Pacemaker activity from submucosal interstitial cells of Cajal drives high-frequency and low-amplitude circular muscle contractions in the mouse proximal colon.
The present study was aimed at elucidating how pacemaker activity (plateau potentials) (mean frequency: 15.9 +/- 2.8 times min(-1)) from submucosal interstitial cells of Cajal (ICC-SM) control spontaneous contractions in the mouse proximal colon. Mechanical activities in the circular muscle direction showed high-frequency (mean frequency: 15.6 +/- 2.7 times min(-1)) and low-amplitude (mean amplitude: 0.01 +/- 0.005 g) (HFLA) rhythmic contractions. Simultaneous recordings of circular muscle mechanical activity and electrical activity from ICC-SM revealed that HFLA contractions were synchronized with plateau potentials (mean frequency: 15.9 +/- 2.8 times min(-1)). Although low-frequency (3.5 +/- 2.1 times min(-1)) and high-amplitude (0.12 +/- 0.03 g) (LFHA) contractions in both longitudinal and circular muscle directions were synchronized with burst of action potentials in both muscle cells, these LFHA contractions were not synchronous with plateau potentials. Intracellular Ca2+ release from the internal stores through IP3 receptors is not a major factor to generate both action potentials differently from plateau potentials. Neither tetrodotoxin nor atropine affected the plateau potentials. The results reveal that the pacemaker activity from ICC-SM drives only the spontaneous HFLA (one-tenth amplitude of the LFHA circular and longitudinal muscle contractions) circular muscle contractions without control by enteric nerves.
Yoneda
S
S
Department of Physiology II, Nara Medical University, Kashihara, Japan.
Fukui
H
H
Takaki
M
M
D000818:Animals; D001683:Biological Clocks / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D003106:Colon / Q000166:cytology* / Q000502:physiology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007413:Intestinal Mucosa / Q000166:cytology* / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008839:Microelectrodes; D009130:Muscle, Smooth / Q000502:physiology*; D009924:Organ Culture Techniques; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D002118:Calcium