June 14, 2005
Drinking for Only Eight Weeks Impairs Learning and Memory in Mice
+ Previous human and animal studies have shown that chronic alcohol consumption can produce deficits in learning and memory.
+ A new rodent study is the first to show that continuous drinking for as little as eight weeks can produce deficits in learning and memory that last up to 12 weeks after drinking stopped.
Both human and animal studies have shown that chronic alcohol consumption can produce deficits in learning and memory. Rodent studies, for example, have shown that chronic alcohol consumption for six months or more can produce permanent deficits and neural damage. A rodent study in the June issue of Alcoholism: Clinical & Experimental Research is the first to show that continuous drinking for as little as eight weeks can produce deficits in learning and memory that last up to 12 weeks after drinking stopped.
"The learning and memory deficits we found in our mice that received eight weeks of alcohol followed by three weeks of withdrawal affect all types of learning and memory," said Susan A. Farr, associate professor of medicine at St. Louis University School of Medicine and corresponding author for the study. "That is, they are global. We found deficits in every type of task we tested the mice in, from complex to simple tasks. Our study is the first to show that drinking for a duration as short as eight weeks produces lasting deficits up to at least 12 weeks after the cessation of alcohol."
"Drinking doesn't just produce a hangover," said D. Allan Butterfield, The Alumni Professor of biological and physical chemistry at the University of Kentucky. "Chronic drinking may lead to permanent cognitive deficits." Butterfield, also director of the Center of Membrane Studies, said these findings are especially troubling for college students who may engage in binge drinking. "People should exercise caution against binge drinking since cognitive deficits may ensue," he said.
Researchers fed eight-week-old male mice, of two different strains, either an alcohol or sucrose diet for eight weeks, followed by a three-week withdrawal period. Learning and long-term memory tests included T-maze footshock avoidance, Greek Cross brightness discrimination, step-down passive avoidance, and shuttlebox active avoidance. "The tasks we used cover many forms of learning," said Farr, "including different motivational factors as well as difficulty levels."
Farr said there were three main findings. "One, that consumption durations as short as eight weeks produce deficits twelve weeks after withdrawal. This is a much shorter duration than previously reported to produce such deficits. The implications are that the deficits are permanent. Two, that the deficits appear to be global, affecting all types of learning. Three, that the deficits are not related to any nutritional or sensory deficits produced by the alcohol. This indicates that the alcohol produced neurochemical changes in the brain important for learning and memory."
"This study demonstrates that the lingering effects of chronic alcohol ingestion are profound," said Butterfield. "Although I am not a behaviorist, my sense of the study suggests that these results, transferable to humans, imply profound deficits in cognition, memory, and learning that are long-lasting."
Farr concurred. "For the average reader," she said, "while one must be cautious going straight from mouse to human, this would be equivalent to a human that drank six to eight beers or one bottle of wine a day every day for six years could experience learning and memory deficits up to nine years after they stopped drinking alcohol."
Farr said that she and Butterfield plan to continue with their investigation of the neurochemical changes in the brain that are producing these deficits.
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