Table 2: Modulation of dopaminergic pathways and their associated changes of dopamine levels in neurological disorders.

DA pathways
DA alterationsDisordersReferences

NigrostriatalDA decreaseParkinson’s disease[4245]
Huntington’s disease[43, 44]
ADHD[46]
DA increaseSchizophrenia[43]
Tourette’s syndrome[47]
ADHD[43]
MesocorticalDA increaseSchizophrenia[43]
Tourette’s syndrome[43]
MesolimbicDA decreaseEpilepsy[48, 49]
Drug addiction[43, 50]
DA increaseObesity[43, 50]
Depression[50]
TuberoinfundibularDA decreasePituitary tumors[51]

There are four major dopaminergic pathways: (1) nigrostriatal pathway, in which substantia nigra neurons innervate the stratum; (2) nesocortical pathway, which links the ventral tegmental area to medial prefrontal, cingulate, and entorhinal cortices; (3) nesolimbic pathway, composed of ventral tegmental area cells projecting to the nucleus accumbens and other limbic areas; (4) tuberoinfundibular, which projects from arcuate and periventricular nuclei of the hypothalamus to the pituitary gland. Abbreviations: DA: dopamine; ADHD: attention-deficit hyperactivity disorder.