While being one of the oldest drugs known to mankind, we know relatively little about the effects of Cocaine on the human brain - and the processes that lead to addiction in some users. Dr. Marco Leyton, of the Montreal Neurological Institute (MNI), McGill University and the McGill University Health Centre, published an article in the journal Biological Psychiatry on May 15, 2009, that not only demonstrates a link between cocaine and the reward circuits in the brain, but also associates the susceptibility to addiction with these mechanisms.

Dr. Leyton administered cocaine, via insufflation (snorting), and a placebo powder on alternating days, to ten, non-addicted participants. Blood tests were taken both before and after taking the drug, and PET (Positron emission tomography) scans were used to measure the dopamine release in the brain of the subjects - as dopamine is known to play a critical role in the brain's response to reward as well as in its response to addictive drugs.

The results of this study showed that sniffing cocaine triggers high levels of dopamine secretion in a central region of the brain called the striatum.

"The ability of cocaine to activate dopamine release varies markedly from person to person. Our study suggests that this is related to how much of the drug the person consumed in the past," explained Dr. Leyton. The more cocaine someone has used in his or her lifetime, the more the brain will secrete dopamine during subsequent cocaine use. "It's possible therefore that the intensity of the reward-circuit response is related to increased susceptibility to addiction," stated Dr. Leyton.

Although their study revealed the relationship between the frequency of drug use, and the intensity of the dopamine secretion observed - the researchers still do not understand the mechanism of action. "Is it the repeated stimulation of the reward circuit that leads to addiction, or is it an inherent sensitivity to addiction that leads to the increased secretion of dopamine?" With other factors (like the subject's personal history) coming into play, this question becomes more difficult to answer.

Whatever the answer, the relationship between dopamine and cocaine means that this hormone could be a potential target for treatment against addiction. More research is required before treatments are available, but this study opens a new door in this direction.

Source: http://www.muhc.ca/