Morphologic and quantitative evaluation of the myenteric plexuses and neurons in the large colon of horses.

This research investigates the number of myenteric plexuses and neurons in the large colon of healthy horses and those with colon disease. The study found that healthy horses had greater myenteric plexus, neuron densities, and longitudinal muscle thickness in certain parts of the colon. Horses with colon damage displayed significantly lower neuron density and myenteric plexus density at specific colon segments. Enteroglial cells, found increased in horses with acute and chronic obstruction, could be a response to myenteric plexus inflammation, impacting bowel function.

Research Methods

• The study was prospective in nature and involved colon samples from 15 clinically normal horses and 31 horses suffering from colon disease.
• These samples were obtained, fixed, and stained using Hematoxylin and Eosin (H&E). This staining technique is commonly used in histology to identify and highlight specific features of cells and tissues.
• The researchers determined the number of myenteric plexuses (networks of nerves in the gastrointestinal system) and neurons, as well as the thickness of the longitudinal muscle in each colon segment for the clinically normal horses.
• The counts from each segment were then compared with each other and with the counts from the same segments in horses with colon disease.

Research Findings

• The results showed that the densities of myenteric plexus and neurons, as well as the thickness of longitudinal muscle, were significantly greater in certain parts of the colon (the pelvic flexure, left dorsal, and transverse colons) in clinically normal horses.
• Horses with chronic obstruction or a history of obstruction had significantly lower neuron density in the pelvic flexure.
• The density of the myenteric plexus was significantly less in certain parts of the colon in horses suffering from a specific type of colon obstruction (strangulating large colon torsion/volvulus). Similarly, neuron density was significantly reduced in all colon segments, apart from the left ventral colon, in these horses.
• The researchers also noted a significant increase in enteroglial cell numbers in myenteric plexuses of horses suffering from both acute and chronic obstruction. These cells can impact bowel function, suggesting a potential response to inflammation in the myenteric plexus.

Conclusions

• The density of the myenteric plexus and neurons can be estimated by evaluating linear counts of H&E-stained colon samples.
• The increase in enteroglial cells could potentially be a result of inflammation in the myenteric plexus. This inflammation might be affecting the regular function of the bowel.
• The understanding derived from this study can be helpful in treating equine colon disease, by possibly identifying the underlying neural deficit and inflammation.