Article: The Tantalizing Links Between Gut Microbes and the Brain [Nature]

“Meanwhile, researchers were starting to uncover ways that bacteria in the gut might be able to get signals through to the brain. Pettersson and others revealed that in adult mice, microbial metabolites influence the basic physiology of the blood–brain barrier4. Gut microbes break down complex carbohydrates into short-chain fatty acids with an array of effects: the fatty acid butyrate, for example, fortifies the blood–brain barrier by tightening connections between cells (see ‘The gut–brain axis’).

“Recent studies also demonstrate that gut microbes directly alter neurotransmitter levels, which may enable them to communicate with neurons. For example, Elaine Hsiao, a biologist now at the University of California, Los Angeles, published research5 this year examining how certain metabolites from gut microbes promote serotonin production in the cells lining the colon — an intriguing finding given that some antidepressant drugs work by promoting serotonin at the junctions between neurons. These cells account for 60% of peripheral serotonin in mice and more than 90% in humans.

“Like the Karolinska group, Hsiao found that germ-free mice have significantly less serotonin floating around in their blood, and she also showed that levels could be restored by introducing to their guts spore-forming bacteria (dominated by Clostridium, which break down short-chain fatty acids). Conversely, mice with natural microbiota, when given antibiotics, had reduced serotonin production. “At least with those manipulations, it’s quite clear there’s a cause–effect relationship,” Hsiao says.”

Read the full article from Nature by Peter Andrey Smith: The Tantalizing Links Between Gut Microbes and the Brain

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Article: The Neurobiology of Grace Under Pressure [Psychology Today]

“Healthy vagal tone is indicated by a slight increase of heart rate when you inhale, and a decrease of heart rate when you exhale. Deep diaphragmatic breathing—with a long, slow exhale—is key to stimulating the vagus nerve and slowing heart rate and blood pressure, especially in times of performance anxiety. A higher vagal tone index is linked to physical and psychological well-being. A low vagal tone index is linked to inflammation, negative moods, loneliness, and heart attacks. 

“Heart disease is the number one killer in America. One way to improve your heart health is to focus on the vagus-friendly lifestyle habits I explore below. Well-conditioned athletes have higher vagal tone because aerobic breathing creates healthy vagal tone, which results in a lower resting heart rate. Healthy cardiac function is directly linked to stimulating the vagus nerve. 

“In 1921, a German physiologist named Otto Loewi discovered that stimulating the vagus nerve caused a reduction in heart rate by triggering the release of a substance he coined Vagusstoff (German: “Vagus Substance”). The “vagus substance” was later identified as acetylcholine and became the first neurotransmitter identified by scientists.  

“Vagusstuff is literally a tranquilizer that you can self-administer simply by taking a few deep breaths with long exhales. You can consciously tap the power of your vagus nerve to create inner-calm on demand. This knowledge alone should be enough to reduce the fear-of-fear-itself and give you grace under pressure next time you need it.”

Read further about the 8 habits for a healthier vagus in Christopher Bergland’s full article at Psychology Today: The Neurobiology of Grace Under Pressure.

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Article: Why the Sexes Don’t Feel Pain the Same Way [Nature]

“To better understand why male and female mice dealt with pain so differently, Sorge and Mogil turned to a pain source that affects all mice. They injured the animals’ sciatic nerves, which run from the lower back down each leg. This led to a form of chronic pain that happens when the body’s pain-detecting system is damaged or malfunctioning. It caused both male and female mice to become extra sensitive to touch.

“Yet even in this case, there were differences. Microglia seemed to have a prominent role in the pain of males, but not in that of female mice2. Sorge and a team of collaborators from three institutions found that, no matter how they blocked microglia, this eliminated the pain hypersensitivity in males alone.

“It’s not that females were immune to pain. They were just as bothered by nerve injury as the males were, but they weren’t using microglia to become hypersensitive to touch. Mogil and Sorge wondered whether another immune component, called a T cell, was behind the chronic pain in females. These cells have a known role in pain sensitization in mice.

“Sorge tried the same nerve injury in female mice lacking T cells. They still became hypersensitive to the fine hairs, but the mechanism now seemed to occur through microglia. In females lacking T cells, blocking the activity of microglia prevented this pain response, just as it did in males. And when the researchers transferred T cells back to female mice that were lacking them, the animals stopped using microglia in nerve-injury pain (see ‘Two routes to pain’).”

Read Amber Dance’s full article at Nature: Why the Sexes Don’t Feel Pain the Same Way

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