Hwangryunhaedok-tang induces the depolarization of pacemaker potentials through 5-HT3 and 5-HT4 receptors in cultured murine small intestine interstitial cells of Cajal

AIM To investigate the effects of a water extract of Hwangryunhaedok-tang（HHTE） on the pacemaker potentials of mouse interstitial cells of Cajal（ICCs）.METHODS We dissociated ICCs from small intestines and cultured. ICCs were immunologically identified using an antic-kit antibody. We used the whole-cell patch-clamp configuration to record the pacemaker potentials generated by cultured ICCs under the current clamp mode（I = 0）. All experiments were performed at 30 ℃-32 ℃RESULTS HHTE dose-dependently depolarized ICC pacemaker potentials. Pretreatment with a 5-HT3 receptor anta-gonist（Y25130） or a 5-HT4 receptor antagonist（RS39604） blocked HHTE-induced pacemaker potential depolarizations, whereas pretreatment with a 5-HT7 receptor antagonist（SB269970） did not. Intracellular GDPβS inhibited HHTE-induced pacemaker potential depolarization and pretreatment with a Ca2+-free solution or thapsigargin abolished the pacemaker potentials. In the presence of a Ca2+-free solution or thapsigargin, HHTE did not depolarize ICC pacemaker potentials. In addition, HHTE-induced pacemaker potential depolarization was unaffected by a PKC inhibitor（calphostin C） or a Rho kinase inhibitor（Y27632）. Of the four ingredients of HHT, Coptidis Rhizoma and Gardeniae Fructus more effectively inhibited pacemaker potential depolarization.CONCLUSION These results suggest that HHTE dose-dependently depolarizes ICC pacemaker potentials through 5-HT3 and 5-HT4 receptors via external and internal Ca2+ regulation and via G protein-, PKC-and Rho kinase-independent pathways.