Ethanol Consumption in Teens and Adults

Alcohol is widely consumed across the United States. While the legal drinking age is 21, adolescents may gain access to alcohol during their teenage years, and some may experience binge drinking prior to adulthood. Jamie Roitman conducted a study on the effects of adolescent ethanol consumption on the orbitofrontal cortex. He focused his studies on the cortico-striatal circuitry, which is a pathway known to be involved with decision making and rewards. He experimented on adolescent rats because their circuitry is still developing, and he found that consistent ethanol consumption during adolescence is correlated with increased risk behavior in adulthood.

While underage drinking has the potential to impact patterns of orbitofrontal cortex activity into adulthood, legal drinking in adults is much more prevalent, and may also lead to a number of effects. In an article written in Scientific American, Bret Stretka describes a study that researches alcohol addiction. In this particular study, researchers experimented on 32 adult rats, and they trained the rats to consume 20% ethanol solution for two months. Following this training, the rats were offered a daily choice of ethanol or a solution of saccharine. They found that 12.5% of rats chose ethanol over saccharine. This experiment was replicated with a larger sample size of 600 animals, and the researchers found that this same approximate percentage of rats chose ethanol over saccharine. Interestingly, this statistic is similar in humans. Stretka writes that the “rate of alcohol misuse in humans is around 15 percent”. Additional research reveals that these rats continued to choose alcohol over saccharine even when the alcohol was delivered with a shock.

To study the differences alcohol addiction may have in brain function, researchers removed brain tissue from their rats. They discovered that a protein known as GAT-3 was found in significantly diminished concentrations in the brains of rats who chose alcohol over saccharine. GAT-3 is believed to be involved with GABA regulation. GABA is a neurotransmitter involved in many processes, but elevated levels of GABA have been implicated in alcohol addiction. Following these results, the researchers expanded their study to include human brain samples, and they found that in individuals who experienced alcohol addiction, GAT-3 was also found in decreased concentrations, especially in the amygdala and reward circuitry. It is hypothesized that altered gene expression in the amygdala and reward circuitry is related to the structural and functional differences in the brains of people who experience alcohol addiction. However, it is not known whether alcohol abuse causes GAT-3 concentrations to decrease, or if individuals who already have lower levels of GAT-3 are predisposed to alcohol addiction. It is possible for these factors to exacerbate one another, and it is also likely that other biological factors outside of GAT-3 expression are involved. In humans, there are many other aspects to consider. Because people do not exist in a controlled lab, factors such as accessibility to alcohol, socioeconomics, stress, and social influences may also play a role in one’s likelihood for abuse.

While this article describes a study that focuses on alcohol consumption in adults rather than adolescents, these experiments nonetheless overlap with Roitman’s research. Perhaps unsurprisingly, Stretka describes altered gene expression in the reward circuitry, which is a brain region that Roitman also studies. These two labs focus on different age groups, but they both research the impact of alcohol consumption. In addition to this, it may be possible for these labs to draw from one another. The researchers described in Stretka’s article may consider whether consistent underage drinking leads to an increased susceptibility to alcohol addiction or abuse in adulthood. Roitman may also consider whether gene expression for various proteins implicated in alcohol addiction are expressed at similar levels prior to and after long-term administration of alcohol in adolescent rats.

It appears additional research is necessary to increase our understanding of the effects of alcohol consumption, as well as the factors that may lead to alcohol abuse. Considering such a vast number of people across the globe consume alcohol throughout their lives, this is a vital area of study.

Citations

Mcmurray, Matthew Stephen, et al. “Consequences of Adolescent Ethanol Consumption on Risk

Preference and Orbitofrontal Cortex Encoding of Reward.” Neuropsychopharmacology, vol. 41, no. 5, 2015, pp. 1366–1375., doi:10.1038/npp.2015.288.

Stetka, Bret. “Scientists Pinpoint Brain Regions That May Be Center of Alcohol Addiction.”

Scientific American, 21 June 2018, https://www.scientificamerican.com/article/scientists-   pinpoint-brain-region-that-may-be-center-of-alcohol-addiction/.