Cocaine in the Brain
The precise chemical action of cocaine in the brain is still being studied. Scientists hope that by understanding all of the minute chemical changes that take place - perhaps at the gene level - that they can discover better treatments for cocaine addiction.
The current understanding of cocaine's function in the brain has to do primarily with dopamine and serotonin, two neurotransmitters ("messenger" chemicals.) Dopamine is involved in the control of mood, motivation, cognition, locomotion, sexuality, and endocrine function. Among serotonin's functions are regulating mood, sleep, and learning.
Cocaine is a terribly powerful psychomotor stimulant. It stimulates the ventral tegmental area (VTA) of the brain, which triggers the nucleus accumbens - one of the brain's key pleasure centers. Cocaine produces its pleasurable effects primarily by blocking the dopamine transporter, another neurotransmitter that is responsible for balancing the level of dopamine in the brain. The transporter essentially recycles excess dopamine rather than allowing it to pool in the synapses (gaps) between neurons. The overload of dopamine in the pleasure centers of the brain leads to the pleasurable feelings (energy and euphoria.)
The more dopamine transporters that are blocked, the more intense the euphoria. Higher doses and faster routes of administration block more transporters and create vivid memories of pleasure from the drug and intense cravings. Because injection and smoking are faster methods of administration, they seem to be the most addicting methods of taking the drug.
Over time, a protein called delta-FosB builds up in the brain and contributes to addiction.