Dopamine is a neurotransmitter, a chemical released by neurons, that sends signals to other nerve cells. Dopamine helps control the brain’s reward and pleasure centers. Within the brain, dopamine levels affect motivation, reinforcement, reward, and sexual gratification. Low dopamine levels may make one more prone to addiction. Dopamine also helps regulate movement. The loss of dopamine neurons in the brain’s area called the substantia nigra causes the symptoms of Parkinson’s disease.