Chapter IX Human forebrain dopamine systems: Characterization of the normal brain and in relation to psychiatric disorders

Impairments of dopaminergic neuronal populations have been strongly implicated in a variety of neurological, psychiatric and drug addiction disorders, mental illnesses. Although most research efforts have been directed toward understanding the dopamine neural system in animals, technological advances over the past two decades have also helped to expand our current knowledge about the discrete anatomical organization of the dopamine system in the human brain. Dopamine neuronal populations have now been characterized in the human brain from the level of gene transcription (using in situ hybridization histochemistry) to the distribution of related proteins (immunohistochemistry) and their receptors (as visualized in vivo by neuroimaging techniques of positron emission tomography (PET) and single photon emission tomography (SPECT). The insights revealed about the human dopaminergic system by these technologies should help in the development of more targeted treatment interventions of neuropsychiatric disorders. In this chapter, we have summarized the current status regarding the neuroanatomical organization of the human dopamine systems with focus on the forebrain. The general organization of the dopamine system, from the level of synthesis, release, uptake and receptors, in the human brain are described with their potential implications for addiction and psychiatric disorders.