Clues to why some smokers get hooked at first puff

Toronto, Aug 7 : Canadian researchers have found clues to why some people get hooked to smoking with their first puff.

New research by the University of Western Ontario at London, about 120 km south of Toronto, is likely to lead to new therapies to help smokers give up the habit.

Steven Laviolette of the department of anatomy and cell biology at this famous university, who led the search, said: "Nicotine interacts with a variety of neuro-chemical pathways within the brain to produce its rewarding and addictive effects."

However, during the early phase of exposure to tobacco, he said, 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," he added.

In their search for answer to this, the researchers found one brain pathway that particularly uses the neurotransmitter dopamine to transmit signals related to nicotine's rewarding properties.

Laviolette said this pathway is called the mesolimbic dopamine system and is involved in the addictive properties of many drugs 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," he said.

Laviolette said his team first identified which specific dopamine receptor subtype controlled the brain's initial sensitivity to nicotine's rewarding and addictive properties. Then they were able to manipulate the receptors to control whether the nicotine was 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 research was published in Journal of Neuroscience Wednesday.