Researchers at the University of Washington (UW) have studied the building blocks of a neurobiological link between alcohol use in the adolescent years and later decision-making impairments with adults. The results of the study were published last week in the Proceedings of the National Academy of Sciences website, and indicate a link between heavy drinkers and adult decision-making. Ilene Bernstein and Nicholas Nasrallah are the authors of the study, Nicholas is a psychology doctoral student at the UW and Ilene a professor of psychology and faculty member of the neurobiology and behavior program.
Nicholas said: “We know early exposure to alcohol and other substances is a predictor of later substance abuse in humans. It is a novel concept to think that early exposure might have long-term cognitive effects. But we can’t test this on people. This model using rats lends support to causal link between early alcohol use and later increased risky decision making.”
Ilene Bernstein said: “We can’t establish causal links based on existing human data but this animal model allowed us to establish this link. Scientists believe regions of the brain, including those implicated in decision making, are slow to develop and development extends into adolescence. This study shows that these late-developing structures in rats are affected by high alcohol use. Rats typically do not drink alcohol, but researchers have found that they will consume ethanol when it is combined with gelatin. For this study, one group of rats was given 24-hour access to a 10 percent solution of ethanol in a tasty gel. The rats were 30 to 49 days old during the experiment, a time span that corresponds to human adolescence. These rats consumed the alcohol-laced gel each day, in amounts equivalent to a large number of drinks in human term.”
Rats do not normally drink alcohol, but researchers have discovered that they consume ethanol when mixed with gelatin. During the study one group of rats received 24 hours a day access to a solution of 10% ethanol in a tasty gel. The rats were between 30 and 49 days old during the experiment, equivalent to the adolescence years of a human. The rats consumed alcohol mixed with the gel daily, in amounts equivalent to high numbers of drinks in human terms. A second group of rats received the gel without alcohol. At the end of 20 days they kept the gel away from both groups. Three weeks later, half of each group was trained to press a lever to receive the gelatin. The certain handle constant gives 2 gelatin, while the ‘uncertain handle’ gives larger gelatin but gives less constant, reflecting casino odds. Part of the training is a forced choice for the rat with only 1 handle, thus the rats were given the opportunity to sample the “payment schedule” of the uncertain lever for that day. Three days of trials were held, with the payoff for the large but uncertain gelatin coming 75% of the time, the next day 50% of the time and the third day only 25%. The alcohol-exposed rats showed a strong preference towards the uncertain lever, even if the chances of the gamblinglever had dropped to pay only 1 in 4 on the third day. The control rats showed quite different behavior, and adapted themselves perfectly to the changing conditions of the experiment, and thus earned more treats than the alcohol exposed rats.
The second experiment tests whether the effects of exposure to alcohol in the adolescent years is persistent in adults, by waiting three months after the gelatin was withdrawn before testing the remaining rats. The effects remained unchanged, suggesting that the influence of alcohol exposure in the adolescent will not become less in adulthood. Bernstein ended by saying: “The known association between behavior and high levels of alcohol use puts people at risk for a number of bad outcomes, particularly substance use,” said Bernstein. “Age of exposure to drugs is the No. 1 factor predictive of substance abuse later in life. Adolescent drinking is an epidemic today. This research raises a concern that if the brain is permanently changed by alcohol we need to place more emphasis on preventing adolescent alcohol use.”
Rats were previously used in a casino gambling experiment which revealed that there are two substances that affect addiction sensitivity.
