A Drug for Down Syndrome

United Press International reports on pentylenetetrazole (PTZ) as a treatment for Down Syndrome (trisomy 21):

Craig Garner, Fabian Fernandez and colleagues found that, after they gave mice genetically engineered to develop Down syndrome 17 daily doses of PTZ in milk, they performed as well as their wild-type counterparts when asked to identify novel objects and navigate a maze that simulated difficulties faced by human children and adults with Down syndrome.
The authors said that they thought this occurred because PTZ blocks the action of a neurotransmitter called GABA that is overproduced in people with Down syndrome and inhibits their ability to learn. When the amount of GABA in the brain was brought into balance with other neurotransmitters, normal learning was possible.

If you're wondering how they gave mice, who only have 20 pairs of chromosomes to start with, a trisomy for a chromosome they don't have, here's a BBC report from 2005 on doing just that.