Strategies for study of the neurochemistry of attention deficit disorder in children.

The interpretation of neurochemical studies of attention deficit disorder (ADD) with hyperactivity is complicated by the variability in diagnosis and by the limitations of single neurochemical measures--whose levels may be compensated by chronic feedback mechanisms. This article reviews previous neurochemical studies of ADD and proposes the use of single-dose neurochemical probes. Administration of a provocative agent with subsequent sequential measures of plasma levels of neurotransmitters, their metabolites, and hormones may help define the responsivity of neurochemical systems. Blood levels of drugs and neurotransmitters following single doses of methylphenidate and clonidine are studied as a strategy to explore the responsivity of dopaminergic and noradrenergic mechanisms in ADD.