'HUFFING' SOLVENT HEADS RIGHT FOR BRAIN

Scientists using brain-imaging techniques have found that a solvent
commonly abused by youngsters behaves much the same as other addictive
drugs, heading straight for the region of the brain known to be linked to
reward and pleasure.

Images taken of the brains of baboons and mice as they absorbed the solvent
toluene found it first hits the same spot as cocaine and other abused drugs
before spreading generally to the entire brain and then being rapidly
dispersed through the kidneys.

"This affinity for brain regions associated with reward and pleasure, as
well as quick uptake and clearance, may help to explain why inhalants are
so commonly abused," said Madina Gerasimov, a chemist at the U.S.
Department of Energy's Brookhaven National Lab in Upton, N.Y. and lead
author of the new research, reported today in the journal Life Sciences.

According to the National Institute on Drug Abuse, 6 percent of American
children have tried inhalants by fourth grade, and 20 percent by eighth grade.

"For the first time, we've shown in living animals where the most commonly
used solvent goes in the brain and the whole body," added Steven Dewey, a
neuroanatomist at Brookhaven and a coauthor of the study.

The team used toluene because it's among the most common industrial
solvents, used in paints, glues and other household products often abused
by inhaling or "huffing," a dangerous habit often involving children in
late elementary and middle school.

To label the solvent for imaging, the chemists replaced some of the
compound's carbon atoms with a radioactive isotope, and then injected the
substance into the experimental animals. The material was injected rather
than inhaled so the scientists could know exactly how much each animal took in.

Then the solvent was tracked using a positron emission tomography camera,
which follows the radioactive signal and shows exactly where the toluene is
located in the body over a period of time. Other tissue samples were taken
to track the movement of toluene as well.

"The theory has always been that the effects of solvents would not be very
specific -- that if you breathed them, they'd go everywhere equally," Dewey
said. "But in fact it looks like there's a regional distribution. They go
to specific reward and pleasure region, just like other abused drugs."

This initial attraction to the brain's reward centers may help explain the
addictive pattern of huffers, while the later redistribution to the entire
brain may help explain the changes and damage observed in huffers. Abuse
can bring about not only brain damage but kidney failure, cardiac arrest
and other life-threatening conditions.

"Huffers have a much more global disease" with changes in brain areas that
may interrupt normal learning and memory more than other drugs, Dewey said.

Gerasimov said besides offering new understanding about the nature and
effects of inhalant abuse, it also represents a technical advance in
radiochemistry. "It's the first time we've been able to label and purify 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 hairsprays. "There isn't a person among us who isn't exposed to
solvents," Gerasimov said.

The researchers are now seeking grants to study other inhalants in animals
and humans, while also seeking to set of a technique where the chemicals
can be inhaled as well as injected before imaging in order to better
understand the mechanisms at work.