Marijuana does nothing to help memory in Alzheimer's: study

Synthetic form of the drug shows a negative effect in high doses
By Pamela Fayerman, Vancouver Sun, February 9, 2010
Marijuana does not appear to improve memory or reverse effects of Alzheimer's disease, according to a University of B.C. study done on mice bred to have genetic mutations for the disease.

"We are a little surprised actually. Originally, we were hoping there would be a positive effect, based on previous research," said Dr. Weihong Song, the Canada Research Chair in Alzheimer's disease and a UBC psychiatry professor.

Wong said in an interview that the experiments were meant to validate research going back about six years that showed that marijuana might protect brain cells from injurious inflammation and even promote regeneration of neurons.

That got scientists excited about the possibility of a benefit, since the brains of Alzheimer's patients shrink as cells die off.

Six researchers affiliated with the Vancouver Coastal Health Research Institute used a synthetic derivative of cannabis called HU210, which is 100 to 800 times more potent than marijuana consumed by humans.

In experiments, mice were initially taught how to get to a desired location in a maze.

The mice that got high dose HU210 did no better than control subject mice, which got no drug, or those that got a low dose.

The study was done on a total of nearly 100 mice -- a third that got a high-dose drug injection, a third that got a lower dose and a control group that didn't get the drug but still had a sham injection to produce the same conditions.

Placed in a circular pool divided in four sections, mice were initially taught where a platform was situated to avoid swimming in the water. Mice that got the drug were no better at remembering where to go. Indeed, all three groups performed about the same.

After the experiments, mice were killed and their brains were examined. Post-mortems showed mice that got the highest dose of the drug had fewer brain cells, pointing to a detrimental effect of marijuana. But even lower doses of the drug impaired learning and memory.

Song concedes it's too early to conclude that medicinal marijuana won't be useful in Alzheimer's disease, especially since the study, published in the journal Current Alzheimer Research, was done in mice and using high doses.

"But what we can say at this point is that the previous research done with rats and mice on the [beneficial] effects of synthetic cannabinoids is not necessarily applicable to humans.

"We can't place too much hope on the benefits of marijuana in Alzheimer's disease at this point," he said, referring to his study, the results of which may not surprise marijuana users who have experienced the blunting effects of the drug on their short or long-term memories.

The scientists were funded by the Canadian Institutes of Health Research, the Jack Brown and Family Alzheimer's Research Foundation and the Michael Smith Foundation for Health Research.

Sun Health Issues Reporter

pfayerman@vancouversun.com
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