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Gastroenterology. 2007 Sep;133(3):907-17. Epub 2007 Jun 20.

Septal interstitial cells of Cajal conduct pacemaker activity to excite muscle bundles in human jejunum.

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  • 1Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA.

Abstract

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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