Antibody elution with 2-me/SDS solution: Uses for multi-layer immunohistochemical analysis of wholemount preparations of human colonic myenteric plexus.

Indirect immunofluorescence is usually restricted to 3-5 markers per preparation, limiting analysis of coexistence. A solution containing 2-mercaptoethanol and sodium dodecyl sulfate (2-ME/SDS) can elute indirect immunofluorescence labelling (i.e. primary antisera followed by fluorophore-conjugated secondary antisera) and has been used for sequential staining of sections. The aim of this study was to test whether 2-ME/SDS is effective for eluting indirect immunofluorescent staining (with primary antisera visualised by fluorophore-coupled secondary antisera) in wholemount preparations. We also analysed how 2-ME/SDS may work and used this understanding to devise additional uses for immunofluorescence in the nervous system. 2-ME/SDS appears to denature unfixed proteins (including antisera used as reagents) but has much less effect on antigenicity of formaldehyde-fixed epitopes. Moieties linked by strong biotin-streptavidin bonds are highly resistant to elution by 2-ME/SDS. Two primary antisera raised in the same species can be applied without spurious cross-reactivity, if a specific order of labelling is followed. The first primary antiserum is followed by a biotinylated secondary, then a tertiary of fluorophore-conjugated streptavidin. The preparation is then exposed to 2-ME/SDS, which has minimal impact on labelling by the first primary/secondary/tertiary combination. However, when this is followed by a second primary antiserum (raised in the same species), followed by a fluorophore-conjugated secondary antiserum, the intervening 2-ME/SDS exposure prevents cross-reactivity between primary and secondary antisera of the two layers. A third property of 2-ME/SDS is that it reduces lipofuscin autofluorescence, although it also raises background fluorescence and strongly enhances autofluorescence of erythrocytes. In summary, 2-ME/SDS is easy to use, cost-effective and does not require modified primary antisera. It can be used as the basis of a multi-layer immunohistochemistry protocol and allows 2 primary antisera raised in the same species to be used together.

Relationships between the results of anorectal investigations and symptom severity in patients with faecal incontinence.

PURPOSE: Anorectal dysfunction is the focus of diagnostic investigations for faecal incontinence. However, severity of incontinence and anorectal investigation results can be discordant. The aim of this study was to define the relationships between anorectal investigation results and incontinence severity to determine which measures, if any, were predictive of incontinence severity. METHODS: Patients presenting for investigation of faecal incontinence completed a symptom questionnaire, anorectal manometry, rectal sensation, pudendal nerve terminal motor latency, and endoanal ultrasound. Bivariate analyses were conducted between the Jorge-Wexner score and investigation results. Subgroup analyses were performed for gender and symptom subtypes (urge, passive, mixed). A multiple regression analysis was performed. RESULTS: Five hundred and thirty-eight patients were included. There were weak correlations between the Jorge-Wexner score and maximal squeeze pressure [r = - 0.24, 95%CI(- 0.31, - 0.16), p < 0.001], and resting pressure [r = - 0.18, (95%CI(- 0.26, - 0.10), p < 0.001]. In men only, there were significant associations between the Jorge-Wexner score and endoanal sonography [IAS defects: t(113) = - 2.26, p = 0.03, d = 0.58, 95%CI(- 4.38, - 0.29)] and rectal sensation (MTV: rs = - 0.24, 95%CI(- 0.41, - 0.06), p = 0.01). No substantial differences were observed in the urge/passive/mixed subgroup analyses. Multiple regression analysis included three variables: age (ß = 0.02, p = 0.17), maximal resting pressure (ß = - 0.01, p = 0.28), and maximal squeeze pressure (ß = - 0.01, p < 0.01). The variance in the Jorge-Wexner score accounted for by this model was < 10%, (R2 = 0.07, p = < 0.01, adjusted R2 = 0.06). CONCLUSION: Anorectal investigations cannot predict the severity of faecal incontinence. This may be due to limitations of diagnostic modalities, the heterogeneity of anorectal dysfunction in these patients, or contributing factors which are extrinsic to the anorectum.

Motility of the left colon in children and adolescents with functional constpation; a retrospective comparison between solid-state and water-perfused colonic manometry.

BACKGROUND: Using water-perfused (WP) high-resolution manometry, we recently demonstrated that children with functional constipation (FC) lacked the postprandial increase in distal colonic cyclic motor patterns that was observed in healthy adults. Our aim was to determine if similar results could be detected using a solid-state (SS) manometry catheter. METHODS: We performed a retrospective analysis of 19 children with FC (median age 11.1 years, 58% male) who underwent colonic manometry with a SS catheter (36 sensors, 3 cm apart). Data were compared with previously published data using a WP catheter (36 sensors, 1.5 cm apart) recorded from 18 children with FC (median age 15 years; 28% male). KEY RESULTS: The cyclic motor patterns recorded by the SS catheter did not differ from those previously recorded by the WP catheter. There was no detected increase in this activity in response to the meal in either group. Long-single motor patterns were recorded in most patients (n = 16, 84%) with the SS catheter. The number of these events did not differ from the WP recordings. In the SS data, HAPCs were observed in 4 children prior to the meal, in 5 after the meal. This did not differ significantly from the WP data. CONCLUSIONS & INFERENCES: These data recorded by SS manometry did not differ from WP manometry data. Regardless of the catheter used, both studies revealed an abnormal colonic response to a meal, indicating a pathology which is not related to the catheter used to record these data.

A new understanding of the physiology and pathophysiology of colonic motility?

BACKGROUND: In recent years, high-resolution manometry has been used in an attempt to gain a greater insight into the physiology/pathophysiology of colonic contractile activity in healthy adults and patients with colonic motility disorders. New colonic motor patterns have been identified and characterized, however, the clinical significance of these findings remains undetermined. PURPOSE: This review will assess the current literature on colonic high-resolution manometry and determine if this procedure has advanced our understanding of colonic motility. The limitations, future directions, and the potential of this technique to assess the effects of treatment upon colonic motor patterns will also be discussed.

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.

Discriminating movements of liquid and gas in the rabbit colon with impedance manometry.

BACKGROUND: High-resolution impedance manometry is a technique that is well established in esophageal motility studies for relating motor patterns to bolus flow. The use of this technique in the colon has not been established. METHODS: In isolated segments of rabbit proximal colon, we recorded motor patterns and the movement of liquid or gas boluses with a high-resolution impedance manometry catheter. These detected movements were compared to video recorded changes in gut diameter. Using the characteristic shapes of the admittance (inverse of impedance) and pressure signals associated with gas or liquid flow we developed a computational algorithm for the automated detection of these events. KEY RESULTS: Propagating contractions detected by video were also recorded by manometry and impedance. Neither pressure nor admittance signals alone could distinguish between liquid and gas transit, however the precise relationship between admittance and pressure signals during bolus flow could. Training our computational algorithm upon these characteristic shapes yielded a detection accuracy of 87.7% when compared to gas or liquid bolus events detected by manual analysis. CONCLUSIONS & INFERENCES: Characterizing the relationship between both admittance and pressure recorded with high-resolution impedance manometry can not only help in detecting luminal transit in real time, but also distinguishes between liquid and gaseous content. This technique holds promise for determining the propulsive nature of human colonic motor patterns.

New insights into neurogenic cyclic motor activity in the isolated guinea-pig colon.

BACKGROUND: The contents of the guinea pig distal colon consist of multiple pellets that move anally in a coordinated manner. This row of pellets results in continued distention of the colon. In this study, we have investigated quantitatively the features of the neurally dependent colonic motor patterns that are evoked by constant distension of the full length of guinea-pig colon. METHODS: Constant distension was applied to the excised guinea-pig by high-resolution manometry catheters or by a series of hooks. KEY RESULTS: Constant distension elicited regular Cyclic Motor Complexes (CMCs) that originated at multiple different sites along the colon and propagated in an oral or anal direction extending distances of 18.3±10.3 cm. CMCs were blocked by tetrodotoxin (TTX; 0.6 µ mol L-1 ), hexamethonium (100 µ mol L-1 ) or hyoscine (1 µ mol L-1 ). Application of TTX in a localized compartment or cutting the gut circumferentially disrupted the spatial continuity of CMCs. Localized smooth muscle contraction was not required for CMC propagation. Shortening the length of the preparations or disruption of circumferential pathways reduced the integrity and continuity of CMCs. CONCLUSIONS & INFERENCES: CMCs are a distinctive neurally dependent cyclic motor pattern, that emerge with distension over long lengths of the distal colon. They do not require changes in muscle tension or contractility to entrain the neural activity underlying CMC propagation. CMCs are likely to play an important role interacting with the neuromechanical processes that time the propulsion of multiple natural pellets and may be particularly relevant in conditions of impaction or obstruction, where long segments of colon are simultaneously distended.

High-resolution colonic motility recordings in vivo compared with ex vivo recordings after colectomy, in patients with slow transit constipation.

BACKGROUND: The pathogenesis of slow transit constipation (STC) remains poorly understood, with intrinsic and extrinsic abnormalities implicated. Here, we present high-resolution colonic manometry recordings from four STC patients recorded before total colectomy, and subsequently, ex vivo, after excision. METHODS: In four female, treatment-resistant STC patients (median age 35.5 years), a fiber-optic manometry catheter (72 sensors spaced at 1 cm intervals) was placed with the aid of a colonoscope, to the mid-transverse colon. Colonic manometry was recorded 2 h before and after a meal. After the colectomy, ex vivo colonic manometry was recorded in an organ bath. Ex vivo recordings were also made from colons from 4 patients (2 male; median age 67.5 years) undergoing anterior resection for nonobstructive carcinoma ('control' tissue). KEY RESULTS: A large increase in 'short single propagating contractions' was recorded in STC colon ex vivo compared to in vivo (ex vivo 61.3 ± 32.7 vs in vivo 2.5 ± 5/h). In STC patients, in vivo, the dominant frequency of contractile activity was 2-3 cycle per minute (cpm), whereas 1-cpm short-single propagating contractions dominated ex vivo. This same 1-cpm frequency was also dominant in control colons ex vivo. CONCLUSIONS & INFERENCES: In comparison to control adults, the colon of STC patients demonstrates significantly less propagating motor activity. However, once the STC colon is excised from the body it demonstrates a regular and similar frequency of propagating activity to control tissue. This paper provides interesting insights into the control of colonic motor patterns.

Characterizing colonic motility in children with chronic intractable constipation: a look beyond high-amplitude propagating sequences.

BACKGROUND: Children with chronic intractable constipation experience severe and long-lasting symptoms, which respond poorly to conventional therapeutic strategies. Detailed characterization of colonic motor patterns in such children has not yet been obtained. METHODS: In 18 children with chronic intractable constipation, a high-resolution water-perfused manometry catheter (36 sensors at 1.5-cm intervals) was colonoscopically placed with the tip at the distal transverse colon. Colonic motor patterns were recorded for 2 h prior to and after a meal and then after colonic infusion of bisacodyl. These data were compared with previously published colonic manometry data from 12 healthy adult controls and 14 adults with slow-transit constipation. KEY RESULTS: The postprandial number of the retrograde cyclic propagating motor pattern was significantly reduced in these children compared with healthy adults (children, 3.1 ± 4.7/h vs healthy adults, 34.7 ± 45.8/h; p < 0.0001) but not constipated adults (4.5 ± 5.6/h; p = 0.9). The number of preprandial long-single motor patterns was significantly higher (p = 0.003) in children (8.0 ± 13.2/h) than in healthy adults (0.4 ± 0.9/h) and in constipated adults (0.4 ± 0.7/h). Postprandial high-amplitude propagating sequences (HAPSs) were rarely observed in children (2/18), but HAPS could be induced by bisacodyl in 16 of 18 children. CONCLUSIONS & INFERENCES: Children with chronic intractable constipation show a similar impaired postprandial colonic response to that seen in adults with slow-transit constipation. Children may have attenuated extrinsic parasympathetic inputs to the colon associated with an increased incidence of spontaneous long-single motor patterns.

Restoration of normal colonic motor patterns and meal responses after distal colorectal resection.

BACKGROUND: Colorectal resections alter colonic motility, including disruption of control by neural or bioelectrical cell networks. The long-term impact of surgical resections and anastomoses on colonic motor patterns has, however, never been assessed accurately. Fibreoptic high-resolution colonic manometry was employed to define motility in patients who had undergone distal colorectal resection. METHODS: Recruited patients had undergone distal colorectal resections more than 12 months previously, and had normal bowel function. Manometry was performed in the distal colon (36 sensors; 1-cm intervals), with 2-h recordings taken before and after a meal, with comparison to controls. Analysis quantified all propagating events and frequencies (cyclical, short single, and long single motor patterns), including across anastomoses. RESULTS: Fifteen patients and 12 controls were recruited into the study. Coordinated propagating events directly traversed the healed anastomoses in nine of 12 patients with available data, including antegrade and retrograde cyclical, short single and long single patterns. Dominant frequencies in the distal colon were similar in patients and controls (2-3 cycles/min) (antegrade P = 0·482; retrograde P = 0·178). Compared with values before the meal, the mean(s.d.) number of dominant cyclical retrograde motor patterns increased in patients after the meal (2·1(2·7) versus 32·6(31·8) in 2 h respectively; P < 0·001), similar to controls (P = 0·178), although the extent of propagation was 41 per cent shorter in patients, by a mean of 3·4 cm (P = 0·003). Short and long single propagating motor patterns were comparable between groups in terms of frequency, velocity, extent and amplitude. CONCLUSION: Motility patterns and meal responses are restored after distal colorectal resection in patients with normal bowel function. Coordinated propagation across healed anastomoses may indicate regeneration of underlying cellular networks.

Neuromechanical factors involved in the formation and propulsion of fecal pellets in the guinea-pig colon.

BACKGROUND: The neuromechanical processes involved in the formation and propulsion of fecal pellets remain incompletely understood. METHODS: We analyzed motor patterns in isolated segments of the guinea-pig proximal and distal colon, using video imaging, during oral infusion of liquid, viscous material, or solid pellets. KEY RESULTS: Colonic migrating motor complexes (CMMCs) in the proximal colon divided liquid or natural semisolid contents into elongated shallow boluses. At the colonic flexure these boluses were formed into shorter, pellet-shaped boluses. In the non-distended distal colon, spontaneous CMMCs produced small dilations. Both high- and low-viscosity infusions evoked a distinct motor pattern that produced pellet-shaped boluses. These were propelled at speeds proportional to their surface area. Solid pellets were propelled at a speed that increased with diameter, to a maximum that matched the diameter of natural pellets. Pellet speed was reduced by increasing resistive load. Tetrodotoxin blocked all propulsion. Hexamethonium blocked normal motor patterns, leaving irregular propagating contractions, indicating the existence of neural pathways that did not require nicotinic transmission. CONCLUSIONS & INFERENCES: Colonic migrating motor complexes are responsible for the slow propulsion of the soft fecal content in the proximal colon, while the formation of pellets at the colonic flexure involves a content-dependent mechanism in combination with content-independent spontaneous CMMCs. Bolus size and consistency affects propulsion speed suggesting that propulsion is not a simple reflex but rather a more complex process involving an adaptable neuromechanical loop.

The use of colonic and anorectal high-resolution manometry and its place in clinical work and in research.

BACKGROUND: In the esophagus, high-resolution manometry (HRM) has become a standard diagnostic tool in the investigation of suspected motility disorders. However, at the opposite end of the digestive tract (i.e., the colon and anorectum), the use of HRM still remains in its infancy, with relatively few published studies in the scientific literature. Further, the clinical utility of those studies that have been performed is largely undetermined. PURPOSE: This review assesses all of the HRM studies published to date from both the colon and anorectum, explores the catheter types used, and attempts to determine the worth of HRM over traditional 'low-resolution' recordings from the same regions. Ultimately, this review addresses whether HRM currently provides information that will benefit patient diagnosis and treatment.

Activation of intestinal spinal afferent endings by changes in intra-mesenteric arterial pressure.

KEY POINTS: A major class of mechano-nociceptors to the intestine have mechanotransduction sites on extramural and intramural arteries and arterioles ('vascular afferents'). These sensory neurons can be activated by compression or axial stretch of vessels. Using isolated preparations we showed that increasing intra-arterial pressure, within the physiological range, activated mechano-nociceptors on vessels in intact mesenteric arcades, but not in isolated arteries. This suggests that distortion of the branching vascular tree is the mechanical adequate stimulus for these sensory neurons, rather than simple distension. The same rises in pressure also activated intestinal peristalsis in a partially capsaicin-sensitive manner indicating that pressure-sensitive vascular afferents influence enteric circuits. The results identify the mechanical adequate stimulus for a major class of mechano-nociceptors with endings on blood vessels supplying the gut wall; these afferents have similar endings to ones supplying other viscera, striated muscle and dural vessels. ABSTRACT: Spinal sensory neurons innervate many large blood vessels throughout the body. Their activation causes the hallmarks of neurogenic inflammation: vasodilatation through the release of the neuropeptide calcitonin gene-related peptide and plasma extravasation via tachykinins. The same vasodilator afferent neurons show mechanical sensitivity, responding to crushing, compression or axial stretch of blood vessels - responses which activate pain pathways and which can be modified by cell damage and inflammation. In the present study, we tested whether spinal afferent axons ending on branching mesenteric arteries ('vascular afferents') are sensitive to increased intravascular pressure. From a holding pressure of 5 mmHg, distension to 20, 40, 60 or 80 mmHg caused graded, slowly adapting increases in firing of vascular afferents. Many of the same afferent units showed responses to axial stretch, which summed with responses evoked by raised pressure. Many vascular afferents were also sensitive to raised temperature, capsaicin and/or local compression with von Frey hairs. However, responses to raised pressure in single, isolated vessels were negligible, suggesting that the adequate stimulus is distortion of the arterial arcade rather than distension per se. Increasing arterial pressure often triggered peristaltic contractions in the neighbouring segment of intestine, an effect that was mimicked by acute exposure to capsaicin (1 µm) and which was reduced after desensitisation to capsaicin. These results indicate that sensory fibres with perivascular endings are sensitive to pressure-induced distortion of branched arteries, in addition to compression and axial stretch, and that they contribute functional inputs to enteric motor circuits.

Colonic motor abnormalities in slow transit constipation defined by high resolution, fibre-optic manometry.

BACKGROUND: Slow transit constipation (STC) is associated with colonic motor abnormalities. The underlying cause(s) of the abnormalities remain poorly defined. In health, utilizing high resolution fiber-optic manometry, we have described a distal colonic propagating motor pattern with a slow wave frequency of 2-6 cycles per minute (cpm). A high calorie meal caused a rapid and significant increase in this activity, suggesting the intrinsic slow wave activity could be mediated by extrinsic neural input. Utilizing the same protocol our aim was to characterize colonic meal response STC patients. METHODS: A fiber-optic manometry catheter (72 sensors at 1 cm intervals) was colonoscopically placed with the tip clipped at the ascending or transverse colon, in 14 patients with scintigraphically confirmed STC. Manometric recordings were taken, for 2 h pre and post a 700 kCal meal. Data were compared to 12 healthy adults. KEY RESULTS: Prior to and/or after the meal the cyclic propagating motor pattern was identified in 13 of 14 patients. However, the meal, did not increase the cyclic motor pattern (preprandial 7.4 ± 7.6 vs postprandial 8.3 ± 4.5 per/2 h), this is in contrast to the dramatic increase observed in health (8.3 ± 13.3 vs 59.1 ± 89.0 per/2 h; p < 0.001). CONCLUSIONS & INFERENCES: In patients with STC a meal fails to induce the normal increase in the distal colonic cyclic propagating motor patterns. We propose that these data may indicate that the normal extrinsic parasympathetic inputs to the colon are attenuated in these patients.

A systematic review of sacral nerve stimulation mechanisms in the treatment of fecal incontinence and constipation.

BACKGROUND: Sacral nerve stimulation (SNS) is now well established as a treatment for fecal incontinence (FI) resistant to conservative measures and may also have utility in the management of chronic constipation; however, mechanism of action is not fully understood. End organ effects of SNS have been studied in both clinical and experimental settings, but interpretation is difficult due to the multitude of techniques used and heterogeneity of reported findings. The aim of this study was to systematically review available evidence on the mechanisms of SNS in the treatment of FI and constipation. METHODS: Two systematic reviews of the literature (performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses framework) were performed to identify manuscripts pertaining to (a) clinical and (b) physiological effects of SNS during the management of hindgut dysfunction. KEY RESULTS: The clinical literature search revealed 161 articles, of which 53 were deemed suitable for analysis. The experimental literature search revealed 43 articles, of which nine were deemed suitable for analysis. These studies reported results of investigative techniques examining changes in cortical, gastrointestinal, colonic, rectal, and anal function. CONCLUSIONS & INFERENCES: The initial hypothesis that the mechanism of SNS was primarily peripheral motor neurostimulation is not supported by the majority of recent studies. Due to the large body of evidence demonstrating effects outside of the anorectum, it appears likely that the influence of SNS on anorectal function occurs at a pelvic afferent or central level.

Quantification of in vivo colonic motor patterns in healthy humans before and after a meal revealed by high-resolution fiber-optic manometry.

BACKGROUND: Until recently, investigations of the normal patterns of motility of the healthy human colon have been limited by the resolution of in vivo recording techniques. METHODS: We have used a new, high-resolution fiber-optic manometry system (72 sensors at 1-cm intervals) to record motor activity from colon in 10 healthy human subjects. KEY RESULTS: In the fasted colon, on the basis of rate and extent of propagation, four types of propagating motor pattern could be identified: (i) cyclic motor patterns (at 2-6/min); (ii) short single motor patterns; (iii) long single motor patterns; and (iv) occasional retrograde, slow motor patterns. For the most part, the cyclic and short single motor patterns propagated in a retrograde direction. Following a 700 kCal meal, a fifth motor pattern appeared; high-amplitude propagating sequences (HAPS) and there was large increase in retrograde cyclic motor patterns (5.6 ± 5.4/2 h vs 34.7 + 19.8/2 h; p < 0.001). The duration and amplitude of individual pressure events were significantly correlated. Discriminant and multivariate analysis of duration, gradient, and amplitude of the pressure events that made up propagating motor patterns distinguished clearly two types of pressure events: those belonging to HAPS and those belonging to all other propagating motor patterns. CONCLUSIONS & INFERENCES: This work provides the first comprehensive description of colonic motor patterns recorded by high-resolution manometry and demonstrates an abundance of retrograde propagating motor patterns. The propagating motor patterns appear to be generated by two independent sources, potentially indicating their neurogenic or myogenic origin.

Peristalsis and propulsion of colonic content can occur after blockade of major neuroneuronal and neuromuscular transmitters in isolated guinea pig colon.

We recently identified hexamethonium-resistant peristalsis in the guinea pig colon. We showed that, following acute blockade of nicotinic receptors, peristalsis recovers, leading to normal propagation velocities of fecal pellets along the colon. This raises the fundamental question: what mechanisms underlie hexamethonium-resistant peristalsis? We investigated whether blockade of the major receptors that underlie excitatory neuromuscular transmission is required for hexamethonium-resistant peristalsis. Video imaging of colonic wall movements was used to make spatiotemporal maps and determine the velocity of peristalsis. Propagation of artificial fecal pellets in the guinea pig distal colon was studied in hexamethonium, atropine, ω-conotoxin (GVIA), ibodutant (MEN-15596), and TTX. Hexamethonium and ibodutant alone did not retard peristalsis. In contrast, ω-conotoxin abolished peristalsis in some preparations and reduced the velocity of propagation in all remaining specimens. Peristalsis could still occur in some animals in the presence of hexamethonium + atropine + ibodutant + ω-conotoxin. Peristalsis never occurred in the presence of TTX. The major finding of the current study is the unexpected observation that peristalsis can occur after blockade of the major excitatory neuroneuronal and neuromuscular transmitters. Also, the colon retained an intrinsic polarity in the presence of these antagonists and was only able to expel pellets in an aboral direction. The nature of the mechanism(s)/neurotransmitter(s) that generate(s) peristalsis and facilitate(s) natural fecal pellet propulsion, after blockade of major excitatory neurotransmitters, at the neuroneuronal and neuromuscular junction remains to be identified.

Neurogenic and myogenic motor activity in the colon of the guinea pig, mouse, rabbit, and rat.

Gastrointestinal motility involves interactions between myogenic and neurogenic processes intrinsic to the gut wall. We have compared the presence of propagating myogenic contractions of the isolated colon in four experimental animals (guinea pig, mouse, rabbit, and rat), following blockade of enteric neural activity. Isolated colonic preparations were distended with fluid, with the anal end either closed or open. Spatiotemporal maps of changes in diameter were constructed from video recordings. Distension-induced peristaltic contractions were abolished by tetrodotoxin (TTX; 0.6 µM) in all animal species. Subsequent addition of carbachol (0.1-1 µM) did not evoke myogenic motor patterns in the mouse or guinea pig, although some activity was observed in rabbit and rat colon. These myogenic contractions propagated both orally and anally and differed from neurogenic propagating contractions in their frequency, extent of propagation, and polarity. Niflumic acid (300 µM), used to block myogenic activity, also blocked neural peristalsis and thus cannot be used to discriminate between these mechanisms. In all species, except the mouse colon, small myogenic "ripple" contractions were revealed in TTX, but in both rat and rabbit an additional, higher-frequency ripple-type contraction was superimposed. Following blockade of enteric nerve function, a muscarinic agonist can evoke propulsive myogenic peristaltic contractions in isolated rabbit and rat colon, but not in guinea pig or mouse colon. Marked differences between species exist in the ability of myogenic mechanisms to propel luminal content, but in all species there is normally a complex interplay between neurogenic and myogenic processes.

Low-resolution colonic manometry leads to a gross misinterpretation of the frequency and polarity of propagating sequences: Initial results from fiber-optic high-resolution manometry studies.

BACKGROUND: High-resolution manometry catheters are now being used to record colonic motility. The aim of this study was to determine the influence of pressure sensor spacing on our ability to identify colonic propagating sequences (PS). METHODS: Fiber-optic catheters containing 72-90 sensors spaced at 1 cm intervals were placed colonoscopically to the cecum in 11 patients with proven slow transit constipation, 11 patients with neurogenic fecal incontinence and nine healthy subjects. A 2 h section of trace from each subject was analyzed. Using the 1 cm spaced data as the gold standard, each data set was then sub-sampled, by dropping channels from the data set to simulate sensor spacing of 10, 7, 5, 3, and 2 cm. In blinded fashion, antegrade and retrograde PS were quantified at each test sensor spacing. The data were compared to the PSs identified in the corresponding gold standard data set. KEY RESULTS: In all subject groups as sensor spacing increased; (i) the frequency of identified antegrade and retrograde PSs decreased (P < 0.0001); (ii) the ratio of antegrade to retrograde PSs increased (P < 0.0001); and (iii) the number of incorrectly labeled PSs increased (P < 0.003). CONCLUSIONS & INFERENCES: Doubling the sensor spacing from 1 to 2 cm nearly halves the number of PSs detected. Tripling the sensor spacing from 1 to 3 cm resulted in a 30% chance of incorrectly labeling PSs. Closely spaced pressure recording sites (<2 cm) are mandatory to avoid gross misrepresentation of the frequency, morphology, and directionality of colonic propagating sequences.