Our brain rewards us for every meal by releasing dopamine, a neurotransmitter that plays a starring role in motivating behavior. According to a new study, dopamine release occurs at two different times: at the time the food is first ingested and another once the food reaches the stomach.
Thanarajah et al combined functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) to assess the brain’s response to food intake and discovered immediate and delayed dopamine release in distinct areas of the human brain; the study authors also identified areas where dopamine release reflected subjective wanting to eat, shedding light on how the brain transforms energetic signals into the desire to eat. Image credit: Thanaraja et al, doi: 10.1016/j.cmet.2018.12.006.
“With the help of a positron emission tomography (PET) technique we developed, we were not only able to find the two peaks of dopamine release, but we could also identify the specific brain regions that were associated with these releases,” said study senior author Dr. Marc Tittgemeyer, a researcher at the Max Planck Institute for Metabolism Research and the Cologne Cluster of Excellence in Cellular Stress and Aging-Associated Disease, both in Germany, and Modern Diet and Physiology Research Center in New Haven, Connecticut.
“While the first release occurred in brain regions associated with reward and sensory perception, the post-ingestive release involved additional regions related to higher cognitive functions.”
In the study, 12 male, normal-weight volunteers (mean age 56 years) received either a palatable milkshake or a tasteless solution while PET data were recorded.
The subjects’ craving or desire for the milkshake was proportionally linked to the amount of dopamine released in particular brain areas at the first tasting.
But the higher the craving, the less delayed post-ingestive dopamine was released.
“On one hand, dopamine release mirrors our subjective desire to consume a food item,” said study co-author Dr. Heiko Backes, a scientist at the Max Planck Institute for Metabolism Research.
“On the other hand, our desire seems to suppress gut-induced dopamine release.”
Suppression of gut-induced release could potentially cause overeating of highly desired food items.
“We continue to eat until sufficient dopamine was released. This hypothesis remains to be tested in further studies,” Dr. Backes said.
The findings were published in the journal Cell Metabolism.
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Sharmili Edwin Thanaraja et al. Food Intake Recruits Orosensory and Post-ingestive Dopaminergic Circuits to Affect Eating Desire in Humans. Cell Metabolism, published online December 27, 2018; doi: 10.1016/j.cmet.2018.12.006
