One candidate gene that has been studied by the COGA investigators is the dopamine D2 receptor gene (DRD2). Dopamine is a brain chemical (i.e., neurotransmitter) that is used by nerve cells in the brain’s “reward center” and other brain regions to transmit nerve signals among nerve cells. During this process, dopamine is released from the signal-emitting nerve cell and attaches to a protein “docking” molecule (i.e., receptor) located on the outer surface of the signal-receiving nerve cells. This interaction triggers electrical and chemical changes in the signal-receiving cell, resulting in the generation of a new nerve signal in that cell. Several types of dopamine receptors exist, including the DRD2 receptor. Furthermore, several variants (i.e., polymorphisms) of the DRD2 receptor exist.
