Changes in the inhibitory responses to electrical field stimulation of intestinal smooth muscle from Trichinella spiralis infected rats

Functional motor changes and morphological alterations have been associated with intestinal inflammation. The aim of this work was to study functional motor changes in inflamed and non-inflamed intestinal segments of Trichinella spiralis infected rats. Thickness of muscle layers and cell infiltration during infection were also evaluated. Segments of rat jejunum and ileum were placed in organ bath and relaxations of the longitudinal muscle in response to electrical field stimulation (EFS) were recorded. During the post-infection (PI) period EFS-induced relaxations in ileum were decreased. Maximal decreases in relaxation were found on day 14-23 PI for ileum, whereas non significant changes were observed in jejunal samples throughout the experimental period. The sensitivity of the EFS-induced relaxations to the NO synthase inhibitor Nω-nitro-l-arginine (L-NNA) and to the soluble guanylate cyclase inhibitor oxadiazolo-quinoxalin-1-one (ODQ) was decreased on day 14 PI for jejunum, whereas in the ileum it lasted from day 14-23 PI. The sensitivity of EFS-induced relaxations to apamin (a small conductance calcium activated potassium channel blocker) disappeared between day 6-23 PI for both jejunum and ileum. In contrast, the sensitivity of the EFS-induced relaxations to the K⁺ channel blockers tetraethylamonium (TEA) and tetrapenthylammonium (TPEA) chloride was similar for healthy tissue and for tissue obtained form infected animals. Distribution and density of NADPH-diaphorase positive neurons was similar in tissue obtained form healthy and infected animals. In conclusion, intestinal inflammation induces functional and structural changes in both worm-free and worm-positive intestinal segments. Increased muscle thickness was similar for both inflamed and noninflamed segments but the most prominent functional changes i.e. a long-lasting decrease of EFS-induced relaxation was found in non-inflamed ileal segments.