Physiology and pathophysiology of colonic motor activity (1)

Flatus-related colorectal and anal motor events

Although complaints of excessive "gas" symptoms are frequently encountered in clinical practice, the physiologic and pathophysiologic grounds of flatus events are poorly understood, partly because of the social taboos associated with the topic and partly because of technical difficulties in measuring flatus. For these reasons, we studied the colorectal and anal motor events occurring during artificially evoked flatus events and compared them to those that occurred spontaneously. Five healthy male volunteers were studied by multilumen probes placed in the left colon and rectum and across the anal canal, to observe the flatus-related motor events that occurred after instillation of air into the colon. Flatus-related spontaneously occurring motor events were also checked in 24-hr motility tracings obtained in three patients with functional bowel disorders. Analysis of the tracings showed that both artificially induced and spontaneously occurring flatus-related motor phenomena were characterized by colonic propagated contractions associated with a rise in rectal pressure and early relaxation of the anal sphincter, in a sequence resembling that observed following swallowing. Spontaneous flatus events were associated with colonic waves of lesser amplitude than those following insufflation of air into the colon.

Pacemaker cells in the gastrointestinal tract: interstitial cells of Cajal

Interstitial cells of Cajal (ICC) were described a century ago as primitive neurons in the intestines. Through the years, ICC have been mistaken for neurons, glial cells, fibroblasts, smooth muscle cells, and macrophages. We identified ICC in the musculature of mouse small intestine by their characteristic morphology and topography, and we analysed the relation between ICC, autonomic nerves, and smooth muscle. Subsequent morphological and electrophysiological evidence has strongly supported our hypotheses that some ICC populations are gut pacemakers and may hold other fundamental regulatory functions (coordinative, mechanoreceptive, mediating nervous input). Recognition of common principles of ICC organization (confinement to specific locations in relation to smooth muscle layers; formation of extensive cellular networks through tight coupling of overlapping thin processes; innervation patterns; characteristic patterns of contact with smooth muscle cells) and ultrastructure (myoid features: basal lamina, caveolae, rich in sER and mitochondria, often prominent filament bundles and dense bands/bodies) has allowed the identification of ICC in the GI musculature of all species investigated. However, variation in organization and ultrastructure is significant, between both species and regions of the GI tract. Our studies of ICC in human intestine permit an extension of the above hypotheses to man and provide a basis for further studies of ICC pathology and pathophysiology. The latter may become a fruitful area of research in the coming decades.

Nitric oxide synthase and VIP distribution in enteric nervous system in idiopathic chronic constipation

Idiopathic chronic constipation has been correlated to neural abnormalities that consist of a reduced number of myenteric plexus neurons and a decreased concentration of VIP-positive nerve fibers within the circular muscle. Recent studies hypothesized the involvement of nitric oxide in motility disorders of the human gut. To date, no information is available on nitric oxide involvement in idiopathic chronic constipation. The density of VIP- and nitric oxide-producing neurons was evaluated by immunocytochemistry using anti-VIP and anti-nitric oxide synthase antibodies in five patients with idiopathic chronic constipation. A low total neuron density was found at the myenteric plexus. The density of VIP-positive neurons was low while that of nitric oxide synthase-positive neurons was high at both plexuses. Our data confirm that idiopathic slow-transit chronic constipation is due to abnormal neurogenic factors. The presence of numerous nitric oxide synthase-positive neurons, all along the colon and at both plexuses, supports the hypothesis that an excessive production of nitric oxide may cause the persistent inhibition of contractions.

Age-related changes in colon motility

To assess age-related changes, we analyzed 32 colon manometry studies of children referred for motility studies and found not to have colonic disease. Colon motility was recorded by endoscopically placed water-perfused catheters. There was an inverse correlation between the number of high-amplitude propagated contractions and age, before and after administration of a meal; colonic contractions different from the high-amplitude propagated contractions increased with age.

Effect of celiac and superior mesenteric ganglionectomy on fasted canine colonic motor activity

The role played by extrinsic nerves in colonic motor activity and motor coordination between the small intestine and the colon in the fasting state was investigated in a canine model. To evaluate motor activity before and after celiac and superior mesenteric ganglionectomy (CSMG), seven strain gauge force transducers were implanted in the small and large bowels of five dogs. No significant differences were observed in the frequency, duration, cycle, or migration time of bursts of contractions from the colon (BCC), or in the duration of the quiescent state before and after CSMG. When small intestinal phase III activity reached the ileocecal junction before and after CSMG, a characteristic contractile pattern, namely, small intestinal phase III activity followed by BCC, was observed at the ileocecal junction. Before and after CSMG, 84% and 83% of the small intestinal phase III activity, respectively, was transmitted to the colon as BCC after reaching the ileocecal junction. However, only 19% and 18% of BCC before and after CSMG, respectively, followed small intestinal phase III activity. These results led us to conclude that the extrinsic nerves exert little effect on fasting colonic motor activity and motor transmission from the small intestine to the colon.

Fractionated irradiation alters enteric neuroendocrine products

Radiation profoundly alters the contractile activity of the small intestine and colon. We hypothesized that some motor changes of the gut might be secondary to impaired neural input to smooth muscle or abnormal release of gut endocrine peptides. The density of products within peptidergic and cholinergic nerves and gut endocrine cells was estimated in six normal controls and six dogs who had received 1500 cGy in six equal fractions of 250 cGy. Choline acetyltransferase, acetylcholinesterase, vasoactive intestinal peptide (VIP), substance P, peptide YY (PYY), and motilin were measured in tissue specimens divided into mucosal-submucosal (MS) and muscularis externa (ME) layers. Tissue samples were obtained from the duodenum, jejunum, ileum, and proximal and distal colon. In addition, serum levels of motilin and PYY were determined before and during the administration of 1500 cGy in four separate dogs instrumented to record upper gut contractile activity. Intrinsic cholinergic activity as estimated by choline acetyltransferase activity was unchanged, while acetylcholinesterase activity increased in the MS layers of distal small bowel and colon. VIP was increased in the MS layers of jejunum and proximal colon as well as in the ME layers the jejunum and ileum. By contrast, substance P increased in the jejunal and proximal colonic MS layers and in the ME layers of the jejunum and ileum. Duodenal and jejunal motilin levels markedly decreased after radiation exposure, while serum motilin levels continued to cycle at a decreased peak level with migrating motor complexes. Colonic PYY remained unchanged but serum PYY levels decreased after irradiation. Increased neuronal synthesis and inhibition of neurotransmitter release are potential explanations for elevated tissue concentrations of VIP, substance P, and acetylcholinesterase. There appeared to be differences in the sensitivity of gut endocrine cells to irradiation. Changes in gut regulatory peptides and cholinergic enzyme activity occur with fractionated doses of abdominal irradiation, while the same schedule of irradiation produces striking changes in the canine small intestinal and colonic motor activity. It is therefore likely that alterations of contractile events may be produced by changes in gut neuroendocrine products.

Effects of CCK-receptor antagonist on colonic motor activity in dogs

This study employed a cholecystokinin (CCK) antagonist to evaluate whether endogenous CCK regulates fasted and fed motor patterns of the colon. Experiments were performed in six conscious dogs, each in duplicate. Motor activity was recorded by four strain gauge transducers implanted on the colon. The effects of the CCK-analogue caerulein and the CCK-antagonist loxiglumide (Rotta, Italy) were studied in fasted and fed states. The motor activity was computed for the area under contractions. Caerulein given as an intravenous bolus of 50 ng kg-1 during a quiescent state caused a burst of phasic and tonic contractions resembling a regular non-migrating motor complex. Physiological doses of 10 ng kg-1 caerulein, which increases plasma CCK-immunoreactivity to postprandial levels, had no effect. Continuous intravenous infusion of 10 mg kg-1 h-1 loxiglumide completely abolished the effects of 50 ng kg-1 caerulein. The motor activity stimulated by the cholinesterase inhibitor neostigmine (10 micrograms kg-1) was not altered by loxiglumide. Loxiglumide given in the fasted state reduced the area under contractions in the proximal colon by 26.8 +/- 12.8% compared to the control without loxiglumide (P < 0.05). The postprandial increase in motor activity in the distal colon, the gastrocolonic response, was significantly inhibited by loxiglumide. Moreover, loxiglumide reduced the area under contractions in the fed state by 25.4 +/- 10.7% and 19 +/- 7.2% in the proximal and distal colon, respectively (P < 0.05). The present results show that loxiglumide acts as a specific antagonist of the actions of CCK on colonic motor activity in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Ulcerative colitis: rectal dilations in a patient with refractory diarrhea. Report of a case

A 45-year-old man with an eight-year history of ulcerative colitis was evaluated for severe, nonbloody diarrhea. Symptoms, which began two years earlier, were characterized by 15 bowel movements per day, accompanied by urgency and incontinence. A reduced rectal compliance was measured at manometry. All conventional treatments were not able to modify the symptoms despite improvement of inflammatory colonic lesions.

PURPOSE

The aim was to reduce bowel movements and incontinence by increasing rectal compliance.

METHODS

Gradual pneumatic dilations of the rectum were performed three times per week for three weeks.

RESULTS

The patient's diarrhea improved dramatically, decreasing in frequency from approximately 15 to only 3 bowel movements per day, while contemporaneously increasing rectal compliance. Such effect, still evident 15 months after discontinuation of dilation, was probably obtained by improvement of viscoelastic features of the intestinal wall.

CONCLUSIONS

Rectal pneumatic dilation may be a successful attempt in some forms of intractable diarrhea in long-lasting ulcerative colitis.

Neurogenic control of myoelectric complexes in the mouse isolated colon

BACKGROUND/AIMS

Little is known about the mechanisms controlling colonic migrating electrical activity. This study investigates the neural processes involved in the generation of migrating myoelectric complexes in the isolated mouse colon.

METHODS

Intracellular electrophysiological recordings were obtained from the circular muscle layer of the mouse colon in vitro in the presence of 2 mumol/L nifedipine.

RESULTS

Complexes occurred approximately every 3 minutes and consisted of 1 mumol/L hyoscine-sensitive rapid oscillations (approximately 2 Hz) superimposed on a slow depolarization (approximately 17 mV); the latter was often preceded by a precomplex hyperpolarization (approximately 7 mV) that was reduced by 250 nmol/L apamin. Five hundred micromolars of hexamethonium or 2 mumol/L of tetrodotoxin abolished the complexes and depolarized the muscle by 8.7 +/- 1.3 mV (n = 9) or 12.1 +/- 1.4 mV (n = 5), respectively. Carbachol (50 nmol/L to 5 mumol/L) produced dose-dependent depolarizations but without rapid oscillations. The nitric oxide synthase inhibitor NG-nitro-L-arginine (100 mumol/L) depolarized the tissue by 17.2 +/- 1.6 mV (n = 8) but had no effect on the rapid oscillations. In the presence of 2 mumol/L tetrodotoxin, 5 mumol/L sodium nitroprusside produced a sustained hyperpolarization (15.5 +/- 2.0 mV; n = 5) but did not restore complexes.

CONCLUSIONS

In the isolated mouse colon, the membrane potential between complexes is maintained by the release of inhibitory neurotransmitters (including nitric oxide), and the formation of complexes involves disinhibition and the simultaneous activation of cholinergic motor nerves.

Human colonic motility: physiological aspects

From the point of view of its motor activity, the human colon is probably the least understood of the abdominal hollow viscera. This is due to several facts: a) its proximal portions are relatively inaccessible due to anatomical reasons; b) there is no reliable animal model due to the considerable anatomic-physiological differences among mammals. For instance, most deductions about human colonic motor activity have been drawn from experiences in cats and dogs, in which the colon displays a cecum which is almost atrophic, and the viscus is featureless and C-shaped, without the haustrations and the sharp angulations seen in man, c) the wide fluctuations of motility in the daily time course of the same individual makes the interpretation of many studies difficult, especially considering the fact that, until recently, most of the studies on human colonic motility have been conducted for relatively short (30-180 min) recording periods. Recently, however, techniques that allow recording from the proximal portions of the human colon have been developed, and prolonged (24 h or more) observations of myoelectrical and contractile events have been achieved, thus improving our knowledge of the normal physiologic properties of the viscus. These informations have furthermore been integrated and confirmed by scintigraphic techniques (less invasive), that allow the measurement of intracolonic flow activity. The purpose of the present paper is to review the physiological aspects of colonic motility in man, quoting animal studies where human ones are lacking. We will briefly introduce some basic concepts, then a more detailed description of the main topic will follow.

Relationship between sleep patterns and human colonic motor patterns

BACKGROUND/AIMS

The precise relationships among colonic motor patterns, depth of sleep, and awakening are incompletely understood. The aim of this study was to correlate human colonic motor patterns with sleep stage, nocturnal arousals, and waking.

METHODS

We monitored sleep and correlated sleep stage, arousals, and waking with pressures (area under curve and propagating contractions) recorded from the entire colon in 11 healthy volunteers.

RESULTS

Propagating contraction frequency (P = 0.01) and area under the curve (P = 0.001) were significantly reduced at night. There was a highly significant correlation between depth of sleep and suppression of area under curve (P = 0.001) and propagating contraction frequency (P = 0.0001). Propagating contractions were eliminated during slow-wave sleep. During rapid eye movement sleep, colonic pressure and propagating contraction frequency increased sharply to levels comparable with those found in stage 2 sleep. Transient arousal from stable sleep, with or without waking, was a potent and immediate stimulus for colonic propagating contractions.

CONCLUSIONS

Sleep per se has a profound inhibitory effect on propagating and nonpropagating activity and is the major determinant of diurnal variation of colonic motility. Propagating contractions are eliminated in slow-wave sleep. Rapid eye movement sleep, arousals, and waking have immediate stimulatory effects on colonic motility.

Manometric patterns of rat colonic motor activity and defecation. Effect of selective 5HT1A agonist 8-OH-DPAT

We investigated in conscious and unrestrained rats, the major patterns of colonic pressure waves, as related to defecation. A manometric low compliance perfusion system, which was set at a very low flow rate (0.03 ml/min), permitted simultaneous recordings of intraluminal pressure in the proximal, transverse, and distal colon. Pressure waves in control rats reflected two types of motor activity: short-duration waves (< 15 sec), that were frequent throughout the colon (about 40-90/hr with aborally decreasing frequency), and propulsive, long-duration, high-amplitude waves (> 15 sec, > 15 mm Hg) that occurred only occasionally (1/hr or less) in the transverse and distal, but not in the proximal colon; these waves appeared to migrate aborally and were associated with defecation. The serotonin 5HT1A agonist 8-OH-DPAT dramatically and dose-dependently increased the frequency of long-duration, high-amplitude waves in the transverse and distal colon, and concurrently promoted defecation; these effects were prevented by the putative 5HT1A antagonist pindolol. We conclude that 5HT1A agonists such as 8-OH-DPAT may promote defecation and occurrence of propulsive waves through the same serotoninergic mechanism.

Distension-stimulated propagated contractions in human colon

To investigate the mechanisms for elicitation of peristaltic activity in the human colon, we studied the effect of balloon distension of the transverse, descending, and sigmoid colon and the rectum. Fifteen healthy subjects were studied by means of a colonoscopically positioned probe carrying a 5-cm latex balloon. After positioning of the probe, stepwise distension was performed for each colonic segment (transverse, descending, sigmoid, rectum), and the onset of large (> 50 mm Hg) and small (< 50 mm Hg) propagated waves was observed. Analysis of the tracings showed: (1) In 8/15 subjects (53.3%), balloon distension elicited propagated contractions, but these contractions were qualitatively different from the spontaneously occurring high-amplitude propagated contractions previously found to occur in association with defecation. Therefore, intraluminal distension is probably not the cause of defecation-associated high-amplitude propagated contractions. (2) Pain reports were poorly correlated with propagated contractions elicited by balloon distension, suggesting that these contractions are not the cause of the pain produced by balloon distension. (3) The transverse colon shows lower pressures, fewer pain reports, and fewer large propagated contractions in response to balloon distension as compared to the descending and the sigmoid colon.

Mucus gel thickness and turnover in the gastrointestinal tract of the rat: response to cholinergic stimulus and implication for mucoadhesion

The thickness of the mucus gel and its turnover rate were measured in the stomach, proximal jejunum, cecum and proximal colon of the rat, using microscopy and staining techniques. The specific mucus-secretory responses to carbachol-induced cholinergic stimulus in these locations were also studied. The mucus gel was found to be the thinnest (18 +/- 1 microns) in the cecum, and the thickest in the stomach (39 +/- 14 microns). The effect of carbachol on mucus secretion was profound and dose dependent in the stomach, and less profound, although still dose dependent, in the proximal jejunum. The least responsive organs were the cecum and the proximal colon, where no effect was observed after three doses of carbachol. Mucus secretion rate was significantly higher in the jejunum (1.1 +/- 0.5 microgram glucose equivalent min-1 cm-2) than in the colon (0.5 +/- 0.2 microgram glucose equivalent min-1 cm-2). Also, the proximal jejunum was more responsive to the carbachol stimulus (mucus secretion rate of 5.4 +/- 2.2 micrograms glucose equivalent min-1 cm-2 after carbachol treatment) than the colon (mucus secretion rate of 1.0 +/- 0.4 micrograms glucose equivalent min-1 cm-2 after carbachol treatment). In vitro mucoadhesion studies with Polycarbophil disks were performed in the mucosal tissues of the stomach, jejunum, cecum and proximal colon of the rat with and without cholinergic (carbachol) stimulus. The adhesion force in the cecum and the colon was significantly stronger than in the stomach and proximal jejunum when the studies were performed at pH 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered motility causes the early gastrointestinal toxicity of irradiation

PURPOSE

Total abdominal radiation produces symptoms of nausea, vomiting abdominal cramping and diarrhea. Each of these symptoms is associated with disordered intestinal motility. This article reviews studies of large and small intestinal contractile activity following radiation exposure.

METHODS AND MATERIALS

Studies of motility utilize strain gauge transducers surgically implanted on the seromuscular layer of the small intestine. All studies were performed in mixed breed dogs to record the occurrence of normal contractions, giant migrating contractions (GMCs) and retrograde giant contractions (RGCs) before, during and after irradiation (22.5 Gy in 9 fractions at 3 fractions/week). Giant migrating contractions and retrograde giant contractions are infrequent in the healthy state. However, in diseased states, GMCs are associated with abdominal cramps and diarrhea, and RGCs precede vomiting.

RESULTS

In fasted animals, fractionated abdominal irradiation dramatically increased the frequency of GMCs, with the incidence peaking after the second dose. The increased frequency of GMCS occurred as early as a few hours after the first radiation fraction, and returned to normal within days of cessation of radiation. RGCs were also significantly increased after abdominal irradiation. The frequency of RGCs was greatest on the first and sixth dose of radiation. Clinically, the dogs developed nausea, vomiting and diarrhea as early as the first day of irradiation. In dogs studied in the fed state, decreased amplitude, duration, and frequency of postprandial contractions occurred. These changes may slow intestinal transit during irradiation. Radiation also produced a striking increase in the frequency of colonic GMCs; these changes in colonic motor activity were associated with diarrhea as early as the second irradiation.

CONCLUSION

Changes in GI motility during fractionated irradiation precede the appearance of histopathological lesions in the GI tract. Thus, the symptoms of nausea, vomiting, and diarrhea experienced during radiotherapy (particularly those within the first week) are directly related to changes in bowel motility. It is hoped that further understanding of the etiology of these distressing symptoms will help to guide their treatment.

Origin and control of gastrointestinal motility

As a result of improved understanding of the origin and control of motility at both the whole organ and the cellular level, a scientific approach to the diagnosis and treatment (both medical and surgical) of motility disorders has evolved. Examples are present for all levels of the gastrointestinal tract. Manometric, myoelectric, and pharmacologic studies have elucidated the role of the lower esophageal sphincter and stomach in the pathogenesis of gastroesophageal reflux and determined the mechanism of successful medical and surgical treatment. Better evaluation of colorectal motility using colonic transit studies, pelvic floor radiography, and rectoanal manometrics has led to a better identification of both the etiology of severe constipation and patients who will have a successful surgical outcome. Studies of normal and abnormal gallbladder motility and responsiveness to hormonal stimulation have shed light on the cellular abnormalities in gallbladder myocytes that predispose to gallstone formation. Finally, since we have learned that certain surgical procedures affect motility in an adverse manner, a better basic understanding of gastrointestinal physiology has led to a better clinical understanding of the mechanism by which the changes occur and to the development of more directed physiologic operations. The classic example is seen in ulcer surgery, where the introduction of highly selective vagotomy instead of truncal vagotomy preserved antral innervation and decreased the incidence of postvagotomy complications. All these concepts and more are addressed in more detail in subsequent articles in this issue.

Pathophysiology of colonic motility disorders

When no identifiable organic cause for colonic symptoms can be found, it is easy for the busy clinician to label the patient neurotic. It is evident that many of these "functional" disorders do reflect an underlying motility disorder, although our understanding is far from clear. However, currently, patients with severe constipation are evaluated in a much more rational manner and, as a consequence, are offered a reasonable therapeutic approach that can be predicted to have a good chance for success. We can hope that as our understanding of irritable bowel syndrome is strengthened, treatment will become more efficacious than the unproved and costly medications that are in use currently. Until dietary modification becomes commonplace, it is unlikely that the incidence of diverticular disease or its complications will change. Already, our understanding of ileus has allowed us to realize the benefits of laparoscopic surgery, and as our knowledge of the various gut hormones and the inhibitory role that some play in intestinal motility grows, ileus, and its resulting prolongation of hospital stay, may become less problematic.

Colonic motor activity

The colon exhibits three types of contractions: individual phasic (short and long duration), organized groups (MMCs and nonmigrating motor complexes), and ultrapropulsive (giant migrating contractions). The individual phasic contractions and the MMCs and nonmigrating motor complexes produce extensive mixing and kneading of fecal material and slow net distal propulsion. The GMCs produce mass movements and expel feces during defecation. All contractions are controlled by myogenic, neural, and chemical mechanisms. The myogenic mechanisms determine the timing and frequency of contractions and the duration and distance of propagation of contractions. The neurochemical mechanisms determine whether the contractions will occur at a given site.

Ambulatory motility patterns of the transposed short segment colon

Ambulatory manometry and pH-metry were performed on 10 asymptomatic patients who had undergone lower oesophageal replacement with the left hemicolon between two and 20 years previously. Recording of the ambient pH in the intrathoracic colon was carried out simultaneously. In every patient the recording, which lasted approximately eight hours, included upright, supine, prandial, and post-prandial periods. The results were analysed both visually and by computer. The emerging motility patterns showed three basic types of wave, based on amplitudes--low amplitude contractions (LAC) measuring < 60 mm Hg, medium amplitude contractions (MAC) of 60-100 mm Hg, and high amplitude contractions (HAC) of 100-200 mm Hg. Additional subtypes were identified in the LACs and MACs. Using software primarily designed for oesophageal motility, the proportion of propulsive (6%-55%) waves could be distinguished from simultaneous or mixed waves, or both. A proportion of propulsive waves was noted in patients who had undergone surgery 10 or more years previously. It is concluded that the transposed colon retains its normal motility pattern but some adaptation to its new location may occur in the long term.

CRF in the paraventricular nucleus of the hypothalamus stimulates colonic motor activity in fasted rats

The influence of corticotropin releasing factor (CRF) microinjected into the paraventricular nucleus of the hypothalamus (PVN) on colonic motility was investigated in conscious, fasted rats. Rats were chronically implanted with a bilateral guide cannula into the PVN and a catheter into the proximal colon to record motor activity manometrically. Microinjection of CRF (0.6 nmol/rat) into the PVN increased both phasic and tonic motor activity in the proximal colon. Atropine sulfate (1 mg/kg, IP) completely abolished the colonic motor response to CRF. Microinjection of CRF (0.6 nmol/rat) into sites outside of the PVN did not modify colonic motor activity. These data show that CRF acts in the PVN to stimulate tonic and phasic motor activity in the proximal colon. Corticotropin releasing factor action is site specific and mediated through cholinergic pathways.

Measurement of electrical activity of the human small intestine using surface electrodes

Electrical activity of the human small intestine is usually measured by implanted or intraluminal electrodes. The application of these invasive techniques is, however, very limited. In this paper, a noninvasive technique is introduced to measure electrical activity of the small intestine by placing electrodes on the abdominal skin over the small intestine. Surface recordings were obtained in ten healthy volunteers, three patients with total gastrectomy and five patients with gastroparesis (a slight degree of paralysis of the mucosal coat of the stomach) with implanted electrodes on the serosa of the duodenum. An omnipresent 9-12 cpm electrical activity was observed in all surface recordings. Our findings from the surface electrodes were consistent with those reported in the literature via implanted or intubated electrodes. It is concluded that the technique described in this paper provides a noninvasive way to measure electrical activity of the small intestine. It may have potential application in medical research and clinical diagnosis.

Straining at stool and laxative taking in an English population

A population-based sample of 834 men (ages 40-69 years) and 1058 women (25-29 years) was investigated with respect to straining to defecate, stool form, bowel habit, and use of laxatives, by means of a questionnaire and a three-stool record form. Straining was common but, contrary to standard teaching, far from universal. It was unrelated to age but was commoner in women than men. Many people underestimated how often they strained. Overall, 32% of defecations in women and 22% of defecations in men were associated with straining to start and 15% and 9%, respectively, with straining to finish. Straining was to some extent related to stool type: the lumpier a stool, the more often it elicited straining. However, it seems likely that straining in some people is just a habit. Use of laxatives was found to be less prevalent than in the past, and most people with evidence of constipation did not use them. Use of laxatives increased with age, and some older people used them inappropriately. The most popular laxatives were based on phenolphthalein, senna, or magnesium.

Impaired colonic motor response to cholinergic stimulation in patients with severe chronic idiopathic (slow transit type) constipation

Chronic idiopathic constipation, especially the slow transit type, is a troubling problem often afflicting young women. The pathophysiological basis for this entity is unknown, although a defective cholinergic innervation has been postulated. We tested the hypothesis that cholinergic colonic innervation is deranged in this condition by studying colonic motor activity after strong cholinergic stimulation with edrophonium chloride in 14 women complaining of slow transit constipation. Unlike healthy subjects, constipated patients showed minimal or no response to edrophonium injection. It is concluded that in slow transit constipation there is an important alteration of colonic cholinergic activity and that edrophonium chloride may represent a useful test drug for colonic pathophysiological investigations.

Intermittent bursts of motor activity in the human rectum and absence of propagation

Manometric recordings from multiple sites were performed to determine the propagating properties of intermittent bursts of motor activity in the human rectum. Pressure changes were recorded simultaneously at 12.5 cm, 10 cm and 7.5 cm from the anal verge in nine healthy subjects for a total recording time of 32 hours, each study lasting 2.7-4.8 hours. The burst motor activity was identified on 19 occasions in 7 of 9 subjects at 12.5 cm; 26 occasions in all subjects at 10 cm; and 11 occasions in 3 of 9 subjects at 7.5 cm. In most cases, the burst motor activity was observed at a single recording site while other recording sites were quiescent. It did not appear to migrate in either an oral or aboral direction. The burst motor activity contained in part runs of pressure waves with a regular frequency: at 12.5 and 10 cm of the recording site, runs of regular pressure waves were dominated by a frequency of 2.5-5 cycle per minute, whereas those at 7.5 cm occurred with a higher frequency and a lower amplitude as compared with the more proximal recording sites. No evidence of propagation of each pressure wave was seen even when the burst occurred simultaneously at more than two recording sites. These results suggest that the intermittent bursts of rectal motor activity occur locally and do not propagate in either on oral or aboral direction. They appear dissimilar to the interdigestive migrating motor complex observed in the more proximal part of the gut.

Contractile activity of the human colon: lessons from 24 hour studies

The motor function of the colon is probably the least understood of the various hollow viscera of the human body. This is partly because of the marked variability of colonic motor function and the short recording periods usually used, generally not exceeding three hours. Most of the data available on human colonic motility originate from investigations conducted in the most distal portions of the viscus, because of technical difficulties in reaching its proximal portions. Although attempts have been made to solve these problems through the ingestion of radiotelemetric pressure sensors, these efforts have been hampered by intermittent signal loss and the inability to control the location of the capsule within the gastrointestinal tract. To overcome these problems, techniques have recently been developed that permit prolonged recordings (24 hours or more) of myoelectrical and contractile activity of the human colon, with both perfused and solid-state manometric systems. The present paper reviews the current experience in 24 hour recording from the human colon, with a primary emphasis on the more forceful propulsive contractile activity associated with the so called mass movements.