DRUG COULD BLOCK CANNABIS 'HIGH'

The psychoactive effects of cannabis could be blocked Scientists have found
a way to stop cannabis users feeling the key mood changes associated with
the drug.

Medication produced from this chemical could help relieve any psychological
dependence felt by cannabis users trying to stop taking it, the researchers
say.

Cannabis works by releasing chemicals which can bind to "receptor sites" in
the brain, in turn leading to the release of mood-altering chemicals within
the organ.

These "cannabinoid receptors" are densely packed in the regions of the
brain concerned with learning and memory, attention and control of movement.

Dr Marilyn Huestis at the National Institute on Drug Abuse in Baltimore,
tested the effects of a chemical developed to block these receptor sites,
preventing the cannabinoids from reaching their target.

Volunteers were either given the "blocking" chemical, or a dud placebo, and
then smoked one marijuana cigarette.

Those who had taken the blocking formula showed significantly reduced
marijuana effects.

Increasing doses of the chemical appeared to have an increasing effect on
the sensation associated with cannabis.

Other physical effects of cannabis were reduced.

Volunteers given the highest dose of the chemical had an increase in heart
rate, but only 59% of what might be expected if cannabis alone had been taken.

Dr Alan Leshner, the director of the National Institute on Drug Abuse,
said: "This research helps point the way toward possible treatment for
those addicted to marijuana and perhaps may be useful in finding effective
treatments for other disorders related to the cannabinoid system."

Controversial theories

The long-term effects of cannabis on the body are still a matter of
controversy.

While researchers at the NIDA have released studies which they say point to
the possibility of physical addiction to the drug, other scientists say
that this is impossible.

A spokesman for the UK advice group Drugscope said a degree of
psychological addiction was present in some users, but no more than this.

He said: "Some users find that they rely on cannabis to get them through
the day, but there is no physical dependency to the drug.

"If this chemical helps release them from this psychological bond, then it
might be of some use."

Medications already exist to help wean addicts off drugs such as heroin by
making them feel desperately ill should they take the drug while the
medicine is in their body.