08-07-2024

Why social drinking feels so different from drinking alone

Earth.com staff writer

Grabbing a drink with friends during happy hour often leaves you feeling sociable, cheerful, and positive. However, drinking alone can sometimes lead to feelings of depression. Researchers now believe they understand why this happens.

“Social settings influence how individuals react to alcohol, yet there is no mechanistic study on how and why this occurs,” said Kyung-An Han, Ph.D., a biologist at the University of Texas at El Paso (UTEP) who studies alcoholism using fruit flies.

Han, along with a team of UTEP faculty and students, has made a significant advancement in understanding the neurobiological process behind social drinking and its effects on feelings of euphoria.

The study, published in a recent issue of the journal Addiction Biology, identifies the brain region stimulated by social drinking.

This discovery could enhance our understanding of Alcohol Use Disorder (AUD), a disease that affected nearly 29.5 million people last year, according to the National Institute on Alcohol Abuse and Alcoholism.

Varied brain responses to drinking

Interestingly, tipsy fruit flies exhibit behaviors similar to intoxicated humans. Despite their unconventional use in studying human behavior, these insects share about 75% of the genes associated with human diseases, Han explained.

Using fruit flies, the team aimed to demonstrate that ethanol, the alcohol in drinks, elicits different reactions in solitary versus group settings, with dopamine – a brain molecule involved in pleasure, motivation, and learning – playing a crucial role in this phenomenon.

The researchers exposed fruit flies, either alone or in groups, to ethanol vapor and measured their movement speed to gauge their response to ethanol.

Flies that “drank alone” showed a slight increase in movement, while those exposed to ethanol in a group setting displayed significantly higher speed and activity.

Next, the team investigated dopamine’s role in the flies’ response to ethanol by comparing a control group with naturally regulated dopamine levels to an experimental group with increased dopamine levels.

The experts found that, in solitary settings, flies with both normal and elevated dopamine levels exhibited a slight increase in activity. However, in social settings, flies with increased dopamine displayed even greater hyperactivity than usual.

“We demonstrated that both social settings and dopamine act together for the flies’ heightened response to ethanol,” said Han, who is also the associate dean in the College of Science.

The researchers then focused on identifying which of the five dopamine receptors in the brain was most significant in this process. They discovered that the D1 dopamine receptor played the most crucial role in the flies’ reaction to ethanol in a social setting.

“The human D1 receptor gene is linked to Alcohol Use Disorder and this study provides experimental validation for it. For the team, the identification of the D1 receptor is crucial as it gives researchers at UTEP and beyond a blueprint for follow up studies,” Han explained.

Significance of the study

Dr. Paul Rafael Sabandal, a research assistant professor in biological sciences and one of the study’s corresponding authors, emphasized the importance of their findings.

“Our work is providing scientific knowledge to support the idea that the brain interprets and processes a person’s social surrounding and has that signal converge into the dopamine system that is also activated by alcohol consumption. It gives us as researchers an idea of which brain area and components may serve as the meeting point for all the signals that contribute to AUD.”

The team’s next steps involve exploring the complexities of how the D1 dopamine receptor serves as the central point for signals related to ethanol, social interaction, and AUD.

“The opportunity to work on projects whose positive impact can be applied at scale is one of the reasons I became a scientist,” Han said. “It’s humbling to know that our work has the potential to help people live better lives and our team is going to continue striving toward achieving that goal.”

This study not only sheds light on the neurobiological mechanisms of social drinking but also opens new avenues for understanding and potentially treating alcohol use disorder.

By identifying the specific brain receptors involved, researchers can better target treatments and interventions to mitigate the effects of alcohol consumption and improve public health outcomes.