Abstract
Neuroimaging studies have suggested the involvement of several brain areas in attentionโdeficit/hyperactivity disorder (ADHD). Genetic investigations have supported the role of both dopamine D4 receptor gene (DRD4) and dopamine transporter gene (DAT1) in the vulnerability to the disorder. This study evaluates whether the presence of risk alleles at DRD4 and/or DAT1 genes is associated with differences in regional cerebral blood flow (rCBF) in a sample of ADHD boys. The rCBF was compared between ADHD patients with and without risk alleles at DRD4 (7โrepeat allele) and/or at DAT1 (homozygosis for the 10โrepeat allele) genes by single photon emission computed tomography (SPECT) during continuous performance test. Images were analyzed using statistical parametric mapping (SPMโ99). No significant differences in rCBF were found both between ADHD boys with and without the 7โrepeat allele at DRD4 locus, as well as between ADHD boys homozygous for the 10โrepeat allele and ADHD subjects with other genotypes at the DAT1 locus. However, a significantly higher perfusion in the right middle temporal gyrus was found in the group with risk alleles at both DRD4 and DAT1 loci (nโ=โ6) compared to ADHD boys without risk alleles at both loci (nโ=โ28) (Pโ<โ0.05). Our findings suggest that a higher recruitment in middle temporal gyrus, an area associated to working memory and selective attention, should exist to compensate a putative effect of the interaction between these dopaminergic genes. ยฉ 2004 WileyโLiss, Inc.