Dopamine: A Mulitfunctional Molecule
Dopamine is a multi-functional molecule.
Neuroscientists say there isn’t a single dopamine system, but three of them: 1) a midbrain system, which controls movement; 2) the Limbic reward system, which, in turn, has “liking” and “wanting” components (for more click on dopamine basics); and 3) one involving the frontal cortex, the site of information processing. (A possible fourth, involving wakefulness, has been proposed but remains controversial.)
The second and third of these systems are implicated in addiction, as they are responsible for “motivation, decision-making, pleasure seeking, inhibitory control and the way we learn and consolidate information and experiences, ” as well as “emotional response and feelings of pleasure and pain.”1
A severe lack of dopamine in the first of the systems, located in the mid-brain, is what is suspected to cause the uncontrollable body movements of Parkinson’s disease. (Ironically, the illegal drug ecstasy has been shown to be effective in treating some Parkinson’s patients.2) Conversely, an excess of dopamine is suspected to cause schizophrenia and may be implicated in Attention Deficit Hyperactivity Disorder (ADHD).3
1. An Anti-Addiction Pill.’, New York Times Magazine, Jun. 25, 2006.
2. Amphetamines Relieve Parkinson’s-Like Symptoms, Newsciencetech.com, July 24, 2006.
3. Study Reveals How ADHS Drugs Work in the Brain, medicalnewstoday.com, June 29, 2006.