Nicotinic Receptors, Nucleus Accumbens and Attention Deficit Hyperactivity Disorder

Abstract

Neuronal nicotinic receptors (nAch) are widely distributed in human brain and they have critical importance on cognitive functions such as attention, learning and memory. We aimed to review anatomic and developmental distribution of nAch of the brain, particular functions of nAch in nucleus accumbens and on pathophysiology of attention deficit hyperactivtiy disorder (ADHD). In addition, we reviewed the outcome of prenatal and early childhood exposure to nicotine and effects of agonistic agents of nicotinic reseptors in terms of attention and learning skills. Method: In this article we reviewed especially the review articles about the relation between ADHD pathophysiology and nicotinic receptors and nucleus accumbens, using mostly "ScienceDirect" and "Mdconsult" medical search motors. Results: ADHD is a common childhood psychiatric disorder and it is assumed as a significant risk factor for several cognitive, behavioral, social, psychological and academical problems. However, its pathophysiological origins are yet to be elucidated. Several models including dopamine (DA), glutamate, norepinephrine dysfunction are suggested. Recently, the research studies with clinical ADHD cases and animal models are increasing in number. These studies mostly propose new hypothesis which integrates the heterogenic pathophysiology on a model. This model particularly involves nucleus accumbens, nicotinic reseptors which directly effects the dopaminergic system and the deficient reward system. Discussion: The "dual pathway hypothesis" could explain firstly the chronic tonic/phasic mesolimbic interaction, and secondly the accompanying psychiatric problems by the synaptic gating model over the nucleus accumbens. In order to explore the differential outcome of the disturbence either innate or acquired, effects of the duration and severity and the differences in developmental stages, further studies are needed.