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Some genes related to the noradrenergic system have been investigated as candidate genes in Attention Deficit Hyperactivity Disorder (ADHD). Through functional brain imaging studies, it has been reported that brain areas such as the prefrontal cortex (PFC), dorsal anterior cingulate cortex, and striatum show abnormal findings in ADHD patients. We have investigated whether there was an association between polymorphism of the noradrenergic system related genes (SLC6A2 and ADRA2A) and regional cerebral blood şow (rCBF) in a Korean ADHD sample.
Methods: A total of thirty-six children (31 boys and 5 girls, mean age: 8.9 (± 1.84) years) participated in this study. Subjects were recruited from the outpatient's clinic of child and adolescent psychiatry in the Seoul National University Hospital. The diagnosis of ADHD was made based on the DSM-IV-TR. All patients were drug naïve at the time of image acquisition. Genotyping of SLC6A2 (G1287A, -3081(A/T)) and ADRA2A (Dral, Mspl) was done. SPM8 (Statistical parametric mapping 8) was used to compare images between the two groups divided by each genotype.
Results: Children with the G/A and A/A genotypes at the SLC6A2 G1287A polymorphism showed decreased rCBF in the right inferior temporal gyrus and the left middle temporal gyrus compared to children with G/G genotype (uncorrected p-value< 0.001). In ADRA2A Mspl polymorphism, children with the C/G and C/C genotypes showed increased rCBF in the left striatum and the left cingulate gyrus and decreased rCBF in the left cerebellar vermis compared to children with G/G genotype. There were no significant rCBF alterations across genotypes in the SLC6A2 -3081(A/T) and ADRA2A Mspl genes.
Conclusion: This study showed that the noradrenergic system related genes might be associated with functional brain abnormalities in children with ADHD.