Summary: Researchers report that eating triggers dopamine release in the human brain at two distinct times—first when food is tasted and again after it reaches the stomach.
Source: Cell Press.
New research from the Max Planck Institute for Metabolism Research in Germany shows that dopamine, a key neurotransmitter involved in pleasure and motivation, is released in the brain at two separate moments during a meal: an immediate response when food is ingested and a delayed response once the food reaches the stomach. The study was published December 27 in the journal Cell Metabolism.
“Using a novel positron emission tomography (PET) technique we developed, we were able to detect two distinct dopamine release peaks and to pinpoint the brain regions associated with each release,” says senior author Marc Tittgemeyer, head of the Institute’s Translational Neurocircuitry Group. “The first, immediate release occurred in areas linked to reward and sensory processing, while the later post-ingestive release involved additional regions associated with higher cognitive functions.”
In the experiment, 12 healthy volunteers received either a palatable milkshake or a tasteless control solution while PET recordings monitored dopamine activity. The researchers also combined PET with functional MRI (fMRI) to map systems-level activation and dopamine release across the brain. The data revealed two separated dopaminergic responses: an orosensory response triggered by tasting the food and a delayed post-ingestive response occurring once the stomach received the nutrients.
One notable finding was how subjective craving related to these two releases. Participants’ reported desire for the milkshake was proportional to the amount of dopamine released in specific brain regions at the first tasting. Paradoxically, greater immediate craving and stronger orosensory dopamine release were associated with a reduced delayed, gut-dependent dopamine response. In other words, the more the brain responded right away to the taste, the less pronounced the later post-ingestive dopamine signal tended to be.
“On one hand, dopamine release mirrors our subjective desire to consume a food item. On the other hand, our desire appears to suppress the gut-induced dopamine response,” explains Heiko Backes, group leader for Multimodal Imaging of Brain Metabolism at the Institute and co-first author on the study along with Sharmili Edwin Thanarajah. The authors suggest this interaction could influence how much we continue to eat: if post-ingestive dopamine is suppressed, we might keep eating until the delayed signal rises to a sufficient level.
Earlier animal studies had shown that the gut can trigger dopamine release in the brain, but this study provides the first direct evidence of both orosensory and post-ingestive dopaminergic responses in humans. By identifying distinct brain regions recruited by each response—sensory and reward areas for the immediate signal and additional higher-order cognitive centers for the delayed signal—the work highlights how peripheral signals from the gut and immediate sensory experience interact to shape eating behavior and desire.
Funding: This research was supported by the German Research Foundation through a Transregional Collaborative Research Center and by the German Centre for Diabetes Research.
Source: Carly Britton, Cell Press.
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Food Intake Recruits Orosensory and Post-ingestive Dopaminergic Circuits to Affect Eating Desire in Humans” by Sharmili Edwin Thanarajah, Heiko Backes, Alexandra G. DiFeliceantonio, Kerstin Albus, Anna Lena Cremer, Ruth Hanssen, Rachel N. Lippert, Oliver A. Cornely, Dana M. Small, Jens C. Brüning, and Marc Tittgemeyer in Cell Metabolism. Published December 27, 2018.
DOI: 10.1016/j.cmet.2018.12.006
Cell Press. “Your Brain Rewards You Twice Per Meal.” NeuroscienceNews. December 27, 2018.
Abstract
Food Intake Recruits Orosensory and Post-ingestive Dopaminergic Circuits to Affect Eating Desire in Humans
Pleasant taste and nutritional value guide food choice and eating behavior. While orosensory features of food (its taste and texture) may be secondary to nutritional value for reinforcement, the brain mechanisms encoding food reward have been unclear. Orosensory signals and peripheral physiological feedback from the gut may act together on dopaminergic circuits to drive intake. In this study, researchers combined fMRI with a novel [11C]raclopride PET method to measure systems-level activation and dopamine release in response to palatable food intake in humans. They identified an immediate orosensory dopamine release and a delayed post-ingestive dopamine release, each recruiting distinct brain regions: specialized integrative pathways and higher cognitive centers. The study also identified brain areas where dopamine release reflected subjective desire to eat. Immediate dopamine release in wanting-related regions was inversely correlated with, and appeared to inhibit, post-ingestive release in the dorsal striatum. These results underscore how brain and peripheral signals interact to reinforce human food intake.