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David Ewing Duncan

A View from David Ewing Duncan

"Natural" Pot Helps Fetal Brains Connect

Marijuana-like cannabinoids appear in a mouse fetus at just the right time to help young neurons connect properly.

  • May 31, 2007

Whoa, dude: what’s this about?

It’s not, like, about smoking dope: it’s about researchers in Sweden and Indiana experimenting with fetal mice whose brains naturally produce a chemical similar to Tetrahydrocannabinol (THC), the active ingredient in marijuana.

Scientists have known from studying women who smoke marijuana during pregnancy that when you add cannabinoids to fetal brain cells, it prevents neurons from making strong connections. But why?

The researchers found that the naturally occurring endocannabinoids (made by the brain) help position the rootlike feelers, called axons, that neurons use to communicate with one another. The process is highly sensitive to the amounts of the chemical, when it’s released, and its location in the brain. Adding THC-like chemicals from the outside throws off this delicate balance.

When researchers added synthetic cannabinoids to the wee little mouse brains, their axons withdrew from the areas of high concentration and moved in other directions.

According to an article posted on ScientificAmerican.com,

The researchers found two groups of brain cells in embryonic mice that carried the CBR proteins for several days during late development. (Mice gestate in 18 or 19 days.) The cells were located in the cortex, the brain region that controls attention and planning in humans and other mammals.

THC would likely affect very similar brain systems in human fetuses, says neuroscientist Yasmin Hurd of the Mount Sinai School of Medicine in New York City, but its concentration would be much higher than that of any endocannabinoid. “It would have an even more pronounced effect on axonal growth and guidance,” she says.

Apparently, a woman’s marijuana smoking during pregnancy causes children to learn more slowly than other kids, but they are just as intelligent–and now we know why. This should convince anyone contemplating smoking a bong near a pregnant woman to cease and desist. It also adds new meaning to the term “dazed and confused.”

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