Turns out, even fruit flies get liquid courage.
A new study from the University of Texas at El Paso shows fruit flies that inhale alcohol with other flies get a bigger dopamine rush than when they’re alone. Like humans, the intoxicated insects behaved livelier when “drinking socially” than alone.
That euphoric buzz may come with a risk, however.
UTEP biologist Kyung-An Han and her team identified dopamine receptor D1 as the one of five types of dopamine receptors in the brain most responsible for the flies’ heightened activity. This is the receptor linked to alcohol use disorder.
Researchers hope that by studying fruit flies they can better understand the combined risk factors and brain area that contribute to alcohol use disorder – or alcohol abuse and dependence – a disease that affects an estimated 28.9 million people in the United States, according to a survey by the National Institute on Alcohol Abuse and Alcoholism.
“In the case of humans, once people start drinking, not everybody who drinks becomes addicted,” Han said. “One of those factors that we don’t fully understand is why some people tend to have more cravings for those euphoric experiences.”
A UTEP research lab is studying fruit flies to learn more about alcohol addiction and its effects on the brain. (Courtesy of the University of Texas at El Paso)
Fruit flies have been used in biomedical research for more than 100 years because the insects share about 75% of the same genes that cause human diseases. Like humans, flies also have a nervous system that responds to dopamine.
These characteristics make fruit flies a good model for simpler human behaviors, said UTEP biologist Paul Rafael Sabandal. For example, fruit flies act like humans when they “drink” alcohol in social settings – first there’s an increase in dopamine, then later they pass out, he said. Flies also experience greater alcohol tolerance the more they drink, Han added.
To conduct the study, researchers exposed fruit flies either alone or in a group to ethanol vapor. Flies can drink or eat food with alcohol, but ethanol vapor makes it easier to control how much alcohol they receive, Sabandal explained.
The team measured the average speed of the solitary flies to the group flies and found the group flies displayed a significant increase in speed and movement.
Researchers then compared the reaction to ethanol in flies with normal dopamine levels with flies with increased dopamine levels. They found similar patterns of behavior and the flies with increased dopamine showed even more hyperactivity than usual.
What contributes to alcohol use disorder?
The study, funded by UTEP’s Orville Edward Egbert, M.D. Endowment fund, was published in the journal Addiction Biology. Next researchers want to study how signals to dopamine receptor D1 contribute to social interaction and alcohol use disorder.
They also want to examine other contributing risk factors, such as how drinking alcohol at a younger versus a later age impacts neurodegeneration, which is a trigger for dementia, Han said. El Paso is estimated to have one of the highest rates of Alzheimer’s in Texas.
Genetics are estimated to contribute up to 60% of the risk for developing alcohol use disorder. Certain genes are related to metabolizing alcohol and there are theoretically some protective factors that explain why some people can drink more than others without becoming dependent on alcohol, Han said.
Age is another influential factor. Surveys indicate people who begin drinking before the age of 15 are more likely to develop alcohol dependence.
While people can get alcohol use disorder at any age, young and developing brains have more synapses – junctions in which nerve cells communicate with each other, Han said. Introducing ethanol at an early age can create a brain state that requires ethanol to be present, she said.
“In human cases, we haven’t fully developed our brains until our mid-20s and anyone younger than that is still maturing,” Sabandal said. “When you have drugs like alcohol or cocaine, you modify the (brain) connections.”
Sabandal said that while this study looked at one behavior type, they’re also interested in looking at other behaviors such as how ethanol affects the brain when it comes to hyper aggression, hypersexuality, sedation and alcohol tolerance.
One small experiment UTEP conducted with a high school teacher and students interning at the university found fruit flies that slept less are less tolerant and have a less euphoric response to ethanol, he said.
Han hopes studies like these can help scientists better understand brain diseases and encourage more students to join their lab at UTEP to continue research.
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