Endotoxin-induced injury of the central, autonomic and enteric nervous systems and intestinal muscularis in Thoroughbred horses.

This research studied the effects of endotoxin on the structure of the equine central, autonomic, and enteric nervous system and intestinal muscular layer, within six Thoroughbred horses with artificially induced endotoxaemia. The study verifies damage caused by endotoxin in these systems and suggests it is due to vasoconstriction or vasospasm.

Research Objectives and Methodology

• The main purpose of this study was to investigate how endotoxin affects the structure of different components of the nervous system and the intestinal muscularis in Thoroughbred horses.
• A secondary objective was to compare the findings with known changes observed in human patients suffering from septic shock.
• The research process involved experimentally inducing endotoxaemia in six Thoroughbred horses and examining the subsequent morphological changes in their bodies.
• By using histology and electron microscopy techniques, researchers were able to identify and analyze lesions, edema, cellular shrinkage, and the presence of erythrocytes and neutrophils.

Key Findings

• The central nervous system of the horses exhibited perivascular edema around the arterioles and ring hemorrhages around veins. These changes were identified as being similar to what is seen in human patients with septic shock.
• In the cranial mesenteric ganglia, there were significant changes suggestive of ischemic alterations, such as neuronal cell bodies becoming pink or red and shrinkage of the cytoplasm. Erythrocytes and neutrophils infiltrated the areas around arterioles, indicating acute focal interstitial inflammation.
• Oedema of the endoneurium and mesoaxon in the nerve fascicles running inside or outside the ganglia was found using transmission electron microscopy.
• In the myenteric layer, neurons showed shrinkage of the cytoplasm with multiple cytoplasmic vacuoles, suggesting ischemic changes.
• The intestinal muscularis showed edematous degeneration and coagulation necrosis in smooth muscle cells, with the cells becoming dissociated.

Conclusions and Implications

• The researchers concluded that endotoxin caused arterionecrosis which has been commonly observed in the autonomic and enteric nervous system and intestinal muscularis, most likely as the result of vasoconstriction or vasospasm.
• The results of the study help to understand better the effects of endotoxin on the equine body and the pathological processes involved in endotoxaemia. Improved understanding could lead to the development of more effective treatment practices for horses suffering from endotoxaemia.