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Updated: Jul 13, 2026

Applications of Spatio-temporal Mapping and Particle Analysis Techniques to Quantify Intracellular Ca2+ Signaling In Situ
Published on: January 7, 2019
Septal interstitial cells of Cajal conduct pacemaker activity to excite muscle bundles in human jejunum
Hyun-Tai Lee1, Grant W Hennig, Neal W Fleming
1Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.
Background & Aims:
Like the heart, intestinal smooth muscles exhibit electrical rhythmicity, which originates in pacemaker cells surrounding the myenteric plexus, called interstitial cells of Cajal (ICC-MY). In large mammals, ICC also line septa (ICC-SEP) between circular muscle (CM) bundles, suggesting they might be necessary for activating muscle bundles. It is important to determine their functional significance, because a loss of ICC in humans is associated with disordered motility. Our aims were therefore to determine the role of ICC-SEP in activating the thick CM in the human jejunum.
Methods:
The mucosa and submucosa were removed and muscle strips were cut and pinned in cross-section so that the ICC-MY and ICC-SEP networks and the CM could be readily visualized. The ICC networks and CM were loaded with the Ca(2+) indicator fluo-4, and pacemaker and muscle activity was recorded at 36.5 +/- 0.5( degrees )C.
Results:
Ca(2+) imaging revealed that pacemaker activity in human ICC-MY can entrain ICC-SEP to excite CM bundles. Unlike the heart, pacemaker activity in ICC-MY varied in amplitude, propagation distance, and direction, leading to a sporadic activation of ICC-SEP.
Conclusions:
ICC-SEP form a crucial conduction pathway for spreading excitation deep into muscle bundles of the human jejunum, necessary for motor patterns underlying mixing. A loss of these cells could severely affect motor activity.
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