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.