SCIENTISTS CRACK 'MUNCHIES' MYSTERY

To those, who, unlike one former US president, did inhale, the effects
of smoking cannabis are well known.

A powerful urge to eat, sometimes known as the munchies, is one common
side effect of taking the illegal drug.

But now scientists have a much clearer picture of why cannabis does
this.

They have discovered that natural relatives of the active ingredient
in cannabis play an important role in regulating appetite.

"We know that smoking cannabis stimulates the appetite, but we were
wondering whether the substances in the brain which work on the same
receptors would have the same effect on appetite," explained Dr George
Kunos.

Dr Kunos is scientific director of the National Institute on Alcohol
Abuse and Alcoholism at the National Institutes of Health in the
United States.

Together with colleagues from Italy, Japan and the US, he found that,
just like cannabis, natural endocannabinoids did indeed stimulate the
appetite.

Mice Studies

He and his colleagues found that mice bred without cannabinoid
receptors did not eat very much, even after being deprived of food.

Normal mice, on the other hand, would eat to compensate for periods of
starvation.

The research also linked cannabinoid levels to leptin, a hormone known
to suppress the appetite and produced by fatty tissue in the body.

When mice get fatter, leptin levels rise and cannabinoid levels fall,
reducing the appetite, it seems.

But there were some surprises.

Complex System

The team found that the regulation of appetite depends on other
mechanisms, too.

Some of the mice they tested should have stayed thin, but developed
alternative ways of compensating for their missing receptors and
regained their appetites.

"Perhaps appetite is such an important matter that the body does not
entrust it to just one pathway," he told BBC News Online.

The implications for drugs to treat appetite problems are
clear:

"If we want to control appetite therapeutically then we have to knock
out more than one pathway.

"Leptin was disappointing in clinical trials," he said.

Natural alternative?

The active ingredient in cannabis is licensed for prescription in the
United States, but as Dr Konos says, it has unwanted psychoactive effects.

"What would make sense would be to try and boost natural levels of
cannabinoids, for instance by blocking the enzyme which degrades
them," he said.

The research is published in the scientific journal Nature.