Scientists believe they have found evidence of a drug which alleviates the learning difficulties associated with Down's Syndrome.
Down's syndrome is caused by an extra chromosome
A Stanford University team in the US looked at a drug once tested as an epilepsy treatment in the 1950s.
The found a once-a-day treatment for over two weeks helped mice overcome the problems associated with the condition, the Journal Nature Neuroscience said.
UK experts said clinical trials were needed to know its impact on humans.
Down's syndrome is one of the most common cause of learning difficulties, affecting around one in 800 births. There are about 60,000 people living with it in the UK.
It is caused by the presence of an extra copy of a chromosome, known as chromosome 21.
Researchers were exploring the possibility that the brains of Down's syndrome patients are too strongly affected by a chemical called GABA, which slows the nerve cell activity in the brain.
The drug they looked at, called pentylenetetrazole or PTZ, works by blocking the action of GABA.
The team gave daily doses of PTZ to mice specially bred to have many of the same genetic differences that cause Down's Syndrome and got them to perform a maze task.
The mice tended to explore the maze in a random way compared to normal mice, but after 17 days treatment, the Down's syndrome mice began exploring more like normal mice.
Further tests showed the mice acted normally for up to two months after the drug was stopped.
Professor Craig Garner, who led the research, said: "This treatment has remarkable potential.
"So many other drugs have been tried that had no effect at all.
"Our findings clearly open a new avenue for considering how cognitive dysfunction in individuals with Down syndrome might be treated."
Researchers are now considering whether to push ahead towards clinical trials to find if the substance has a similar effect in humans.
However, they warned PTZ is not currently approved for use in humans and in high doses is known to cause seizures.
Carol Boys, chief executive of the Down's Syndrome Association, said the research was welcome.
But she added: "We must remember that this research has been conducted with mouse models.
"At this stage the compound PTZ is not approved for human use and until extensive further clinical trials with real people have been conducted it will be impossible to predict how this drug might affect the lives and abilities of people with Down's syndrome."