Depolarizing effects of daikenchuto on interstitial cells of cajal from mouse small intestine

Background: Daikenchuto (DKT; TJ-100, TU-100)a traditional herbal medicineis used in modern medicine to treat gastrointestinal (GI) functional disorders. Interstitial cells of Cajal (ICCs) are the pacemaker cells of the GI tract and play important roles in the regulation of GI motility. Objective: The objective of this study was to investigate the effects of DKT on the pacemaker potentials (PPs) of cultured ICCs from murine small intestine. Materials and Methods: Enzymatic digestions were used to dissociate ICCs from mouse small intestine tissues. All experiments on ICCs were performed after 12 h of culture. The whole-cell patch-clamp configuration was used to record ICC PPs (current clamp mode). All experiments were performed at 30-32°C. Results: In current-clamp modeDKT depolarized and concentration-dependently decreased the amplitudes of PPs. Y25130 (a 5-HT₃ receptor antagonist) or SB269970 (a 5-HT₇ receptor antagonist) did not block DKT-induced PP depolarizationbut RS39604 (a 5-HT₄ receptor antagonist) did. Methoctramine (a muscarinic M₂ receptor antagonist) failed to block DKT-induced PP depolarizationbut pretreating 4-diphenylacetoxy-N-methylpiperidine methiodide (a muscarinic M₃ receptor antagonist) facilitated blockade of DKT-induced PP depolarization. Pretreatment with an external Ca²⁺-free solution or thapsigargin abolished PPsand under these conditionsDKT did not induce PP depolarization. FurthermoreGinseng radix and Zingiberis rhizomes depolarized PPswhereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Conclusion: These results suggest that DKT depolarizes ICC PPs in an internal or external Ca²⁺-dependent manner by stimulating 5-HT₄ and M₃ receptors. Furthermorethe authors suspect that the component in DKT largely responsible for depolarization is probably also a component of Ginseng radix and Zingiberis rhizomes.