For many, the first fag is just for the sake of trying out smoking, but for some, this first puff turns out to be a life time of addiction. Scientists have now attributed this tendency to the brain's procession of 'rewarding' and addictive properties of nicotine.
In their new study, researchers at The University of Western Ontario have said that the mechanism behind the brain's processing of the 'rewarding' and addictive properties of nicotine, may explain why some people seemingly become hooked with their first smoke.
Led by Steven Laviolette of the Department of Anatomy and Cell Biology at the Schulich School of Medicine & Dentistry, the study could lead to new therapies to prevent nicotine dependence and to treat nicotine withdrawal when smokers try to quit.
"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," explained Laviolette.
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The scientists particularly found one brain pathway that uses the neurotransmitter 'dopamine' to transmit signals related to nicotine's rewarding properties.
This pathway is called the 'mesolimbic' dopamine system and is involved in the addictive properties of many drugs of abuse, including cocaine, alcohol and nicotine.
"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," said Laviolette.The team then identified which specific dopamine receptor subtype controlled the brain's initial sensitivity to nicotine's rewarding and addictive properties and were able to manipulate these receptors to control whether the nicotine is processed as rewarding or aversive.
"Importantly, our findings may explain an individual's vulnerability to nicotine addiction, and may point to new pharmacological treatments for the prevention of it, and the treatment of nicotine withdrawal," said Laviolette.
The paper is published in the latest issue of the Journal of Neuroscience.