- Dopamine
It has two different pathways. One is called mesostriatal pathway and the mesolimbocortical pathway.
The mesostriatal Pathway originates at the substantia nigra (part of the basal ganglia, which is responsible for movement) and project to the striatum (caudate and putamen, also part of the basal ganglia, responsible to movement). Therefore, this pathway is responsible for movement. So the loss of the dopaminergic neurons in substantia nigra would lead to diseases such as Parkinson's disease.
the mesolimbocortical pathway originates in the VTA (Ventral tegmental area) and project into the limbic system which includes the amygdala(aggression and fear), nucleus accumbens, the hippocampus (formation of new memories). (the limbic system is mostly responsible for emotions). This pathway is responsible for the reward system. Abnormities in the mesolimbocortical pathway leads to schizophrenia.
VTA
