[Mb-civic] weed - it's good for the brain!

[Jonathon B]

By DAWN WALTON 

Friday, October 14, 2005 Posted at 3:57 AM EDT

>From Friday's Globe and Mail
 
 Calgary — Forget the stereotype about dopey potheads.
It seems marijuana could be good for your brain.

While other studies have shown that periodic use of
marijuana can cause memory loss and impair learning
and a host of other health problems down the road, new
research suggests the drug could have some benefits
when administered regularly in a highly potent form. 

Most "drugs of abuse" such as alcohol, heroin, cocaine
and nicotine suppress growth of new brain cells.
However, researchers found that cannabinoids promoted
generation of new neurons in rats' hippocampuses.

Hippocampuses are the part of the brain responsible
for learning and memory, and the study held true for
either plant-derived or the synthetic version of
cannabinoids.

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"This is quite a surprise," said Xia Zhang, an
associate professor with the Neuropsychiatry Research
Unit at the University of Saskatchewan in Saskatoon.

"Chronic use of marijuana may actually improve
learning memory when the new neurons in the
hippocampus can mature in two or three months," he
added.

The research by Dr. Zhang and a team of international
researchers is to be published in the November issue
of the Journal of Clinical Investigation, but their
findings are on-line now.

The scientists also noticed that cannabinoids curbed
depression and anxiety, which Dr. Zhang says, suggests
a correlation between neurogenesis and mood swings.
(Or, it at least partly explains the feelings of
relaxation and euphoria of a pot-induced high.)

Other scientists have suggested that depression is
triggered when too few new brain cells are created in
the hippocampus. One researcher of neuropharmacology
said he was "puzzled" by the findings. 

As enthusiastic as Dr. Zhang is about the potential
health benefits, he warns against running out for a
toke in a bid to beef up brain power or calm nerves.

The team injected laboratory rats with a synthetic
substance called HU-210, which is similar, but 100
times as potent as THC (delta-9-tetrahydrocannabinol),
the compound responsible for giving marijuana users a
high.

They found that the rats treated regularly with a high
dose of HU-210 -- twice a day for 10 days -- showed
growth of neurons in the hippocampus. The researchers
don't know if pot, which isn't as pure as the
lab-produced version, would have the same effect. 

"There's a big gap between rats and humans," Dr. Zhang
points out. 

But there is a lot of interest -- and controversy --
around the use of cannabinoids to improve human
health. 

Cannabinoids, such as marijuana and hashish, have been
used to address pain, nausea, vomiting, seizures
caused by epilepsy, ischemic stroke, cerebral trauma,
tumours, multiple sclerosis and a host of other
maladies.

There are herbal cannabinoids, which come from the
cannabis plant, and the bodies of humans and animals
produce endogenous cannabinoids. The substance can
also be designed in the lab.

Cannabinoids can trigger the body's two cannabinoid
receptors, which control the activity of various cells
in the body.

One receptor, known as CB1, is found primarily in the
brain. The other receptor, CB2, was thought to be
found only in the immune system.

However, in a separate study to be published today in
the journal Science, a group of international
researchers have located the CB2 receptor in the brain
stems of rats, mice and ferrets. 

The brain stem is responsible for basic body function
such as breathing and the gastrointestinal tract. If
stimulated in a certain way, CB2 could be harnessed to
eliminate the nausea and vomiting associated with
post-operative analgesics or cancer and AIDS
treatments, according to the researchers.

"Ultimately, new therapies could be developed as a
result of these findings," said Keith Sharkey, a
gastrointestinal neuroscientist at the University of
Calgary, lead author of the study.

(Scientists are trying to find ways to block CB1 as a
way to decrease food cravings and limit dependence on
tobacco.)

When asked whether his findings explain why some swear
by pot as a way to avoid the queasy feeling of a
hangover, Dr. Sharkey paused and replied: "It does not
explain the effects of smoked or inhaled or ingested
substances." 



		
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