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A new US study has added to existing knowledge concerning the million or so brain cells in our gut by making use of lab mice to show that it can also grow new ones under the control of the neurotransmitter serotonin. The findings might be used to develop new drugs for gastrointestinal disorders, which affect around 25 per cent of adults inside the US every day, and come second only towards the common cold as the reason most Americans miss function, said the researchers.

The study, which will be the very first to show that the adult intestine can make new neurons within the enteric nervous system (ENS), was led by Drs Mintsai Liu, and Michael D Gershon, at Columbia University within the City of New York and is published inside the five August concern of The Journal of Neuroscience.

Liu and Gershon and colleagues utilised a serotonin-related drug to add neurons towards the adult enteric nervous system, which they stated was the first time this had been carried out.

“Conceivably, treatment with compounds of this type can be employed inside the future to help repair a damaged or congenitally defective enteric nervous method with no resorting to an invasive procedure,” they told the media.

So what is the ENS?

Scientists have identified evidence of what numerous of us already suspected: our brains and our guts “talk” to every other. In truth they are so intimately connected that some believe the gut and also the brain should be viewed as portion of 1 method.

We all know our gut is sensitive to emotions: we have “butterflies” in our stomach, we really feel nauseous in certain circumstances, and some experiences can be “gut wrenching”. These are all visceral manifestations of anxiety, anger, sadness, elation. Doctors know it is crucial to bear this in thoughts when treating gastrointestinal disorders that seem to have no obvious physical or infectious trigger.

Our 30-foot long gut is embedded with cells of the enteric nervous system, the ENS, a complex method of around 100 million nerves which is usually referred to as our “second brain”. The ENS supervises the processes of digestion and stays in close contact with, and is heavily influenced by, the central nervous program (the CNS) which comprises the brain and spinal cord.

When the fetus grows within the womb, the ENS develops from the same tissue as the CNS, and in a lot of respects its structure mirrors that of the brain in that it has sensory and motor neurons supported by a protective structure of glial cells which acts a bit like “scaffolding”. The ENS and CNS also use a lot of of the same chemical messengers or neurotransmitters inclusing acetylcholine and serotonin. Such communication explains obvious things like why we stop eating when we are full, or why we feel sick or lose our appetite on the morning of an important exam.

Until lately, neuroscientists believed that new neurons only grew in fetal brains and also the neurons we had at birth had been the ones we kept for life and that was it. But now we know that the CNS does make new neurons throughout adulthood.

And with this study, Liu and Gershon and colleagues show that under specific conditions, such as those controlled by serotonin, the ENS can also make new neurons.

It was about four decades ago that researchers discovered that our bowels contain high levels of serotonin 5-HT. In reality a recently developed drug, tegaserod, designed to treat constipation and irritable bowel syndrome targets the serotonin receptor 5-HT4. Even so, the drug, which received approval from the US Food and Drug Administration in 2002, was later withdrawn because it was thought it may well cause heart attacks.

Liu and Gershon and colleagues found that the 5-HT4 receptor and, by inference, serotonin, are intimately involved in controlling the production of new ENS neurons following birth.

They compared mice that had the 5-HT4 receptor (“normal” mice) with mice that didn’t. Compared with the normal mice, the mice that lacked the receptor had exactly the same number of neurons at birth, but they waned as the mice got older.

Also, when the researchers gave the normal mice a drug that stimulated the 5-HT4 receptor, they identified not simply that it enhanced the post-birth production of ENS neurons but it protected the ones that were already there.

Dr Arturo Alvarez-Buylla of the University of California, San Francisco, an expert in stem-cell neurobiology and developmental neuroscience who was not involved using the study, stated that Liu and Gershon and colleagues had helped to clarify some unanswered questions about the gastrointestinal method. He stated their finding:

“Not only suggests that new enteric neurons can be generated in the adult, but that activation of the serotonin receptor is required for this method.”

“The enteric nervous method has a extremely huge number of neurons, yet we know extremely little about their progressive loss throughout life and regardless of whether they can be regenerated,” he added.

The research was funded by the National Institutes of Wellness and Novartis, the drug business that makes tegaserod.

The Journal of Neuroscience.

Source: Society for Neuroscience; The Sensitive Gut, Harvard Well being Publications.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
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