Study identifies previously unknown neuronal activity in the gut.

The enteric nervous system (ENS) is known as the second brain, or the brain in the gut, due to the fact it can operate independently of the central nervous system (CNS). Despite the known role of the ENS in generating motor activity in the colon, observing ENS neurons in action has been a challenge.  Now, a study from researchers led by Flinders University shows how the gut acts independently of the brain and central nervous system through its own neuronal activity.  The team states they have used a novel high-tech methodology to accurately record the nerve activities of the ‘second brain’ in the body.  The study is published in the journal JNeurosci.

Previous studies indicate it is a long-standing mystery in vertebrates as to how the ENS generates neurogenic contractions of smooth muscle in the gastrointestinal tract. It is well-known that myogenic pacemaker cells exist in the gastrointestinal tract to produce contractions. However, the mechanisms underlying the source of the neurogenic contractions of smooth muscle in the gastrointestinal tract remains unknown.  The current study demonstrates how a previously unknown rhythmic activity generates so-called colonic migrating motor complexes to transport fecal pellets through the mouse colon

The current study utilizes high-resolution neuronal imaging system and simultaneous electrophysiological recordings from the smooth muscle cells in an isolated whole mouse colon to record the activity of about 400,000 individual neurons in the ENS. Results show this technique successfully tracks how this activity transports fecal pellets through the mouse colon.  Data findings verify a previously unknown pattern of neuronal activity in the peripheral nervous system.

The group explains their data verifies the ENS really is the second brain as it is capable of functioning independently of any other neural inputs, and until this study, it was unclear how large populations of neurons in the ENS led to contractions of the intestine.  They go on to add they have been able to see precisely how tens of thousands of individual neurons in the ENS are activated to cause smooth muscle contractions that underlie propulsion of colonic content.  They conclude it is these contractions that propel waste through the last leg of the digestive system.

The team surmises their findings identify a previously unknown pattern of neuronal activity in the peripheral nervous system.  For the future, the researchers state the next step would be to understand how the ENS is activated during chronic constipation, a condition affecting millions of people around the world who rely on medication for relief.

Source: Flinders University

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