ObjectiveTo prove that the interstitial cells of cajal (ICCs) are the pacemaker of gallbladder smooth muscle in guinea pigs.MethodsThe contraction of gallbladder was observed by isometric transducer and spontaneous electrophysiology was recorded in vivo and in vitro.ICCs were damaged with methylene and illumination.The ICCs were isolated by collagenase digestion and the morphology of single ICC was analyzed.C-kit expression was detected by laser confocal microscopy to identify the isolated ICCs.Spontaneous currents of ICCs were recorded with EPC-10 Patch Clamp.ResultsSlow wave and action potential were recorded in gallbladder in vivo, with the frequency of slow wave being (58±3.2) bpm (n=16).Methylene blue and illumination treatment led to decrease or disappearance of slow wave and action potentials.Some cells isolated from gallbladder smooth muscle (\[5±1.2\]%, n=12)showed the morphological characteristics of ICCs under light microscope, with (21±4)% of the cells were positive for c-kit.When the membrane potential was at -60 mV, the frequency of spontaneous inward currents was (58.4±3.5) bpm (n=21) and the amplitude was -(72±3.5) pA.ConclusionICC-like cells are present in the gallbladder smooth muscle of the guinea pigs, and participate in the pacemaking of spontaneous current and action potential of gallbladder smooth muscle.