Dopamine neurotransmitter, molecular model. Dopamine is a chemical released by the brain as a neurotransmitter and a hormone. It has been intensively studied as it plays a crucial role in the brain's reward and pleasure pathways. It is released when a pleasurable new stimulus is encountered, and directs the brain to find more of the stimulus. For this reason it plays a significant role in addiction, not only to drugs that release or mimic dopamine (such as cocaine) but also to gambling and other social addictions. Lack of dopamine is linked to numerous disorders, such as Parkinson's disease, depression and schizophrenia.