Brain Pathway Yields Clues to Cigarette Addiction

TUESDAY, Aug. 5 (HealthDay News) -- New insight into how the brain processes the rewarding and addictive properties of nicotine sheds light on why some people seem to become addicted once they have their first cigarette, say Canadian researchers.

"Nicotine interacts with a variety of neurochemical pathways within the brain to produce its rewarding and addictive effects. However, during the early phase of tobacco exposure, many individuals find nicotine highly unpleasant and aversive, whereas others may become rapidly dependent on nicotine and find it highly rewarding. We wanted to explore that difference," study leader Steven Laviolette, of the department of anatomy and cell biology at the Schulich School of Medicine & Dentistry, University of Western Ontario, said in a university news release.

One brain pathway in particular uses the neurotransmitter dopamine to transmit signals related to nicotine's rewarding properties, the researchers noted. This pathway -- the mesolimbic dopamine system -- also plays a role in addiction to a number of other substances, such as alcohol and cocaine.

"While much progress has been made in understanding how the brain processes the rewarding effects of nicotine after the dependence is established, very little is known about how the mesolimbic dopamine system may control the initial vulnerability to nicotine; that is, why do some individuals become quickly addicted to nicotine while others do not, and in some cases, even find nicotine to be highly aversive," Laviolette said.

He and his colleagues identified the specific dopamine receptor subtype that controls the brain's initial sensitivity to nicotine's rewarding and addictive properties. In addition, the researchers were able to manipulate these receptors to control whether nicotine is processed as rewarding or unpleasant.

The findings could lead to new therapies to prevent nicotine addiction and to treat nicotine withdrawal when smokers try to kick the habit.

The study was published in the current issue of theJournal of Neuroscience.

More information

The U.S. National Institute on Drug Abuse has more about cigarettes and other tobacco products.

SOURCE: University of Western Ontario, news release, Aug. 5, 2008