Washington, Sep 5 (IANS): US researchers may have identified a compound that appears to reverse the learning deficits associated with Down Syndrome in lab mice.

While the use of the compound, a small molecule known as a sonic hedgehog pathway agonist, has not been proven safe for testing on people with Down Syndrome, researchers said Wednesday their experiments hold promise for developing drugs similar to it, reports Xinhua.

Down Syndrome is one of the most common chromosomal abnormalities in children, and a leading cause of intellectual disability.

It occurs when people have three instead of the two usual copies of the chromosome 21.

As a result of this "trisomy", people with Down Syndrome have extra copies of more than 300 genes, leading to intellectual disabilities, distinctive facial features and sometimes heart problems and other health effects.

In their study, the researchers from the Johns Hopkins University and the US National Institute of Health conducted experiments on mice to give them extra copies of about half of the genes found in humans.

The researchers injected the mice the compound right after their birth and found that single injection enabled the cerebellum of the rodents' brains to grow to a normal size.

"Most people with Down Syndrome have a cerebellum that's about 60 percent of the normal size," lead author Roger Reeves of the Johns Hopkins University School of Medicine argued.

"We treated the Down Syndrome-like mice with a compound we thought might normalise the cerebellum's growth, and it worked beautifully," he said.

"What we didn't expect were the effects on learning and memory, which are generally controlled by the hippocampus, not the cerebellum," he said.

The team tested the mice who had been given the dose with the mice who suffered with the syndrome, and normal mice in a variety of ways, and found that the treated mice did just as well as the normal ones on a test of locating a platform while swimming in a so-called water maze.

Further research, however, is needed to know why exactly the treatment works and if it can be altered for human use, the researchers wrote in the journal Science Translational Medicine.