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 that the gut has a mind of its own, acting independently of the brain and central nervous system. The team state that 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 show that 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 that generate contractions. However, the mechanisms underlying the generation of 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 utilises 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 that 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 explain the ENS has been called the second brain because it is really a brain of its own, which can function independently of any other neural inputs. 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 which underlie propulsion of colonic content. They conclude that it is these contractions which propel waste through the last leg of the digestive system; until this study, no one had any idea exactly how large populations of neurons in the ENS led to contractions of the intestine.
The team surmise that their findings identify a previously unknown pattern of neuronal activity in the peripheral nervous system, which provides a blueprint to understand how dysfunctional neurogenic motor patterns may arise along the colon. 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