That electric feeling pg. 3
Children with ADHD have a paradoxical response to methylphenidate – they become less hyperactive, not more. They are better able to pay attention and are less impulsive, and they don’t become addicted to the drug. This suggests that there’s something different about their dopamine transporter, or about the complex interplay of molecules that carry dopamine messages through their brains.
And this is where the new science comes in.
ADHD appears to be highly heritable – meaning that it tends to run in families, especially when the disorder persists into adolescence and adulthood. Scientists believe that genetic mutations or variations may be involved, at least in some “subtypes” of ADHD.
The search for ADHD genes began with the observation that the drugs used to the treat the disorder act primarily on the dopamine system. To date, the strongest candidates are the genes for the D4 dopamine receptor and the dopamine transporter, for which variations, also called polymorphisms, have been found in studies of children with ADHD and their families.
To test the reaction time of a genetically engineered mouse that displays ADHD-like behaviors, Michael McDonald, Ph.D. and his colleagues at Vanderbilt University Medical Center shine brief flashes of light through one of three holes in the mouse's cage.