Summary: A new UCSF study challenges the longstanding idea that signals from the stomach are the primary controllers of meal termination. The research shows that taste—the mouth’s immediate sensory feedback—plays a leading role in rapidly curbing how quickly and how much we eat, while slower gut signals provide longer-lasting satiety. This finding reframes how scientists understand appetite control and may shape future strategies for weight-loss treatments.
Researchers report that neurons deep in the brainstem react almost instantly to oral taste signals to slow ingestion, whereas a different set of brainstem neurons responds to visceral feedback from the gut on a slower timescale. These complementary mechanisms work together to regulate eating behavior, and the discovery has implications for understanding how GLP-1–based weight-loss drugs like Ozempic and Wegovy exert their effects.
Key Facts:
- Taste perception triggers rapid brainstem responses that restrain the pace of eating.
- Two distinct groups of brainstem neurons—PRLH and GCG—act on different timescales to control feeding.
- Understanding this dual mechanism clarifies how GLP-1–targeting weight-loss drugs affect appetite and could guide improved therapeutic approaches.
Source: UCSF
Background and main finding.
Conventional wisdom has held that signals from the stomach and intestines tell the brain when to stop eating. UC San Francisco scientist Zachary Knight, PhD, and his team revisited that assumption and found a more nuanced picture. Using new imaging techniques to examine the caudal nucleus of the solitary tract (cNTS) in awake, behaving mice, the researchers discovered that oral sensory cues—taste and the act of ingestion—activate a subset of brainstem neurons almost immediately and constrain the speed and duration of eating episodes. Gut-derived signals arrive later and sustain satiety for much longer periods.
Knight and colleagues focused on two principal cell types in the cNTS that promote non-aversive satiety: PRLH (prolactin-releasing hormone) neurons and GCG (glucagon-like peptide–expressing) neurons. When nutrients were directly infused into the stomach, PRLH neurons displayed sustained activation due to visceral signals, consistent with classical models. But during normal oral consumption, those sustained visceral responses were dramatically reduced. Instead, PRLH neurons adopted a phasic pattern tightly tied to each bite, driven by taste and oral sensation.
Lead author Truong Ly, PhD, developed the tools that made it possible to record this activity in an awake mouse for the first time. Ly found that PRLH neurons control the duration of short feeding bursts—seconds-long episodes of eating—effectively providing rapid feedback that slows the pace of ingestion when the mouth signals match the expected sensory profile of food. In practical terms, one system increases consumption when food tastes rewarding, while the other monitors ingestion pace and signals to slow down to avoid overconsumption.
Two timescales of appetite control.
PRLH neurons act within seconds, using orosensory information to limit how quickly individual feeding bouts proceed. In contrast, GCG neurons respond to mechanical and nutrient-related signals from the gut over tens of minutes, tracking the cumulative amount eaten and enforcing longer-lasting satiety. This sequential, multi-timescale signaling constitutes a feed-forward and feedback loop: orosensory signals anticipate intake and temporarily slow eating, while visceral feedback confirms total consumption and sustains fullness.
Importantly, GCG neurons are tied to the release of GLP-1, the hormone that GLP-1 receptor agonist drugs mimic. Those drugs target the same brainstem region now accessible with Ly’s techniques, offering a new way to dissect how these medications reduce appetite and produce weight loss. By teasing apart the contributions of oral and visceral feedback, researchers aim to design therapies or behavioral strategies that better align with an individual’s eating patterns and compress or extend these signaling windows for improved outcomes.
Implications and next steps.
A clearer mapping of how taste and gut signals converge in the brainstem opens avenues for personalized interventions—pharmacological or behavioral—that optimize the interplay between fast-acting oral cues and slower gut-derived satiety. The UCSF team plans to explore how taste-driven signals interact with gut feedback during meals and how these neural circuits might be modulated to curb overeating without causing aversive effects.
Co-authors: Nilla Sivakumar, Zhengya Liu, Naz Dundar, Brooke C. Jarvie, Anagh Ravi, Olivia K. Barnhill and Heeun Jang of UCSF, and Jun Y. Oh, Sarah Shehata, Naymalis La Santa Medina, Heidi Huang, Wendy Fang, Chris Barnes, Chelsea Li, Grace R. Lee and Jaewon Choi of HHMI.
Funding: Supported by NIH grants R01-DK106399 and F31-DK137586.
About this hunger and taste research news
Author: Robin Marks ([email protected])
Source: UCSF
Contact: Robin Marks – UCSF
Image credit: Neuroscience News
Original Research: Open access. “Sequential appetite suppression by oral and visceral feedback to the brainstem” by Zachary Knight et al., published in Nature.
Abstract
Sequential appetite suppression by oral and visceral feedback to the brainstem
Meal termination is governed by dedicated neural circuits in the caudal brainstem. Understanding how these circuits convert sensory signals generated during feeding into dynamic behavioral control has been a major challenge. The caudal nucleus of the solitary tract (cNTS) is the first central site where many meal-related signals are integrated, yet how the cNTS processes ingestive feedback during ongoing behavior was previously unknown.
This study describes how PRLH and GCG neurons—two principal cNTS cell types that promote non-aversive satiety—are regulated during ingestion. PRLH neurons exhibited sustained activation by visceral feedback when nutrients were infused into the stomach, but during oral consumption these sustained responses diminished. Instead, PRLH neurons shifted to a phasic pattern time-locked to ingestion and linked to taste. Optogenetic manipulations showed that PRLH neurons control the duration of seconds-timescale feeding bursts, revealing a mechanism whereby orosensory signals feed back to restrain the pace of ingestion.
By contrast, GCG neurons responded to mechanical gut feedback, tracked the amount consumed, and promoted satiety that persisted for tens of minutes. These findings reveal that sequential negative feedback from the mouth and the gut engages distinct caudal brainstem circuits that control feeding behaviors operating on short and long timescales.