If you walked past the same bar every day on the way home from work, most days, you would barely register it. But if one day you accidentally skipped lunch, you might suddenly have the urge to enter the bar and order a drink, explained Associate Professor of Neuroscience Karla Kaun.
A new study led by Brown researchers examines this relationship between hunger and alcohol.
“Without you even realizing it, the cues that are coming from the bar — maybe the smell that’s coming from it, or a cute sign of a martini glass in the window — (are) attracting you,” Kaun, the study’s principal investigator, said in an interview with The Herald.
The study found that silencing or activating a neuron in flies’ brains that releases octopamine — a neurotransmitter associated with physiological experiences like hunger — influenced how soon the flies found alcohol rewarding.
Kaun explained that a fly’s reaction to alcohol is similar to a human’s. At first, flies might think alcohol is “kind of gross” and “smells bad,” Kaun said.
But “if you give them enough that they can feel the pharmacological effects and then let them sleep it off, they remember (alcohol) as rewarding and not aversive,” she said. “Alcohol and other drugs of abuse hijack these pathways in fly brains, much like they do in our brains.”
The team came across this hunger circuit when Kavin Nuñez PhD’21 decided to keep the flies starved after a routine experiment. The starved flies moved towards the alcohol faster than the fed flies, Nuñez said.
Nuñez found that the neuron VUMa3 was driving this effect.
When a fly is hungry, VUMa3 is activated and “talks to the pathway that normally works when the fly is not hungry,” Kaun said.
This research is significant in “figuring out the fundamental puzzle pieces through which alcohol can be felt as rewarding and remembered as rewarding,” Kaun said. She added that the scientists on this study are trying to understand cravings at a molecular level “because we actually don’t have a very good way to stop cravings right now.”
Individuals recovering from alcohol use disorders are instructed to avoid stressors, such as getting too hungry or sleep-deprived, Kaun said. This research may help explain why.
Associate Professor of Behavioral and Social Sciences and of Psychiatry and Human Behavior Carolina Haass-Koffler, who was not involved in the study but is collaborating with the researchers on a follow-up, said that these findings help explain how motivations to drink intensify under certain physiological conditions.
This research suggests that the brain’s response to a cue associated with alcohol “is not fixed,” Haass-Koffler said. “It continues to be very dynamic between the experiences that you have.”
Elizabeth Rosenbaum is a senior staff writer covering science and research.
