The researchers discovered two interesting things when testing mice in the study. It was found that daily doses were required for several days before any effect was detected and the effect lasted for up to two months after the drug was withdrawn.
The scientists found that affected mice were significantly better able to identify novel objects and navigate a maze tasks that simulate difficulties faced by children and adults with Down syndrome after being fed 17 daily doses of milk containing a compound called pentylenetetrazole, or PTZ.
PTZ has been primarily used for the study of epilepsy in animals. In 1982 the FDA withdrew approval for the use of PTZ in humans because no clear clinical benefit had been established.
The researchers believe that the key to the improvement lies in the fact that PTZ blocks the action of an inhibitory neurotransmitter called GABA. It is thought that Down syndrome patients have too much GABA-related inhibition, making it difficult to process information.
“This suggests that it's not just the removal of the excess inhibition that allows learning to occur, but that we're instead strengthening synapses through some type of long-lasting neuronal adaptation,” said Craig Garner, professor of psychiatry and behavioral sciences and co-director of Stanford’s Down Syndrome Research Center.
The researchers cautioned that PTZ treatment did not improve the learning capabilities of normal mice. The investigators are now considering a clinical trial to test whether the compound has a similar effect in humans with Down syndrome.