From Wikipedia, the free encyclopedia. A dopamine antagonist is a drug which blocks dopamine receptors by receptor antagonism. There are five known types of dopamine receptors in the human body; they are found in the brain, peripheral nervous system, blood vessels, gastrointestinal tract and the kidney.here are five known types of dopamine receptors in the human body; they are found in the brain, peripheral nervous system, blood vessels, gastrointestinal tract and the kidney.