PLATELET ALPHA(2)-ADRENERGIC RECEPTOR-BINDING AND THE EFFECTS OF D-AMPHETAMINE IN BOYS WITH ATTENTION-DEFICIT HYPERACTIVITY DISORDER

Presynaptic inhibitory alpha-adrenergic receptors are involved in regu lating the release of norepinephrine (NE) through a negative feedback mechanism mediated by NE. Increased alpha(2)-adrenergic receptor activ ity suggests decrease NE release and activity, while decreased alpha(2 )-adrenergic activity suggests increase NE release and activity. A lar ge body of evidence suggests the involvement of a disturbance in NE ac tivity in the pathophysiology of attention deficit hyperactivity disor der (ADHD) in childhood. Platelet alpha(2)-adrenergic receptor binding was compared in 23 boys aged 7-12 with the diagnosis of ADHD and 11 n ormal controls. The ADHD boys tended to have lower levels of alpha(2)- binding than controls. The administration of d-amphetamine in a double -blind placebo-controlled crossover design did not have any effect on alpha(2)-receptor binding in ADHD boys. Nonresponders to d-amphetamine had the lowest alpha(2)-receptor binding compared to responders and c ontrols. These findings suggest a normal alpha(2)-adrenergic activity in ADHD boys responders to d-amphetamine and a possible increase in NE release in ADHD boys nonresponders to d-amphetamine due to decreased alpha(2)-adrenergic receptors.