Rat study shows how marijuana may ease Alzheimer's

WASHINGTON, Oct 19 (Reuters) Marijuana may help reduce the risk of Alzheimer's disease by reducing inflammation in the brain, US researchers reported.

Tests on rats showed that a compound found in marijuana stopped the loss of brain cells seen in inflammation and improved the animals' memories.

The findings, presented yesterday to a meeting of the Society for Neuroscience in Atlanta, may help explain some studies that suggest people who regularly smoked marijuana in the 1960s and 1970s are now less likely than others the same age to develop Alzheimer's disease -- the most common cause of dementia.

And caffeine may have similar effects, said Gary Wenk, a professor of psychology at Ohio State University.

''The baby boomers are just getting old enough now that we can just see this,'' Wenk said in a telephone interview.

His team used a widely studied drug called WIN-55212-2, or WIN for short, which is a synthetic compound similar to marijuana. WIN affects receptors -- molecular doorways -- on cells that are called cannabinoid receptors.

WIN has been tested against pain and inflammation in diseases such as Alzheimer's and multiple sclerosis.

Wenk's team infused the rats' brains with a compound that that mimics the inflammation found in Alzheimer's patients.

They treated some of the rats with WIN daily for those three weeks, and then tested the rats by making them swim in a water maze -- a standard test of rodent memory and learning.

''Old rats tend to be pretty bad at navigating the maze. It's kind of like an elderly person trying to find his way around a house that he's not familiar with,'' Wenk said.

But the older rats that were given WIN did better on the test, Wenk said.

''We are not going to go out and suggest that people start smoking marijuana,'' Wenk added. Researchers need to narrow down the compounds that are having the effects and try to make a ''high-free'' alternative, he said.

His team also found that caffeine may have similar effects, but in younger rats.

''These (compounds) fall into the category of things that millions of people have abused over decades,'' Wenk said. ''So when there is a subtle effect, it will show up.'' It is not clear when it is too late to begin fighting brain inflammation, Wenk said. Alzheimer's is clearly a process that takes years to do its full damage.

But he said his study was good news.

''What we found is old animals have the receptors and they actually get better if we treat them with the drug. If we give an old rat a high enough dose ... we will reduce their brain inflammation and what we actually do is make them smarter as we do it,'' Wenk said.

Last week researchers at the Scripps Research Institute in California found that marijuana's active ingredient, THC, can prevent another Alzheimer's process -- the formation of brain-clogging plaques.

More than 4.5 million people in the United States alone have Alzheimer's, which gradually destroys the brain and has no cure.

That number is expected to balloon as the population ages.

Also yesterday, the National Institutes of Health announced it would provide million over six years to researchers to conduct several new trials into ways to prevent Alzheimer's, although WIN is not among them.

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