Aim: Vasopressin exerts robust influences on social communication and behavior in humans. Apelin is a relatively novel neuropeptide that could counteract vasopressin's actions and has been shown to be closely related with a broad range of physiological functions. Abnormalities in vasopressin and apelin have been detected in a variety of psychiatric disorders, but their relation to attention-deficit hyperactivity disorder (ADHD) is unknown. In the present study, we explored the plasma levels of vasopressin and apelin-13 in children with ADHD.Methods: Thirty-four children with ADHD and 36 healthy controls were enrolled in this study. The severity of ADHD symptoms was assessed via Conners' Parent Rating Scale and Conners' Teacher Rating Scale. Plasma levels of vasopressin and apelin-13 were measured using commercial enzymelinked immunosorbent assay kits.
Results:The mean plasma apelin-13 levels were significantly higher in male children with ADHD than in male control subjects; no significant difference was found between the groups for plasma apelin-13 levels in girls or in the entire subject cohort. Plasma vasopressin levels did not show any significant differences between groups. There were no significant correlations between plasma levels of these neuropeptides and scores for Conners' Parent Rating Scale and Conners' Teacher Rating Scale.
Conclusion:Our results suggest a sex-specific association between plasma apelin-13 levels and ADHD. Apelin-13 may play a role in the etiopathogenesis of ADHD either with a direct impact on the apelin receptor or via its opposing effect on the vasopressinergic system. Key words: apelin-13, attention-deficit hyperactivity disorder, children, plasma, vasopressin.A TTENTION-DEFICIT HYPERACTIVITY DISOR-DER (ADHD) is a childhood-onset neurodevelopmental condition characterized by inattention, hyperactivity, and/or impulsivity that can persist into adulthood with deleterious effects on social, academic, and behavioral outcomes.1 The etiology of ADHD involves complex interactions of neuroanatomical and neurochemical systems, but the precise neurobiological mechanisms underlying the disorder are currently unclear. Understanding the etiopathogenesis of ADHD would aid in both its diagnosis and in the development of new treatments for this complex disorder.The vasopressinergic system in the brain participates in the modulation of social behaviors, including social communication, parental care, parent-offspring bonding, pair-bonding, and sexual behavior.2 Because social deficiencies are core symptoms of autism spectrum disorders (ASD), in recent years, a growing number of studies have investigated the potential relation between the vasopressinergic system and ASD. [3][4][5] These studies have yielded conflicting results regarding the alteration of blood vasopressin concentrations