Molecular model of a dopamine molecule (red) bound to a dopamine receptor D1 (blue) in a cell membrane (orange). D1 is the most abundant of the dopamine receptor subtypes in the central nervous system (CNS). Dopamine is one of the most important neurotransmitters in the CNS. It plays a critical role in the way the brain controls movement. Underproduction of dopamine results in the movement disorder Parkinson's disease. Excess dopamine may contribute to psychotic illnesses, notably schizophrenia. Dopamine also acts as a hormone, inhibiting the release of the hormone prolactin, which stimulates and maintains lactation, from the pituitary gland.