Dopamine.
Dopamine is one of the neurotransmitters in the brain that play a major role in addiction. It affects brain processes that control movement, emotional response, and ability to experience pleasure and pain, similar to adrenaline, another chemical messenger. People who use drugs, including alcohol, do so because they like what the drugs do to their brains. All drugs of abuse from alcohol to nicotine to heroin cause a series of temporary changes in the brain that produce the "high." One of these changes is the rise in available levels of certain neurotransmitters associated with feelings of pleasure. Among these is dopamine. (Deth, 2000) The pleasure of a favorite Tv show, or a bowl of favorite ice cream may all be related to a rise in dopamine levels in the normal person's brain. Drugs of abuse also boost dopamine levels. When a person takes a hit of crack cocaine or a cigarette, these drugs cause a spike in dopamine levels in the brain, and a rush of euphoria and pleasure. While it is not the only chemical involved in drug abuse, experts believe that dopamine is a major one. Regulation of dopamine plays a major part in our mental and physical health. (Nash, 2000) Neurons containing neurotransmitter dopamine are located in the midbrain in an area called the substantia nigra. In Parkinson's disease the dopamine transmitting neurons in this area die. As a result, the brains of people with Parkinson's disease almost have no dopamine. To help relieve their symptoms, L-DOPA, a drug that can be converted in the brain to dopamine is given to them.(Greenfield, 2001).
Cocaine and other abused drugs can alter dopamine function. These drugs may have different actions. The specific action depends on which dopamine receptors the drugs stimulate or block and how well they mimic dopamine. These drugs produce their effects by changing the flow of neurotransmitters.