Brain-imaging study offers clues to inhalant abuse—huffing
These baboon brain scans show where toluene, a common solvent, goes in the brain two minutes after it was injected into the animals. The red end of the scale indicates the highest concentration. The image on the left shows that toluene quickly enters the brain's striatal region (arrows), the area directly associated with reward and pleasure. The image on the right shows toluene entering deep cerebellar nuclei, the brain region involved in voluntary movement. These findings are in agreement with clinical evidence that toluene abusers ("huffers") experience a rapid "high," and also suffer neurological symptoms such as ataxia (lack of coordination) and slurred speech.
First images of inhalants in the brain reveal why solvents may be so addictive, in a Department of Energy
Brookhaven National Laboratory study, which will appear in the April 26 issue of the journal Life Sciences.
April 22, 2002—Inhalant abuse, also known as "huffing," is a rapidly growing health problem,
particularly among young people. However, little is known about how inhaled chemicals affect the brain
and body. Now, scientists at the Brookhaven National Laboratory—inspired by schoolchildren who
wanted to know more about huffing—have produced the first-ever images showing what parts of the
brain and body are most affected by toluene, a commonly inhaled solvent. The study, which was
performed in baboons and mice, appears in the April 26 issue of the journal Life Sciences (available
online April 15).
The images show that toluene moves into the brain rapidly and initially affects the same brain regions as cocaine and other
abused drugs. Then, toluene spreads more generally to the entire brain before clearing the body rapidly via the kidneys.
"This affinity for brain regions associated with reward and pleasure, as
well as the quick uptake and clearance, may help to explain why
inhalants are so commonly abused," said lead author Madina
Gerasimov, a Brookhaven chemist.
"For the first time, we have shown in living animals where the most
commonly used solvent goes in the brain and the whole body," said
Brookhaven neuroanatomist Stephen Dewey, a coauthor.
"This study was really born out of my going to elementary schools,
where I've been giving talks about Brookhaven's addiction research
since 1995," said Dewey. During his talks, children as young as fourth
and fifth graders would sometimes ask him about huffing. "After about
the third or fourth time someone asked me, I proposed that we develop
a way to label and image solvents, which seem to be a 'gateway' drug
of abuse for some young children," he said.
The team chose toluene because it is one of the most common industrial solvents, found in paints, glues, and other household
products often abused by huffers. To label the toluene, Brookhaven chemists replaced some of the compound's carbon atoms
with a radioactive isotope, carbon-11. This radiolabeled toluene was then injected into the experimental animals. (The scientists
used injection rather than inhalation as an administration route so that they would know precisely how much toluene the animals
The level of the radioisotope was then measured using a positron emission tomography (PET) camera, which picks up the
radioactive signal, shows exactly where the toluene is located in the body, and tracks its location over time. Other
tissue-sampling methods were used to track the toluene as well.
The scientists were surprised by the findings. "I couldn't believe it," Dewey said. "The theory has always been that the effects of
solvents would not be very specific—that if you breathe them in they'd go everywhere equally," he said. "But, in fact, it looks like
there's a regional distribution. They go to specific regions associated with reward and pleasure, just like other abused drugs.
Then over time, they redistribute."
The initial specificity for the brain's reward centers may help to explain the addictive potential of inhalants, while the redistribution
to the entire brain seems to mirror clinical changes observed in huffers. Unlike other drug abusers, who have damage in the
reward centers, Dewey explained, "huffers have a much more global disease," with changes in areas of the brain that may
interrupt normal learning and memory more quickly than other drugs.
In addition to offering insight into the nature and effects of inhalant abuse, Gerasimov said this study is also a technical advance in
radiochemistry. "It's the first time chemists have labeled and purified a solvent for imaging," she said. This may open up a whole
new field of study into the effects of a wide array of solvents found in common, everyday products from cleaning fluids to
"There isn't a person among us who isn't exposed to solvents," Dewey said.
The Brookhaven team is already applying for grants to study other inhalants, first in animals and then in humans. They are also
working to develop a method to study these chemicals in inhaled as well as injected form to further their understanding of the
mechanisms.—by Karen McNulty Walsh
Media contacts: Karen McNulty Walsh, Brookhaven National Laboratory, (631) 344-8350, email@example.com Mona S. Rowe, Brookhaven National Laboratory, (631) 344-5056, firstname.lastname@example.org Technical contacts: Stephen Dewey, Brookhaven National Laboratory, email@example.com Madina Gerasimov, Brookhaven, National Laboratory, firstname.lastname@example.org
Related Web Links
For Parents: "What Every Parent Should Know About Inhalent
Abuse," by Stephen Dewey, Brookhaven National Laboratory
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Author: Karen McNulty Walsh,
a Senior Public Affairs Representative at Brookhaven
National Laboratory since September 1999, has an
MA in science journalism from New York University
and a BA in biology from Vassar College. She was
previously the editor of Science World,
a science magazine for middle-school children, and
Zillions, a kids' version of Consumer
Reports. For more science news, see see Brookhaven's
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