http://www.medicalnewstoday.com/med..hp?newsid=48127

Medical Cannabis Is A Blunt Tool

Article Date: 28 Jul 2006 - 0:00am (PDT)

IF anecdotes and ancient medicine are to be trusted, cannabis is a
wonder drug. Yet results of clinical trials have been mixed and its use
in modern medicine remains limited. Now it seems the reasons may be
practical as much as political and cultural: there are fundamental
problems with how our bodies respond to the stuff.

Some compounds in cannabis, including THC and cannabidiol, interfere
with a natural signalling system throughout our brains, nerves and
immune system. This system, which produces its own cannabis-like
compounds called endocannabinoids, plays a role in many medical
conditions including pain, epilepsy, multiple sclerosis, Parkinson's
disease, depression and schizophrenia.

Because the system is so widespread, smoking or ingesting cannabis is
bound to have varied effects, including its influence on the mind. Now
it seems that even with purified cannabis extracts, changing the
amount, time or place of a dose could produce completely opposite
effects on the body, according to evidence presented at the Federation
of European Neuroscience Societies (FENS) meeting in Vienna earlier
this month. This could explain why the medical benefits have proved so
difficult to harness.

In one study, Vincenzo Di Marzo of the National Research Council in
Pozzuoli, Italy, boosted levels of an endocannabinoid called
andandamide in rats engineered to develop an Alzheimer's-like disease.
This appeared to protect the rats from memory loss and nerve
degeneration. But if the rise was prolonged, cannabinoids became
ineffective or even damaging.

Beat Lutz of the university of Mainz in Germany found a similar paradox
in models of epilepsy in mice. Anandamide is synthesised during
epileptic fits, providing a natural calming effect. "If we apply
cannabinoids we should protect from seizures," says Lutz. "But no,
we actually get worsening of seizures in mice."

He believes he has found the reason. The main class of cannabinoid
receptor, called CB1 receptors, occurs in two distinct populations of
neurons, those that excite neighbouring neurons and those that inhibit
them - so cannabinoids can have opposite effects depending on which
neurons they hit. David Baker, a multiple sclerosis expert at
University college London has found the same problem in MS. Mice that
have been engineered to have a condition like MS and no CB1 receptors
suffer much worse nerve damage than those with normal CB1 receptors,
suggesting that cannabinoids are involved in protecting against the
nerve damage seen in MS. But other experiments in mice have shown that
cannabinoid signalling also prompts release of stress hormones called
glucocorticoids that can kill neurons.

The greatest anecdotal evidence for the medical benefits of cannabis
comes from its painkilling properties, and animal models have produced
promising results. Yet even here new evidence suggests that an
endocannabinoid called NADA binds not only to cannabinoid receptors but
to a completely different class of receptor as well, where it mimicks
the effect of a pain-producing chemical called capsaicin, says J.
Michael Walker of Indiana university in Bloomington, who also presented
his research at FENS. This may explain why human trials of cannabis for
the treatment of pain have produced mixed results.

"The problem with cannabis is that there's no way of targeting the
drug to any particular place," says Baker.

The answer will be to manipulate the system from within, he says. New
ways of amplifying natural cannabinoid release include reuptake
inhibitors that prolong this release just as Prozac does for serotonin.
Such methods look promising for a range of conditions from pain and
cancer to nerve degeneration and MS.

Other methods now being tried in the lab include the manipulation of
enzymes that make and deliver endocannabinoids, as well as compounds
that stimulate and block them. Drugs that bind to CB1 receptors and
alter their efficiency are also being discovered, says Roger Pertwee,
director of pharmacology at GW Pharmaceuticals, based in Porton Down
Science Park, Wiltshire, UK. His company developed Sativex, the first
pharmaceutical cannabis extract to gain clinical approval.

Ironically, the first offshoot of endocannabinoid research to gain
clinical approval, last month, has the opposite effect to cannabis:
Acomplia (rimonabant), an appetite suppressant, works by blocking CB1
receptors (New Scientist, 8 July, p 5).

About the NEW SCIENTIST

scientific publication

NEW SCIENTIST
Reed Business Information Limited,
151 Wardour St
London
W1F 8WE

enquiries@newscientist.com
http://www.newscientist.com

Report this post to a moderator

[  Post Follow-up to this message ]

Cowboy wrote:

> http://www.medicalnewstoday.com/med..hp?newsid=48127
>
> Medical Cannabis Is A Blunt Tool

I  agree.   It might surprise some people to hear me say that, but it's
true.

There's a problem nonetheless.. and it's this:

Cannabis is less toxic, has fewer side effects, and is physically and
psychologically better tolerated by the majority of its therapeutic users
than any other drug (with the exception of simple irritative bronchitis,
which can happen if it's smoked often - and there are many ways of using it
that will prevent this side-effect).   Even a US Drug Enforcement Agency
administrative Justice has declared..

"Marijuana is the safest therapeutically active substance known to man..
safer than many foods we commonly consume."
- DEA Judge Francis L. Young

Report this post to a moderator

[  Post Follow-up to this message ]