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Binge drinking spiked Tang damages teenage monkeys’ brains

09-12810 cropped.JPGBesides behavioural immaturity and experimental curiosity, the teenage years are also marked by brain development—making the rise of adolescent binge drinking particularly worrisome to neuroscientists.

Now, researchers show in PNAS today that alcohol decreases the levels of stem cells in the brain, which may lower its ability to repair damage. “The public expects adolescence to be an age when you try new things and you can fight out stuff,” says Chitra Mandyam from the Scripps Research Institute in La Jolla, California. “But when you’re still developing as an individual, if you change the capacity of the brain to maintain whatever it’s trying to maintain, you alter the balance of the brain as it grows.”

Mandyam’s team bartended for seven adolescent male rhesus monkeys, offering them Tang mixed with ethanol to a potency of 6% (that’s higher than your average American bar brew).

After establishing that all the test monkeys could be big drinkers, the researchers allowed only four of them to continue drinking the citrus flavoured cocktail once a day for 11 months. “Monkeys love to drink. They’re like humans,” Mandyam says. The legal blood alcohol level (BAL) limit for driving is 0.08. These four monkeys were intoxicated with BALs between 0.1 to 0.3. (That’s about 10 or 12 cans of beer.)

Then the researchers examined the brains of the monkeys that kept drinking two and a half months after making them quit cold turkey and found that they had an 80-90% reduction in the stem cells of a portion of their brain known as the hippocampus, compared with the monkeys kept sober.

The hippocampus is necessary for spatial learning, short and long term memory, and executive functioning. (It’s not solely responsible for those activities, but if you need to remember what exit to take when driving home, what your mom’s name is, or what two plus two equals, you need your hippocampus to work.) The hippocampus is also a place where the adult brain can generate new brain cells. The region produces stem cells that give rise to progenitor cells that mature into neurons, which then get incorporated into the existing hippocampal neural circuitry. This is called neurogenesis.

“These stem cells go through several milestones to become neurons,” says Mandyam, who looked upstream and found that alcohol reduces the stem cells and the progenitor cells that become new neurons. Previous researchers have shown that substance abuse decreases neurogenesis in the hippocampus, but how that happens has remained unknown. In this new study, the researchers found that the alcohol targeted the immature brain cells in adolescents, reducing the amount of new neurons born. “You’re messing with brain plasticity early on,” Mandyam says. “If you inhibit the cells so early in life, the chances of having normal production of cells later on in life is very unlikely.”

Even after a period of abstinence, the researchers still saw decreases in stem cells, progenitors, and neurons in the binge-drinking monkeys’ brains. The study suggests binge drinking during adolescent years might produce some of the memory deficits seen in adulthood due to decreases in adult neurogenesis.

“It’s very devastating to see what chronic binge drinking does to the adolescent brain,” Mandyam says.

Image: Stem cells highlighted in the monkey brain. Chitra D. Mandyam

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    Baycare Dental said:

    Interesting facts about stem cells and the effect of drinking in Monkeys…

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