Dopamine neurotransmitter molecule. Computer model showing the molecular structure of the human neurotransmitter and hormone dopamine. Dopamine plays a crucial role in the brain's reward and pleasure pathways. It is released by the brain when a pleasurable new stimulus is encountered, and directs the brain to find more of the stimulus. As such it plays a significant role in addiction. Lack of dopamine is linked to numerous disorders, such as Parkinson's disease, depression and schizophrenia. Atoms are represented as spheres and are colour-coded: carbon (black), hydrogen (white), nitrogen (blue) and oxygen (red).