Pubdate: Fri, 14 Oct 2005
Source: New Scientist (UK)
Copyright: New Scientist, RBI Limited 2005
Contact:  http://www.newscientist.com/
Details: http://www.mapinc.org/media/294
Author: Kurt Kleiner
Cited: Journal of Clinical Investigation DOI:10.1172/JCI25509)
Cited: https://www.the-jci.org/article.php?id=25509

MARIJUANA MIGHT CAUSE NEW CELL GROWTH IN THE BRAIN

A synthetic chemical similar to the active ingredient in marijuana
makes new cells grow in rat brains. What is more, in rats this cell
growth appears to be linked with reducing anxiety and depression. The
results suggest that marijuana, or its derivatives, could actually be
good for the brain.

In mammals, new nerve cells are constantly being produced in a part of
the brain called the hippocampus, which is associated with learning,
memory, anxiety and depression. Other recreational drugs, such as
alcohol, nicotine and cocaine, have been shown to suppress this new
growth. Xia Zhang of the University of Saskatchewan in Saskatoon,
Canada, and colleagues decided to see what effects a synthetic
cannabinoid called HU210 had on rats' brains.

They found that giving rats high doses of HU210 twice a day for 10
days increased the rate of nerve cell formation, or neurogenesis, in
the hippocampus by about 40%.

Just like Prozac?

A previous study showed that the antidepressant fluoxetine (Prozac)
also increases new cell growth, and the results indicated that it was
this cell growth that caused Prozac’s anti-anxiety effect. Zhang
wondered whether this was also the case for the cannabinoid, and so he
tested the rats for behavioural changes.

When the rats who had received the cannabinoid were placed under
stress, they showed fewer signs of anxiety and depression than rats
who had not had the treatment. When neurogenesis was halted in these
rats using X-rays, this effect disappeared, indicating that the new
cell growth might be responsible for the behavioural changes.

In another study, Barry Jacobs, a neuroscientist at Princeton
University, gave mice the natural cannabinoid found in marijuana, THC
(D9-tetrahydrocannabinol)). But he says he detected no neurogenesis,
no matter what dose he gave or the length of time he gave it for. He
will present his results at the Society for Neuroscience meeting in
Washington DC in November.

Jacobs says it could be that HU210 and THC do not have the same effect
on cell growth. It could also be the case that cannabinoids behave
differently in different rodent species - which leaves open the
question of how they behave in humans.

Zhang says more research is needed before it is clear whether
cannabinoids could some day be used to treat depression in humans.
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MAP posted-by: Matt Elrod