# Electricity of the colon



## SpAsMaN* (May 11, 2002)

http://physiologyonline.physiology.org/cgi...t/full/15/6/291


> quote:The rhythmoneuromuscular apparatus of the gastrointestinal (GI) tract is more complicated than a syncytium of smooth muscle cells innervated by motor neurons. For many years, morphological studies of the tunica muscularis noted the presence of additional specialized cells that are commonly referred to as interstitial cells of Cajal (ICC). ICC were frequently found in close association with nerves, and in many cases they were described as "intercalated" between nerve terminals and smooth muscle cells (2). ICC were also observed to form gap junction connections with each other and with neighboring smooth muscle cells. Thus the electric syncytium of the tunica muscularis of the GI tract is composed of at least two cell types. Morphology also suggested that the innervation of the smooth muscle might be indirect and mainly occur via synapse-like structures between nerves and ICC. These studies were interesting and provocative, but it was only possible to speculate about the function of ICC from morphological analyses. Intensive work on animal models (primarily mouse, guinea pig, and dog) during the past decade has provided physiological evidence that ICC provide the pacemaker activity typical of phasic GI muscles of the stomach, small bowel, and colon (i.e., electric slow waves; cf. Ref. 9). Pacemaker ICC are generally found in the region of the myenteric plexus in the space between the circular and longitudinal muscle layers. We refer to the cells in the myenteric region as IC-MY. ICC along the submucosal surface of the circular muscle layer in the colon (IC-SM) are also able to generate pacemaker activity, particularly in larger animals such as the dog. IC-MY and IC-SM form extensive networks within pacemaker regions. These cells also extend into the bulk of the muscle layers in the septa that divide bundles of smooth muscle cells. Thus pacemaker activity is not necessarily confined to the myenteric and submucosal pacemaker regions, but these pacemakers are dominant in intact muscles. Fine processes of pacemaker ICC interconnect via gap junctions, and electric connections are also made with neighboring smooth muscle cells. Thus electric events occurring in ICC are capable of conducting to smooth muscle cells. Simultaneous recordings of electric activity from IC-MY and nearby smooth muscle cells have demonstrated that electric activity occurs first in IC-MY and then initiates electric responses in the smooth muscle cells (3). Connections between ICC are necessary for regenerative propagation of slow waves, and extension of ICC networks into the septa between muscle bundles may provide propagation pathways for transmission of slow waves through the tunica muscularis (perhaps analogous to the Purkinje fibers in the heart). Networks of IC-MY and some of the ultrastructural features of IC-MY are shown in Fig. 1.


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## SpAsMaN* (May 11, 2002)

http://www.ncbi.nlm.nih.gov/entrez/query.f...7&dopt=Abstract High-conductance chloride channels generate pacemaker currents in interstitial cells of Cajal. Huizinga JD, Zhu Y, Ye J, Molleman A. Department of Medicine, McMaster University, Hamilton, Ontario, Canada. huizinga###mcmaster.ca BACKGROUND & AIMS: Interstitial cells of Cajal (ICCs) are responsible for slow, wave-driven, rhythmic, peristaltic motor patterns in the gastrointestinal tract. The aim was to identify and characterize the ion channels that generate the underlying pacemaker activity. METHODS: Single ion channel recordings were obtained from nonenzymatically isolated ICCs and studied by using the cell attached and inside-out configurations of the patch clamp technique. RESULTS: A high-conductance chloride channel was observed in ICCs that was spontaneously and rhythmically active at the same frequency as the rhythmic inward currents defining ICC pacemaker activity, 20-30 cycles/min at room temperature. Main conductance levels occurred between 122-144 pS and between 185-216 pS. Periodicity in the channel opening coincided with periodicity in membrane potential change, hence, at the single channel level, chloride channels were seen to be associated with the generation of rhythmic changes in membrane potential. CONCLUSIONS: ICCs harbor high-conductance chloride channels that participate in the generation of pacemaker activity and may become a target for pharmacologic treatment of gut motor disorders. ----------------------------------------------- Microprocessor controlled movement of solid colonic content using sequential neural electrical stimulation http://gut.bmjjournals.com/cgi/content/full/50/4/475 Quote:"....The use of a microprocessor controlled system with flexible patterns of stimulation makes this method individually adjustable, depending on the physiological requirements of the organ. The method suggested in this article has been tested only in acute experiments in dogs. Evaluation of the long term effects of this technique on the tissue surrounding the stimulating electrodes, accommodation, and absorption calls for future investigation on chronic animal models. The development of possible secondary effects such as pain must also be studied before applying this method to humans. In conclusion, a method for neural electrical stimulation is proposed using a microprocessor controlled sequential stimulation with flexible and adjustable parameters to artificially produce and propagate contractions in peristaltic fashion. The technique accelerated significantly the movement of solid content thus demonstrating the feasibility of future implantable microelectronic stimulators for the colon. " ------------------------------------------------ Natural pacemakers in the G.I. tract. http://www.biomed.cas.cz/physiolres/pdf/2003/52_1.pdf The ICC cells in the gut are equivalent to the cells of the heart,maybe that's why Propulsid(Prucopalide) has been banned in the US because of the arythmia cause to the heart. ------------------------------------------- Inertia of the colon :http://archsurg.ama-assn.org/cgi/content/abstract/138/9/1007 Electric Activity of the Colon in Subjects With Constipation Due to Total Colonic Inertia An Electrophysiologic Study Ahmed Shafik, MD, PhD; Ali A. Shafik, MD; Olfat El-Sibai, MD, PhD; Randa M. Mostafa, MD, PhD Arch Surg. 2003;138:1007-1011. Background Idiopathic constipation may result from colonic inertia, which affects the whole colon or is localized to an area of the colon. The colon exhibits electric activity in the form of slow waves or pacesetter potentials (PPs) and action potentials (APs), which are coupled with elevated colonic pressure. The APs are claimed to be responsible for colonic motor activity. Hypothesis Colonic electric activity is disordered in patients with constipation due to colonic inertia. Methods Electric activity was studied in 11 patients with colonic inertia and constipation (mean Â± SD age, 42.8 Â± 6.6 years; 7 women) who underwent total colectomy. Eight volunteers who had no gastrointestinal complaints (mean Â± SD age, 40.6 Â± 5.8 years; 5 women) acted as controls. Control subjects underwent laparotomy for hernia repair (n = 7 patients) and for removal of a mesenteric cyst (n = 1 patient). During the operation, 2 monopolar silverâ€"silver chloride electrodes were applied to the cecum and the ascending, transverse, descending, and sigmoid colon. Results Electric waves (PPs and APs) were recorded from all parts of the colon in control subjects. The waves were monophasic, negatively deflected, and had regular rhythm. The wave variables from the 2 electrodes of each segment of the colon were identical and reproducible. They progressively increased aborally. In the colonic inertia group, 5 patients had recorded waves from the cecum and ascending colon but no waves from the rest of the colon. The wave variables were significantly lower than those of the controls (P = .02). In the remaining 6 patients, no waves were registered from the whole colon. Conclusions Regular electric waves were recorded from the colons of control subjects. The aboral increase of their frequency, amplitude, and conduction velocity suggests that colonic motile activity increases analward, reaching its maximum in the sigmoid colon to expel its solid contents. We postulate that constipation in patients with colonic inertia is attributable to weak or absent electric activity, the cause of which is unknown. A disorder of the interstitial cells of Cajal, which generate electric activity, is suggested to have a role in inducing diminished or absent colonic motor activity, a point that should be investigated. From the Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo (Drs A. Shafik and A. A. Shafik), the Department of Surgery, Faculty of Medicine, Menoufia University, Shebin El-Kom (Dr El-Sibai), and the Department of Physiology, Faculty of Medicine, Zagazig University, Benha (Dr Mostafa), Egypt. ---------------------------------------------- Post subject: Colonic Pacing A Therapeutic Option for colonic inertia. http://archsurg.ama-assn.org/cgi/content/abstract/139/7/775 Colonic Pacing A Therapeutic Option for the Treatment of Constipation Due to Total Colonic Inertia Ahmed Shafik, MD, PhD; Ali A. Shafik, MD; Olfat El-Sibai, MD, PhD; I. Ahmed, MB, BCh, MCh Arch Surg. 2004;139:775-779. Hypothesis The treatment of constipation caused by total colonic inertia is problematic and its results are unsatisfactory. We speculated that colonic pacing would initiate electric activity in the inertial colon and effect rectal evacuation. Methods Nine patients with constipation due to total colonic inertia (age range, 39-52 years; 7 women, 2 men) were enrolled in the study. One pacing electrode was applied to each of the 4 potential colonic pacemaker sites, and 2 to 3 temporary recording electrodes were applied distally. A stimulator was embedded subcutaneously in the inguinal area. Home pacing was practiced after patients were trained; the recording electrodes were removed before home pacing was started. Results Colonic pacing evoked electric waves, which effected defecation in 6 of the 9 patients. Three of these 6 patients had spontaneous defecation after a few months of pacing, and their electrodes and stimulators were removed. In the other 3 of these 6 patients, the pacemakers are still in place and continue to effect rectal evacuation. Colonic pacing did not produce rectal evacuation in 3 patients and is believed to have failed because of an advanced stage of colonic inertia. Conclusion Colonic pacing induced rectal evacuation in 66.6% of the patients with total colonic inertia. No complications were encountered. We suggest that colonic pacing be considered as a new therapeutic option in the treatment of total colonic inertia. From the Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo (Drs A. Shafik, A. A. Shafik, and Ahmed), and the Department of Surgery, Faculty of Medicine, Menoufia University, Shebin El-Kom (Dr El-Sibai), Egypt


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