Nicotine
as a Gateway Drug
ScienceDaily (Nov. 2,
2011) — A landmark study
in mice identifies a biological mechanism that could help explain how tobacco
products could act as gateway drugs, increasing a person's future likelihood of
abusing cocaine and perhaps other drugs as well, according to the National
Institute on Drug Abuse (NIDA), part of the National Institutes of Health. The
study is the first to show that nicotine might prime the brain to enhance the
behavioral effects of cocaine.
The gateway drug model
is based upon epidemiological evidence that most illicit drug users report use
of tobacco products or alcohol prior to illicit drug use. This model has
generated significant controversy over the years, mostly relating to whether
prior drug exposure (to nicotine, alcohol or marijuana) is causally related to
later drug use. Before now, studies have not been able to show a biological
mechanism by which nicotine exposure could increase vulnerability to illicit
drug use.
In the current study, by
researchers at Columbia University, New York City, and published in Science
Translational Medicine, mice exposed to nicotine in their drinking water
for at least seven days showed an increased response to cocaine. This priming
effect depended on a previously unrecognized effect of nicotine on gene
expression, in which nicotine changes the structure of the tightly packaged DNA
molecule, reprograms the expression pattern of specific genes, in particular
the FosB gene that has been related to addiction, and ultimately alters the
behavioral response to cocaine.
To examine whether the
results from this study paralleled findings in humans, the researchers
reexamined statistics from the 2003 National Epidemiological Study of Alcohol
Related Consequences to explore the relationship between onset of nicotine use
and degree of cocaine dependence. 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.
These findings in mice
suggest that if nicotine has similar effects in humans, effective smoking
prevention efforts would not only prevent the negative health consequences
associated with smoking but could also decrease the risk of progression and
addiction to cocaine and possibly other illicit drug use. In the meantime, this
mouse model provides a new mechanism to study the gateway theory from a
biological perspective.
"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," said Eric Kandel, M.D., of Columbia University Medical
Center and a senior author of the study. "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."
For more information on
nicotine and cocaine, go towww.drugabuse.gov/drugpages/nicotine.html andwww.drugabuse.gov/drugpages/cocaine.html.
http://www.sciencedaily.com/releases/2011/11/111102161259.htmNicotine as a Gateway Drug
