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(回答先: 都市部の４カ月児、７割以上の家庭が寝かしつけるのは夜10時以降 【日本睡眠学会速報】（MedWave） 投稿者 シジミ 日時 2005 年 7 月 01 日 21:23:47)
イルカは生後1月眠らず、その母親も子を見守って眠らない
http://www.newscientist.com/article.ns?id=dn7606
Newborn dolphins go a month without sleep
* 18:43 29 June 2005
* NewScientist.com news service
* Andy Coghlan
【ワシントン共同】１日に必要な睡眠時間を決めるのに重要とみられる遺伝子を、米ウィスコンシン大のチームがショウジョウバエで見つけた。似た機能の遺伝子は人間にもあり、睡眠障害の治療法研究に役立ちそうだ。
チームは、１日に９〜１５時間眠り、睡眠不足になると活動の能率が落ちるなど、人の眠りと共通点が多いハエに注目。さまざまな遺伝子変異を持つ９０００種のショウジョウバエを片っ端から調べて平均の約３分の１しか眠らないハエを見つけ、特定の遺伝子のアミノ酸１個が変異していることを確かめた。遺伝子は「シェーカー」と呼ばれ、細胞の表面にカリウムイオンの出入り口を作り、神経の信号伝達を正常に保つ働きがあった。
毎日新聞 2005年5月16日 東京朝刊
http://news.independent.co.uk/world/science_technology/story.jsp?story=633688
Gene that dictates how long we need to sleep is discovered
By Steve Connor, Science Editor
28 April 2005
Scientists believe they have identified the gene that affects the chemistry of sleep, determining whether we are capable of sleeping for a little as three hours a night without ill effects.
The discovery could explain why the ability to remain awake happily for half the night appears to run in some families, who may carry a genetic mutation that disrupts normal sleep patterns. Researchers hope it will open the way to understanding the chemical basis of sleep so new drugs can be developed to overcome the effects of prolonged sleep disruption.
A study has found that the gene controls biochemical "channels" that determine the flow of charged particles - potassium ions - into the critical regions of the brain involved in sleep.
Scientists at the University of Wisconsin-Madison believe they have for the first time shown how a single gene can affect sleep.
"This research offers the possibility of developing a new class of compounds that could affect potassium channels in the brain rather than the brain-chemical systems targeted currently," said Chiara Cirelli, a professor of psychiatry at Wisconsin and lead author of the study. The study, published in the journal Nature, involved screening 9,000 mutant fruit flies to see how genetic mutations affect their sleeping patterns.
Like humans, fruit flies need between six and 12 hours of sleep each night and show signs of physical stress if they are deprived of rest. But some flies carrying a mutation in a gene called "shaker" were happy with just a few hours' sleep.
When the short-sleeping flies were put through a series of tests, they performed as well as normal flies even though they slept for just a third as long. The scientists believe the findings are directly relevant to humans.
"The more behaviours we look at, in terms of sleep, the more we find that sleep in fruit flies is very, very similar to sleep in mammals," Professor Cirelli said. Like humans, sleep-deprived flies need to catch up on their sleep to get back to normal and young flies need more sleep than older flies, which like humans suffer increasingly from sleep disruption the older they become.
The scientists believe that the shaker gene controls the potassium channels that determine whether the body drifts into the deep sleep associated with slow brain waves - as opposed to the light, fast-wave sleep when there is rapid eye-movement (REM) and dreaming.
A detailed analysis of the mutation revealed that it prevented potassium ions from passing freely through the channels in the membrane of nerve cells in the brain. The short-sleeping flies, however, did not live as long as normal flies.
"Humans have the same kind of genes and potassium channels," Professor Cirelli said.
"Our hypothesis is that if you don't have potassium channels, you won't get slow waves. The cell membrane will remain activated, preventing long periods of deep, non-REM sleep."
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