Rely on Gut Feeling? How the Second Brain in Gut Communicates

Summary: Viscerofugal neurons inside the gut wall communicate to other neurons outside of the gut, near the spinal cord, to send messages to the brain.

Source: Flinders University

You’re faced with a big decision so your second brain provides what’s normally referred to as “gut instinct,” but how did this sensation reach you before it was too late?

The enteric nervous system (ENS) is an extensive network of neurons and transmitters wrapped in and around the human gut with the prime function of managing digestion, but researchers at Flinders University are delving into the complexity of this brain like system to uncover it’s secret capabilities.

In a new study published in the eNeuro journal, Professor Nick Spencer’s laboratory has identified a particular type of neuron in the gut wall that communicates signals to other neurons outside the gut, near the spinal cord and up to the brain.

“There is significant interest in how the gut communicates with the brain as a major unresolved issue because of growing evidence that many diseases may first start in the gut and then travel to the brain, an example of which is Parkinson’s Disease,” says Professor Spencer.

“The new study has uncovered how viscerofugal neurons provide a pathway so our gut can ‘sense’ what is going on inside the gut wall, then relay this sensory information more dynamically than was previously assumed to other organs, like the spinal cord and brain which influence our decisions, mood and general wellbeing.”

This shows a brain
This study represents a big step towards understanding ENS functions and the complexity of the gut and brain connection through the neurons that allow communication in the body. Image is in the public domain.

The results reveal why the ENS might play an increasingly important part on human health, and could shed light on potential new treatments for conditions like Parkinson’s disease.

This study represents a big step towards understanding ENS functions and the complexity of the gut and brain connection through the neurons that allow communication in the body.

Professor Spencer says there is increasing interest in understanding how the nervous system in the gut (ENS) communicates with the brain, to give us all those sensations we know of.

“What is particularly exciting about the gut, is that it is unlike all other internal organs (e.g. heart, liver, bladder) because the gut has its own nervous system, which can function independently of the brain or spinal cord. Understanding how the gut communicates and controls other organs in the body can lead to important breakthroughs for disease treatment and this is an important step in the right direction.”

About this neuroscience research article

Source:
Flinders University
Media Contacts:
Press Office – Flinders University
Image Source:
The image is in the public domain.

Original Research: Closed access
“A novel mode of sympathetic reflex activation mediated by the enteric nervous system”. by TJ Hibberd, WP Yew, BN Chen, M Costa, SJ Brookes and NJ Spencer. eNeuro.


Abstract

A novel mode of sympathetic reflex activation mediated by the enteric nervous system

Enteric viscerofugal neurons provide a pathway by which the enteric nervous system (ENS), otherwise confined to the gut wall, can activate sympathetic neurons in prevertebral ganglia. Firing transmitted through these pathways is currently considered fundamentally mechanosensory. The mouse colon generates a cyclical pattern of neurogenic contractile activity, called the colonic motor complex. Motor complexes involve a highly coordinated firing pattern in myenteric neurons with a frequency of ∼2Hz. However, it remains unknown how viscerofugal neurons are activated and communicate with the sympathetic nervous system during this naturally-occurring motor pattern. Here, viscerofugal neurons were recorded extracellularly from rectal nerve trunks in isolated tube and flat-sheet preparations of mouse colon held at fixed circumferential length. In freshly dissected preparations, motor complexes were associated with viscerofugal firing at 2Hz that aligned with 2Hz smooth muscle voltage oscillations. This behavior persisted during muscle paralysis with nicardipine. Identical recordings were made after 4-5 days organotypic culture during which extrinsic nerves degenerated, confirming that recordings were from viscerofugal neurons. Single unit analysis revealed the burst firing pattern emerging from assemblies of viscerofugal neurons differed from individual neurons, which typically made partial contributions, highlighting the importance and extent of ENS-mediated synchronization. Finally, sympathetic neuron firing was recorded from the central nerve trunks emerging from the inferior mesenteric ganglion. Increased sympathetic neuron firing accompanied all motor complexes with a 2Hz burst pattern similar to viscerofugal neurons. These data provide evidence for a novel mechanism of sympathetic reflex activation derived from synchronized firing output generated by the ENS.

SIGNIFICANCE STATEMENT

Significant interest exists in how the gut can control other body systems. Enteric viscerofugal neurons uniquely project axons out the gut wall forming circuits with prevertebral sympathetic neurons. Long considered principally transmitting mechanosensory information, a new mechanism is demonstrated here whereby a synchronized ENS-generated firing pattern underlying natural gut motor behaviour is also relayed through populations of viscerofugal neurons. Remarkably, this caused parallel firing in sympathetic neurons in the pattern generated by the ENS. This did not require dynamic mechanical activity. The identification of this mechanism revises the current concept of sympathetic reflexes being simply distension reflexes.

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