A toke a day keeps memory loss at bay

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HEATHER SOKOLOFF AND JOSH WINGROVE

From Thursday's Globe and Mail

November 20, 2008 at 4:20 AM EST

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Small doses of marijuana improve the function of aging brains, scientists find

 

Turns out a few dances with Mary Jane can do wonders for an aging brain.

 

Yes, a daily toke in later-middle and old age can help slow memory loss, or the onset of diseases such as Alzheimer's, Parkinson's and multiple sclerosis, a new study suggests.

 

It's a pre-emptive strike, one not effective at reversing previous memory loss. But aging boomers still shouldn't go overboard, researchers say. In tests on lab rats, all it took was the equivalent of one human puff.

 

"We are not trying to make anyone high," said Gary Wenk, professor of psychology and neuroscience at Ohio State University. "We are trying to tease out the positive aspects of this plant."

 

The benefit was found in a synthetic compound identical to tetrahydrocannabinol, or THC, the psychoactive substance in marijuana, which researchers say activated areas of aged brains in rats affected by memory loss, and stimulated the formation of new brain cells.

 

Prof. Wenk, who presented the research in Washington, yesterday at the annual meeting of the Society for Neuroscience, was motivated to look into the effects of marijuana on aging brains after repeatedly noticing the drug mentioned on the blogs of patients with MS who use it to curb pain. Memory impairment is connected to such chronic brain inflammation.

 

"There was discussion of smoking a little pot to reduce inflammation, which makes their disease less painful," Prof. Wenk said.

 

Pot is popular among older sufferers, because conventional anti-inflammatory medications are not effective in older brains.

 

"Millions of people have used this plant for thousands of years," Prof. Wenk said. "There is a lot of evidence that there are some interesting things going on in the brains of these people."

 

So, while testing with rats, researchers used a THC-like drug, called WIN-55212-2, to activate receptors in the brain's endocannabinoid system - usually stimulated by smoking marijuana - which involves memory, appetite, mood and pain response.

 

After three weeks, the rats were given a memory test where they were placed in a small swimming pool to determine how well they used visual cues to find a platform hidden under the surface of the water.

 

The treated rats were given enough of the drug to boost brain cells, though not enough to get high, and did better in the swimming-pool test than the control - strait-laced rats without THC - in learning and remembering how to find the hidden platform.

 

"Old rats are not very good at that task," said Yannick Marchalant, co-author of the study and assistant professor of psychology at Ohio State. "When we gave them the drug, it made them a little better at that task."

 

They also experienced reduced inflammation and growth of new brain cells.

 

The researchers hope their findings could lead to the development of a drug to stave off memory loss in people with a history of degenerative disease in their families.

 

"The model could be used for anyone at risk," Prof. Marchalant said. "Perhaps 20 years before the usual onset of the decline in memory."

 

Cannabis joins a long list of taboo substances now shown to reduce brain inflammation. Nicotine, alcohol and caffeine have also been shown to do so, possibly leading to reduced memory loss later in life.

 

"What is it about coffee, what is it about smoking and what is it about marijuana that is causing us to see these effects?" Prof. Wenk asked. "Different compounds that may be bad for one part of the brain may be good for another."

 

Heather Sokoloff is a writer in Montreal.