Quantitative assessment of physiological and behavioural parameters in healthy dairy cows evoked by transcutaneous electrical nerve stimulation of the udder

Visceral pain triggered by traction on the ileocecal ligament with ileitis

Background

Visceral pain is a common symptom of several gastrointestinal disorders. Despite tremendous progress in understanding its basic mechanisms, it remains a significant health challenge for clinicians. The present study quantified the intensity of visceral pain using ileocecal ligament traction on an inflamed ileum in goats.

Materials and methods

A total of 36 male goats weighing 20.05±2.1 kg were randomly allocated equally into a 2,4,6-trinitrobenzenesulfonic acid (TNBS) group (n=18) and a saline group (n=18). Ileitis was induced via the injection of 30 mg TNBS dissolved in 30% ethanol into the ileal wall through a laparotomy. An equal volume of normal saline was injected into the ileal wall of the saline goats. Behavioral responses to traction (2, 4, and 6 N) on the ileocecal ligament were observed on days 3, 7, and 14. Six goats from each group received a laparotomy and partial intestinal resection for ileal sample collection immediately after behavioral testing on days 3, 7, and 14. Ileal histopathological changes were assessed and concentrations of myeloperoxidase, IL-1β, IL-6, and TNFα investigated using enzyme-linked immunosorbent assay.

Results

The TNBS-treated goats exhibited remarkably increased macroscopic scores, mast-cell counts, myeloperoxidase, and TNFα concentrations on days 3 and 7 compared to the saline group, and increased microscopic scores and IL-1β and IL-6 concentrations on days 3–14. The TNBS-treated goats exhibited behavioral changes in response to traction in the same pattern as their microscopic changes and cytokine levels. The traction force correlated positively with pain-behavior responses.

Conclusion

Traction on the ileocecal ligament of goats with ileitis provoked an apparent, stable, and reproducible ileum-derived pain. The current model may be helpful in evaluating the efficacy of new drugs for the management of visceral pain and in investigating its underlying mechanisms.