Mechanism underlying post-infectious motility disorders

Abstract

Fbllt: Center forGw&romtwmlo~i~wl Research, K.U. Lmm, Leuvan, Belgium. Post-inflammatory dysmotility is a well established clinical entity: postviral gastroparesis I, irritable bowel syndrome following infectious gastroenteritis 2 and motor disturbances in non-inflamed areas and in-between inflammatory events in inflammatory bowel disease 3 have all been reported. The association of intestinal inflammatory states with abnormalities of motility, both in man and experimental animals, is well established 3-6. Several animal studies have concentrated on the effect of inflammation and the influence of inflammatory mediators on neuromuscular activity 5 6. Studies in the Trichinella spiralis jejunitis model in rats have demonstrated altered expression and release of neurotransmitters from both the extrinsic and the intrinsic innervation, and a number of inflammatory mediators have been implicated in these changes 5 6. The mechanisms underlying motor disturbances that persist after a transient inflammation have received less attention. Ethanol/TNBS application has been widely used to induce acute and chronic inflammation in rat colon, guinea pig ileum and rat jejunum. We used this model to investigate post-inflammatory motility changes and the underlying mechanisms comparing this model of intestinal inflammation to water-treated controls. Using histology and myeloperoxidase activity, we observed that ethanol/TNBS induced a transient jejunal inflammation, which completely resolved within one week after induction ‘. We used serosal electromyography (EMG) electrodes to record motor activity after resolution of the inflammation. Compared to controls, TNBStreated animals had a lower proportion of propagated activity fronts (40/62 vs 13/39, p<O.O05). The number of phases 3, i.e., aborally migrating activity fronts followed by a phase 1, was significantly decreased in the TNBS group compared to controls (2+0.3 vs 5.4kO.7 per hour, respectively, ~~0.01). Consequently, the interval between these phases 3, corres-ponding to the MMC cycle length, increased significantly (44.7k4.4 vs 165~3.0 min, p<O.OOl). Triple labelling immunohistochemistry was used to evaluate neurotransmitter content of the myenteric neurons in longitudinal muscle-myenteric plexus preparations. Immunoreactivity for neuron specific enolase (NSE) was used as a pan-neuronal marker. Cholinergic neurons were visualized by antibodies for the enzyme choline acetyltransferase (ChAT), whereas nitrergic neurons were visualized by antibodies for the enzyme, nitric oxide synthase (NOS). Specific antibodies were also used to identify neurons containing vasoactive intestinal polypeptide (VIP). In the triple labelling experiments, the number of NSE-immunoreactive neurons per ganglion one week after administration of TNBS or water did differ significantly (3 1.3kO.7 vs 30.720.8, NS). Likewise, the number of ChAT-IR cells did not differ between the two groups (28.5rtO.7 vs 28.3kO.7, NS), but the number of nNOS-IR neurons was significantly lower in TNBS-treated animals (1.820.2 cells per ganglion compared to 3.520.2, p<O.O005). In the double labelling experiments, the number of nNOS-/VIP+neurons did not vary significantly (1.2&O. 1 cells per ganglion vs 1.3kO.1, NS). The number of nNOS+/VIP+ neurons (2.9kO.2 cells per vs 3.8kO.2, p<O.O05) and the number of nNOS+/VIPneurons