STUDY TURNS POT WISDOM ON ITS HEAD

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.

"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."