Pubdate: Mon, 05 Mar 2012
Source: Globe and Mail (Canada)
Copyright: 2012 The Globe and Mail Company
Contact:  http://www.theglobeandmail.com/
Details: http://www.mapinc.org/media/168
Author: Adriana Barton

PAIN RELIEF WITHOUT MEMORY LAPSES? MARIJUANA STUDY HOLDS OUT HOPE

At last there's hope for medical marijuana users who have trouble 
staying on task after a dose of pot.

Cannabis is an effective treatment for conditions such as chronic 
pain, nausea, seizures, cerebral trauma and tumours. But the drug's 
therapeutic potential has been limited by its side effects, including 
temporary impairment of working memory.

A team of neuroscientists has discovered that memory lapses due to 
marijuana intoxication aren't related solely to how neurons react to 
THC, the drug's major psychoactive ingredient.

Instead, THC short-circuits working memory by interfering with 
passive cells, called astrocytes, long believed to exist solely to 
support and feed active neurons.

The findings could lead to the development of a THC-based drug that 
controls pain without affecting memory.

The research, published Friday in the journal Cell, is the first to 
show that astrocytes play a major role in spatial working memory, 
says co-author Xia Zhang, a neuroscientist at the University of 
Ottawa Institute of Mental Health Research at The Royal. In this new 
model, he says, "a supporting actor becomes the leading actor."

The findings may help scientists researching spatial working memory 
problems in patients with conditions such as schizophrenia and 
Alzheimer's, he says.

Spatial working memory is used in activities such as route finding, 
driving, figural reasoning (geometry) and sports (remembering and 
carrying out complex plays).

Dr. Zhang and researchers including Giovanni Marsicano of INSERM in 
Bordeaux, France, used chemicals and peptides to block spatial 
working memory impairment in mice and rats given injections of THC.

The peptide used to block the negative side effects of marijuana was 
patented by the Brain Research Institute at the University of B.C.

"Our study on both rats and mice suggests that the same mechanism 
underlying marijuana impairment of working memory is likely 
applicable to humans," Dr. Zhang says.

The catch is that blocking the undesirable side effect would likely 
wipe out the euphoria associated with the drug as well, Dr. Zhang says.

Asked whether the tradeoff would be attractive to patients, he 
replied, "maybe, but I'm not a pot smoker."
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MAP posted-by: Jay Bergstrom