According to the latest research smoking tobacco may increase the chances of someone abusing cocaine later in life by priming the brain to be more receptive to the Class A drug.
The study comes from the National Institute on Drug Abuse in Maryland that is the first of its kind to show how nicotine can change the brain in a way that enhances the behavioral effects of cocaine. It could help explain why so many drug-using teenagers tend to start with cigarettes and alcohol before moving on to more illegal substances.
The proposition that taking legal drugs could make a person more vulnerable to illegal drugs has caused much controversy since it was first suggested in 1975. This is the first study to find a biological mechanism which could prove such a causal link does exist.
In the current study, researchers led by Dr. Amir Levine at Columbia University in New York, found mice exposed to nicotine through their drinking water for one week showed an increased response to cocaine. This priming effect depended on the previously unrecognized impact that nicotine made on gene expression. It was found to reprogram specific genes linked to addiction ultimately making the brain more responsive to harder drugs.
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 team found that the results paralleled findings in humans after they reexamined statistics from the 2003 National Epidemiological Study of Alcohol Related Consequences. They found that the rate of cocaine dependence was higher among cocaine users who smoked prior to starting cocaine compared to those who tried cocaine prior to smoking.
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.
The findings, published in Science Translational Medicine, suggest smoking prevention would not only prevent the damaging effects of the habit but could also decrease the risk of progression and addiction to cocaine and other illegal drugs. “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.
Senior author, Dr Eric Kandel, said, “Now that we have a mouse model of the actions of nicotine as a gateway drug this will allow us to explore the molecular mechanisms by which alcohol and marijuana might act as gateway drugs. In particular, we would be interested in knowing if there is a single, common mechanism for all gateway drugs or if each drug utilizes a distinct mechanism.”
“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.
Brain cells form multiple coordinate systems to guide behavioral actions