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A Toast to Memory

November 2, 2006
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In the long run, it's been determined that a drink or two a day may be good for the brain.

Researchers have found that moderate amounts of alcohol -- amounts equivalent to a couple of drinks a day for a person ---- improved the memories of laboratory rats.

Such a finding may have implications for serious neurodegenerative diseases like Alzheimer's, according to Matthew During, the study's senior author and a professor of molecular virology, immunology and cancer genetics at Ohio State University.

"There is some evidence suggesting that mild to moderate alcohol consumption can protect against diseases like Alzheimer's in humans," said During. "But it's not apparent how this happens."

He and his colleague, Margaret Kalev-Zylinska, a postdoctoral researcher at the University of Auckland, in New Zealand, uncovered a neuronal mechanism that may help explain the link between alcohol and improved memory.

"We saw a noticeable change on the surface of certain neurons in rats that were given alcohol," he explained. "This change may have something to do with the positive effects of alcohol on memory."

During and Kalev-Zylinska designed a special liquid diet for the rats. One formulation included a low dose of alcohol, comparable to two or three drinks a day for a human, while the other diet included a much higher dose of alcohol, comparable to six or seven drinks a day for a human. A third group of rats was given a liquid diet without alcohol. All animals were given their respective diets daily for four weeks.

The researchers measured the rats' blood-alcohol levels three times throughout the study. Toward the end of the study, they subjected the rats to two different memory tasks.

Rats given low doses of alcohol spent about three times longer examining a new object rather than a familiar one than did rats on the alcohol-free diet. Rats that were given the high dose of alcohol spent equivalent amounts of time checking out both objects, suggesting that they were unable to differentiate the old object from the new one.

For the second task, rats were placed in a box with two chambers separated by a door. One was well-lit, while the adjacent chamber was dark.

Timing Their Moves

After placing a rat in the well-lit chamber and then lifting the door, the researchers timed how quickly the rats entered the dark chamber (rats are nocturnal, and naturally prefer dark spaces.)

Once inside the dark chamber, the rat received a mild electric shock to its feet.

The researchers repeated this same experiment 24 hours later, keeping track of how long it took for the animal to enter the dark chamber.

"The results suggest that both doses of alcohol moderately improved the animals' ability to remember this negative event -- since they seemed hesitant to go into the dark area," said During.

"People who drink to forget bad memories may actually be doing the opposite by reinforcing the neural circuits that control negative emotional memory," he added.

At the end of the study, the researchers analyzed brain and liver tissue from each animal. They found that low levels of alcohol increased the expression of a particular receptor, NR1, on the surface of neurons in a region of the brain, the hippocampus, that plays a role in memory.

Researchers think NR1 plays a role in memory and learning.

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