Nicotine may strengthen an individual's response to cocaine. (Spencer Platt / Getty Images )
Nicotine appears to be a potent "gateway" drug that enhances the effects of cocaine and possibly boosts the chances of becoming addicted, researchers reported Wednesday in a landmark paper on drug addiction.
While the study was performed in lowly mice, the findings suggest that reducing smoking and the use of other tobacco products -- and even nicotine replacement products and exposure to secondhand smoke -- in humans may have the bilateral impact of curbing addiction to other addictive substances.
"If our findings in mice apply to humans, a decrease in smoking rates in young people would be expected to lead to a decrease in cocaine addiction," the authors wrote.
Researchers led by Dr. Amir Levine at Columbia University in New York treated mice with nicotine and then exposed them to cocaine. The mice whose brains had been exposed to nicotine responded differently to the cocaine (exhibiting more characteristics of addiction) compared to mice who weren't exposed first to nicotine. Reversing the order of the drugs by exposing mice to cocaine first then nicotine had no such effect on behavior.
Further, the study demonstrated that nicotine influences substances called histone proteins in the reward center of the brain that in turn activates certain genes and leads to an exaggerated response to cocaine.
The research needs to be confirmed and raises many questions. But the implications are numerous and profound, such as whether reduced nicotine usage would lower the rates of other drug addictions. In a related analysis, Levine and his colleagues reviewed data on cocaine use among a group of high school students. They found that 81% of the youths who started using cocaine did so in a month when they were actively smoking tobacco and only 18.8% did so when they were not smoking.
Moreover, treatment of nicotine addiction may help promote recovery of cocaine addiction, the authors note. Currently, many individuals in substance-abuse recovery programs who also smoke are prescribed nicotine-replacement products to help them quit smoking. But behavioral smoking cessation strategies may be more appropriate if nicotine is actually augmenting cocaine addiction.
Finally, do the findings of this study apply to other gateway drugs? It's not clear if the relationship is specific to nicotine and cocaine or whether alcohol and marijuana -- substances that are also described as gateway drugs because they are typically used prior to experimentation with other drugs -- bolster the risk of addiction as well.
"One wonders whether the prevailing focus on marijuana as a putative premier precursor drug might have kept researchers from more seriously exploring the possibility that nicotine -- which is, in fact, one of the two drugs (the other being alcohol) that children and adolescents are most likely to obtain first -- could have a strong claim to that moniker," said Dr. Nora Volkow, director of the National Institute on Drug Abuse, in a commentary accompanying the study.
The papers are published in the journal Science Translational Medicine.
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