Researchers in the United States have discovered that an old drug once used to study epilepsy substantially improved learning and memory in mice with Down syndrome symptoms.
They believe the drug pentylenetetrazole, or PTZ, may improve learning in children and adults with Down syndrome.
Furthermore the beneficial effects of PTZ, continued for two weeks after treatment and the researchers say this suggests the drug can make long-term changes in the brain as some psychiatric drugs do.
Dr. Craig Garner, a professor of psychiatry and a director of the Down Syndrome Research Center at California's Stanford University, says the treatment has remarkable potential and may help scientists understand what causes the mental retardation seen in Down syndrome patients.
The researchers are now considering a clinical trial to test whether the compound has a similar effect in humans with Down syndrome.
More than 300,000 people in the U.S. have Down syndrome, which is caused by an extra copy of chromosome 21.
It is the most frequent genetic cause of mental retardation and occurs in about one in every 800 births; it is also associated with childhood heart disease, leukemia and early onset Alzheimer's disease.
As many as 5,000 children are born each year in the United States with Down syndrome.
The majority of people have two copies of each chromosome and the additional activity of the genes on the third copy of chromosome 21 is thought to cause the symptoms of Down syndrome.
Symptoms range from moderate mental retardation to very mild disability but many of those with Down syndrome also have health problems, in particular heart trouble.
Fabian Fernandez, a graduate student in Garner's laboratory had been working on the theory that the brains of Down's patients are too strongly affected by a chemical called GABA, a neurotransmitter, or message-carrying chemical, that stops brain cells from becoming too excited.
The researchers used a mouse model of Down syndrome for their study in which about 150 genes are triplicated.
The mice used exhibited many of the cognitive problems that afflict human Down syndrome patients.
Fernandez found that after being fed 17 daily doses of milk containing a compound called pentylenetetrazole, or PTZ, the affected mice were significantly better able to identify novel objects and navigate a maze.
The treated mice performed as well as their wild-type counterparts for up to two months after drug treatment was discontinued.