杏吧原创

LEARNING and memory problems have been reversed in mice with a syndrome that mimics Down鈥檚.

Catherine Spong and colleagues at the National Institutes of Health in Bethesda, Maryland, found they could prevent developmental problems in mice engineered to have Down鈥檚 syndrome by injecting their mothers with two proteins, called NAP and SAL, while they were still in the womb. This treatment would carry many risks for humans, so the team wondered whether the proteins might also help adult mice.

Spong鈥檚 team engineered mice to have an extra chromosome 16, which causes similar problems to those caused by an extra chromosome 21 in humans, the trigger for Down鈥檚 (see picture). The mice then had to find a submerged platform in a water maze using visual cues. Down鈥檚 mice usually take twice as long to find the platform as healthy mice. However, after four days of oral treatment with NAP and SAL, the Down鈥檚 mice learned to navigate the maze just as easily as normal mice.

NAP and SAL are fragments of proteins normally produced by glial cells 鈥� brain cells that provide nourishment to neurons. We know that glial cells malfunction in people with Down鈥檚. Mice treated with the proteins had markers of healthy glial function that were missing in the untreated Down鈥檚 mice.

In a second experiment, the team investigated whether the treatment caused changes in chemicals known to be involved in 鈥渓ong-term potentiation鈥� (LTP) 鈥� a type of brain activity key to memory formation. People and mice with Down鈥檚 have decreased levels of many chemicals involved in this process. However, treated mice appeared to have increased levels of a receptor called NR2B that is responsible for initiating LTP (). , co-director of Stanford University鈥檚 Down Syndrome Research Center in California, says this study makes one thing clear: 鈥淟earning disabilities and mental retardations that were considered permanent are treatable.鈥�