Marijuana's effect on brain doubled

Marijuana's effect on brain doubled, study indicates  Second type of cells affected, too, Ottawa researcher says
By Tom Spears, Ottawa Citizen
Marijuana impairs the brain by acting on two types of brain cell at once, a new Ottawa study shows.

And the implication, the lead researcher says, is that there's another side to the brain that neuroscientists hadn't realized.

For the past century, the accepted theory was that marijuana acted on neurons to impair working memory. Working memory is the system of holding on to information so that the brain can think about it and make decisions without being distracted. For instance, it allows a person to drive a car, listen to the radio, think about what will happen at the end of the car ride and watch for pedestrians all at once.

Marijuana impairs working memory, an effect that can last for a day or more after heavy pot-smoking.....click "Read More" below....
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At the Royal Ottawa Mental Health Centre, Xia Zhang and his team have found that there's more to this impairment than interference with neurons.

Pot's psychoactive chemical, THC, also acts on a second type of brain cells called astroglial cells.

"Glial cells make up 90 per cent of the brain cells," Zhang said, "whereas neurons only make up 10 per cent."

The various types of glial cells have always been seen as having a support role, nourishing and otherwise helping the neurons so that the neurons can do the real brain work, he said. But his study showing that glial cells have a role in memory opens up the possibility that they are far more involved in neuron-like work than anyone had realized.

The study is published in the research journal Cell. The co-author is Giovanni Marsicano, a scientist at France's national health research institute, INSERM.

"This is the first evidence that glial cells modulate working memory," Zhang said. It's "very surprising" to other researchers in the field. They don't believe it" when they first hear of this work.

It's likely that brain research will now broaden to explore the roles that glial cells may have in a wide variety of brain functions, he said. Zhang is also on the faculty of the University of Ottawa.

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