Cool! Science and Cell reveal that the "sixth sense" is hidden in the intestines and can be connected to the brain at a second speed.

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Cool! Science and Cell reveal that the "sixth sense" is hidden in the intestines and can be connected to the brain at a second speed.

2018-09-26 00:25:32 200 ℃
Bio-Exploration
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Beautiful before the important speech After eating a big meal, I feel dizzy... We can vaguely feel that there is some mysterious connection between the internal organs and the brain. But the mechanism behind it has not been cracked. Until recently, scientists have finally discovered that our gut has a more direct connection to the brain through a neural circuit, which allows it to transmit signals in seconds! This finding may lead to the development of new therapies for diseases such as obesity, eating disorders, and even depression and autism related to intestinal problems.

The sensory neurons in the intestine tell the vagus nerve (yellow) and the brain, our stomach How it works (Source: NICOLLE R. FULLER)

01

Intestinal - the second brain of the human body

The human intestine is lined with more than 100 million nerve cells - this is actually equivalent to our Second brain." In fact, the intestines “talk” to the brain, which in turn releases hormones into the bloodstream, telling us whether it is hungry in about 10 minutes.

However, the latest two studies from the top journals Science and Cell show that the gut has a more direct connection to the brain through a neural circuit! This "intuitive" type of communication pathway is more direct and faster than the diffusion of hormones, allowing the intestinal tract to transmit signals in seconds.

02

Science: sixth Sense - vagus nerve

In 2010, Duke University neuroscientist Diego Bohórquez opened an amazing discovery through electron microscopy: the intestinal endocrine cells are located on the inner wall of the intestine, which stimulates digestion and Hormones that suppress hunger, they have foot-like processes, similar to synaptic neurons used to communicate with each other. Bohórquez knows that enteroendocrine cells can send hormone information to the central nervous system, but he also wants to know if they can “talk” to the brain through electrical signals like neurons. If this is the case, they will have to send a signal through the vagus nerve, which passes from the intestine to the brainstem.

In order to verify this hypothesis, he and his colleagues injected a fluorescent rabies virus into the colon of mice, spread through the synapse of neurons, and waited for the endocrine cells and their "partners" to be spotted. bright. The researchers reported in the September 21 issue of Science that these "partners" are vagus nerve cells.

DOI: 10.1126/science.aat5236

In the Petri dish, enteroendocrine cells Extends to the vagus nerve and forms synaptic connections with each other. Surprisingly, these cells even secrete glutamate, a neurotransmitter involved in the sense of smell and taste, and vagus cells can capture this in 100 milliseconds. Material, this is faster than blinking!

Bohórquez points out that this is much faster than the hormones that travel from the intestines to the brain through the blood. The dullness of hormones may be responsible for the failure of many appetite-suppressing drugs. The next step, he said, is to investigate whether this visceral-brain signal provides the brain with important information about the nutritional and caloric values ​​of the food we eat.

He said that ultra-fast visceral-brain signaling has some distinct advantages, such as the detection of toxins and poisons. Not only that, there may be other benefits to detecting visceral content in real time, and further exploration is needed.

Although many problems still exist before the clinical significance becomes clear, the researchers are still excited about this: "This is a cool new problem."

03

Cell: Left and Right Vagus - Satisfaction and Reward >

September 20, another study published in the journal Cell provides additional clues about how visceral sensory cells benefit us.

DOI:https://doi.org/10.1016/j.cell.2018.08.049

< Specifically, the researchers combined different viruses carrying molecular tools to enable them to visually activate vagus nerve cells that are connected to the gut, causing the vagus nerve cells of other organs to remain silent. This advanced technology, known as "optogenetics," allows researchers to use light to manipulate the activity of a set of pre-specified neurons.

Studies have shown that laser stimulation increases the level of mood-enhancing neurotransmitters called dopamine in the rodent brain, which is essential for rewards and motivation. Further trials have found that the reward neurons of the right vagus nerve are subject to the same constraints as the reward neurons of the central nervous system, which means that they combine peripheral sensory cells with previously drawn brain reward neurons. The group is connected.

Surprisingly, left vagus nerve is related to satiety, but has nothing to do with rewards. The anatomy of the research team also revealed for the first time that the left and right vagus branches rise asymmetrically toward the central nervous system.

Ivan de Araujo, a neuroscientist at the Icahn School of Medicine in Mount Sinai, who led the study of Cell, points out that the two papers together help explain why vagus nerves can be used to treat severe depression in people. And why, on a basic level, eating makes us feel good. "Even if located outside the brain, these neurons are fully consistent with the definition that reward neurons can drive motivation and increase happiness," he concluded.

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2)A gut-brain neural circuit for nutrient sensory transduction

3)A Neural Circuit for Gut-Induced Reward

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