A study by Flinders University researchers has provided new insights into how the colon functions and actually expels its contents and could lead to new diagnostics tools and treatments for gastrointestinal disorders to address problems with bowel movements leading to constipation, diarrhoea and pain.
Propulsion of intestinal contents is controlled by millions of neurons within the wall of the gut, known as the enteric nervous system. Capable of operating independently of the brain, a functioning enteric nervous system is essential for life - but exactly how it functions has been a mystery.
By unravelling the neural circuits of the enteric nervous system in guinea pigs and humans Professor Marcello Costa and colleagues are able to understand how the enteric nervous system ensures that food is slowly mixed and propelled along the digestive tube, allowing for absorption of nutrients and excretion of waste.
“For the first time we have combined video recording intestinal movements with a pressure-measuring manometric probe, enabling movements, pressures and electrical activities to be recorded all at the same time within the colon,” explained Costa. “This powerful combination of techniques applied to a guinea pig colon identified several distinct neural mechanisms involved in the propulsion of colonic contents. This answers the deceptively simple question of how neural mechanisms within the colon manage the propulsion of bowel contents.”
The paper, ‘Roles of three distinct neurogenic motor patterns during pellet propulsion in guinea pig distal colon’, published in the Journal of Physiology, noted that there are at least three neural mechanisms which are not directly involved in propulsion: cyclic motor complexes, transient neural events and distal colon migrating motor complexes.
In excised guinea‐pig colon, the researchers simultaneously recorded high resolution manometry, video‐imaging of colonic wall movements and electrophysiological recordings from smooth muscle, which enabled us to identify mechanisms that underlie the propulsion of colonic content. The results show that the intermittent propulsion during emptying of the multiple natural faecal pellets is due to the intermittent activation of cyclic motor complexes and this is facilitated by transient neural events. The loss or dysfunction of these activities is likely to underlie disordered gastrointestinal transit.
"The findings also show how studies in human and animals can be complementary, identifying fundamental mechanisms that are shared across species - in this case guinea pigs and humans,” he concluded. “Currently we treat intestinal disorders by addressing the symptoms, such a stopping-up diarrhoea or softening stools to ease constipation, but as a result of this new understanding of the neural networks of the enteric system, clinicians may be able to develop treatments that treat the cause of the problems."