 Most of the dopamine pathways (i.e., neurons that use the neurotransmitter dopamine to communicate with other neurons) that project out of the ventral tegmental area are part of the reward system; in these pathways, dopamine acts on D1-like receptors or D2-like receptors to either stimulate (D1-like) or inhibit (D2-like) the production of cAMP.The GABAergic medium spiny neurons of the striatum are components of the reward system as well.The glutamatergic projection nuclei in the subthalamic nucleus, prefrontal cortex, hippocampus, thalamus, and amygdala connect to other parts of the reward system via glutamate pathways.