Intentional consumption of alcohol from fermented beverages has played a role in shaping society for several millennia. Today, many college students in the United States countdown the days to their first “legal” drink. Unfortunately, alcohol consumption oftentimes goes beyond a social custom, instead becoming a habitually excessive behavior with potentially destructive consequences both for the abuser and broader society. Alcohol abuse is a medical and economic problem, costing the United States an estimated $223.5 billion and 88,000 alcohol-related deaths each year according to the National Institutes of Health.
Alcohol abuse is especially devastating in pregnant women, as prenatal alcohol exposure has been shown to cause developmental effects in children, known as “fetal alcohol syndrome.” The extent to which the offspring of affected children are impacted, however, has not been explored. Recent work by Michael E. Nizhinikov et al. addresses this, demonstrating that exposure to low and moderate amounts of alcohol intake in early stages of fetal development can affect not only the directly affected individual, but also his or her progeny. These effects include an increased risk of future alcohol abuse and alterations in alcohol sensitivity, creating the potential for cycles of abuse that can accumulate over time in a society.
Nizhinikov and colleagues performed studies on rats to model alcohol exposure and abuse. These rodents are more behaviorally complex than mice and show a high propensity to abuse if given access to alcohol. Three groups of pregnant rats were used as “generation 0” in this study: (1) an untreated control group that provided a baseline to which experimental results can be compared; (2) a group that was force-fed water; and (3) a group that was force-fed ethanol, the type of alcohol found in fermented beverages.
To determine whether the effect of alcohol intake during the gestational period was transgenerational, subsequent tests were done across three generations of rats. Generation 1 was the offspring of generation 0, the animals that received distinct prenatal treatment. These rats went through the same mating period as generation 0, but received no alcohol exposure during pregnancy. This was repeated for another two generations.
Animals from each group and each generation were tested for sensitivity to and potential for “addiction” to alcohol by a series of tests. The first test measured how much alcohol was voluntarily consumed by each rat from the three experimental groups when left available in the animal’s cage. The second test measured the sensitivity to a specific dose of alcohol, using the loss-of-righting reflex (LORR) as a tool to determine the degree of physical impairment caused by alcohol. Similar to tests administered by law enforcement officers after stopping a suspected drunk driver, the LORR test measures how long it takes a rat to correct its posture after being placed off-balance on its side or back. The final test measured blood alcohol content, which reflects how well an animal is able to metabolize ethanol after administration of a fixed dose.
The results were remarkable, showing that across all three generations, rats from the group that had initial prenatal ethanol exposure at “generation 1” voluntarily consumed more alcohol than the other groups. The first two generations of this group also had a shorter LORR at moderate alcohol exposure of 3.5 grams per kilogram of body weight. This latter observation suggests that these animals had a blunted sensitivity to the effects of ethanol, despite showing an increased blood alcohol content. In contrast, the experimental group treated with water had similar alcohol consumption to the control group that received no treatment.
This study demonstrates that prenatal alcohol exposure does not simply impact the initial victims, but also their offspring. In a sense, developmental exposure to ethanol “hard wires” both the desire for and loss of sensitivity to alcohol, increasing the likelihood of future abuse and addiction.
While the precise effect alcohol has on the brain was not determined in this study, the authors hypothesize that the increase in alcohol consumption could be result of associative learning, which reinforces perceived “positive” experiences with behavior that leads to the same neurological “reward.”
Although this theory accounts for the effect on the first generation, the impact on following generations is more complex, most likely involving heritable genetic modification as well. This finding is sobering because it implies that the choices we make now regarding alcohol consumption, especially during pregnancy, can have a lasting impact for several generations.
