DURHAM, N.C. -- Duke University Medical Center researchers report experiments
with brain tissue show that alcohol severely disrupts a biochemical process
associated with memory formation in young animals, but that alcohol is much
less potent in brain tissue from mature animals.
According to the researchers, the findings provide compelling scientific
evidence upon which health policy and laws aimed at preventing underage
drinking may be based.
"Until now, we have had no hard scientific data to back up our alcohol
laws for young people," said principal investigator H. Scott Swartzwelder,
professor of psychology at Duke and a research scientist at the Durham VA
Medical Center. "It's always been a moral message or an authoritarian
message. But now we can say to young people that even occasional and moderate
drinking might impair your brain's memory systems more than it would an
adult's."
The new study, published in the December issue of Alcoholism: Clinical and
Experimental Research, demonstrates the deleterious effects of alcohol on
a key memory-associated neural process known as long-term potentiation (LTP).
In LTP, successive signals from neighboring cells tend to make neurons more
sensitive to activation from those cells. Therefore, LTP is a process by
which experience can lay down preferred memory pathways in the brain.
In his experiments, Swartzwelder tested the effects of alcohol on a specific
part of the brain known as the hippocampus, believed to be a center for
learning.
"The hippocampus is very similar in rats and in humans," Swartzwelder
said. "Rats, just like humans, need to learn new things. In evolutionary
terms, the hippocampus is a very old structure, so the hippocampal process
of filtering and encoding new information is quite similar."
The Duke experiments consisted of measuring the electrical activity of nerves
in thin slices of hippocampal tissue kept alive in culture dishes. The immature
rats were between the ages of 20 and 25 days, roughly equivalent to late
childhood or early adolescence in humans, while the mature rats studied
ranged in age from 80 to 100 days, comparable to young adulthood in humans.
"Our study showed that alcohol almost completely blocked the initiation
of LTP in immature brains, while the same amounts had practically no effect
at all on LTP initiation in mature brains," Swartzwelder said. "The
findings, thus, provide scientific data to support a prohibition of underage
drinking.
"Children and teenagers are at the time in their lives when they are
acquiring huge amounts of information," Swartzwelder continued. "At
this particular point in life, the brain is more plastic and susceptible.
This also happens to be the time of life when there is a great deal of pressure
to drink alcohol."
The latest findings build upon results published last spring, when the same
Duke researchers demonstrated that even small amounts of alcohol severely
depress the activity of receptors on the surface of nerve cells in the immature
brain responsible for processing new information.
Now that the Duke medical center researchers have demonstrated the negative
effects of alcohol at the physiological level, their next step is to conduct
experiments on living rats of different ages to determine the effects of
alcohol on the animals' behavior.
Swartzwelder's research is supported by grants from the Veterans Administration
system, as well as from the Alcoholic Beverage Medical Research Foundation.
Joining him in the studies were Wilkie A. Wilson, research professor of
pharmacology and Mohammed Tayyeb in pharmacology.