Vol. 12, No. 3, 2006 Page 6


People who start drinking by the age of 14 are five times more likely to become alcoholics than people who hold off on drinking until the age of 21, with genes strongly implicated as a reason for the association between early drinking and alcoholism. However, a new study suggests an additional reason for the relationship: early exposure of the brain to alcohol may short-circuit the growth of brain cells, impairing the learning and memory processes that protect against addiction. Thus, young drinkers may suffer a double-whammy: first from the genes that predispose them to early drinking, and then from the damage to brain cells that drinking causes.

Fulton Crews and colleagues administered three different amounts of ethanol to male rats when the rats were between 35 and 40 days old (the "adolescent" period for rats). The researchers report that alcohol powerfully inhibited the proliferation of neural progenitor cells (NPC), an effect that was dose-dependent but occurred at all levels of alcohol exposure. In adolescence, the researchers say, NPC contribute to the growth of new brain cells in areas of the forebrain and the hippocampus. Crews et al. say their analysis also showed a reduced formation of new cells in the rats' brains 28 days after exposure to alcohol.

The researchers say, "The extensive proliferation and survival of adolescent NPC may contribute to the plasticity and maturation of the brain that occurs during the transition from adolescence to adulthood." The researchers add, "Adult NPC are hypothesized to contribute to learning and memory, as well as affective state and mood. Thus, our findings of decreased NPC proliferation and lost neurons one month after a single dose of ethanol suggest that adolescent binge drinking could disrupt learning, affective state and other behaviors undergoing maturation during adolescent brain development."

Crews and colleagues note that one-third of high school students and 44% of college students "binge drink" at least once every two weeks, consuming an average of 14 drinks per episode. This amount, the researchers say, is sufficient to achieve blood levels similar to the highest dose of alcohol used in their study–a dose that almost completely blocked NPC proliferation.


"Neurogenesis in adolescent brain is potently inhibited by ethanol," F. T. Crews, A. Mdzinarishvili, D. Kim, J. He, and K. Nixon, Neuroscience, Vol. 137, 2006, 437-445. Address: Fulton Crews, Department of Pharmaceutical Sciences, University of Kentucky, 725 Rose Street, Lexington, KY 40536-0509, ftcrews@med.unc.edu.

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