Origin and propagation of individual slow waves along the intact feline small intestine

First published online on December 21, 2007.
Experimental Physiology (2007)
DOI: 10.1113/expphysiol.2007.039180
Wim J Lammers 1* Betty Stephen 1
1 United Arab Emirates University
* To whom correspondence should be addressed. E-mail: wlammers@uaeu.ac.ae.
The pattern of propagation of slow waves in the small intestine is not clear. Specifically, it is not known whether propagation is determined by a single dominant ICC-MP pacemaker unit or whether there are multiple active pacemakers. To determine this pattern of propagation, waveforms were recorded simultaneously from 240 electrodes distributed along the whole length of the intact isolated feline small intestine. After the experiments, the propagation patterns of successive individual slow waves were analyzed.In the intact small intestine, there was only a single slow wave pacemaker unit active and this was located at or 6-10 cm from the pyloric junction. From this site, slow waves propagated in the aboral direction at gradually decreasing velocities. The majority of slow waves (73%) reached the ileocaecal junction while the remainder waves were blocked. Ligation at 1-4 locations led to a) decrease in the distal frequencies, b) disappearance of distal propagation blocks, c) increase in velocities, d) emergence of multiple and unstable pacemaker sites and, e) propagation from these sites in the aboral and oral directions. In conclusion, in the quiescent small intestine, a single pacemaker unit dominates the organ with occasional propagation blocks of the slow waves thereby producing the well-known frequency gradient.