The dopamine D2 receptor: new surprises from an old friend.

Drugs acting at dopamine D2 receptors (D2R) are commonly used to alleviate symptoms produced by diseases such as Parkinson's disease, schizophrenia, and depression. A limitation to the use of these drugs is that they sometimes afflict patients with severe side effects. This review discusses recent evidence for several proteins that represent novel mediators of the downstream consequences of D2R activation, since selective targeting of particular D2R-mediated signaling pathways could lead to the development of improved treatments for these devastating diseases.