Nicotinic receptors, nucleus accumbens and attention deficit hyperactivity disorder
Özet
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 receptors in terms of attention and learning skills. Method: In this article we reviewed especially the review articles about the relationship between ADHD pathophysiology and nicotinic receptors and nucleus accumbens, using mostly "ScienceDirect' and 'Mdconsult" medical search engines. Results: ADHD is a common childhood psychiatric disorder and it is assumed as a significant risk factor for severe cognitive, behavioral, social, psychological, and academical problems. However, its pathophysiological origins are yet to be elucidated. Several models including dopamine (DA), glutamate, and norepinephrine dysfunction are suggested. Recently, the research studies with clinical ADHD cases and animal models are increasing in number. These studies mostly propose a new hypothesis which integrates the heterogenic pathophysiology on a model. This model particularly involves nucleus accumbens, nicotinic receptors which directly effects the dopaminergic system and the impaired reward circuitry. 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.
