Most dopamine-producing neurons are located in two clusters in the midbrain: the ventral tegmental area and the substantia nigra. The axons that extend outward from these two clusters of neurons form the neural circuits known as the dopaminergic pathways. Two of these dopaminergic pathways—the mesolimbic pathway and the nigrostriatal pathway—are the neural pathways primarily affected in schizophrenia and are therefore the most important ones to examine in looking for treatments (fig. 4.3).
