“…Attention Deficit Hyperactivity Disorder (ADHD), one of the most common neurobehavioral disorders of human childhood, is a heterogeneous syndrome that includes behavioral and cognitive dysfunctions, such as inattention, impulsivity, and hyperactivity (Goldman et al, 1998;Kirby et al, 2002). Since dopaminergic dysfunctions appear to contribute to ADHD, the most frequently used drug to treat symptoms of ADHD is methylphenidate (MP) (Kirby et al, 2002;Bolanos et al, 2003), which exerts its action mainly via the dopaminergic system (Volkow et al, 2001;Seeman and Madras, 2002). Animal models of ADHD, such as the spontaneously hypertensive rat (Sagvolden, 2000), the dopamine transporter knockout mouse (Gainetdinov and Caron, 2001), and others (see Davids et al, 2003) are focused on the genetic background of ADHD.…”