UC San Francisco researchers identified a slow dopamine pathway linking the gut and brain that helps explain how flavors become enjoyable over time, based on mouse experiments and small human imaging studies.
By Hermes-Vector AI Desk
Scientists at the University of California, San Francisco have identified a slow-acting dopamine pathway connecting the gut and brain that helps explain how people learn to like flavors they initially dislike, such as bitter coffee. The research was published November 4 in Nature.
Dopamine is a chemical messenger involved in motivation, reward, and learning. Most prior research has focused on fast dopamine signals that appear within seconds of encountering something rewarding. The new study examines a slower system that responds to information coming from inside the body, allowing the brain to learn about the benefits of food after it has been consumed.
When food enters the digestive tract, specialized sensors detect nutrients such as sugar and fat. That information travels toward the brain, where it can produce a dopamine response that builds gradually and continues for several minutes.
"We've shown that this slow dopamine system is what drives us to learn to like certain foods over time, and we can see where and how that happens," said Zachary Knight, PhD, professor of Physiology and senior author of the study.
Knight worked with James Grove, PhD, who was a graduate student at the time. They introduced nutrients directly into the stomachs of mice while monitoring dopamine activity throughout their brains. The researchers used either sugar water or a liquid resembling a milkshake, which allowed them to separate the effects of nutrients from the experience of tasting food.
The results revealed a powerful, prolonged dopamine response in a specific brain region called the anterior basolateral amygdala, or BLA.
The researchers then interrupted the newly identified pathway in mice. The animals continued eating normally but lost the ability to learn that an unfamiliar flavor was associated with receiving calories. In the opposite experiment, after mice tasted a flavor containing no calories, the researchers artificially activated dopamine fibers in the BLA. The animals developed a preference for that flavor even though it provided no nutritional reward.
The researchers also looked for evidence that a comparable process occurs in humans. Dana Small, PhD, a psychologist at Yale University, revisited data from an earlier positron emission tomography (PET) study involving 13 men. Participants had consumed either a milkshake or a drink without calories. Her analysis found that dopamine release following nutrient delivery was especially concentrated in the left side of the BLA.
A separate study led by Marc Tittgemeyer, PhD, and his colleagues used functional magnetic resonance imaging (fMRI) to examine 38 adults after they consumed glucose, a simple sugar. They observed increased activity in the same brain region.
In both mice and humans, nutrients produced a considerably stronger dopamine response in the left BLA than in the corresponding region on the right. Why the left side plays such a prominent role remains unanswered.
The causal experiments, in which the pathway was blocked or switched on, were done in mice. The human data come from brain imaging that shows a similar pattern in a small number of participants: 13 men in one study and 38 adults in another. That points to a shared mechanism, but it does not show that people form food preferences in exactly the same way.
Knight's team did not investigate GLP-1 medications in the new study, so it remains unknown whether they influence the dopamine pathway the researchers identified.
The findings offer a possible explanation for why an initially unpleasant flavor can gradually become enjoyable. Once the brain connects the taste of coffee with caffeine's stimulating effects, Knight explained, "that coffee starts to taste a lot better."
The research was supported by the National Institutes of Health (grants R01-DK106399, R01-DK138127, R01-NS116626, and R01-DK145100 and F31-NS120468).
Sources
This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
The day's checked news, by email
One short email a day with the top stories. Free, and you can unsubscribe in one click.
Or follow for the latest news:
No comments yet. Start the discussion.
University of Oklahoma paleontologists found a 450-million-year-old crinoid fossil with preserved tube feet, only the second known example of soft tissue in crinoids.
Back-to-back storms in the U.S. Southwest raised Navajo Reservoir by nearly 60 feet between September 20 and November 7, 2026, bringing it to 108 percent of average capacity for that date.