Large bowel myoelectrical activity in man

The bioelectrical conduction system around the ileocecal junction defined through in vivo high-resolution mapping in rabbits

Coordinated contractions across the small and large intestines via the ileocecal junction (ICJ) are critical to healthy gastrointestinal function and are in part governed by myoelectrical activity. In this study, the spatiotemporal characteristics of the bioelectrical conduction across the ICJ and its adjacent regions were quantified in anesthetized rabbits. High-resolution mapping was applied from the terminal ileum (TI) to the sacculus rotundus (SR), across the ICJ and into the beginning of the large intestine at the cecum ampulla coli (AC). Orally propagating slow wave patterns in the SR did not entrain the TI. However, aborally propagating patterns from the TI were able to entrain the SR. Bioelectrical activity was recorded within the ICJ and AC, revealing complex interactions of slow waves, spike bursts, and bioelectrical quiescence. This suggests the involvement of myogenic coordination when regulating motility between the small and large intestines. Mean slow wave frequency between regions did not vary significantly (13.74-17.16 cycles/min). Slow waves in the SR propagated with significantly faster speeds (18.51 ± 1.57 mm/s) compared with the TI (14.05 ± 2.53 mm/s, P = 0.0113) and AC (9.56 ± 1.56 mm/s, P = 0.0001). Significantly higher amplitudes were observed in both the TI (0.28 ± 0.13 mV, P = 0.0167) and SR (0.24 ± 0.08 mV, P = 0.0159) within the small intestine compared with the large intestine AC (0.03 ± 0.01 mV). We hypothesize that orally propagating slow waves facilitate a motor-brake pattern in the SR to limit outflow into the ICJ, similar to those previously observed in other gastrointestinal regions.NEW & NOTEWORTHY Competing slow wave pacemakers were observed in the terminal ileum and sacculus rotundus. Prevalent oral propagation in the sacculus rotundus toward the terminal ileum potentially acts as a brake mechanism limiting outflow. Slow waves and periods of quiescence at the ileocecal junction suggest that activation may depend on the coregulatory flow and distention pathways. Slow waves and spike bursts in the cecum impart a role in the coordination of motility.

Generation of Gut Motor Patterns Through Interactions Between Interstitial Cells of Cajal and the Intrinsic and Extrinsic Autonomic Nervous Systems

The musculature of the gastrointestinal tract is a vast network of collaborating excitable cell types. Embedded throughout are the interstitial cells of Cajal (ICC) intertwined with enteric nerves. ICC sense external stimuli such as distention, mediate nerve impulses to smooth muscle cells, and provide rhythmic excitation of the musculature. Neural circuitry involving both the intrinsic and extrinsic autonomic nervous systems, in collaboration with the ICC, orchestrate an array of motor patterns that serve to provide mixing of content to optimize digestion and absorption, microbiome homeostasis, storage, transit, and expulsion. ICC are specialized smooth muscle cells that generate rhythmic depolarization to the musculature and so provide the means for peristaltic and segmenting contractions. Some motor patterns are purely myogenic, but a neural stimulus initiates most, further depolarizing the primary pacemaker cells and the musculature and/or initiating transient pacemaker activity in stimulus-dependent secondary ICC pacemaker cells. From stomach to rectum, ICC networks rhythmically provide tracks along which contractions advance.

Interstitial cells of Cajal and human colon motility in health and disease

Our understanding of human colonic motility, and autonomic reflexes that generate motor patterns, has increased markedly through high-resolution manometry. Details of the motor patterns are emerging related to frequency and propagation characteristics that allow linkage to interstitial cells of Cajal (ICC) networks. In studies on colonic motor dysfunction requiring surgery, ICC are almost always abnormal or significantly reduced. However, there are still gaps in our knowledge about the role of ICC in the control of colonic motility and there is little understanding of a mechanistic link between ICC abnormalities and colonic motor dysfunction. This review will outline the various ICC networks in the human colon and their proven and likely associations with the enteric and extrinsic autonomic nervous systems. Based on our extensive knowledge of the role of ICC in the control of gastrointestinal motility of animal models and the human stomach and small intestine, we propose how ICC networks are underlying the motor patterns of the human colon. The role of ICC will be reviewed in the autonomic neural reflexes that evoke essential motor patterns for transit and defecation. Mechanisms underlying ICC injury, maintenance, and repair will be discussed. Hypotheses are formulated as to how ICC dysfunction can lead to motor abnormalities in slow transit constipation, chronic idiopathic pseudo-obstruction, Hirschsprung's disease, fecal incontinence, diverticular disease, and inflammatory conditions. Recent studies on ICC repair after injury hold promise for future therapies.

Intraoperative serosal extracellular mapping of the human distal colon: a feasibility study

BACKGROUND

Cyclic motor patterns (CMP) are the predominant motor pattern in the distal colon, and are important in both health and disease. Their origin, mechanism and relation to bioelectrical slow-waves remain incompletely understood. During abdominal surgery, an increase in the CMP occurs in the distal colon. This study aimed to evaluate the feasibility of detecting propagating slow waves and spike waves in the distal human colon through intraoperative, high-resolution (HR), serosal electrical mapping.

METHODS

HR electrical recordings were obtained from the distal colon using validated flexible PCB arrays (6 × 16 electrodes; 4 mm inter-electrode spacing; 2.4 cm2, 0.3 mm diameter) for up to 15 min. Passive unipolar signals were obtained and analysed.

RESULTS

Eleven patients (33-71 years; 6 females) undergoing colorectal surgery under general anaesthesia (4 with epidurals) were recruited. After artefact removal and comprehensive manual and automated analytics, events consistent with regular propagating activity between 2 and 6 cpm were not identified in any patient. Intermittent clusters of spike-like activities lasting 10-180 s with frequencies of each cluster ranging between 24 and 42 cpm, and an average amplitude of 0.54 ± 0.37 mV were recorded.

CONCLUSIONS

Intraoperative colonic serosal mapping in humans is feasible, but unlike in the stomach and small bowel, revealed no regular propagating electrical activity. Although sporadic, synchronous spike-wave events were identifiable. Alternative techniques are required to characterise the mechanisms underlying the hyperactive CMP observed in the intra- and post-operative period.

NEW FINDINGS

The aim of this study was to assess the feasibility of detecting propagating electrical activity that may correlate to the cyclic motor pattern in the distal human colon through intraoperative, high-resolution, serosal electrical mapping. High-resolution electrical mapping of the human colon revealed no regular propagating activity, but does reveal sporadic spike-wave events. These findings indicate that further research into appropriate techniques is required to identify the mechanism of hyperactive cyclic motor pattern observed in the intra- and post-operative period in humans.

Characterization of haustral activity in the human colon

Contraction patterns of the human colon are rarely discussed from the perspective of its haustra. Colonic motility was analyzed in 21 healthy subjects using 84-sensor manometry catheters with 1-cm sensor spacing. Capsule endoscopy and manometry showed evidence of narrow rhythmic circular muscle contractions. X-ray images of haustra and sensor locations allowed us to identify manometry motor activity as intrahaustral activity. Two common motor patterns were observed that we infer to be associated with individual haustra: rhythmic pressure activity confined to a single sensor, and activity confined to a section of the colon of 3-6 cm length. Intrahaustral activity was observed by 3-4 sensors. Approximately 50% of the haustra were intermittently active for ∼30% of the time; 2,402 periods of haustral activity were analyzed. Intrahaustral activity showed rhythmic pressure waves, propagating in mixed direction, 5-30 mmHg in amplitude at a frequency of ∼3 cpm (range 2-6) or ∼12 cpm (range 7-15), or exhibiting a checkerboard segmentation pattern. Boundaries of the haustra showed rhythmic pressure activity with or without elevated baseline pressure. Active haustra often showed no boundary activity probably allowing transit to neighboring haustra. Haustral boundaries were seen at the same sensor for the 6- to 8-h study duration, indicating that they did not propagate, thereby likely contributing to continence. The present study elucidates the motility characteristics of haustral boundaries and the nature of intrahaustral motor patterns and paves the way for investigating their possible role in pathophysiology of defecation disorders.NEW & NOTEWORTHY Here, we present the first full characterization and quantification of motor patterns that we infer to be confined to single haustra, both intrahaustral activity and haustral boundary activity, in the human colon using high-resolution manometry. Haustral activity is intermittent but consistently present in about half of the haustra. Intrahaustral activity presents as a cyclic motor pattern of mixed propagation direction dominated by simultaneous pressure waves that can resolve into checkerboard segmentation, allowing for mixing, absorption, and stool formation.

Bioelectrical Signals for the Diagnosis and Therapy of Functional Gastrointestinal Disorders

Coordinated contractions and motility patterns unique to each gastrointestinal organ facilitate the digestive process. These motor activities are coordinated by bioelectrical events, sensory and motor nerves, and hormones. The motility problems in the gastrointestinal tract known as functional gastrointestinal disorders (FGIDs) are generally caused by impaired neuromuscular activity and are highly prevalent. Their diagnosis is challenging as symptoms are often vague and difficult to localize. Therefore, the underlying pathophysiological factors remain unknown. However, there is an increasing level of research and clinical evidence suggesting a link between FGIDs and altered bioelectrical activity. In addition, electroceuticals (bioelectrical therapies to treat diseases) have recently gained significant interest. This paper gives an overview of bioelectrical signatures of gastrointestinal organs with normal and/or impaired motility patterns and bioelectrical therapies that have been developed for treating FGIDs. The existing research evidence suggests that bioelectrical activities could potentially help to identify the diverse etiologies of FGIDs and overcome the drawbacks of the current clinically adapted methods. Moreover, electroceuticals could potentially be effective in the treatment of FGIDs and replace the limited existing conventional therapies which often attempt to treat the symptoms rather than the underlying condition.

Electrogastrography for psychophysiological research: Practical considerations, analysis pipeline, and normative data in a large sample

Electrogastrography (EGG) is the noninvasive electrophysiological technique used to record gastric electrical activity by means of cutaneous electrodes placed on the abdomen. EGG has been so far mostly used in clinical studies in gastroenterology, but it represents an attractive method to study brain-viscera interactions in psychophysiology. Compared to the literature on electrocardiography for instance, where practical recommendations and normative data are abundant, the literature on EGG in humans remains scarce. The aim of this article is threefold. First, we review the existing literature on the physiological basis of the EGG, pathways of brain-stomach interactions, and experimental findings in the cognitive neuroscience and psychophysiology literature. We then describe practical issues faced when recording the EGG in young healthy participants, from data acquisition to data analysis, and propose a semi-automated analysis pipeline together with associated MATLAB code. The analysis pipeline aims at identifying a regular rhythm that can be safely attributed to the stomach, through multiple steps. Finally, we apply these recording and analysis procedures in a large sample (N = 117) of healthy young adult male and female participants in a moderate (<5 hr) to prolonged (>10 hr) fasting state to establish the normative distribution of several EGG parameters. Our results are overall congruent with the clinical gastroenterology literature, but suggest using an electrode coverage extending to lower abdominal locations than current clinical guidelines. Our results indicate a marginal difference in EGG peak frequency between male and female participants, and that the gastric rhythm becomes more irregular after prolonged fasting.

Colon Myoelectric Activity Measured After Open Abdominal Surgery with a Noninvasive Wireless Patch System Predicts Time to First Flatus

BACKGROUND

Passage of flatus after abdominal surgery signals resolution of physiological postoperative ileus (POI) and often, particularly after complex open surgeries, serves as the trigger to initiate oral feeding. To date, there is no objective tool that can predict time to flatus allowing for timely feeding and optimizing recovery. In an open, prospective study, we examine the use of a noninvasive wireless patch system that measures electrical activity from gastrointestinal smooth muscles in predicting time to first flatus.

METHODS

Eighteen patients who underwent open abdominal surgery at El Camino Hospital, Mountain View, CA, were consented and studied. Immediately following surgery, wireless patches were placed on the patients' anterior abdomen. Colonic frequency peaks in the spectra were identified in select time intervals and the area under the curve of each peak times its duration was summed to calculate cumulative myoelectrical activity.

RESULTS

Patients with early flatus had stronger early colonic activity than patients with late flatus. At 36 h post-surgery, a linear fit of time to flatus vs cumulative colonic myoelectrical activity predicted first flatus as much as 5 days (± 22 h) before occurrence.

CONCLUSIONS

In this open, prospective pilot study, noninvasive measurement of colon activity after open abdominal surgery was feasible and predictive of time to first flatus. Interventions such as feeding can potentially be optimized based on this prediction, potentially improving outcomes, decreasing length of stay, and lowering costs.

Overlooked Long-Term Complications of Colorectal Surgery

While colorectal surgery has been documented to have some of the highest complication rates in the surgical field, some of the more common, functional complications are often overlooked in the literature and in discussion with patients. Urinary, sexual, and defecatory dysfunction are common after colorectal surgery, especially after pelvic dissections, and may severely impact the postoperative quality of life for patients. These complications include urinary retention, erectile dysfunction, retrograde ejaculation, dyspareunia, infertility, and low anterior resection syndrome. The majority is rooted in autonomic nerve damage, both sympathetic and parasympathetic, that occurs during mobilization and resection of the sigmoid colon and rectum. While not all of these postoperative complications are preventable, treatment strategies have been developed to ameliorate the impact on quality of life. Given the high incidence and direct effect on patients, clinicians should be familiar with the etiology, prevention, and treatment strategies of these complications to provide the highest quality of care.

Hyperactive cyclic motor activity in the distal colon after colonic surgery as defined by high-resolution colonic manometry

BACKGROUND

Recovery after colonic surgery is invariably delayed by disturbed gut motility. It is commonly assumed that colonic motility becomes quiescent after surgery, but this hypothesis has not been evaluated rigorously. This study quantified colonic motility through the early postoperative period using high-resolution colonic manometry.

METHODS

Fibre-optic colonic manometry was performed continuously before, during and after surgery in the left colon and rectum of patients undergoing right hemicolectomy, and in healthy controls. Motor events were characterized by pattern, frequency, direction, velocity, amplitude and distance propagated.

RESULTS

Eight patients undergoing hemicolectomy and nine healthy controls were included in the study. Colonic motility became markedly hyperactive in all operated patients, consistently dominated by cyclic motor patterns. Onset of cyclic motor patterns began to a minor extent before operation, occurring with increasing intensity nearer the time of surgery; the mean(s.d.) active duration was 12(7) per cent over 3 h before operation and 43(17) per cent within 1 h before surgery (P = 0.024); in fasted controls it was 2(4) per cent (P < 0·001). After surgery, cyclic motor patterns increased markedly in extent and intensity, becoming nearly continuous (active duration 94(13) per cent; P < 0·001), with peak frequency 2-4 cycles per min in the sigmoid colon. This postoperative cyclic pattern was substantially more prominent than in non-operative controls, including in the fed state (active duration 27(20) per cent; P < 0·001), and also showed higher antegrade velocity (P < 0·001).

CONCLUSION

Distal gut motility becomes markedly hyperactive with colonic surgery, dominated by cyclic motor patterns. This hyperactivity likely represents a novel pathophysiological aspect of the surgical stress response. Hyperactive motility may contribute to gut dysfunction after surgery, potentially offering a new therapeutic target to enhance recovery.

The "rectosigmoid brake": Review of an emerging neuromodulation target for colorectal functional disorders

The regulation of gastrointestinal motility encompasses several overlapping mechanisms including highly regulated and coordinated neurohormonal circuits. Various feedback mechanisms or "brakes" have been proposed. While duodenal, jejunal, and ileal brakes are well described, a putative distal colonic brake is less well defined. Despite the high prevalence of colonic motility disorders, there is little knowledge of colonic motility owing to difficulties with organ access and technical difficulties in recording detailed motor patterns along its entire length. The motility of the colon is not under voluntary control. A wide range of motor patterns is seen, with long intervals of intestinal quiescence between them. In addition, the use of traditional manometric catheters to record contractile activity of the colon has been limited by the low number of widely spaced sensors, which has resulted in the misinterpretation of colonic motor patterns. The recent advent of high-resolution (HR) manometry is revolutionising the understanding of gastrointestinal motor patterns. It has now been observed that the most common motor patterns in the colon are repetitive two to six cycles per minute (cpm) propagating events in the distal colon. These motor patterns are prominent soon after a meal, originate most frequently in the rectosigmoid region, and travel in the retrograde direction. The distal prominence and the origin of these motor patterns raise the possibility of them serving as a braking mechanism, or the "rectosigmoid brake," to limit rectal filling. This review aims to describe what is known about the "rectosigmoid brake," including its physiological and clinical significance and potential therapeutic applications.

Consistency of cutaneous electrical activity of the human colon with respect to serosal slow waves: A simulation study

The serosal slow waves in the human colon are complex, since their amplitude and frequency vary over time. Therefore, this study employed a simulation to investigate the consistency between serosal slow waves and cutaneous electrical activity by evaluating whether changes of the cutaneous waveform features due to anatomical and physiological parameters are detectable in the cutaneous electrical activity. The simulation results indicated that (a) changes in the dipole moment involve detectable changes in the amplitude of the cutaneous electrical activity; (b) changes in the annular band velocity induce modifications in the cutaneous signal frequency; and (c) changes in the anatomical factors affect both the amplitude and the frequency of the cutaneous signal. Therefore, we observed that there is consistency between serosal slow waves and cutaneous electrical activity. On these bases, we think that modifications in the cutaneous electrical activity observed in our study could represent the marker of specific physiological motor activity of the colon, and such information can improve the recording of the experimental measurements of the cutaneous electrical activity of the colon in humans.

Modelling Human Colonic Smooth Muscle Cell Electrophysiology

The colon is a digestive organ that is subject to a wide range of motility disorders. However, our understanding of the etiology of these disorders is far from complete. In this study, a quantitative single cell model has been developed to describe the electrical behaviour of a human colonic smooth muscle cell (hCSMC). This model includes the pertinent ionic channels and intracellular calcium homoeostasis. These components are believed to contribute significantly to the electrical response of the hCSMC during a slow wave. The major ion channels were constructed based on published data recorded from isolated human colonic myocytes. The whole cell model is able to reproduce experimentally recorded slow waves from human colonic muscles. This represents the first biophysically-detailed model of a hCSMC and provides a means to better understand colonic disorders.

Interstitial cells of Cajal (ICC) in equine colic: an immunohistochemical study of horses with obstructive disorders of the small and large intestines

REASONS FOR PERFORMING STUDY

The gastrointestinal pacemaker cells, the interstitial cells of Cajal (ICC), have been implicated in several human gastrointestinal dysmotility syndromes. Recently, the involvement of these cells in equine gastrointestinal diseases has been investigated in cases of equine grass sickness where a significant reduction in ICC density was observed.

OBJECTIVE

To investigate ICC density in equine obstructive gastrointestinal disorders using immunohistochemical labelling methods.

METHODS

Intestinal samples were analysed from 44 horses undergoing exploratory surgery for colic and from 11 control animals subjected to euthanasia for conditions not related to the gastrointestinal tract. Immunohistochemical labelling of ICC was carried out using an anti-c-Kit antibody. Two independent observers assessed ICC density using a semiquantitative grading system.

RESULTS

There was a significant reduction in ICC density in horses with large colon disorders compared to the controls (P<0.01). Horses with strangulating lesions of the small intestine showed no difference when compared to the controls.

CONCLUSIONS

There was a reduction in ICC density in horses with large intestinal disorders.

POTENTIAL RELEVANCE

The reduction in ICC density may be associated with the clinical findings as well as recurrent colic episodes observed in a number of these cases. This immunohistochemical study provides a basis for future functional electrophysiological investigations to determine the precise effect of ICC reduction on equine intestinal motility.

Fasting and postprandial small intestinal slow waves non-invasively measured in subjects with total gastrectomy

BACKGROUND AND AIM

Slow wave is essential to initiate gastrointestinal tract motility. Subjects with total gastrectomy (TG) provide an opportunity to study small intestinal slow wave in the absence of stomach interference. The aims of this study were to determine the origin of 3 cycles per min (cpm) slow wave recorded via electrogastrogram (EGG) and the characteristics of putative small intestinal slow waves in TG subjects.

METHODS

Thirty-three subjects with TG (25 male, age: 44-83 years) were consecutively enrolled. In each subject, the myoelectricity-like signals of the gastrointestinal tract were recorded using 3-channel EGG. Fourier transform-based spectral analysis was performed to derive the EGG parameters including dominant frequency/power, % normal rhythm (2-4 cpm), and power ratio.

RESULTS

Neither visual nor spectral analysis of the EGG revealed any waves at a frequency of about 3 cpm. The most frequently observed peaks in the power spectra of all subjects were those at approximately 1, approximately 6 and approximately 11 cpm with occurrences of 97%, 6.1% and 90.9%, respectively. Based on visual analysis of all recorded signals, the approximately 11 cpm signal was exactly rhythmically recorded rather than the approximately 1 cpm. The recorded approximately 11 cpm wave had a frequency of 10.9 +/- 1.0 cpm in the fasting state and 10.9 +/- 1.3 cpm in the fed state (NS), and a power of 31.5 +/- 3.2 dB in the fasting state and 35.2 +/- 3.8 dB in the fed state (P < 0.0001). None of other factors, including sex, age, and body mass index, had any impact on this approximately 11 cpm wave.

CONCLUSIONS

Small intestinal slow wave can be recorded non-invasively using EGG via cutaneous electrodes in TG subjects. Sex, age and body mass index have no effect on the intestinal slow waves. The power rather than frequency of intestinal slow wave is increased after a solid meal.

Spectral analysis of colonic intraluminal pressure in patients who received a colonic replacement following radical esophagectomy

The aim of this study was to evaluate the motor activity of the interposed colonic segment in patients who had received a colonic replacement following radical esophagectomy using spectral analysis and a 24 hr activity graph. The 24-hr ambulatory pressure waves were recorded in the replaced colon after esophagectomy (n=8) using a solid-state manometric catheter (MicroDigitrapper, Synetics). Motility and spectral analyses of the intraluminal pressure waves were performed by Multigram and Gastrosoft (Synetics). It was revealed that after a meal the 3 cpm (cycles per minute) component of the motility index increased but the 12-15 cpm component decreased. The diurnal rhythm showed that colonic motility was high in the daytime and low during sleep. In contrast, duodenal motility was relatively high even during sleep. The motility index increased as the postoperative period increased. The motility of the replaced colon was higher during the daytime and after meals. The higher motility after meals was characterized by an increase in the 3 cpm component. These motor characteristics may help the function of the replaced colon as a substitute for the esophagus.

Electrical activity from colon overlaps with normal gastric electrical activity in cutaneous recordings

The stability of EGG recordings is affected by a variety of artifacts. The aim of this study was to investigate possible overlapping of dominant frequencies in recorded cutaneous electrical activity arising simultaneously from the stomach and/or colon. Ten normal volunteers, eight posttotal colectomy patients, and four patients posttotal gastrectomy were studied. Fasting cutaneous recordings were obtained using four pediatric ECG electrodes attached to the abdominal surface. Electrical activity was recorded and digitally analyzed using custom-designed software. Spectral analysis after gastrectomy and colectomy showed persistence of power peaks in the gastric electrical activity range of frequency (2.5-3.75 cpm). In conclusion, noninvasively obtained colonic frequencies overlap EGG. This hypothesis is supported by the persistence of power peaks in the EGG range of frequency after gastrectomy and colectomy. Therefore, we conclude that contribution of electrical activity arising from the colon could substantially affect EGG recordings.

Electrical activity from colon overlaps with normal gastric electrical activity in cutaneous recordings

The stability of EGG recordings is affected by a variety of artifacts. The aim of this study was to investigate possible overlapping of dominant frequencies in recorded cutaneous electrical activity arising simultaneously from the stomach and/or colon. Ten normal volunteers, eight posttotal colectomy patients, and four patients posttotal gastrectomy were studied. Fasting cutaneous recordings were obtained using four pediatric ECG electrodes attached to the abdominal surface. Electrical activity was recorded and digitally analyzed using custom-designed software. Spectral analysis after gastrectomy and colectomy showed persistence of power peaks in the gastric electrical activity range of frequency (2.5-3.75 cpm). In conclusion, noninvasively obtained colonic frequencies overlap EGG. This hypothesis is supported by the persistence of power peaks in the EGG range of frequency after gastrectomy and colectomy. Therefore, we conclude that contribution of electrical activity arising from the colon could substantially affect EGG recordings.

Anorectal anatomy and physiology

Knowledge of anorectal anatomy is essential for understanding the normal function of the anorectum. Its physiology is more complex, however. The maintenance of continence depends on several factors, and today clinicians have a better understanding of the usual sequence of events that leads to defecation. The extensive number of investigative techniques that have evolved have permitted better understanding of the disorders of the anal sphincters, rectum, and pelvic floor.

Control of motility patterns in the human colonic circular muscle layer by pacemaker activity

1. This study characterized the electrical and mechanical activities of human colonic muscle strips obtained from either the ascending, descending or sigmoid colon of patient volunteers during elective colon resections. 2. Rhythmic contractile activity was observed in colonic circular muscle strips in the absence of external stimuli. This activity persisted in the presence of atropine, phentolamine, propranolol, tetrodotoxin and Nomega-nitro-L-arginine but was abolished by nifedipine. 3. The activity of whole circular muscle (WCM) was compared with that of the myenteric half (MCM), the submucosal half (SCM) and the interior (ICM) of the circular muscle layer. WCM exhibited a prominent 2-4 contractions min-1 contractile pattern which was also present in strips of SCM. In contrast, MCM and ICM exhibited slow (0.3-0.6 contractions min-1), long duration contractions with superimposed higher frequency contractions (17-18 contractions min-1). 4. Resting membrane potential (Vm), recorded at various positions through the thickness of WCM strips did not differ and averaged -50 mV. 5. Slow waves were observed in 83 % of muscles. They averaged 12 mV in amplitude, 9.4 s in duration and had a frequency of 2-4 contractions min-1. Slow waves were greatest in amplitude near the submucosal edge and decreased with distance away from this edge. Each slow wave was associated with a transient contraction. 6. Near the myenteric edge, rapid fluctuations of Vm with a mean frequency of 18 contractions min-1 were recorded in 67 % of muscles. Spiking activity was common and was superimposed upon slow waves and rapid Vm fluctuations. 7. In summary, slow waves were identified in the human colonic circular muscle layer which arise at or near the submucosal edge. These electrical events give rise to a 2-4 contractions min-1 contractile rhythm which is characteristic of the intact muscle layer. Thus, the nature and spatial organization of pacemaker activity in the human colon bears significant resemblance to other animal models, such as the dog and pig.

Electrical activity recorded from abdominal surface before and after gastric surgery in man

To explain the role of the different portions of the stomach in the genesis of electrical signal obtained from abdominal surface (Electrogastrography, EGG), the EGG was recorded in 6 patients with gastric cancer and 7 with duodenal ulcer before and after total gastrectomy or Billroth II gastric resection, respectively. Eight patients undergoing cholecystectomy entered the study as controls. The spectral frequency components were subdivided into ranges, and the dominant frequency and power were calculated for each range before and after surgery. The power profile, expressed as difference in power percentages before and after surgery for each frequency range, was obtained. The power profile from total gastrectomy or gastric resection was clearly different from that resulting from cholecystectomy in the 2.6-3.5 cycles per minute range (cholecystectomy vs gastric resection, P = 0.009; cholecystectomy vs gastrectomy, P = 0.012). No difference in power profile between total gastrectomy and gastric resection was demonstrated. Since total and partial gastrectomized patients showed a similar power profile, EGG signal corresponded to the electrical activity of the distal two third of the stomach.

Electrogastrography prior to and following total gastrectomy, subtotal gastrectomy, and gastric tube formation

On electrogastrography (EGG) spectral analysis, an activity of 3 cycles per minute (cpm) is supposed to be specific for the stomach. After total or subtotal gastrectomy, the original site of the stomach is occupied mainly by the intestine. We attempted to determine if intestinal activity could be recorded in this region with EGG. Epigastric recordings were performed in patients prior and following gastrointestinal or control surgeries. Spectral analysis, using the maximal entropy method and ensemble means was applied to data analysis from these recordings. Preoperatively, the majority of the power peaks were found around 3, 6, and 11 cpm. The postprandial-to-fasting power ratio of all of these power peaks increased significantly postprandially (P < 0.05-0.01). Following total gastrectomy, the power peak around 3 cpm disappeared or was significantly diminished in amplitude (P < 0.05). The postoperative-to-preoperative power ratio ranged from 0.03 to 0.10 (P < 0.001-0.01). However, the power peak around 11 cpm did not significantly change prior to or following total gastrectomy, and the 11 cpm peak appeared relatively dominant. Simultaneous manometric studies in the Roux limb demonstrated a correlation between the power spectral frequency of EGG and manometry at 11 cpm. Therefore, the 11 cpm peak appeared to reflect jejunal or Roux limb electrical activity. The postoperative to preoperative power ratio for the 3 cpm also was significantly reduced following subtotal gastrectomy and gastric tube formation in patients in the postprandial state (P < 0.05-0.001).

Motility and sensation of the rectosigmoid and the rectum in patients with anorectal malformations

Motility of the rectosigmoid and rectum and reservoir function of the rectum after surgery for anorectal malformations were investigated in 32 patients (17 with high type, 6 with intermediate type, and 9 with low type anomaly) aged 5 to 16 years. All 32 patients were examined manometrically as well as with a newly devised myoelectrical method. Manometry showed that the values of maximum anal pressure and anorectal pressure difference in the high type were significantly lower than those in the low type. However, the incidence of contractile activity of the rectosigmoid was not significantly different between these two groups. The threshold sensation pressure and the maximum tolerable pressure in the high type were significantly higher than those in the low type, and the rectal compliance in the high type was significantly lower than that in the low type. Electromyography was recorded at 8 cm and 5 cm from the anal verge. Two types of slow waves were observed, a faster rhythm and a slower rhythm. Their frequency was similar in the three groups. However, the numbers of spike bursts in the high type and intermediate type were significantly higher than those in the low type. These results indicate that in addition to an inadequate anal resting pressure a loss of optimal rectal sensation or rectal reservoir function might be associated with fecal incontinence in the high type and that increased spike bursts might play some role in rectal motility.

Morphine effects on human colonic myoelectric activity in the postoperative period

Colonic myoelectrical activity was studied in 25 patients, 18 of whom received morphine sulfate, using bipolar electrodes placed in the ascending and descending colon during laparotomy. Baseline myoelectrical activity was recorded daily, then morphine (3 to 15 mg) was administered intravenously, intramuscularly, or epidurally, and recordings continued. Seven activity patterns were observed during recovery from postoperative ileus. During the first 2 postoperative days, morphine at any dose did not affect colon myoelectrical activity. From the third postoperative day on, morphine given intravenously or intramuscularly initiated clusters of short, nonmigrating, phasic spike bursts occurring on each successive slow wave in 14 of 18 patients, which lasted for 30 to 45 minutes. When morphine was administered epidurally, there was no colonic response in any patient. These findings suggest that: (1) morphine intravenously or intramuscularly induces predominantly nonmigrating colonic spike bursts; (2) morphine-induced activity alters the normal pattern of colonic motility during recovery from postoperative ileus; and (3) these phenomena are not due to direct action of morphine on the spinal cord since epidural morphine had no effect.

In vitro electro-mechanical activity of the human colon. Simultaneous recording of the electrical patterns of the two muscle layers

Electrical and mechanical activity on longitudinal and circular layers of the human sigmoid colon were simultaneously studied. Recordings were obtained from two electrode sites spaced 3 cm apart in a piece of colon which had been resected surgically and perfused in an organ bath. Spontaneous electrical activity of the colon showed slow waves and spikes. Slow waves were present for only 24.5% and 12% of the recording time on the longitudinal and circular layers, respectively, and they appeared as localized activity which was irregular in amplitude and varying in frequency. Electrical coupling between the two muscle layers was rarely seen and slow waves were not associated with pressure changes. Spiking activity were recorded as short and long spike bursts on both muscle layers. Short spike bursts were localized activity superimposed on slow waves. The associated mechanical activity, which consisted of single weak pressure changes or prolonged contractions with summation, was determined by slow wave frequency. Long spike bursts were seen at irregular intervals and were either propagated or not propagated activity associated with electrical oscillations ranging from 24 to 46 cpm. Mechanical activity consisted of sustained tonic contractions propagated or not propagated in the same way as the electrical pattern. Coordinated electrical activity of the two muscle layers seldom occurred when spontaneous activity was being recorded. Electrical activity on both muscle layers was very sensitive to stretching and could be initiated or modulated by pharmacological agents. In particular, our findings showed that stimulation induced coordinated spiking activity on the two muscle layers and caused mechanical activity, propagated orally or aborally, which consisted of long lasting, high amplitude contractions.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ambulation on recovery from postoperative ileus

To determine whether ambulation hastens recovery from ileus following laparotomy, 34 patients were studied, 10 of whom followed an ambulatory regimen beginning on postoperative day 1 (group A). The other 24 patients (group C) did not become ambulatory until postoperative day 4. All patients underwent placement of seromuscular bipolar recording electrodes on the Roux limb, if present, stomach, jejunum, and colon at laparotomy. Group A was recorded before and after ambulation so comparisons could be made to determine if ambulation had an acute effect on myoelectric activity. Group A preambulation and group C recordings were compared to judge whether there was an over-all effect of ambulation on myoelectric recovery. No effect on slow wave frequency or percentage of slow waves with associated spike potentials was noted acutely or overall in the stomach, colon, or jejunum in continuity with the duodenal pacemaker. Transient increases in phase II spike activity in patients having a Roux limb and their jejunum distal to the enteroenterostomy were noted on postoperative days 1 to 2, but these differences resolved by postoperative days 3 or 4. The data suggest that ambulation as a means to help resolve postoperative ileus and its accompanying cramps and bloating may be more perceived than real.

Concordance between colonic myoelectrical signals recorded with intramuscular electrodes in the human rectosigmoid in vivo

The myoelectrical activity of the human rectosigmoid colon was studied simultaneously in six subjects at two sites using two pairs of fine wire bipolar electrodes. The electrodes were spaced 2-5 cm apart in the rectosigmoid after insertion into the smooth muscle layers under direct vision at sigmoidoscopy. The electrodes were implanted at positions between 8 and 25 cm from the anal verge in different subjects. The frequency of myoelectrical burst activity together with the burst duration recorded by each electrode pair was examined. The relation of burst frequency and burst duration in the higher and lower placed electrodes was also assessed. In none of the subjects was three evidence of synchrony between the electrode pairs. In addition, there was no relation between the relative position of the electrodes and the intrinsic frequency of duration of myoelectrical bursts. It is concluded that regions of smooth muscle in the unstimulated human colon in vivo act independently and that there is no effective common neuromuscular drive under these conditions.

Gastrointestinal myoelectric and clinical patterns of recovery after laparotomy

The objective of this study was to define the patterns of myoelectric activity that occur throughout the gastrointestinal tract during normal recovery from laparotomy. Electrodes were placed on the stomach, jejunum, and transverse colon of 44 patients undergoing laparotomy. Basal electric rhythms in all areas showed no changes in frequency after operation (up to 1 month). Gastric spike wave activity showed a gradient of increasing activity from fundus to antrum. Antral spike activity was unchanged during the study. Jejunal spike activity was present in the earliest recordings and occurred in 45.9% +/- 3.5% to 59.9% +/- 5.5% of slow waves. Recovery of normal colon discrete and continuous electric response activity occurred on postoperative day 5.9 +/- 1.5. Bowel sounds returned on day 2.4 +/- 0.5 and passage of flatus and stool occurred on day 5.1 +/- 0.2. The myoelectric parameters measured are not absolutely predictive of uneventful recovery from postoperative ileus but they are, as a group, more informative than any currently available clinical criteria.

Electrical activity recorded from abdominal surface after gastrectomy or colectomy in humans

The visceral electrical activity recorded from the abdominal surface was studied before and after either total gastrectomy or colectomy. The patterns obtained from fast Fourier transform analysis demonstrated the disappearance of the power peak of approximately 3 cpm after gastrectomy, whereas colectomy did not result in the disappearance of the power peak of approximately 3 and 8-12 cpm. Only the frequencies of approximately 3.5-7.5 cpm were not present after colon surgery. These data demonstrate that the spectral power peaks at frequencies of approximately 3 cpm are entirely related to the stomach because they disappear after gastrectomy; the power peaks between 3.5 and 7.5 cpm are related to the colon because they are present after gastrectomy but not after colectomy; the power peaks between 7.5 and 11 cpm are related to the small intestine because they are present after either gastrectomy or colectomy. The authors conclude that the electrical activity recorded from the abdominal surface and analyzed by fast Fourier transform gives reliable information concerning the electrical activity of the stomach and small intestine, although it is less reliable concerning the electrical activity of the colon.

Colonic slow-wave analysis. Limitations of usefulness of fast Fourier transform (FFT)

The fast Fourier transform (FFT) has been used to determine frequency components of colonic slow-wave activity. We studied the effect of (1) recorder filter characteristics, (2) number of data points and, (3) data window overlap technique and ingestion of a 1000-kcal meal on the resulting power spectrum. Human rectosigmoid slow-wave activity was recorded in nine normal subjects and stored on FM tape for computer analysis. The dynograph filter characteristics were tested using square wave signals, and derived compensation factors were applied to the FFT before viewing. The dynograph filter, when set to optimize visualization of slow waves, attenuates low frequencies nonlinearly. Failure to compensate for the dynograph filter results in inaccurate detection of slow-wave frequencies. FFT of 1-min data gives a different power spectrum than an FFT of 4 min data, indicating a rapidly changing waveform. FFT's of 1 min of data when examined over time fail to demonstrate a consistent frequency spectrum, confirming this conclusion. The lower frequencies in the normal human rectosigmoid are present at the greatest power. These studies indicate that the colon has slow waves of irregular frequencies, in contrast to the stomach or small intestine. No change in the dominant frequency was seen following the ingestion of a 1000-kcal meal.

Human rectosigmoid electromyography: a new approach and some pitfalls

A method has been developed to record directly myoelectrical activity from the smooth muscle of the colon of intact subjects using pairs of intramuscular wires. Discrete bursts of myoelectrical activity occurred at 4-20 per min. A small interelectrode distance in this method allows contamination of colonic myoelectrical activity by the electromyogram of skeletal muscle to be excluded. This artefact has not been considered in previous recordings of 'colonic' activity.

Effect of secoverine on colonic myoelectric activity in diverticular disease of the colon

The effect of secoverine on colonic smooth muscle was measured in patients with diverticular disease and in healthy subjects. The frequency of slow wave activity was determined using the fast Fourier transform (FFT) and peak identification analysis (SWSA). The mean slow wave frequency was similar (6 cycles/minute) in healthy subjects using both analytic methods. The slow wave frequency in patients with diverticular disease was similar to that in healthy subjects. The peak frequency measured with SWSA was uniformly higher than that measured with FFT. Secoverine, a muscarinic antagonist, did not affect the slow wave frequency. Eating a 1000-kcal meal initiates an increase in colonic spike activity (22 +/- 2 spike potential/30 min) (P less than 0.001) in healthy subjects during the immediate postprandial period. The gastrocolonic response in patients with diverticular disease was prolonged for 60 min. Secoverine inhibited the gastrocolonic response in patients with diverticular disease. These studies suggest patients with diverticular disease have a similar slow wave frequency as healthy subjects, the gastrocolonic response is prolonged in patients with diverticular disease, and secoverine inhibits the colonic response.

Elastic fibers in musculature of rectosigmoid colon: normal findings in children and changes in Hirschsprung's disease--a preliminary report

In order to determine the possible implication of elastin in spasticity of the aganglionic segment in Hirschsprung's disease the elastic fibers in the colon at rectosigmoid level were studied in seven surgical specimens of aganglionic bowel and in seven normal controls. Elastic fibers in both the muscle layers of normal bowel are thin, tend to be straight, and follow the line of muscle fasciculi. In aganglionic bowel, however, the fibers are more numerous and thicker in both layers, and in the longitudinal layer they are laid down in spirals. The total elastin content is increased by approximately 100% as compared with controls. These structural and quantitative changes in the elastin may contribute both to the spasticity and to the increased elasticity of the aganglionic segment.

Control of human colonic motor function

Human colonic motility is governed by control mechanisms involving the electrical activity of the smooth muscle cell membranes, the intrinsic and extrinsic nervous activity, and hormonal action. The structural bases for neural and myogenic control have not been demonstrated. However, gap junctions are lacking between muscle cells, and nerves are not close to smooth muscle cells. The myogenic control, as observed in vitro, is described and compared with results obtained from different in vivo techniques. In vitro and in vivo measurements are critically evaluated, and a reconciliation between them attempted. No appropriate animal model is available to help resolve different findings and interpretations. Neural control of colon motility is exerted probably through modulation of myogenic activity as well as directly. The activities of extrinsic nerves, intrinsic motor nerves and afferent nerves are integrated within the colon, at prevertebral ganglia and in the spinal cord in animals, but similar data are not available for the human. There is a lack of studies directly relating transit to motility and conventional beliefs need reexamination.

Resolution of postoperative ileus in humans

Bipolar electrodes were placed in the ascending and descending colon of 13 patients during laparotomy. The magnitude of their operations varied from exploratory laparotomy to total gastrectomy. The magnitude and length of the operations performed did not correlate positively with the duration of postoperative ileus. Signals were recorded for up to 4 hours daily for up to 8 days after operation during periods of rest and, in some patients, after administration of epidural or parenteral morphine sulfate. Power spectrum analyses of electrical control activity (ECA) showed dominant frequencies in both lower (2-9 cpm) and higher (9-14 cpm) ranges. During postoperative recovery, the mean ECA frequencies in right and left colon were relatively constant, but a variety of dominant ECA frequency relationships were observed. The modal pattern in the right colon was a shift in the dominant frequency from the higher to the lower range as recovery progressed, while the modal pattern in the left colon was persistent dominance of ECA in the higher frequency range. Electrical response activity (ERA) initially was comprised of only random, disorganized single bursts but became progressively more complex through the initial 3 postoperative days with the appearance of more organized bursts and clusters, some of which propagated very slowly (about 5 cm/min) both orad and aborad. ERA recovery culminated, typically on the third or fourth postoperative day, with the return of long bursts of continuous ERA, some of which propagated at a higher velocity (about 80 cm/min) and exclusively in the aborad direction and which were accompanied by passage of flatus or by defecation.

Human colonic smooth muscle: electrical and contractile activity in vitro

Extracellular electrical and contractile activities were recorded in vitro from strips of human colonic smooth muscle obtained at the time of surgery. Serosal electrical activity of longitudinally oriented strips from the taenia and intertaenial region was characterised by continuous oscillation at a frequency of 28 +/- 1/min. Contractions were marked electrically by a series of oscillations upon which spikes were superimposed. The electrical activity recorded from the submucosal surface of circularly oriented strips exhibited oscillations at 24 +/- 4/min, a frequency significantly lower (p less than 0.001) than that recorded from the serosal surface of similar preparations. The contractile force and frequency was dependent upon the part of the colon from which the strip originated; the most powerful contractions were recorded from strips of sigmoid colon. The contractile frequency of circularly oriented strips from the right colon was 6.3 +/- 0.6/min, significantly higher (p less than 0.001) than that of strips from the left colon (3.4 +/- 0.3/min). Stretching these strips caused an increase in contractile frequency to that of the electrical oscillation.

Electrophysiologic control of motility in the human colon

Characteristics of electrical activities, and the relationship between electrical and motor activities, were studied in circular and longitudinal (taenia) muscle of the human colon that was obtained from 21 individuals. Recordings were obtained with suction electrodes, the sucrose-gap method, and microelectrodes. The circular muscle electrical activity consisted of oscillatory activity of relatively low amplitude, with a frequency range from 4.5 to 60 cycle/min. Spiking activity was present on most oscillations. Contractile activity was associated with individual oscillations at frequencies below 12 cycle/min. Contractions related to periods of oscillations at frequencies above 12 cycle/min showed summation resulting in prolonged contractions. In these periods, oscillations were either of relatively high amplitude, or had superimposed spiking activity. Longitudinal muscle activity consisted of slow electrical oscillations at frequencies between 24 and 36 cycle/min with spiking activity superimposed on most oscillations. Contractions were related to bursts of such activity. These findings provide the electrophysiologic basis for short and prolonged phasic contractions and for sustained contractions of the human colon muscle layers. Activities in both muscle layers were myogenic in nature, were very sensitive to stretch, and could be initiated or modulated by nervous activity.

Intracellular electrical activity in circular muscle of canine colon

In vivo and extracellular in vitro studies of colon muscle have led to a great deal of disagreement on the characteristics of slow wave activity. As intracellular recordings of electrical activity in single cells give clear records which are easier to analyse, we used this method to study the slow wave activity of the circular muscle of three different parts of the canine colon. Mucosa was removed from segments of proximal, mid and distal canine colon and specimens from each segment were mounted in an organ bath perfused with oxygenated Krebs' solution. Membrane potential, amplitude and frequency of slow waves were measured using intracellular electrodes. Slow wave activity was present at a single, continuous frequency of 4-6 cpm in the circular muscle at all the sites studied in canine colon. There was no significant frequency gradient along the colon: the membrane potential and amplitude of slow waves did not differ significantly in the three parts of the colon.

Vagal control of colonic motility in the anaesthetized ferret: evidence for a non-cholinergic excitatory innervation

Spontaneous colonic motility in the urethane-anaesthetized ferret consists of two distinct types of contraction which correspond to the patterns recorded myoelectrically in conscious animals. This motility was abolished or greatly reduced when nervous conduction was prevented in the cervical vagi by cooling to below 4 degrees C. On rewarming the nerves the colonic motility returned, after a short latency, to the pre-cool level. Atropine transiently abolished colonic motility. On its return the motility was significantly reduced but still sensitive to vagal integrity. Thus the atropine-resistant colonic motility was also abolished or markedly reduced by cooling the cervical vagi to below 4 degrees C. On rewarming there was a longer latency for the return of motility compared to that before atropinization. Electrical vagal stimulation produced, after a short latency, large-amplitude colonic contractions. Following atropine, the short-latency response to electrical vagal stimulation was replaced in the majority of animals by a long-latency response whose characteristics were quite different from those of the cholinergic response. These results are consistent with the vagus containing two functional motor pathways to the colon, one to cholinergic post-ganglionic neurones and the other operating via a non-cholinergic mechanism.

Electrical activities of the muscle layers of the canine colon

The spontaneous electrical and mechanical activities of the circular and longitudinal muscle layers of the canine colon were studied. The smooth muscle cells of the circular muscle layer exhibited regular, omni-present myogenic slow-wave activity at a frequency ranging from 4 to 7 c/min. With intracellular micro-electrodes, the slow-wave amplitude was 21-38 mV and its duration 3-6 sec. The 'resting' membrane potential was -60 to -76 mV. Some slow waves had superimposed spike bursts on their peak depolarizations and only these were associated with phasic contractions. It is concluded that they serve a pace-maker function similar to their counterpart in the small intestine. The longitudinal muscle layer exhibited periods of electrical activity alternating with periods of electrical quiescence. During the activity periods electrical oscillations occurred at a frequency of 13-35 c/min with spikes on top of them. Each electrical activity period was associated with a prolonged 'tonic' contraction. The duration of these periods was 30-120 sec and their frequency 0.4-1.1 period/min. This activity is similar to that recorded from the longitudinal muscle of the guinea-pig caecum despite the anatomical differences. The electrical activity periods of the longitudinal muscle appeared to require an excitatory input (stretch and/or acetylcholine release). Provided the strips were not excessively stretched, atropine abolished all electrical and motor activity. Stretching prolonged the electrical activity periods until they eventually fused together and the muscle developed maintained tone. Simultaneously recording from both layers showed that, although electrotonic spread between the two layers is probably insignificant, the activity of the two layers was co-ordinated. Only those slow waves of the circular layer that occurred during the electrical activity periods of the longitudinal layer had superimposed spikes. It is suggested that this co-ordination may indicate that the two muscle layers may be commanded by a common input from periodically active, cholinergic intramural neurones. It is proposed that the complex patterns of colonic electrical and motor activities may be explained as consisting of two major components: one arising from the longitudinal (long spike bursts, high-frequency oscillations and tonic contractions) and the other from the circular layer (slow waves, short spike and phasic contractions). Simultaneous electrical records from the two muscle layers and the mucosa failed to show a consistent relationship between the mucosal record and the activity of either layer. Caution should be exercised in the interpretation of intraluminally derived electrical recordings.

Electrical and contractile activities of the human rectosigmoid

Electrical and mechanical activities were recorded from the rectosigmoid of normal subjects using an intraluminal recording tube with two sets of bipolar electrodes and strain gauges. Four distinct types of electrical activities were recorded. (1) Electrical control activity (ECA). This activity varied in amplitude and frequency over time and the control waves were not phase-locked. The means of dominant frequency components in the lower and higher frequency ranges were 3.86 +/- 0.18 SD and 10.41 +/- 0.46 SD c/min, respectively. The overall dominant frequency component was mostly in the lower frequency range of 2.0-9.0 c/min. (2) Discrete electrical response activity (DERA). This activity appeared as short duration bursts (less than 10 s) of response potentials whose repetition rate was in the total colonic electrical control activity frequency range of 2.0-13.0 c/min. The mean duration of this activity was 2.24 +/- 1.30 SD s. (3) Continuous electrical response activity (CERA). This activity appeared as long duration bursts (greater than 10 s) of response potentials which were not related to electrical control activity. Its mean duration was 14.78 +/- 3.68 SD s. This activity generally did not propagate. (4) Contractile electrical complex (CEC). This activity appeared as oscillations in the frequency range of 25-40 c/min and was also not related to electrical control activity. This activity propagated, sometimes proximally and sometimes distally. Its mean duration was 18.87 +/- 9.22 SD s. The latter three types of electrical activities were all associated with different types of contractions. These contractions, however, did not always occlude the lumen. Colonic electrical control activity controls the appearance of discrete electrical response activity in time and space. The mechanism of generation of continuous electrical response activity and contractile electrical complex is not yet known.

Effect of stress, meal and neostigmine on rectosigmoid electrical control activity (ECA) in normals and in irritable bowel syndrome patients

An intraluminal probe with two sets of bipolar electrodes (4 cm apart) was used to record electrical control activity (ECA) from the rectosigmoid of 17 normal subjects and 16 IBS patients in the resting state, during neutral and stressful interviews, and after a meal or neostigmine. Fast Fourier transform method was used for the frequency analysis of ECA. The ECA was present at all times in both the groups but was variable in frequency and amplitude and was phase-unlocked during all recording periods. Up to four frequency components were observed in the lower frequency range (LFR) of 2.0-9.0 c/min and up to two in the higher frequency range (HFR) of 9.0-13.0 c/min during all recording periods. The frequency and organization of ECA were not significantly different between the normal and the IBS groups in the resting state. Neutral and stressful interviews did not significantly affect the mean ECA frequency in either of the groups but the mean ECA frequency of the dominant frequency component in LFR was lower in IBS patients than in the normal subjects during the stressful interview. Meal and neostigmine did not significantly affect the ECA frequency or its organization in either of the groups. It appears from this study that alternations in colonic ECA may not form the basis of motility disorder in irritable bowel syndrome.