Dopamine is an organic chemical that plays several important roles in the brain and body. In the brain, dopamine functions as a neurotransmitter — a chemical released by neurons (nerve cells) to send signals to other nerve cells. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior.
The anticipation of most types of rewards increase the level of dopamine in the brain, and many addictive drugs increase dopamine neuronal activity. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory.