When you eagerly dig into a long-awaited dinner, it's traditionally believed that signals from your stomach to your brain stop you eating so much. However, a research team recently discovered that it's our sense of taste that immediately pulls us back from eating food overly on a hungry day. Stimulated by the perception of flavor, a set of brain cells become active to quickly curtail food intake.
Previous studies have suggested that the food taste may control how fast we eat, but it's been impossible to study relevant brain activities during eating because brain cells that control this process are located deep in our brains, making them hard to access or record in an awake animal. New techniques developed by the team allowed for the first-ever imaging and recording of a brainstem structure critical for feeling full, called NTS, in an active mouse.
The new study found that when researchers put food directly into the mouse's stomach, brain cells called PRLH were activated by signals from the gut (消化道), in line with traditional thinking. However, when they allowed the mice to eat the food as they normally would, those signals from the gut didn't show up. Instead, the PRLH brain cells switched to a new activity pattern that was entirely controlled by signals from the mouth. "It's astonishing that these cells were activated by the perception of taste, " said researchers. "It shows that there are other components of the appetite-control system that deserves our attention. "
The PRLH-activated slowdown also makes sense in terms of timing. The taste of food allows PRLH to switch their activity in seconds. In contrast, another group of brain cells, called CGC, takes several minutes to respond to signals from the gut. The good thing is that CGC can hold back hunger for a much longer time. These two sets of brain cells interact to work together: one uses taste to slow down eating, while the other signals that you are full.
Understanding how body signals regulate appetite could improve weight-loss programs for the overweight by making use of interactions between signals from different brain cell sets.
