Hunger is a powerful feeling with important biological underpinnings. It signals the body to forage for food, which is a behavior crucial to avoiding extreme hunger and ensuring survival. When we are hungry, we crave food, and when we finally get to eat, our body rewards us with pleasurable sensations and a general state of happiness.
Rüdiger Klein’s department at the Max Planck Institute for Biological Intelligence in Germany studies the brain networks that underlie feeding behavior in mice. For this, the researchers carried out an in-depth analysis of the different cell types in a region of the brain known as the central amygdala.
Previously, the amygdala had been studied primarily in the context of feelings such as fear and reward, while the regulation of eating was thought to occur in different parts of the brain, such as the hypothalamus.
Christian Peters, postdoctoral researcher in the department
Nine cell groups
Peters and his colleagues examined individual cells in the central amygdala, studying messenger RNA molecules, the cells’ working copies of their genes. The analysis revealed that the cells are organized into nine different groups. Some of these groups stimulate appetite, while others inhibit it and regulate the production of messenger RNA when mice eat or fast.
We now have a much better understanding of the diversity of cell types and physiological processes that promote feeding in the central amygdala. Our research reveals for the first time that the hunger hormone ghrelin also acts on cells in the central amygdala.
There, it activates a small set of cell clusters, collectively marked by the presence of the Htr2a protein, to increase nutrition.
Ghrelin and its functions
We believe ghrelin has multiple functions. When mice are hungry, ghrelin activates appetite-related brain regions to predispose the animals to eat. Additionally, the hormone increases activity in brain circuits like the amygdala that confer rewards, which likely serve as an incentive to eat more food.
Other brain circuits, such as the hypothalamus, which regulate the body’s metabolism, take over and signal the mice that it’s important to eat to survive.
Feeling hungry or full has a profound impact on physical and emotional well-being, as everyone probably knows from the pleasurable sensations associated with tasty foods.
The neural networks that convey these feelings are clearly linked to those that control eating, but we still don’t fully understand how they influence each other.
“If we uncover these connections, we will better understand the neural processes involved in pathological eating behaviors such as overeating,” concludes Christian Peters. “There are numerous biological factors that contribute to this complex behavior, and we need to look at physiological processes to understand these factors.”
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Source: Olhar Digital