MARIJUANA, COCAINE SHARE BRAIN TARGETS

NEW YORK (Reuters Health) - The same brain cell targets that respond to
marijuana are involved in the craving faced by cocaine addicts trying to
quit, scientists say. The finding may help doctors come up with ways stop
cocaine addiction, according to researchers from the Netherlands and the US
National Institute on Drug Abuse.

Dr. Taco De Vries from Vrije Universiteit in Amsterdam and associates
studied the role of the cannabinoid system--the parts of the brain involved
in our response to marijuana--to determine whether marijuana-like drugs or
their inactive mimics would affect cocaine-seeking behavior in rats.

SR141716A, a marijuana mimic that blocks the cannabinoid targets in the
brain, significantly blocked cocaine-seeking behavior brought on by
re-exposure to cocaine and by re-exposure to the cues associated with
cocaine use, the investigators found.

The mimic did not, however, reduce the cocaine-seeking behavior brought on
by stress, according to the report in the October issue of Nature Medicine.

In contrast, the researchers note, HU210 (a marijuana-like drug) actually
caused a return of cocaine-seeking behavior.

"The biggest problem of a drug addict is not the fact that he is taking
drugs, but what happens if he is not taking the drug--when he or she feels
the urge to take drugs," De Vries told Reuters Health.

"In our opinion," De Vries added, "medication should be directed to control
the drug-seeking part and not drug-taking part of this behavior."

But so far there is no such effective medication.

"Even though there are many social and psychological factors that can
facilitate relapse, an agent that 'takes the edge off' craving would
provide an invaluable complement to behavioral therapy and psychotherapy,"
adds Dr. Danielle Piomelli from University of California, Irvine, in a
related commentary.

"By unraveling the mechanisms in the brain that play a role in the
persistence of drug-seeking behavior, we will be able to develop medication
that may cure drug addicts," De Vries said.

SOURCE: Nature Medicine 2001;10:1099-1100, 1151-1154.