Drunken rats offer insight in study of cells

The research offers hope of finding a new way to speed healing among alcoholics.
RALEIGH NEWS & amp; OBSERVER
CHAPEL HILL, N.C. -- Inside a University of North Carolina research building, white rats stumble inside clear plastic cartons. Others walk dragging their bellies. A few are dead still, flat on their backs.
Soused, every last one of them.
On the surface the scene looks comical. But at its core it is dead serious. These drunken rats are teaching the world startling facts about alcohol's toll on brains.
Discovery
Scientists Fulton T. Crews and Kimberly Nixon have discovered that heavy drinking slows the birth of new brain nerve cells, or neurons, in animals. Sobered-up rats produce more than normal amounts of neurons.
That might explain why the brains of alcoholic rats, just like the brains of alcoholic people, shrink during chronic drinking but grow after the abuse stops. Life-saving behavioral changes often accompany that growth.
Alcoholic people who abstain regularly from drink can regain the ability to see how drinking harms them and their families, something heavy drinkers go blind to. If such insight is tied to replenishing neurons, medicine may get a new way to speed healing among alcoholics.
Exercise appears to encourage the birth of new neurons, scientists now say. Putting adults in situations where they learn definitely does. And certain drugs, including some antidepressants, are thought to have similar effects.
"More experiments are needed, but this is a first tantalizing step," said Antonio Noronha, director of the National Institute of Alcohol Abuse and Alcoholism's division of neuroscience and behavior.
None of this new line of research would be possible without the rats.
For decades, scientists thought that adult humans and other animals had a finite number of neurons. But brain stem cells producing neurons even in adults were discovered in 1997.
Counting new cells made in living human brains is impossible. So Crews, who runs the university's Bowles Center for Alcohol Studies, asked Nixon in 2001 to find out how alcohol affects the production of new neurons in rats. Nixon, a research scientist working for Bowles, found a way to chemically tag the new nerve cells and then tally them at different stages.
Each experiment is painstaking. Nixon and others in the Crews lab regularly dose their animals over four days at eight-hour intervals to mimic drinking binges.
They serve the rats doses of ethanol mixed with Ensure, the nutritional supplement, aiming for blood-alcohol levels up to 0.3, much higher than the 0.08 tolerated in drivers. Amounts vary depending on how each animal responds.
Dosing at 7 a.m., 3 p.m. and 11 p.m. becomes routine during regular four-day forced binges. The scientists stay awake one full night to watch over the animals while they withdraw. Then they sober up the rodents.
The animals are killed at different points, depending on the experiment. Each time, researchers inject a rat's body with a form of formaldehyde that hardens its brain. Then they slice one portion of each brain into thousands of slivers, a job that takes an hour and a half each time.