HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 549/1/207    most recent 2003.040097v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ward, S. M. Articles by Sanders, K. M. Search for Related Content PubMed PubMed Citation Articles by Ward, S. M. Articles by Sanders, K. M.

Propagation of slow waves requires IP₃ receptors and mitochondrial Ca²⁺ uptake in canine colonic muscles

Sean M. Ward, Salah A. Baker, Andrew de Faoite and Kenton M. Sanders

In the gastrointestinal (GI) tract electrical slow waves yield oscillations in membrane potential that periodically increase the open probability of voltage-dependent Ca²⁺ channels and facilitate phasic contractions. Slow waves are generated by the interstitial cells of Cajal (ICC), and these events actively propagate through ICC networks within the walls of GI organs. The mechanism that entrains spontaneously active pacemaker sites throughout ICC networks to produce regenerative propagation of slow waves is unresolved. Agents that block inositol 1,4,5-trisphosphate (IP₃) receptors and mitochondrial Ca²⁺ uptake were tested on the generation of slow waves in the canine colon. A partitioned chamber apparatus was used to test the effects of blocking slow-wave generation on propagation. We found that active propagation occurred along strips of colonic muscle, but when the pacemaker mechanism was blocked in a portion of the tissue, slow waves decayed exponentially from the point where the pacemaker mechanism was inhibited. An IP₃ receptor inhibitor, mitochondrial inhibitors, low external Ca²⁺, and divalent cations (Mn²⁺ and Ni²⁺) caused exponential decay of the slow waves in regions of muscle exposed to these agents. These data demonstrate that the mechanism that initiates slow waves is reactivated from cell-to-cell during the propagation of slow waves. Voltage-dependent conductances present in smooth muscle cells are incapable of slow-wave regeneration. The data predict that partial loss of or disruptions to ICC networks observed in human motility disorders could lead to incomplete penetration of slow waves through GI organs and, thus, to defects in myogenic regulation.

This article has been cited by other articles:

				R. A. Faville, A. J. Pullan, K. M Sanders, and N. P. Smith A Biophysically Based Mathematical Model of Unitary Potential Activity in Interstitial Cells of Cajal Biophys. J., July 1, 2008; 95(1): 88 - 104. [Abstract] [Full Text] [PDF]

				O. B. Balemba, A. C. Bartoo, M. T. Nelson, and G. M. Mawe Role of mitochondria in spontaneous rhythmic activity and intracellular calcium waves in the guinea pig gallbladder smooth muscle Am J Physiol Gastrointest Liver Physiol, February 1, 2008; 294(2): G467 - G476. [Abstract] [Full Text] [PDF]

				B. Lavoie, O. B. Balemba, M. T. Nelson, S. M. Ward, and G. M. Mawe Morphological and physiological evidence for interstitial cell of Cajal-like cells in the guinea pig gallbladder J. Physiol., March 1, 2007; 579(2): 487 - 501. [Abstract] [Full Text] [PDF]

				O. B. Balemba, M. J. Salter, T. J. Heppner, A. D. Bonev, M. T. Nelson, and G. M. Mawe Spontaneous electrical rhythmicity and the role of the sarcoplasmic reticulum in the excitability of guinea pig gallbladder smooth muscle cells Am J Physiol Gastrointest Liver Physiol, April 1, 2006; 290(4): G655 - G664. [Abstract] [Full Text] [PDF]

				G. Boddy and E. E. Daniel Role of L-Ca2+ channels in intestinal pacing in wild-type and W/WV mice Am J Physiol Gastrointest Liver Physiol, March 1, 2005; 288(3): G439 - G446. [Abstract] [Full Text] [PDF]

				S. M Ward, R. E. Dixon, A. de Faoite, and K. M Sanders Voltage-dependent calcium entry underlies propagation of slow waves in canine gastric antrum J. Physiol., December 15, 2004; 561(3): 793 - 810. [Abstract] [Full Text] [PDF]

				J. E. Bradley, U. A. Anderson, S. M. Woolsey, K. D. Thornbury, N. G. McHale, and M. A. Hollywood Characterization of T-type calcium current and its contribution to electrical activity in rabbit urethra Am J Physiol Cell Physiol, May 1, 2004; 286(5): C1078 - C1088. [Abstract] [Full Text] [PDF]

				G. Boddy, A. Bong, W. Cho, and E. E. Daniel ICC pacing mechanisms in intact mouse intestine differ from those in cultured or dissected intestine Am J Physiol Gastrointest Liver Physiol, April 1, 2004; 286(4): G653 - G662. [Abstract] [Full Text] [PDF]