|Same Genes May Underlie Alcohol and Nicotine Co-Abuse
Vulnerability to both alcohol and nicotine abuse may be influenced by the same
genetic factor, according to a recent study supported by the National Institute
on Alcohol Abuse and Alcoholism (NIAAA), part of the National Institutes of Health
In the study, two genetically distinct kinds of rat — one an innately heavy-drinking
strain bred to prefer alcohol (“P” rats), the other strain bred to not prefer
alcohol (“NP” rats) — learned to give themselves nicotine injections by pressing
a lever. Researchers found that P rats took more than twice as much nicotine
as NP rats. Their findings were reported recently in the Journal of Neuroscience.
"Our findings suggest that the genetic factor underlying the high alcohol consumption
seen in P rats may also contribute to their affinity for nicotine," said lead
author A.D. Lê, Ph.D., a NIAAA-supported researcher at Toronto's Centre for Addiction
and Mental Health and University of Toronto.
Researchers have known for some time that people who smoke are more likely
to drink alcohol than non-smokers. Similarly, smoking is three times more common
in people with alcoholism than in the general population. Since previous studies
have also determined that genetics plays an important role in both alcohol and
nicotine addictions, researchers have hypothesized that the same gene or genes
may influence the co-abuse of these substances.
Investigating this hypothesis in human studies is stymied by the possibility
that alcohol use leads to nicotine use, and vice versa. However, in the current
study, researchers showed that the P rats’ affinity for nicotine could be demonstrated
before the animals were ever exposed to alcohol.
P rats were also found to be more vulnerable to nicotine relapse than NP rats.
Researchers withheld nicotine from the rats until their lever pressing occurred
infrequently. Then, both P and NP rats were given a single nicotine injection.
P rats, but not NP rats, resumed pressing the lever previously associated with
The researchers also showed that the P rats’ apparent genetic vulnerability
to alcohol and nicotine does not appear to extend to other drugs of abuse. When
P and NP rats learned to press a lever to receive cocaine, each group took about
the same amount of that drug. The authors note that the lack of a difference
in cocaine self-administration indicates that the difference between P and NP
rats in nicotine self-administration is not due to a general “reward deficit” in
“Selectively-bred P rats have been a reliable and useful animal model for studying
diverse behavioral and physiological characteristics of alcohol abuse,” notes
NIAAA Director and study co-author Ting-Kai Li, M.D. “These findings suggest
that they may be as useful for studying nicotine addiction. And by expanding
our knowledge of the genetic underpinnings of alcohol and nicotine co-morbidity
these findings will inform our efforts to address those important public health
Other co-authors included Drs. Z. Li, D. Funk, and M. Shram, of the Centre for
Addiction and Mental Health, and Dr. Yavin Shaham of the Behavioral Neuroscience
Branch, National Institute on Drug Abuse, part of the National Institutes of
The National Institute on Alcohol Abuse and Alcoholism, part of the National
Institutes of Health, is the primary U.S. agency for conducting and supporting
research on the causes, consequences, prevention, and treatment of alcohol
abuse, alcoholism, and alcohol problems and disseminates research findings
to general, professional, and academic audiences. Additional alcohol research
information and publications are available at www.niaaa.nih.gov.
The National Institutes of Health (NIH) — The Nation's Medical Research
Agency — includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. It is the primary federal
agency for conducting and supporting basic, clinical and translational medical
research, and it investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.