| Summary: | Aim: The present study was conducted in an attempt to find possible direct mechanisms of action of Clostridium difficile toxins A and B (TCdA and TCdB) on contractility of isolated rat intestinal smooth muscles, as the contractive pathways affected by the toxins and responsible for motility disorders remain unclear. Materials and methods: Adult male Wistar rats were used in our experiments. Longitudinal smooth muscle (SM) preparations of proximal colon were isolated and their contractile activity was isometrically registered. The samples were mounted in tissue baths and exogenously treated with acetylcholine (ACh), serotonin (5-HT), dopamine, norepinephrine, TCdA and TCdB. The potential of TCdA and TCdB to affect the action of these mediators on SM activity was examined. Results: The experiments have shown that exciting action of ACh and 5-HT on colonic contractility is enhanced by TCdA rather than TCdB. Conversely, relaxing effect of dopamine and norepinephrine on contractile activity of colonic SM is under impact of TCdB but not TcdA. TCdA has a stronger direct effect on in vitro SM sensitivity to ACh and 5-HT than TCdB.Conclusions: TCdA and TCdB affect directly the contractile reactivity of isolated rat colon smooth muscle. TCdA has a stronger direct effect on smooth muscle sensitivity to acetylcholine and 5-HT than TCdB. Such a trend has not been established for dopamine and norepinephrine.
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