Why Nicotine Appeals To Some And Repels Others
Researchers in Canada claim to have found regions of the brain that may explain why some people can become addicted to nicotine after their first cigarette.
Scientists were able to manipulate brain cells in rats to control which rats in the study enjoyed their first exposure to nicotine and which were repelled by it.
Researchers hope their new findings may open the door for new treatments of nicotine addiction.
"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 Dr. Steven Laviolette of the University of Western Ontario, who reported his findings in the Journal of Neuroscience.
Previous studies have been able to find certain reasons why some people get hooked after their first cigarette and others do not. A study published last October in the journal Pediatrics, found teens who felt relaxed after their first drags on a cigarette were far more likely to become addicted to smoking.
"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," Laviolette said.
Researchers sought to discover an explanation for the difference by studying the brains of lab rats, which have similar brain structures to humans.
They found two areas in the reward circuit of the brain called nucleus accumbens. They found specific receptors of the message-carrying chemical dopamine in the core and shell of the nucleus accumbens controlled whether the rats enjoyed or were repelled by nicotine.
When the researchers blocked two types of dopamine receptors — D-1 and D-2 — with drugs delivered to these areas of the nucleus accumbens, the rats experienced nicotine as a positive, rewarding experience.
"We were able to switch nicotine’s aversive effects to rewarding effects," Laviolette said.
Perhaps more importantly, the researchers also were able to reverse this process, making the nicotine unpleasant in rats that had the equivalent of a "pack-a-day" nicotine addiction.
These areas also played a role in nicotine withdrawal symptoms, researchers noted. That discovery could be crucial to new methods aimed at helping people kick the habit.
"If we can develop pharmacological treatments to target those regions, we can basically affect the development of nicotine addiction by controlling the brain’s perception of nicotine’s rewarding effects," Laviolette said.
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