CHICAGO -- September 8, 2009 -- Results from brain scans suggest an association between a reduction in the transmission of dopamine markers with symptoms of inattention for individuals with attention deficit/hyperactivity disorder (ADHD), according to a preliminary study published in the September 9 issue of JAMA.
Nora D. Volkow, MD, National Institute on Drug Abuse, Bethesda, Maryland, and colleagues conducted a study to determine whether there are abnormalities in the mesoaccumbens in patients with ADHD.
The researchers produced brain images with positron emission tomography (PET) to measure dopamine synaptic markers (transporters and D2/D3 receptors) in 53 nonmedicated adults with ADHD and 44 healthy controls.
"This study provides evidence in favour of the predicted disruption in the mesoaccumbens dopamine pathway in ADHD," the authors wrote. "With PET imaging, lower D2/D3 receptor and DAT (dopamine transporters) availability in those with ADHD than in the control group was documented in 2 key brain regions for reward and motivation."
"The lower than normal D2/D3 receptor and DAT availability in the accumbens and midbrain regions supports the hypothesis of an impairment of the dopamine reward pathway in ADHD."
"Our findings of an association of the mesoaccumbens dopamine pathway with ADHD inattention symptoms may have clinical relevance," they continued. "This pathway plays a key role in reinforcement-motivation and in learning stimuli-reward associations, and its involvement in ADHD supports the use of interventions to enhance the saliency of school and work tasks to improve performance."
"Both motivational interventions and contingency management have been shown to improve performance in ADHD patients," the authors wrote. "Also stimulant medications have been shown to increase the saliency of a cognitive task in proportion to the drug-induced dopamine increases in striatum."
SOURCE: JAMA
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