A mouse study published today in Molecular Psychiatry sheds light on how a particular version of a dopamine receptor in the brain (called D4) could play a role in an individual's likelihood of developing Attention Deficit Hyperactivity Disorder. Dysfunction of this version of the D4 receptor has been associated with ADHD as well as other conditions characterized by disordered impulse control, including drug addiction. In the study, NIH News explains:
...researchers inserted three variants of the dopamine D4 receptor into cells and into mice so that they could investigate differences in biological activities. The researchers found that the D4.7 variant, unlike its D4.2 and D4.4 counterparts, was not able to interact with the short version of the dopamine type 2 (D2S) receptor to reduce glutamate release in a brain region associated with impulsivity and symptoms of ADHD in humans.