MSGID: 1:317/3 646ee48f   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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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   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   
      
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   Story Source: Materials provided by Max-Planck-Gesellschaft. Note:   
   Content may be edited for style and length.   
      
      
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   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   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230524182043.htm   
      
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