Investigation of the serotonin 2C receptor gene in attention deficit hyperactivity disorder in UK samples

In this study we investigated the association between ADHD and two polymorphisms C-759T (rs3813929) and G-697C (rs518147) in the promoter region of the HTR2C gene using a sample of 180 UK ADHD probands and their parents. We have shown that the -697G allele was significantly over-transmitted to affected ADHD probands (P = 0.017). No association was detected between the C-759T polymorphism and ADHD. Haplotype analysis of the two markers revealed no significantly increased transmission of any haplotype to ADHD.The findings provide evidence that the G-allele of the G-697C HTR2C polymorphism may be involved in the development of ADHD. The results replicate one of the findings published recently.Attention deficit hyperactivity disorder (ADHD) is a childhood onset, neurodevelopmental disorder characterized by inattention, hyperactivity and impulsivity. Molecular genetic and pharmacological studies suggest the involvement of the dopaminergic, serotonergic and noradrenergic neurotransmitter systems in the pathogenesis of ADHD. Polymorphic variants in several genes involved in regulation of the dopamine, and related neurotransmitter pathways are reported to be associated with ADHD [1-3].Serotonin is a neurotransmitter in human brain, and involved in a variety of functions including learning, aggression and cognitive processes [4,5]. The serotonin receptors have been classified into at least seven families (5-HT1-7). The 5-HT2C receptor (HTR2C) gene is located on human chromosome Xq24. The previous studies showed that the 5-HT2C receptor is a key contributor to control of central dopamine functions [6,7] and may play an important role in the aetiology of mental disorders, including ADHD. ADHD is much more frequent in males than females [8,9]. Genes coding to the X chromosome have been suspected as candidates for ADHD [10-14].Yuan et al. [15] have suggested that the single nucleotide substitution polymorphisms in the upstream region of the 5-HT2C receptor could be involved in t