Double negative feedback in the back of the brain mediats the consumption of food and water guided by a sense of eating.

on !-- 24, 2020, cell published a paper by the Scott M. Sternson Research Group at the Howard Hughes Institute of Medicine in the United States, Hindbrain Double-Negative Feedback Mediates Palatability-Guided Food and Water Water.
Researchers found that glutamate neurons in a new brain region in the brain's brain region, periLC, encoded information about the deliciousness of food or drink, and maintained mouse behavior at the feeding or water intake stage through two-way inhibitory feedback, which determines how much water the animals ate or measured each time.
In accordance with the calcium signal activity of these neurons in the body, together with the mice's eating or water intake behavior inhibits such neurons, can simulate changing the food deliciousness (palatability shifting), even if the mice are not hungry or thirsty state, but also without changing the number of times the mice eat or water intake, can effectively increase the time of each intake.
explains why, even after a full meal, it's hard to resist a bite of some delicious desserts or delicious milk teas.
By tracking the structure and function of the loop through the whole brain of mice and the hunger loop, the researchers found a series of brain regions commonly used by the two types of loops, including the rarely reported peri-locus coeruleus (periLC).
The nucleology, located in the back of the brain, near the fourth brain chamber, is only occasionally mentioned in brain anatomy studies in rats, and has not been precisely located in the latest mouse brain structure map published by the Allen Institute.
given that periLC belongs to the common downstream brain region of the hunger and thirst ring, the researchers ventured to speculate that the brain region was closely related to eating behavior and water-feeding behavior.
a number of repeated attempts, the researchers developed a calcium imaging experiment that stabilized the recording of deep brain regions in the back of the brain in free-moving mice (Figure 1).
brain is located at the very end of the brain and is directly connected to the spinal nerve.
animals are in a state of sobriety and free movement, the brain trunk will shift significantly with the twisting of the neck muscles during exercise.
how to implant endoscope devices in brain-dry positions for real-time calcium imaging has become a common challenge in the field.
the specific modification of the implanted lenses, Dr. Gong successfully recorded various dynamic changes in the free movement of neurons in the mice.
correlation studies have shown that some glutamate neurons in periLC are closely related to the eating behavior of mice and the consummatory phase in water-photographing behavior.
glutamate neurons are activated during this process and the other part is suppressed.
, glutamate neurons react in a messy and unresponsive way.
but through careful comparison and research, you will find that it is not enough.
Allows mice to ingest solutions of different flavors, observe the activity of these glutamate neurons, and then perform image processing and unsupervised groupings to find that solutions of a similar nature, such as sugar and water that mice like when hungry and thirsty, acid and salty, bitter and high-salt water, are used when they are hungry. Glutamate cells for excitable reactions and glutamate cells that inhibit reactions come from the same subsysty; for solutions that are diametrically opposed, such as sweet and bitter water, glutamate cells that inhibit reactions still come from the same sub-group, but glutamate cells that react excitedly to sweet and bitter water belong to two different sub-groups of cells.
That is, for drinks of a similar nature, both excitable and inhibitory reactions are homogeneity, but for heterogeneic drinks, the excited glutamate cells belong to different sub-groups, can simply and crudely represent the 'good or bad' nature of the drink.
glutamate cells, which inhibit reactions, have nothing to do with the nature of the food or drink.
But it is interesting to see how these inhibitory glutamate neurons react when eating or eating, which is closely related to the deliciousness of food or drink: in the same drinking volume, the inhibitory response to sweet water is greater than to water, while the reaction to bitter water is the smallest of all the test solutions.
the size of the glutamate cell inhibitory reaction represents the extent to which the food or drink is 'good or bad', or the degree of taste.
in a series of correlation experiments, the researchers ruled out the illusion that tongue or facial muscle movements might cause in mice's eating or watering behavior, demonstrating a correlation between the presence of inhibitory reactions and food or drinking itself.
What's more, allowing mice to eat autonomously, from hunger to food and drink, found that the reactions of these inhibitory glutamate neurons were better at tracking the time each time they ate than the reactions of excitable glutamate neurons.
because in this experimental system, eating time is closely related to the amount of food we eat, this means that inhibitory reactions are better able to track the amount of food we often say about each meal.
likely, glutamate neurons that inhibit the reaction received information about the deliciousness of food or drink, and based on this information encoded the current length of time mice ate.
" calcium imaging and other correlation experiments provide us with a lot of important first-hand information, giving us a basis for bold guesses.
but more importantly, to validate such a possibility through modeling and experimentation," stressed the paper's first author, Yu.
Based on the in-body activity characteristics of periLC inhibitory glutamate neurons, the researchers artificially divided the free eating process in mice into two-minute time blocks, including two alternating characteristics: one two-minute time block did not include any interference, and the other time block once the mice ate, the photogenetic method inhibited the activity of glutamate neurons in periLC, and the results were compared between the two time blocks in the group.
the researchers predict that this inhibitory response to increased levels of these cells will make mice mistakenly think that plain food or pure water becomes more delicious, increasing the length of time each time they eat or take water.
!--/ewebeditor:page--!--ewebeditor:page title"--indeed, the researchers finally found that when periLC glutamate neurons were inhibited, the mice ate or measured significantly more water.
More importantly, this increase is not due to an increase in the number of times you eat or take water, but from a longer time spent eating or drinking water each time, that is, not eating or drinking more, but eating or drinking more each time.
This reaction is very specific, and if the inhibitory effects of this photogenetics are randomly distributed, i.e. not associated with the eating or watering behavior of mice, no significant changes in eating or watering behavior are seen (Figure 2).
further mathematical modeling showed that the length distribution of each auto-eating or watering time in mice conformed to the exponential distribution characteristics, while the effect of inhibiting periLC glutamate neurons changed the coefficient beta in the exponential function.
is similar to the coefficient that changed the state in the Markov model.
1/beta is the probability of leaving the eating or watering behavior, and 1-1/beta is the probability of staying in the current eating or watering behavior (Pstay).
inhibition of periLC glutamate neurons, mediated by photogenetics, successfully increased the probability of staying in the current eating or watering behavior by about 5%, significantly increasing the time per feeding or watering (Figure 3).
In addition, when mice were given two bottles of the same concentration or different concentrations of sucralose solution at the same time, if the pair mice licked one side of the solution to inhibit periLC glutamate neurons, will change the original preference for both bottles of solution: will increase the match inhibition of that side of the solution preference, even if this side was relatively less like the low concentration of sucralose solution side.
because the sucralose solution does not contain any nutrients, the preference for it directly represents the hedony value of consuming food or beverages, which is an important indicator of deliciousness.
experiments have shown that changing the inhibition of periLC glutamate neurons can simulate changing the deliciousness of the solution, further confirming that these neurons encode the deliciousness of the food or water they consume.
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