Effects of Prunus mume Siebold & Zucc. in the pacemaking activity of interstitial cells of Cajal in murine small intestine

Interstitial cells of Cajal (ICCs) function as pacemaker cells in the gastrointestinal (GI) tract and therefore, serve an important role in regulating GI motility. The effects of a species of plum (Prunus mume Siebold & Zucc.) on cultured ICC cluster-induced pacemaker potentials in the mouse small intestine were investigated, and the effects of a methanolic extract of Prunus mume (m-PM) on ICC pacemaker activities were examined using the whole-cell patch-clamp technique. ICC pacemaker membrane potentials were depolarized by m-PM in a concentration dependent manner in current clamp mode. 4-Diphenylacetoxy-N-methyl-piperidine methiodide, which is a muscarinic 3 (M₃) receptor antagonist, was able to block m-PM-induced pacemaker potential increases, whereas methoctramine, which is a muscarinic 2 (M₂) receptor antagonist, was not. When 1 mM guanosine diphosphate β-5 was present in the pipette solution, m-PM induced slight pacemaker depolarization. Following pretreatment in bath solution of Ca²⁺-free solution or a Ca²⁺-ATPase inhibitor in endoplasmic reticulum, the pacemaker currents were inhibited. Furthermore, pretreatment with PD98059, SB203580 or SP600125, which is a c-jun NH2-terminal kinase inhibitor, blocked m-PM-induced ICC potential depolarization. Furthermore, m-PM inhibited transient receptor potential melastatin (TRPM) 7 channels, but did not affect Ca²⁺-activated Cl^- channels. These results suggest that m-PM is able to modulate pacemaker potentials through the muscarinic M₃ receptor, via G-protein and external and internal Ca²⁺, in a mitogen-activated protein kinase and TRPM7-dependent manner. Therefore, m-PM may provide a basis for the development of a novel gastroprokinetic agent.