Thursday, 15 March 2012

Scientists Link Alcohol to Brain Shrink

Consuming substantial amounts of alcohol shrinks critical brain regions in genetically vulnerable rodents, Brookhaven scientists have found in efforts to further map the biology of addiction in people.
The research by a team of brain experts at Brookhaven National Laboratory in Upton confirms that heavy drinking affects individuals differently. Much of that difference, the experts say, is determined by variability in brain chemistry from one person to the next.
The Long Island team wrote its latest chapter in the neurobiology of alcohol addiction by observing mice fed water spiked with pure ethanol.
Analyzing MRI images of the rodents revealed severe brain shrinkage only among those animals that lacked a certain protein known as the dopamine receptor, said Greek-American neuroscientist Peter Thanos, who led the research.
Think of a receptor as the lock into which a key fits.

In this case, dopamine, the brain’s pleasure chemical, is the key that fits into the dopamine protein receptor. The mice were specially bred to lack the receptor, mimicking humans who have low levels of it.
These mice suffered shrinkage in key areas of the brain, Thanos said.
In humans, he added, these brain regions are vital centers for processing speech, sensory information, motor signals — and for forming long-term memories.
The pattern of brain damage found in mice “mimics a unique aspect of brain pathology observed in human alcoholics, so this research extends the validity of using these mice as a model for studying human alcoholism,” Thanos said.
Absence of the receptor, Thanos added, helps explain why alcohol damage was so widespread and detrimental in the vulnerable mice.
By comparison, rodents possessing an intact dopamine receptor, known more precisely as the D2 receptor, did not experience brain shrinkage, which suggested to Thanos that a healthy receptor protects the brain.
Extrapolating to humans, Thanos said his findings also help explain why the same amounts of alcohol can affect people differently. While humans would never completely lack a D2 receptor, he said, some can have very low levels and likely experience more brain damage as a result of their addiction compared with those whose D2 is healthy.
“The receptors themselves are found in specific areas in the brain,” Thanos said, “so this shows us . . . [the receptors] are able to modulate the effects of alcohol.
“When you have D2 in higher levels, that serves as a form of protection,” Thanos said.
Alcoholism affects nearly 18 million people in the United States, according to statistics from the National Institute on Alcohol Abuse and Alcoholism. Understanding the interplay between everything from pleasure genes to social situations that encourage drinking can help addiction specialists develop better prevention and treatment strategies, experts say.
“These studies should help us better understand the role of genetic variability in alcoholism and alcohol-induced brain damage in people,” said Foteini Delis, a neuroanatomist at Brookhaven.
(Source: Brookhaven National Laboratory)

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