In the current study, the UT Southwestern researchers used mice that were genetically engineered to carry the mutant human gene for Huntingtons, causing symptoms and death of brain cells similar to those seen in the disease. The study focused on an area of the brain called the striatum, which plays a critical role in relaying signals concerning motion and higher thought and receives signals from several brain regions.
The striatum is primarily made up of nerve cells called medium spiny neurons, which undergo widespread death in Huntingtons. One major input to the striatum comes from an area called the substantia nigra, which controls voluntary movements and sends signals to the striatum via nerve cells that release dopamine.
The researchers conducted various coordination tests on both normal and genetically manipulated mice. Engineered mice given a drug that increased brain dopamine levels performed worse on these tasks, while TBZ protected against this effect. Most importantly, TBZ appears to reduce significantly cell loss in the striatum of the engineered mice, the scientists report.
More research is needed to determine whether this protective effect might also be present in humans, and also whether at-risk people would benefit from the drug, Dr. Bezprozvanny said.
Clinical trials in humans would be very difficult, however, because trials require many participants and there is no easy way to score effectiveness of a presymptomatic drug, Dr. Bezprozvanny said. Thus, his future studies in animals will look at the effectiveness of TBZ given just after initial symptoms have developed. This situation simulates what would probably happen in a human trial, he said.