胞凝集素的荷爾蒙，在調(diào)節(jié)我們?nèi)粘Ｋ咭?guī)律中扮演重要角色。人體自身分泌褪黑激素，而且大多數(shù)生物夜晚比白天分泌得更多。

　　此外，一些人通過體外補(bǔ)充褪黑素改善睡眠，緩解飛機(jī)時差感、平衡季節(jié)性情緒失調(diào)。

　　褪黑素對記憶的影響

　　但是，休斯頓大學(xué)的科學(xué)家們研究表明：褪黑素阻礙記憶形成。

　　研究人員想弄清楚體內(nèi)生物鐘如何影響新生記憶的形成。研究人員發(fā)現(xiàn)斑馬魚白天學(xué)習(xí)能力很好;夜晚卻很差，而夜晚褪黑素分泌旺盛。研究人員懷疑褪黑素影響學(xué)習(xí)和記憶。

　　褪黑素對學(xué)習(xí)的影響

　　白天，研究人員喂給斑馬魚褪黑素，促進(jìn)斑馬魚夜晚褪黑素分泌。

　　研究人員發(fā)現(xiàn)大量的褪黑素沒有直接影響學(xué)習(xí)本身，但是卻很大程度地使斑馬魚的記憶衰退，斑馬魚不記得學(xué)過的東西。

　　接著，科學(xué)家們抑制斑馬魚體內(nèi)的褪黑素的作用：抑制藥物阻礙褪黑素受體。斑馬魚褪黑素分泌量沒改變，但是褪黑素不能影響不了大腦。

　　阻礙褪黑素

　　褪黑素的作用受阻，斑馬魚新生記憶能力明顯改善，夜晚也很好。

　　該項(xiàng)研究帶給人類潛在好處。例如，褪黑素受體的阻礙能影響人夜晚的認(rèn)知能力，那么對于那些夜班工作者和熬夜備考的學(xué)生都有所幫助。