SCIENCE TAKES A POT-SHOT AT THE MUNCHIES

Scientists have found that marijuana-like substances naturally produced in
the brain stimulate appetite - a finding that not only offers clues to
treating obesity but also explains why pot smokers get the "munchies".

The study suggests these endocannabinoids are part of the brain's complex
system controlling when and how much to eat.

Scientists have known for several years about the existence of these
substances, which are similar to the active ingredient in marijuana but do
not make people high. However, their exact role in the brain was unclear.

In a study published in the latest issue of the journal Nature, researchers
found mice that had been genetically altered so they could not respond to
endocannabinoids ate less than normal mice did. The mice lacked "receptor"
structures that endocannabinoids activate in the brain.

And when ordinary mice were given a substance that blocked endocannabinoids
from acting at these receptors, they ate less than normal as well.

The findings help explain why marijuana users get a ravenous hunger - the
"munchies" - after smoking pot.

"We know that the marijuana that gets absorbed activates these receptors,
and now we show that activation of these receptors is involved in the
increase of appetite," said Dr George Kunos, who led the study as
scientific director of the National Institute on Alcohol Abuse and
Alcoholism at the National Institutes of Health. "It was assumed that was
probably correct. This just provides the evidence."

Dr Kunos said the study also suggested endocannabinoids were part of the
complex neural circuitry controlled by leptin, a hormone that tells the
brain when it is time to lose weight. Already, leptin is known to reduce
levels of several other appetite-enhancing substances.

It is unknown how endocannabinoids are created by the body, or precisely
how they work. But the study found they can operate independently of the
level of certain other appetite-triggering substances.

That suggests it is unlikely that efforts to control weight gain or loss
with any single drug will be effective, Dr Kunos said.

Others agreed.

"It suggests that it will probably not be possible to deliver, in a
pharmaceutical sense, a single magic bullet or knockout punch against these
systems in the brain, since they are so highly redundant and backed up,"
said Dr Rudy Leibel, head of molecular genetics at Columbia University.