It is well known that alcohol acts as a general anxioloytic and that
anxiety and alcohol dependence frequently occur together. But the effect of
alcohol on anxiety has been difficult to pin down clinically, and reports in
the literature of this comorbidity are unclear about how and in whom it
Now scientists have identified a central amygdaloid signaling pathway
involved in anxiety-like and alcohol-drinking behavior in rats that sheds
light on the regulation of these two behaviors.
Subhash Pandey, Ph.D., an associate professor of psychiatry and director of
neuroscience and alcoholism research at the University of Illinois, and
colleagues in the Department of Psychiatry at the University of Illinois and
at the Jesse Brown VA Medical Center in Chicago found that rats bred to prefer
alcohol (P) showed more anxiety-like behavior and drank more than rats with no
preference for alcohol (NP).
A report of his study, which was funded by the National Institute on
Alcohol Abuse and Alcoholism (NIAAA), appears in the October 3 Journal of
Anxiety-like behavior was measured using a maze with open and closed arms:
the greater the "anxiety" level the longer time rats spent in the
Analysis of the rats' brains revealed that addicted rats had lower levels
of cAMP responsive element-binding protein (CREB) than NPY rats did. CREB or
cAMP in the central amygdala is associated with high anxiety and
alcohol-drinking behaviors. Also, levels of neuropeptide NPY were lower in
addicted rats. NPY regulates several neurotransmitters and plays a role in
anxiety and alcohol-drinking behaviors.
The coupling of CREB and NPY regulates NPY production.
More remarkably, drinking reduced anxiety-like behavior in addicted rats,
an effect associated with increased CREB function and NPY production. In
addition, administering compounds that promote CREB function and NPY
production also reduced anxiety and drinking in addicted rats.
More significantly, disrupting CREB function and NPY production in NP rats
provoked anxiety-like behavior and promoted drinking.
This is the first direct evidence that a hereditary deficiency of the CREB
protein is associated with high anxiety and drinking behaviors. Genetically,
high anxiety levels are important in the promotion of higher alcohol
consumption in humans, and drinking is a way for anxious people to
Pandey and his colleagues proposed that in nonaddicted rats, decreased
CREB-dependent NPY production might be a preexisting condition for anxiety and
"These experiments, conducted in rats selectively bred to have a high
affinity for alcohol, help us address questions about the potential role that
anxiety might play in human alcoholism," said NIAAA Director Ting-Kai
Li, M.D. "They may reveal potential targets for therapy of anxiety and
Psychiatric News asked addiction-research experts for their
reactions to the findings.
"Some individuals may drink to relieve preexisting stress, and this
study suggests that innately lower levels of CREB in parts of the amygdala may
identify these individuals," said Sarah Book, M.D., an assistant
professor of psychiatry at the Charleston Alcohol Research Center of the
Medical University of South Carolina.
"Drug development can then target an at-risk population of
individuals with an anxiety disorder who drink to cope with their anxiety.
Identification of at-risk populations who drink because alcohol 'normalizes'
an underlying anxiety disorder is a fruitful research area," she
Book said that in future work it would be important to see if similar
results are seen in this and in other animal models of anxiety. Her group, as
well as others, have proposed that using alcohol to ameliorate a negative
sensation such as anxiety (negative reinforcement) may explain why some
individuals with anxiety disorders develop alcohol dependence comorbid with
their preexisting anxiety disorder.
In a related commentary in the journal Gary Wand, M.D., wrote, "These
provocative data suggest that a CREB-dependent neuromechanism underlies high
anxiety-like and excessive alcohol-drinking behavior." Wand is a
professor of medicine and psychiatry and director of the Endocrine Training
Program at Johns Hopkins University School of Medicine.
He said that the data need to be replicated and then placed in context with
two other important neurotransmitter systems in the amygdala:
corticotropin-releasing factor-mediated (CRF-mediated) and GABA-mediated
"This is an outstanding finding and very interesting,"
commented George Koob, Ph.D., a professor of psychiatry and psychology at the
University of California at San Diego and director of the Division of
Psychopharmacology at Scripps Research Institute.
But Koob believes that Pandey has only one piece of the picture. Along with
Wand, Koob believes another factor that needs to be investigated is CRF, which
plays a role in the brain's ability to manage an internal response to daily
"CRF is just the opposite of NPY," he explained. "When
NPY goes down, CRF goes up, and vice versa. And we find that CRF antagonists
have some of the effects [Pandey] sees when he increases NPY."
While all the experts interviewed praised the study, some questioned the
pros and cons of extrapolating results in animal models to human behavior.
"Although the brain structures and the molecular events described may
help to understand human neurobiology, the capacity to model human drinking
behavior or alcohol's effects in humans through the use of rodent models is
limited," cautioned Henry Kranzler, M.D., a professor of psychiatry and
assistant dean for clinical research at the University of Connecticut School
For example, although the role of NPY is well established in feeding and
drinking behavior in rodents, Kranzler said the literature on its role in
human drinking behavior is much less clear. "Similarly, the modeling of
anxiety in rodents is limited, so the complex relations of anxiety and
drinking behavior in humans are, in my view, not adequately modeled in
rodents," he added.
"I think this is very exciting research, and it illuminates a
potential mechanism for one of the ways genetics may influence the likelihood
of alcoholism dependence," said Mark. Willenbring, M.D., director of
NIAAA's Division of Treatment and Recovery Research.
"There are multiple pathways to developing dependence and this may be
one of them. It certainly fits clinically, and there is a strong relationship
between anxiety disorders and heavy drinking," he said.
He explained that what is called "anxiety behavior" in animal
models is an inference, and researchers still do not know very much about how
that happens in humans. This is one of the limitations of using animal
"Deficits in Amygdaloid cAMP-Responsive Element-Binding
Protein Signaling Play a Role in Genetic Predisposition to Anxiety and
Alcoholism" can be accessed at<www.jci.org/cgi/search?fulltext=pandey&journalcode=jci>
by clicking on the article title. ▪