Impulsivity and motor activity in aged, male Ts65Dn mice.

Attention deficit/hyperactivity disorder (ADHD) is more prevalent in children with Down syndrome than in typically developing children. The defining characteristics of ADHD include inattention, impulsivity, and hyperactivity. The main purpose of this study was to determine whether a mouse model of Down syndrome exhibited higher levels of impulsivity than controls. A secondary aim was to examine the effects of d-amphetamine (0.1-10 mg/kg) and fenfluramine (0.3-10 mg/kg) on impulsivity. Seven male Ts65Dn and 9 male littermate control (LC) mice were trained under a response inhibition schedule of reinforcement; the main measure of impulsivity under this schedule is the mean wait time. After behavior stabilized, the mean wait time for the Ts65Dn mice was indistinguishable from that of the LC mice. Administration of 1 mg/kg d-amphetamine increased the mean wait time in both Ts65Dn and LC, though it was statistically significant only for the LC. However, no dose of fenfluramine altered the mean wait time in Ts65Dn or LC mice. An additional aim of these studies was to determine whether Ts65Dn mice displayed higher levels of motor activity than LC mice. A comparison of running wheel activity revealed no difference between Ts65Dn and LC mice. Thus, the results of the current studies suggest that aged, male Ts65Dn mice are no different from age-matched LC mice in terms of impulsivity or motor activity.