Effects of STW 5 and STW 6 on rat ileal and colonic preparations: A comparative study

STW 5 (Iberogast®) is a fixed combination of nine plant extract with Iberis amara L. (STW 6) as its main component. It is successfully used for treatment of functional dyspepsia or irritable bowel syndrome (IBS). Because clinical data suggest an inflammatory etiology of IBS the influence of STW 5 and STW 6 on tone and acetylcholine (ACh)-induced contractions of intact and inflamed intestinal preparations was examined. We used 1–1.5cm long ileum and colon preparations of male Wistar rats to analyze region specific differences. Inflammation was induced by intraluminal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS, 10mM, 30min). STW 5 (64–512µg/ml) concentration dependently reduced the tone and decreased ACh-induced contractions of intact ileal and colonic preparations. STW 6 in equivalent concentrations (3–24.1µg/ml) neither affected tone nor contractility. TNBS-induced inflammation was accompanied by a significantly reduced ACh contractions and morphological disturbances. Co-incubation of TNBS with STW 5 (512µg/ml) or STW 6 (24.1µg/ml) partially normalized the TNBS-induced attenuation of ACh-induced contractions andmorphological damage in ileum preparations, whereas in inflamed colon segments only the co-incubation of TNBS with STW 6 in a high concentration (24.1µg/ml) revealed similar effects.

In conclusion, STW 5 influenced ACh contractions and tone in intact ileal and colonic preparations, whereas STW 6 does not contribute to these effects. In TNBS-inflamed ileum preparations STW 5 as well as STW 6 normalized morphological and contractile disturbances, while in colon preparations STW 6 but not STW 5 was effective. Our study confirms region specific effects of STW 5 and its main component STW 6.

Keywords: Inflammation, Ileum, Colon, Gastrointestinal motility, Iberogast, Iberis amara