Never forget

 作者:高戌曹     |      日期:2019-03-07 10:12:09
By Alison Motluk IF YOUR grandparents are becoming a bit forgetful, it might be because getting old is stressing them out. Scientists believe that memory deteriorates during normal ageing because older people cannot grow new neurons in the brain’s hippocampus. These new brain cells are needed to form memories about recent events. Ron McKay and Heather Cameron at the National Institutes of Health near Washington DC wanted to find out why the neurons stop dividing in old age. They knew that levels of stress hormones known as corticosteroids are often up to three times as high in elderly people as in younger adults. They also knew that stress in younger people can temporarily impair memory. So they wondered whether removing stress hormones might improve old people’s memory. To test their idea, they took young adult rats and older rats and removed all their adrenal glands, which produce most of the corticosteroids. Then they examined how many new neurons formed in the rats’ brains. It turned out that the neurons divided much more in the absence of stress hormones—and the effect was just as marked in the elderly rats as in the younger ones. “The result is really dramatically clear,” says McKay. The finding shows that the capacity to grow new neurons is there well into old age, but it is blocked by stress hormones (Nature Neuroscience, vol 2, p 894). This opens up the possibility of designing a family of drugs that block the effects of stress hormones in the brain, allowing neurons to sprout and memory to stay healthy. Says McKay: