Cholinergic activity of intestinal muscle in vitro taken from horses with and without equine grass sickness.

This study examines the muscle activity in the intestines of horses diagnosed with Equine Grass Sickness (EGS), a neurological disorder affecting the digestive system. The research analyses the extent of damage caused by EGS to different regions of the bowel and suggests an increased sensitivity in certain receptors of horses with acute cases of the disease.

Context and Objective

• The research was conducted to understand the impact and behavior of Equine Grass Sickness (EGS) on the motility of the intestine in horses. EGS is a severe disease that causes degeneration and depletion of neurons in horses.
• It’s the first functional study that measures the motility of intestines taken post mortem from horses affected by EGS, comparing it with healthy horses.

Methodology

• Tissue samples from the small intestine of both healthy and EGS-affected horses were suspended in an organ bath to analyze their motility in vitro – meaning outside their normal biological context.
• The researchers also conducted a close examination of the activity and functionality of the cholinergic system – the part of the nervous system that uses the neurotransmitter acetylcholine – in these horses.
• Test drug Physostigmine was used to enhance the motility of all muscle strips for the purpose of the study.

Findings

• The research found that tissues from horses suffering from Acute Grass Sickness (AGS), a severe form of EGS, exhibited the longest latency period before a measurable response to the Physostigmine could be observed.
• Difference in the extent of damage to different regions of the intestine was noted. The ileum (the last part of the small intestine) appeared to be more affected by EGS than the duodenum (the first part of the small intestine).
• Duodenal strips showed a significant enhancement in the rate of spontaneous contractions for both normal and EGS-affected tissue, which was not the case with ileal strips.
• The research also found a suggested hypersensitivity in muscarinic receptors (receptors in the nervous system that play several roles including regulation of heart rate and movement of smooth muscle) when using the bethanecol, particularly with AGS samples.

Conclusion

• The study provided crucial insights into how EGS affects the horse’s intestinal muscle activity, hinting at an increased sensitivity in some nervous system receptors in cases of AGS and showcasing a differentiated extent of damage to various bowel regions.