How tasty is the food?
A hormone and specialized brain cells regulate feeding behavior in mice


Date:
May 24, 2023
Source:
Max-Planck-Gesellschaft
Summary:
A hormone and specialized brain cells regulate feeding behavior
in mice.


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FULL STORY ==========================================================================
To know when it's time for a meal -- and when to stop eating again --
is important to survive and to stay healthy, for humans and animals alike.

Researchers at the Max Planck Institute for Biological Intelligence investigated how the brain regulates feeding behavior in mice. The team
found that the hormone ghrelin activates specialized nerve cells in a
brain region known as the amygdala. Here, the interaction between ghrelin
and the specialized neurons promotes food consumption and conveys hunger
and the pleasant and rewarding feelings associated with eating.

Hunger is a powerful sensation with important biological underpinnings. It signals the body to look for food, which is a crucial behavior to prevent starvation and ensure survival. When we're hungry, we crave for food --
and when we finally get to eat, our body rewards us with pleasant feelings
and a general state of happiness.

A network of brain circuits and signaling pathways orchestrates the eating behavior of humans and animals and elicits the associated sensations. One
of the central players in this network is the hormone ghrelin. It is
released by stomach cells when humans and animals are hungry or fasting,
and promotes feeding behavior.

The department of Ru"diger Klein at the Max Planck Institute for
Biological Intelligence studies the brain networks that underly feeding behavior in mice.

To this end, the researchers conducted a thorough analysis of
the different cell types in a brain region known as the central
amygdala. "Previously, the amygdala had mostly been studied in the
context of feelings like fear and reward, while the regulation of
feeding was thought to happen in different parts of the brain, such as
the hypothalamus," says Christian Peters, a postdoctoral researcher in
the department.

Nine cell clusters Peters and his colleagues analyzed individual cells
in the central amygdala, studying messenger RNA molecules -- the cell's
working copies of their genes.

The analysis revealed that the cells are organized into nine different
cell clusters. Some of these clusters promote appetite while others
inhibit it, and they adjust their production of messenger RNAs when the
mice are fed or fasting.

"We now have a much better understanding of the diversity of cell
types and the physiological processes that promote feeding in the
central amygdala," says Ru"diger Klein. "Our research uncovers for the
first time that the 'hunger hormone' ghrelin also acts on cells in the
central amygdala." There, it activates a small subset of cell clusters, collectively marked by the presence of the protein Htr2a, to increase
feeding.

Multiple functions for ghrelin The scientists found that the Htr2a
neurons became active after an overnight fast or when stimulated by the
hormone ghrelin. The cells also responded when the researchers presented
food to the mice. "We think that ghrelin performs multiple functions,"
explains Christian Peters. "When mice are hungry, ghrelin activates
the appetitive brain regions to predispose the animals for eating. In
addition, the hormone enhances the activity in brain circuits, such as
the amygdala, that confer rewards, which is likely an incentive to eat additional food." This way, ghrelin increases the palatability of food
in proportion to how satiated the mice currently are.

After a fasting diet, when the animals were very hungry the activity
of Htr2a neurons was not needed to start feeding, presumably because
the tastiness of food is less important under these conditions. "Other
brain circuits, for example the hypothalamus, which regulate the body's metabolism, take over and signal the mice that it's important to eat in
order to survive," says Christian Peters.

Feeling hungry or satiated has profound impacts on physical but also
on emotional wellbeing, as probably everyone knows by the pleasures
associated with eating tasty food. "The neuronal networks that convey
these feelings are obviously linked to those that control eating,
yet it is not fully understood how exactly they influence each other,"
says Ru"diger Klein.

"If we figure out these connections, we will better understand the
neuronal processes that are involved in pathological eating behaviors,
such as overeating," concludes Christian Peters. "There are numerous
biological factors that contribute to such a complex behavior and
we have to look at the physiological processes to understand these
factors." Ultimately, this knowledge might lead to novel therapeutic
approaches to alleviate eating disorders. For now, the research lays
the groundwork for further studies to investigate how specific neuron populations are involved in the neuronal circuits that control feeding. It
also adds another important piece to the puzzle of understanding how
the brain orchestrates behavior.

* RELATED_TOPICS
o Mind_&_Brain
# Neuroscience # Brain_Injury # Psychology #
Nutrition_Research
o Plants_&_Animals
# Mice # Biology # Animal_Learning_and_Intelligence # Food
* RELATED_TERMS
o Neurobiology o Pituitary_gland o Stem_cell o Oxytocin o
Aggression o Brain_tumor o Melatonin o Thyroid_hormone

========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Christian Peters, Songwei He, Federica Fermani, Hansol Lim,
Wenyu Ding,
Christian Mayer, Ru"diger Klein. Transcriptomics reveals amygdala
neuron regulation by fasting and ghrelin thereby promoting
feeding. Science Advances, 2023; 9 (21) DOI: 10.1126/sciadv.adf6521 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230524182043.htm

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