Ingesting yeast extract causes excitation of neurogenic and myogenic colonic motor patterns in the rat

Fermented foods play a significant role in the human diet for their natural, highly nutritious and healthy attributes. Our aim was to study the effect of yeast extract, a fermented substance extracted from natural yeast, on colonic motility to better understand its potential therapeutic role. A yeast extract was given to rats by gavage for 3 days, and myogenic and neurogenic components of colonic motility were studied using spatiotemporal maps made from video recordings of the whole colon ex vivo. A control group received saline gavages. The yeast extract caused excitation of the musculature by increasing the propagation length and duration of long-distance contractions, the major propulsive activity of the rat colon. The yeast extract also evoked rhythmic propulsive motor complexes (RPMCs) which were antegrade in the proximal and mid-colon and retrograde in the distal colon. RPMC activity was evoked by distention-induced neural activity, but it was myogenic in nature since we showed it to be generated by bethanechol in the presence of tetrodotoxin. In conclusion, ingestion of yeast extract stimulates rat colon motility by exciting neurogenic and myogenic control mechanisms.

Transcutaneous Electrical Acustimulation Improves Constipation Symptoms and Accelerates Colonic Transit in Patients With Slow Transit Constipation Through Autonomic Mechanism

OBJECTIVES

Nearly half of patients with slow transit constipation (STC) are not completely satisfied with their traditional remedies. We aimed to evaluate the therapeutic value and possible involved mechanism of transcutaneous electrical acustimulation (TEA) at ST36 in patients with STC.

MATERIALS AND METHODS

Seventy patients with STC were randomly divided into TEA (n = 35) and sham-TEA (n = 35) to undergo a two-week treatment with TEA at ST36 or sham point. After the two-week treatment, 18 patients from each group randomly underwent a few physiological tests, including the electrocardiogram (ECG), anorectal manometry, colon transit test, and blood drawing. After a two-week washout period, TEA was performed in both groups for two weeks.

RESULTS

Spontaneous bowel movements per week were increased, and scores of constipation symptoms were decreased, after a two-week blind TEA but not sham-TEA, which were sustained after a two-week washout period. Improvement in quality of life and psychologic states also was observed with blind TEA treatment. Mechanistically, the two-week blind TEA accelerated colon transit assessed by barium strip excretion rate (the effect was sustained after a two-week washout period), enhanced vagal nerve activity evaluated by the spectral analysis of heart rate variability derived from the ECG, and decreased circulating vasoactive intestinal peptide.

CONCLUSIONS

Noninvasive TEA relieves constipation and improves quality of life and psychologic states in patients with STC, and the effects are sustained for ≥two weeks. The therapeutic effects of TEA may be attributed to the acceleration of colon transit and decrease of vasoactive intestinal peptide mediated through the vagal mechanism.

Involvement of the autonomic nervous system in colonic contractions in conscious Suncus murinus

BACKGROUND

Colonic motility is regulated by various factors along the gut-brain axis; however, detailed mechanisms are unknown. This study aimed to examine the involvement of the autonomic nervous system in colonic motility. Suncus murinus (suncus) is a small laboratory mammal suitable for gastrointestinal motility studies.

METHODS

Colonic motility and concomitant feeding and defecation behaviors in vagotomized and reserpine-administered suncus were recorded simultaneously for 24 h. Furthermore, we performed immunohistochemistry on tyrosine hydroxylase (TH) and in situ hybridization on corticotropin-releasing hormone (CRH) in suncus brain. Additionally, we examined c-Fos expression in the brain using immunohistochemistry in conscious suncus with colorectal distension.

KEY RESULTS

In vagotomized suncus, clustered giant migrating contractions (GMCs), consisting of strong contractions occurring in a short time, were observed, and the percentage of GMCs without defecation increased. The frequency of GMCs in the reserpine-administered suncus increased during a light period (ZT0-4, 4-8) and decreased during a dark period (ZT16-20, 20-24) compared to a vehicle group. Additionally, the percentage of GMCs without defecation in the reserpine-administered suncus increased. Suncus TH-immunopositive neurons were found in the locus coeruleus (LC), as shown in rodents. In contrast, CRH mRNA-expressing cells were not observed in a region assumed to be the Barrington's nucleus (Bar). Furthermore, colorectal distension in conscious suncus induced c-Fos expression in LC TH neurons.

CONCLUSIONS & INFERENCES

Our results suggest that the vagus and sympathetic nerves are not required for induction of GMCs in vivo. However, they are likely to exert a modulatory role in control of GMC frequency in Suncus murinus.

Functional and Transcriptomic Characterization of Postnatal Maturation of ENS and SIP Syncytium in Mice Colon

The interplay of the enteric nervous system (ENS) and SIP syncytium (smooth muscle cells-interstitial cells of Cajal-PDGFRα+ cells) plays an important role in the regulation of gastrointestinal (GI) motility. This study aimed to investigate the dynamic regulatory mechanisms of the ENS-SIP system on colon motility during postnatal development. Colonic samples of postnatal 1-week-old (PW1), 3-week-old (PW3), and 5-week-old (PW5) mice were characterized by RNA sequencing, qPCR, Western blotting, isometric force recordings (IFR), and colonic motor complex (CMC) force measurements. Our study showed that the transcriptional expression of Pdgfrα, c-Kit, P2ry1, Nos1, and Slc18a3, and the protein expression of nNOS, c-Kit, and ANO1 significantly increased with age from PW1 to PW5. In PW1 and PW3 mice, colonic migrating movement was not fully developed. In PW5 mice, rhythmic CMCs were recorded, similar to the CMC pattern described previously in adult mice. The inhibition of nNOS revealed excitatory and non-propulsive responses which are normally suppressed due to ongoing nitrergic inhibition. During postnatal development, molecular data demonstrated the establishment and expansion of ICC and PDGFRα+ cells, along with nitrergic and cholinergic nerves and purinergic receptors. Our findings are important for understanding the role of the SIP syncytium in generating and establishing CMCs in postnatal, developing murine colons.

Macrophage regulation of the "second brain": CD163 intestinal macrophages interact with inhibitory interneurons to regulate colonic motility - evidence from the Cx3cr1-Dtr rat model

Intestinal macrophages are well-studied for their conventional roles in the immune response against pathogens and protecting the gut from chronic inflammation. However, these macrophages may also have additional functional roles in gastrointestinal motility under typical conditions. This is likely to occur via both direct and indirect influences on gastrointestinal motility through interaction with myenteric neurons that contribute to the gut-brain axis, but this mechanism is yet to be properly characterised. The CX3CR1 chemokine receptor is expressed in the majority of intestinal macrophages, so we used a conditional knockout Cx3cr1-Dtr (diphtheria toxin receptor) rat model to transiently ablate these cells. We then utilized ex vivo video imaging to evaluate colonic motility. Our previous studies in brain suggested that Cx3cr1-expressing cells repopulate by 7 days after depletion in this model, so we performed our experiments at both the 48 hr (macrophage depletion) and 7-day (macrophage repopulation) time points. We also investigated whether inhibitory neuronal input driven by nitric oxide from the enteric nervous system is required for the regulation of colonic motility by intestinal macrophages. Our results demonstrated that CD163-positive resident intestinal macrophages are important in regulating colonic motility in the absence of this major inhibitory neuronal input. In addition, we show that intestinal macrophages are indispensable in maintaining a healthy intestinal structure. Our study provides a novel understanding of the interplay between the enteric nervous system and intestinal macrophages in colonic motility. We highlight intestinal macrophages as a potential therapeutic target for gastrointestinal motility disorders when inhibitory neuronal input is suppressed.

Haustral rhythmic motor patterns of the human large bowel revealed by ultrasound

Effective and widely available strategies are needed to diagnose colonic motility dysfunction. We investigated whether ultrasonography could generate spatiotemporal maps combined with motor pattern frequency analysis, to become a noninvasive method to characterize human colon motor patterns. Abdominal colonic ultrasonography was performed on healthy subjects (N = 7), focusing on the detailed recording of spontaneous haustral activities. We developed image segmentation and frequency analysis software to analyze the motor patterns captured. Ultrasonography recordings of the ascending, transverse, and descending colon identified three distinct rhythmic motor patterns: the 1 cycle/min and the 3 cycles/min cyclic motor pattern were seen throughout the whole colon, whereas the 12 cycles/min cyclic motor pattern was identified in the ascending colon. The rhythmic motor patterns of the human colon that are associated with interstitial cells of Cajal-associated pacemaking activity can be accurately identified and quantified using ultrasound.NEW & NOTEWORTHY Ultrasonography in the clinical field is an underutilized tool for assessing colonic motility; however, with the addition of frequency analysis techniques, it provides a method to identify human colonic motor patterns. Here we report on the 1, 3, and 12 cpm rhythmic motor patterns. Ultrasound has the potential to become a bedside assessment for colonic dysmotility and may reveal the health of interstitial cells of Cajal (ICC) pacemaker activities.

Estrogen increases the expression of BKCa and impairs the contraction of colon smooth muscle via upregulation of sphingosine kinase 1

Estrogen (E2) may impair the contraction of colonic smooth muscle (SM) leading to constipation. Large conductance Ca2+ -activated K+ channels (BKCa ) are widely expressed in the smooth muscle cells (SMCs) contributing to hyperpolarization and relaxation of SMCs. Sphingosine kinase 1 (SphK1) is known to influence the expression of BKCa . We aimed to elucidate the potential underlying molecular mechanism of BKCa and SphK1 that may influence E2-induced colonic dysmotility. In ovariectomized rats, SM contraction and expression of BKCa , SphK1, sphingosine-1-phosphate receptor (S1PR) were analyzed after the treatment with vehicle, BSA-E2, E2, and E2 receptor antagonist. The role of BKCa , SphK1, and S1PR in E2-induced SM dysmotility was investigated in rat colonic SMCs. The effect of SphK1 on SM contraction as well as on the expression of BKCa and S1PR was analyzed in SphK1 knock-out mutant mice and wild-type (WT) mice treated with or without E2. The E2-treated group exhibited a weak contraction of colonic SM and a delayed colonic transit. The treatment with E2 significantly upregulated the expression of BKCa , SphK1, S1PR1, and S1PR2, but not S1PR3, in colon SM and SMCs. Inhibition of BKCa , SphK1, S1PR1, and S1PR2 expression attenuated the effect of E2 on Ca2+ mobilization in rat colon SMCs. WT mice treated with E2 showed impaired gastrointestinal motility and enhanced expression of BKCa , S1PR1, and S1PR2 compared with those without E2 treatment. Conversely, in SphK1 knock-out mice treated with E2, these effects were partially reversed. E2 increased the release of S1P which in turn could have activated S1PR1 and S1PR2. Loss of SphK1 attenuated the effect of E2 on the upregulation of S1PR1 and S1PR2 expression. These findings indicated that E2 impaired the contraction of colon SM through activation of BKCa via the upregulation of SphK1 and the release of S1P. In the E2-induced BKCa upregulation, S1PR1 and S1PR2 might also be involved. These results may provide further insights into a therapeutic target and optional treatment approaches for patients with constipation.

Circadian rhythms in colonic function

A rhythmic expression of clock genes occurs within the cells of multiple organs and tissues throughout the body, termed "peripheral clocks." Peripheral clocks are subject to entrainment by a multitude of factors, many of which are directly or indirectly controlled by the light-entrainable clock located in the suprachiasmatic nucleus of the hypothalamus. Peripheral clocks occur in the gastrointestinal tract, notably the epithelia whose functions include regulation of absorption, permeability, and secretion of hormones; and in the myenteric plexus, which is the intrinsic neural network principally responsible for the coordination of muscular activity in the gut. This review focuses on the physiological circadian variation of major colonic functions and their entraining mechanisms, including colonic motility, absorption, hormone secretion, permeability, and pain signalling. Pathophysiological states such as irritable bowel syndrome and ulcerative colitis and their interactions with circadian rhythmicity are also described. Finally, the classic circadian hormone melatonin is discussed, which is expressed in the gut in greater quantities than the pineal gland, and whose exogenous use has been of therapeutic interest in treating colonic pathophysiological states, including those exacerbated by chronic circadian disruption.

Impaired colonic motility in high-glycemic diet-induced diabetic mice is associated with disrupted gut microbiota and neuromuscular function

Background

Similar to the high-fat diet (HFD), the high-glycemic diet (HGD) contributes to the development and progression of type 2 diabetes mellitus (T2DM). However, the effect of HGD on gastrointestinal motility in T2DM and its underlying mechanisms remain unclear.

Methods

Thirty C57BL/6J mice were randomly designated into the normal-feeding diet (NFD) group, HFD group, and HGD group. The plasma glucose, plasma insulin, and gastrointestinal motility were examined. Meanwhile, the tension of isolated colonic smooth muscle rings was calculated, and the gut microbiota was analyzed by 16s rDNA high-throughput sequencing.

Result

After 16 weeks of HGD feeding, obesity, hyperglycemia, insulin resistance, and constipation were observed in HGD mice. Autonomic contraction frequency of the colonic neuromuscular system and electrical field stimulation-induced contractions were reduced in HGD mice. On the contrary, neuronal nitric oxide synthase activity and neuromuscular relaxation were found to be enhanced. Finally, gut microbiota analysis revealed that Rhodospirillaceae abundance significantly increased at the family level in HGD mice. At the genus level, the abundance of Insolitispirillum increased remarkably, whereas Turicibacter abundance decreased significantly in HGD mice.

Conclusion

HGD induced constipation in obese diabetic mice, which we speculated that it may be related to neuromuscular dysmotility and intestinal microbiota dysbiosis.

Parkinson's disease constipation effect of electroacupuncture at ST25 through colonic motility and enteric neuropathology

Background

The enteric nervous system (ENS) plays a central role in developing Parkinson's disease (PD) constipation, and the regulation of the ENS may be a key component in treating PD constipation. Electroacupuncture (EA) can effectively treat constipation symptoms in PD, but research on its specific mechanisms, especially in terms of ENS, is relatively lacking. Therefore, we investigated whether EA at ST25 promotes the restoration of ENS structure and colonic motor function in the rotenone-induced PD constipation rat model.

Methods

In this study, we evaluated constipation symptoms by stool characteristics, excretion and water volume, and whole gut transit time and observed colonic motility regulation through colonic motion detection and pathological changes in the colonic myenteric nervous plexus by transmission electron microscopy and immunofluorescence staining.

Results

EA significantly improved the constipation symptoms and positively adjusted the colonic motility in rotenone-induced PD constipation rats. At the same time, EA reversed the rotenone-induced colonic myenteric nervous plexus injury and regulated the ratio of inhibitory and excitatory neurotransmitters.

Conclusion

Our results indicate that EA treatment of PD constipation may be mediated through the adjustment of ENS.

Effect of Caffeine on Colonic Manometry in Children

OBJECTIVES

Coffee and caffeinated products have been widely consumed for many centuries. Previous adult studies have suggested that both coffee and decaffeinated beverages induce colonic motility. However, no study has been conducted in pediatrics, and the role of caffeine alone in pediatric colonic motility needs to be explored.

METHODS

A prospective study of pediatric patients undergoing standard colonic motility testing that were able to consume caffeinated coffee, decaffeinated coffee, and caffeine tablet during colonic manometry. Patients who had a gastrocolonic reflex and high amplitude propagated contractions (HAPCs) in response to intraluminal administration of bisacodyl in the colon were included in the final analyses.

RESULTS

Thirty-eight patients were recruited, 22 of which were excluded, 11 due to abnormal studies (no HAPC seen in response to intraluminal response to bisacodyl), and 11 due to inability to consume all study agents or complete the study. Sixteen patients met criteria for final analyses. Intracolonic bisacodyl produced a larger area under the curve (AUC) compared to all other agents. Caffeinated coffee resulted in a higher AUC, motility index (MI), and time to HAPC compared with decaffeinated coffee ( P < 0.05). There was no significant difference between caffeinated coffee and caffeine tablet, or caffeine tablet and decaffeinated coffee.

CONCLUSIONS

Caffeine is indeed a colonic stimulant; however, other components of caffeinated and non-caffeinated beverages likely induce colonic response and require further evaluation for possible use as a colonic stimulant.

The Effect of Biorelevant Hydrodynamic Conditions on Drug Dissolution from Extended-Release Tablets in the Dynamic Colon Model

The in vitro release of theophylline from an extended-release dosage form was studied under different hydrodynamic conditions in a United States Pharmacopoeial (USP) dissolution system II and a bespoke in vitro tubular model of the human colon, the Dynamic Colon Model (DCM). Five biorelevant motility patterns extracted from in vivo data were applied to the DCM, mimicking the human proximal colon under baseline conditions and following stimulation using polyethylene glycol or maltose; these represent the lower and upper bounds of motility normally expected in vivo. In the USPII, tablet dissolution was affected by changing hydrodynamic conditions at different agitation speeds of 25, 50 and 100 rpm. Applying different motility patterns in the DCM affected the dissolution profiles produced, with theophylline release at 24 h ranging from 56.74 ± 2.00% (baseline) to 96.74 ± 9.63% (maltose-stimulated). The concentration profiles of theophylline were markedly localized when measured at different segments of the DCM tube, highlighting the importance of a segmented lumen in intestine models and in generating spatial information to support simple temporal dissolution profiles. The results suggested that the shear stresses invoked by the unstimulated, healthy adult human colon may be lower than those in the USPII at 25 rpm and thus insufficient to achieve total release of a therapeutic compound from a hydroxyethyl cellulose matrix. When operated under stimulated conditions, drug release in the DCM was between that achieved at 25 and 50 rpm in the USPII.

Diurnal changes of colonic motility and regulatory factors for colonic motility in Suncus murinus

BACKGROUND

The aim of this study was to investigate the fundamental mechanisms of colonic motility in the house musk suncus (Suncus murinus) as an established animal model of gut motility.

METHODS

To measure gut motility in free-moving conscious suncus, strain gauge force transducers were implanted on the serosa of the colon and gastric body.

KEY RESULTS

We recorded diurnal changes in colonic motility and observed the relationship between feeding and colonic motility. Giant migrating contractions (GMCs) of the colon were invariably detected during defecation and tended to increase during the dark period, thereby indicating that colonic motility has a circadian rhythm. Given that GMCs in the suncus were observed immediately after feeding during the dark period, we assume the occurrence of a gastrocolic reflex in suncus, similar to that observed in humans and dogs. We also examined the factors that regulate suncus GMCs. Intravenous administration of 5-HT (100 µg/kg), substance P (10 and 100 µg/kg), calcitonin gene-related peptide (10 µg/kg), and α2 adrenergic receptor antagonist yohimbine (0.5, 1, and 3 mg/kg) induced GMC-like contractions, as did intragastric and intracolonic administration of the transient receptor potential vanilloid 1 agonist, capsaicin (1 mg/kg).

CONCLUSIONS & INFERENCES

These results indicate that the fundamental mechanisms of colonic motility in suncus are similar to those in humans and dogs, and we thus propose that suncus could serve as a novel small animal model for studying colonic motility.

Propulsive colonic contractions are mediated by inhibition-driven poststimulus responses that originate in interstitial cells of Cajal

The peristaltic reflex is a fundamental behavior of the gastrointestinal (GI) tract in which mucosal stimulation activates propulsive contractions. The reflex occurs by stimulation of intrinsic primary afferent neurons with cell bodies in the myenteric plexus and projections to the lamina propria, distribution of information by interneurons, and activation of muscle motor neurons. The current concept is that excitatory cholinergic motor neurons are activated proximal to and inhibitory neurons are activated distal to the stimulus site. We found that atropine reduced, but did not block, colonic migrating motor complexes (CMMCs) in mouse, monkey, and human colons, suggesting a mechanism other than one activated by cholinergic neurons is involved in the generation/propagation of CMMCs. CMMCs were activated after a period of nerve stimulation in colons of each species, suggesting that the propulsive contractions of CMMCs may be due to the poststimulus excitation that follows inhibitory neural responses. Blocking nitrergic neurotransmission inhibited poststimulus excitation in muscle strips and blocked CMMCs in intact colons. Our data demonstrate that poststimulus excitation is due to increased Ca2+ transients in colonic interstitial cells of Cajal (ICC) following cessation of nitrergic, cyclic guanosine monophosphate (cGMP)-dependent inhibitory responses. The increase in Ca2+ transients after nitrergic responses activates a Ca2+-activated Cl− conductance, encoded by Ano1, in ICC. Antagonists of ANO1 channels inhibit poststimulus depolarizations in colonic muscles and CMMCs in intact colons. The poststimulus excitatory responses in ICC are linked to cGMP-inhibited cyclic adenosine monophosphate (cAMP) phosphodiesterase 3a and cAMP-dependent effects. These data suggest alternative mechanisms for generation and propagation of CMMCs in the colon.

Effect of coconut water and milk on heat stress-induced gastrointestinal tract dysmotility in rats: Role of oxidative stress and inflammatory response

The potential effects of coconut water (CCW) and milk (CCM) on gastrointestinal motility {intestinal transit (IT), intestinal fluid accumulation (IFA) and colonic motility}, tissue oxidative, and inflammatory responses in heat-stressed rats were investigated. There were four (4) temperature exposure groups; (i) Control at 30°C, (CON), (ii) heat-stressed (HS) group exposed to the ambiance of 40°C, (iii) heat-stressed pre-treated with coconut water (HS+ CCW), and (iv) coconut milk (HS + CCM). Skin temperatures (ST) and rectal temperatures (RT) were taken daily, before and after 2 hr heat exposure. GE, IT, and IFA were assessed using standard methods while colonic motility was assessed by colonic bead expulsion (CBE) time after the 14-day exposure. Serum cortisol and lipid peroxidation, antioxidant enzyme activities, inflammatory cytokines in intestinal samples were assessed. Stomach and intestinal morphology were equally examined on histomorphometry. Increased GE, IT, IFA, and colonic motility were observed in HS. CCW and CCM reversed the increases in GE, IT, IFA, and colonic motility in the heat-stressed rats (p < .05). Elevated serum cortisol level and intestinal MDA were significantly reduced in the CCW and CCM treated. Tissue GPx, T-AOC, and T-SOD were all enhanced in HS + CCW and HS + CCM. While tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were suppressed in the HS group, interleukin-4 (IL-4) and interleukin-10 (IL-10) were enhanced with CCW and CCM. Altered intestinal morphology in the HS was also significantly mitigated by CCW and CCM. We showed that coconut water and milk could ameliorate intestinal dysmotility associated with heat stress via oxidative stress reduction and suppression of inflammatory responses. PRACTICAL APPLICATIONS: Heat stress impacts negatively on intestinal health and integrity in both humans and animals via oxidative stress and inflammation. Conversely, coconut has demonstrated anti-oxidative and anti-inflammatory properties in health and medicinal applications. From the findings of this study, coconut water and milk display beneficial potentials against the untoward heat stress effect on gastrointestinal health.

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.

Novel intrinsic neurogenic and myogenic mechanisms underlying the formation of faecal pellets along the large intestine of guinea-pigs

Soft faecal material is transformed into discrete, pellet-shaped faeces at the colonic flexure. Here, analysis of water content in natural faecal material revealed a decline from cecum to rectum without significant changes at the flexure. Thus, pellet formation is not explained by changes in viscosity alone. We then used video imaging of colonic wall movements with electromyography in isolated preparations containing guinea-pig proximal colon, colonic flexure and distal colon. To investigate the pellet formation process, the colonic segments were infused with artificial contents (Krebs solution and 4-6% methylcellulose) to simulate physiological faecal content flow. Remarkably, pellet formation took place in vitro, without extrinsic neural inputs. Infusion evoked slowly propagating neurogenic contractions, the proximal colon migrating motor complexes (∼0.6 cpm), which initiated pellet formation at the flexure. Lesion of the flexure, but not the proximal colon, disrupted the formation of normal individual pellets. In addition, a distinct myogenic mechanism was identified, whereby slow phasic contractions (∼1.9 cpm) initiated at the flexure and propagated short distances retrogradely into the proximal colon and antegradely into the distal colon. There were no detectable changes in the density or distribution of pacemaker-type interstitial cells of Cajal across the flexure. The findings provide new insights into how solid faecal content is generated, suggesting the major mechanisms underlying faecal pellet formation involve the unique interaction at the colonic flexure between antegrade proximal colon migrating motor complexes, organized by enteric neurons, and retrograde myogenic slow phasic contractions. Additional, as yet unidentified extrinsic and/or humoral influences appear to contribute to processing of faecal content in vivo. KEY POINTS: In herbivores, including guinea-pigs, clearly defined faecal pellets are formed at a distinct location along the large intestine (colonic flexure). The mechanism underlying the formation of these faecal pellets at this region has remained unknown. We reveal a progressive and gradual reduction in water content of faecal content along the bowel. Hence, the distinct transition from amorphous to pellet shaped faecal content could not be explained by a dramatic increase in water reabsorption from a specific site. We discovered patterns of anterograde neurogenic and retrograde myogenic motor activity that facilitate the formation of faecal pellets. The formation of 'pellet-like' boluses at the colonic flexure involves interaction of an antegrade migrating motor complex in the proximal colon and retrograde myogenic slow phasic contractions that emerge from the colonic flexure. The findings uncover intrinsic mechanisms responsible for the formation of discrete faecal scybala in the large intestine of a vertebrate.

Motor patterns in the proximal and distal mouse colon which underlie formation and propulsion of feces

BACKGROUND

In herbivores, the proximal and distal colonic regions feature distinct motor patterns underlying formation and propulsion of fecal pellets, respectively. Omnivores, such as mice and humans, lack a similar clear anatomical transition between colonic regions. We investigated whether distinct processes form and propel content along the large intestine of a mouse (an omnivore).

METHODS

We recorded propulsive and non-propulsive neurogenic motor activity in mouse large intestine under six different stimulus conditions of varying viscosities. Gut wall movements were recorded by video and smooth muscle electrical behavior recorded with extracellular suction electrodes.

KEY RESULTS

Three major neurally mediated motor patterns contributed to pellet formation and propulsion. (1) Pellet-shaped boluses are pinched off near the ceco-colonic junction and slowly propelled distally to a transition located at 40% length along the colon. (2) At this functional colonic flexure, propulsion speed is significantly increased by self-sustaining neural peristalsis. Speed transition at this location also occurs with artificial pellets and with spontaneously formed boluses in the empty colon. (3) Periodic colonic motor complexes (CMCs) were present in all conditions reaching a maximal frequency of about 0.4 cpm and extending across the proximal and distal colon with faster speed of propagation.

CONCLUSIONS AND INFERENCES

The three motor patterns share a unique underlying fundamental property of the enteric circuits, which involve extended ensembles of enteric neurons firing at close to 2 Hz. The demonstration of distinct functional differences between proximal and distal colon in rabbit, guinea pig, and now mouse raises the possibility that this may be an organizational principle in other mammalian species, including humans.

A novel mechanism for acute colonic pseudo-obstruction revealed by high-resolution manometry: A case report

BACKGROUND

Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic dysmotility and is associated with considerable morbidity. The pathophysiology of ACPO is considered to be multifactorial but has not been clarified. Although colonic motility is commonly assumed to be hypoactive, there is little direct pathophysiological evidence to support this claim.

METHODS

A 56-year-old woman who developed ACPO following spinal surgery underwent 24 h of continuous high-resolution colonic manometry (1 cm resolution over 36 cm) following endoscopic decompression. Manometry data were analyzed and correlated with a three-dimensional colonic model developed from computed tomography (CT) imaging.

RESULTS

The distal colon was found to be profoundly hyperactive, showing near-continuous non-propagating motor activity. Dominant frequencies at 2-6 and 8-12 cycles per minute were observed. The activity was often dissociated and out-of-phase across adjacent regions. The mean amplitude of motor activity was higher than that reported from pre- and post-prandial healthy controls. Correlation with CT imaging suggested that these disordered hyperactive motility sequences might act as a functional pseudo-obstruction in the distal colon resulting in secondary proximal dilatation.

CONCLUSIONS

This is the first detailed description of motility patterns in ACPO and suggests a novel underlying disease mechanism, warranting further investigation and identification of potential therapeutic targets.

Optimizing Autonomic Function Analysis via Heart Rate Variability Associated With Motor Activity of the Human Colon

The parameters of heart rate variability (HRV) can non-invasively assess some autonomic activities, and HRV is influenced by many bodily actions. Although parasympathetic activity is the primary driver of colonic propulsive activity, and sympathetic activity a major inhibitor of colonic motility, they are rarely measured and almost play no role in diagnosis of colon motor dysfunction or in standard treatments. Here we set out to optimize HRV analysis of autonomic nervous system changes related to human colon motility. The electrocardiogram and impedance were recorded in synchrony with colonic motor patterns by high-resolution manometry. Respiratory sinus arrhythmia (RSA), root mean square of successive differences of beat-to-beat intervals (RMSSD), the Baevsky Index or Sympathetic Index (SI), and the ratios of SI/RSA and SI/RMSSD were shown to indicate a marked increase in parasympathetic and withdrawal of sympathetic activity during the high-amplitude propagating pressure waves (HAPWs). Strong associations were seen with HAPWs evoked by a meal and rectal bisacodyl indicating a marked increase in parasympathetic and withdrawal of sympathetic activity during the gastrocolic reflex and the defecation reflex. When HAPWs occurred in quick succession, parasympathetic activation (RSA and RMSSD) occurred in a rhythmic fashion. Hence, during propulsive motor patterns, an overall shift in autonomic activity toward increased parasympathetic control was shown to be reflected in HRV. HRV assessment may therefore be valuable in the assessment of autonomic dysfunction related to colonic dysmotility.

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.

NLRP3 at the crossroads between immune/inflammatory responses and enteric neuroplastic remodelling in a mouse model of diet-induced obesity

BACKGROUND AND PURPOSE

Enteric neurogenic/inflammation contributes to bowel dysmotility in obesity. We examined the role of NLRP3 in colonic neuromuscular dysfunctions in mice with high-fat diet (HFD)-induced obesity.

EXPERIMENTAL APPROACH

Wild-type C57BL/6J and NLRP3-KO (Nlrp3^-/- ) mice were fed with HFD or standard diet for 8 weeks. The activation of inflammasome pathways in colonic tissues from obese mice was assessed. The role of NLRP3 in in vivo colonic transit and in vitro tachykininergic contractions and substance P distribution was evaluated. The effect of substance P on NLRP3 signalling was tested in cultured cells.

KEY RESULTS

HFD mice displayed increased body and epididymal fat weight, cholesterol levels, plasma resistin levels and plasma and colonic IL-1β levels, colonic inflammasome adaptor protein apoptosis-associated speck-like protein containing caspase-recruitment domain (ASC) and caspase-1 mRNA expression and ASC immunopositivity in macrophages. Colonic tachykininergic contractions were enhanced in HFD mice. HFD NLRP3^-/- mice developed lower increase in body and epididymal fat weight, cholesterol levels, systemic and bowel inflammation. In HFD Nlrp3^-/- mice, the functional alterations of tachykinergic pathways and faecal output were normalized. In THP-1 cells, substance P promoted IL-1β release. This effect was inhibited upon incubation with caspase-1 inhibitor or NK₁ antagonist and not observed in ASC^-/- cells.

CONCLUSION AND IMPLICATIONS

In obesity, NLRP3 regulates an interplay between the shaping of enteric immune/inflammatory responses and the activation of substance P/NK₁ pathways underlying the onset of colonic dysmotility. Identifying NLRP3 as a therapeutic target for the treatment of bowel symptoms related to obesity.

Characterization of alternating neurogenic motor patterns in mouse colon

BACKGROUND

Colonic motor complexes (CMCs) have been widely recorded in the large intestine of vertebrates. We have investigated whether in the smooth muscle, a single unified pattern of electrical activity, or different patterns of electrical activity give rise to the different neurogenic patterns of motility underlying CMCs in vitro.

METHODS

To study differences of the CMCs between proximal and distal colon, we used a novel combination of techniques to simultaneously record muscle diameter and force at multiple sites along the whole mouse colon ex vivo. In addition, electrical activity of smooth muscle was recorded by suction electrodes.

KEY RESULTS

Two distinct types of CMCs were distinguished; CMCs that propagated along the entire colon (complete CMC) and CMCs which were restricted to the proximal colon (incomplete CMC). The two types of CMC often occurred in the same preparations. Incomplete CMCs had longer bursts of smooth muscle action potentials than complete CMCs and propagated more slowly. Interestingly, both types of CMC were associated with similar frequency bursts of smooth muscle action potentials at ~2.4 Hz. In the most proximal colon, an additional firing frequency was detected close to ~7 Hz generating multiple peaks within each CMC.

CONCLUSIONS & INFERENCES

We report distinct characteristics underlying complete and incomplete CMCs in isolated mouse colon. Recognizing these distinct patterns of motility will be important for future interpretation of analysis of murine colonic motility recordings. The identification of alternating patterns of motor activity in proximal colon, but not distal colon may reflect specific neural mechanisms for fecal pellet formation.

Decreased smooth muscle function, peristaltic activity, and gastrointestinal transit in dystrophic (mdx) mice

BACKGROUND

Duchenne muscular dystrophy (DMD) is characterized by the lack of dystrophin in skeletal, cardiac, and smooth muscle. Slow colonic transit and constipation are common in DMD patients and animal models of DMD. However, the cause of this hypocontractility and the expression of contractile proteins in smooth muscle are unknown. The aim of the study was to investigate the expression of contractile proteins in the colonic smooth muscle and the function of the colon in control and mdx mice.

METHODS

Muscle contraction was measured in muscle strips and isolated muscle cells. Peristaltic activity was measured in ex vivo preparations by spatiotemporal mapping, and gastrointestinal (GI) transit in vivo was measured by the distribution of fluorescent marker along the intestine and colon. mRNA expression of contractile proteins smoothelin, caldesmon, calponin, and tropomyosin was measured by qRT-PCR.

RESULTS

Expression of mRNA for contractile proteins was decreased in colonic smooth muscle of mdx mice compared with control. Contraction in response to acetylcholine and KCl was decreased in colonic muscle strips and in isolated muscle cells of mdx mice. Distension of ex vivo colons with Krebs buffer induced peristalsis in both control and mdx mice; however, significantly fewer full peristaltic waves were recorded in the colons of mdx mice. GI transit was also inhibited in mdx mice.

CONCLUSION AND INFERENCES

The data indicate that the lack of dystrophin causes decrease in colonic smooth muscle contractility, peristalsis, and GI transit and provides the basis for analysis of mechanisms involved in smooth muscle dysfunction in DMD.

Human resident gut microbe Bacteroides thetaiotaomicron regulates colonic neuronal innervation and neurogenic function

BACKGROUND AND AIMS

As the importance of gut-brain interactions increases, understanding how specific gut microbes interact with the enteric nervous system (ENS), which is the first point of neuronal exposure becomes critical. Our aim was to understand how the dominant human gut bacterium Bacteroides thetaiotaomicron (Bt) regulates anatomical and functional characteristics of the ENS.

METHODS

Neuronal cell populations, as well as enteroendocrine cells, were assessed in proximal colonic sections using fluorescent immunohistochemistry in specific pathogen-free (SPF), germ-free (GF) and Bt conventionalized-germ-free mice (Bt-CONV). RNA expression of tight junction proteins and toll-like receptors (TLR) were measured using qPCR. Colonic motility was analyzed using in vitro colonic manometry.

RESULTS

Decreased neuronal and vagal afferent innervation observed in GF mice was normalized by Bt-CONV with increased neuronal staining in mucosa and myenteric plexus. Bt-CONV also restored expression of nitric oxide synthase expressing inhibitory neurons and of choline acetyltransferase and substance P expressing excitatory motor neurons comparable to those of SPF mice. Neurite outgrowth and glial cells were upregulated by Bt-CONV. RNA expression of tight junction protein claudin 3 was downregulated while TLR2 was upregulated by Bt-CONV. The enteroendocrine cell subtypes L-cells and enterochromaffin cells were reduced in GF mice, with Bt-CONV restoring L-cell numbers. Motility as measured by colonic migrating motor complexes (CMMCs) increased in GF and Bt-CONV.

CONCLUSION

Bt, common gut bacteria, is critical in regulating enteric neuronal and enteroendocrine cell populations, and neurogenic colonic activity. This highlights the potential use of this resident gut bacteria for maintaining healthy gut function.

Distinct patterns of myogenic motor activity identified in isolated human distal colon with high-resolution manometry

BACKGROUND

Colonic high-resolution manometry (HRM) has been used to reveal discrete, propagating colonic motor patterns. To help determine mechanisms underlying these patterns, we used HRM to record contractile activity in human distal colon ex vivo.

METHODS

Surgically excised segments of descending (n = 30) or sigmoid colon (n = 4) were immersed in oxygenated Krebs solution at 36°C (n = 34; 16 female; 67.6 ± 12.4 years; length: 24.7 ± 3.5 cm). Contractility was recorded by HRM catheters. After 30 minutes of baseline recording, 0.3 mM lidocaine and/or 1 mM hexamethonium were applied. Ascending neural pathways were activated by electrical field stimulation (EFS; 10 Hz, 0.5 ms, 50 V, 5-s duration) applied to the anal end before and after drug application.

RESULTS

Spontaneous propagating contractions were recorded in all specimens (0.1-1.5 cycles/minute). Most contractions occurred synchronously across all recording sites. In five specimens, rhythmic antegrade contractions propagated across the full length of the preparation. EFS evoked local contractions at the site of stimulation (latency: 5.5 ± 2.4 seconds) with greater amplitude than spontaneous contractions (EFS; 29.3 ± 26.9 vs 12.1 ± 14.8 mm Hg; P = .02). Synchronous or retrograde propagating motor patterns followed EFS; 71% spanned the entire preparation length. Hexamethonium and lidocaine modestly and only temporarily inhibited spontaneous contractions, whereas TTX increased the frequency of contractile activity while inhibiting EFS-evoked contractions.

CONCLUSIONS AND INFERENCES

Our study suggests that the propagated contractions recorded in the organ bath have a myogenic origin which can be regulated by neural input. Once activated at a local site, the contractions do not require the propulsion of fecal content to sustain long-distance propagation.

Cyanidin-3-O-Glucoside Improves Colonic Motility During Severe Acute Pancreatitis by Inhibiting the H2S-Regulated AMPK/mTOR Pathway

BACKGROUND

Cyanidin-3-O-glucoside (C3G) is an important anthocyanin that can modulate digestive system functioning. Inflammation associated with severe acute pancreatitis (SAP) induces H2S production, which impairs the gastrointestinal (GI) system. We investigated the effects of C3G in attenuating SAP-associated colonic motility loss by examining the H2S level and activity of AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway.

METHODS

A rat model of SAP was induced using sodium taurocholate, and the effect of C3G on colonic mobility, H2S production, and the inflammatory response was investigated. AMPK/mTOR pathway changes were detected to assess the pathways by which H2S influences colonic mobility in SAP-model rats. The mechanism underlying H2S function was further examined by subjecting colonic muscle cells (CMCs) to C3G, SAP plasma and an AMPK activator.

RESULTS

Administering C3G improved colonic motility but suppressed the inflammatory response and H2S production in the SAP-model rats, which was associated with inhibiting the AMPK/mTOR pathway. Furthermore, activating the AMPK/mTOR pathway in CMCs promoted inflammation but suppressed Ca2+ levels, even after administering C3G.

CONCLUSION

Administering C3G may improve SAP-associated colonic mobility by inhibiting the H2S-mediated AMPK/mTOR pathway.

Effects and sites of action of a M1 receptor positive allosteric modulator on colonic motility in rats and dogs compared with 5-HT4 agonism and cholinesterase inhibition

BACKGROUND

Muscarinic receptor 1 positive allosteric modulators (M1PAMs) enhance colonic propulsive contractions and defecation through the facilitation of M1 receptor (M1R)-mediated signaling. We examined M1R expression in the colons of 5 species and compared colonic propulsion and defecation caused by the M1PAM, T440, the 5-HT₄ agonist, prucalopride, and the cholinesterase inhibitor, neostigmine, in rats and dogs.

METHODS

M1R expression was profiled by immunostaining and in situ hybridization. In vivo studies utilized male SD rats and beagle dogs. Colonic propulsive contractions were recorded by manometry in anesthetized rats. Gut contractions in dogs were assessed using implanted force transducers in the ileum, proximal, mid, and distal colons.

KEY RESULTS

M1R was localized to neurons of myenteric and submucosal plexuses and the epithelium of the human colon. A similar receptor localization was observed in rat, dog, mouse, and pig. T440 enhanced normal defecation in rats in a dose-dependent manner. Prucalopride also enhanced defecation in rats, but the maximum effect was half that of T440. Neostigmine and T440 were similarly effective in enhancing defecation, but the effective dose of neostigmine was close to its lethal dose. In rats, all 3 compounds induced colonic contractions, but the associated propulsion was strongest with T440. In dogs, intestinal contractions elicited by T440 propagated from ileum to distal colon. Prucalopride and neostigmine also induced intestinal contractions, but these were less well coordinated. No loss of effectiveness of T440 on defecation occurred after 5 days of repeated dosing.

CONCLUSION AND INFERENCES

These results suggest that M1PAMs produce highly coordinated propagating contraction by actions on the enteric nervous system of the colon. The localization of M1R to enteric neurons in both animals and humans suggests that the M1PAM effects would be translatable to human. M1PAMs provide a potential novel therapeutic option for constipation disorders.

Prodromal Intestinal Events in Alzheimer's Disease (AD): Colonic Dysmotility and Inflammation Are Associated with Enteric AD-Related Protein Deposition

Increasing evidence suggests that intestinal dysfunctions may represent early events in Alzheimer’s disease and contribute to brain pathology. This study examined the relationship between onset of cognitive impairment and colonic dysfunctions in a spontaneous AD model before the full development of brain pathology. SAMP8 mice underwent Morris water maze and assessment of faecal output at four, six and eight months of age. In vitro colonic motility was examined. Faecal and colonic Aβ, tau proteins, α-synuclein and IL-1β were assessed by ELISA. Colonic citrate synthase activity was assessed by spectrophotometry. Colonic NLRP3, caspase-1 and ASC expression were evaluated by Western blotting. Colonic eosinophil density and claudin-1 expression were evaluated by immunohistochemistry. The effect of Aβ on NLRP3 signalling and mitochondrial function was tested in cultured cells. Cognitive impairment and decreased faecal output occurred in SAMP8 mice from six months. When compared with SAMR1, SAMP8 animals displayed: (1) impaired in vitro colonic contractions; (2) increased enteric AD-related proteins, IL-1β, active-caspase-1 expression and eosinophil density; and (3) decreased citrate synthase activity and claudin-1 expression. In THP-1 cells, Aβ promoted IL-1β release, which was abrogated upon incubation with caspase-1 inhibitor or in ASC^-/- cells. Aβ decreased mitochondrial function in THP-1 cells. In SAMP8, enteric AD-related proteins deposition, inflammation and impaired colonic excitatory neurotransmission, occurring before the full brain pathology development, could contribute to bowel dysmotility and represent prodromal events in AD.

The cyclic motor patterns in the human colon

BACKGROUND

High-resolution colonic manometry gives an unprecedented window into motor patterns of the human colon. Our objective was to characterize motor activities throughout the entire colon that possessed persistent rhythmicity and spanning at least 5 cm.

METHODS

High-resolution colonic manometry using an 84-channel water-perfused catheter was performed in 19 healthy volunteers. Rhythmic activity was assessed during baseline, proximal balloon distention, meal, and bisacodyl administration.

KEY RESULTS

Throughout the entire colon, a cyclic motor pattern occurred either in isolation or following a high-amplitude propagating pressure wave (HAPW), consisting of clusters of pressure waves at a frequency centered on 11-13 cycles/min, unrelated to breathing. The cluster duration was 1-6 minutes; the pressure waves traveled for 8-27 cm, lasting 5-8 seconds. The clusters itself could be rhythmic at 0.5-2 cpm. The propagation direction of the individual pressure waves was mixed with >50% occurring simultaneous. This high-frequency cyclic motor pattern co-existed with the well-known low-frequency cyclic motor pattern centered on 3-4 cpm. In the rectum, the low-frequency cyclic motor pattern dominated, propagating predominantly in retrograde direction. Proximal balloon distention, a meal and bisacodyl administration induced HAPWs followed by cyclic motor patterns.

CONCLUSIONS AND INFERENCES

Within cyclic motor patterns, retrograde propagating, low-frequency pressure waves dominate in the rectum, likely keeping the rectum empty; and mixed propagation, high-frequency pressure waves dominate in the colon, likely promoting absorption and storage, hence contributing to continence. Propagation and frequency characteristics are likely determined by network properties of the interstitial cells of Cajal.

On the nature of high-amplitude propagating pressure waves in the human colon

Characterization of high-amplitude propagating pressure waves (HAPWs or HAPCs) plays a key role in diagnosis of colon dysmotility using any type of colonic manometry. With the introduction of high-resolution manometry, more insight is gained into this most prominent propulsive motor pattern. Here, we use a water-perfused catheter with 84 sensors with intervals between measuring points of 1 cm throughout the colon, for 6-8 h, in 19 healthy subjects. The catheter contained a balloon to evoke distention. We explored as stimuli a meal, balloon distention, oral prucalopride, and bisacodyl injection, with a goal to optimally evoke HAPWs. We developed a quantitative measure of HAPW activity, the "HAPW Index." Our protocol elicited 290 HAPWs. 21% of HAPWs were confined to the proximal colon with an average amplitude of 75.3 ± 3.3 mmHg and an average HAPW Index of 440 ± 58 mmHg·m·s. 29% of HAPWs started in the proximal colon and ended in the transverse or descending colon, with an average amplitude of 87.9 ± 3.1 mmHg and an average HAPW Index of 3,344 ± 356 mmHg·m·s. Forty-nine percent of HAPWs started and ended in the transverse or descending colon with an average amplitude of 109.3 ± 3.3 mmHg and an average HAPW Index of 2,071 ± 195 mmHg·m·s. HAPWs with and without simultaneous pressure waves (SPWs) initiated the colo-anal reflex, often abolishing 100% of anal sphincter pressure. Rectal bisacodyl and proximal balloon distention were the most optimal stimuli to evoke HAPWs. These measures now allow for a confident diagnosis of abnormal motility in patients with colonic motor dysfunction.NEW & NOTEWORTHY High-amplitude propagating pressure waves (HAPWs) were characterized using 84 sensors throughout the entire colon in healthy subjects, taking note of site of origin, site of termination, amplitude, and velocity, and to identify optimal stimuli to evoke HAPWs. Three categories of HAPWs were identified, including the associated colo-anal reflex. Proximal balloon distention and rectal bisacodyl were recognized as reliable stimuli for evoking HAPWs, and a HAPW Index was devised to quantify this essential colonic motor pattern.

Effects of O-1602 and CBD on TNBS-induced colonic disturbances

BACKGROUND

This study attempted to provide the effects and mechanisms of two cannabinoids, O-1602 and cannabidiol (CBD), on colonic motility of 2,4,6-trinitro-benzene sulfonic acid (TNBS) colitis.

METHODS

TNBS was used to induce the model of motility disorder. G protein-coupled receptor 55 (GPR55) expression was detected using real-time PCR and immunohistochemistry in colon. Pro-inflammatory cytokines and myeloperoxidase were also measured. The colonic motility was measured by upper GI transit in vivo and recorded using electrical stimulation organ bath technique in vitro. Freshly isolated smooth muscle from the rat colon were applied to determine the membrane potential and Ca²⁺ -ATPase activity, respectively.

KEY RESULTS

CBD or O-1602 separately improved inflammatory conditions significantly in TNBS-induced colitis rats. However, sole CBD pretreatment reduced GPR55 expression, which was up-regulated in TNBS colitis. O-1602 and CBD each lowered MPO and IL-6 levels remarkably in TNBS colitis, while TNF-α levels experienced no change. CBD rescued the downward colonic motility in TNBS colitis in vivo; however, it decreased the upward contraction of the smooth muscle strip under electrical stimulation in vitro. Pretreatment with CBD prevented against TNBS-induced changes of Ca²⁺ -ATPase activity of smooth muscle cells. However, membrane potential of the smooth muscle cells decreased by TNBS experienced no change after O-1602 or CBD import.

CONCLUSIONS & INFERENCES

The present study suggested that CBD participated in the regulation of colonic motility in rats, and the mechanisms may be involved in the regulation of inlammatory factors and Ca²⁺ -ATPase activity through GPR55.

A novel postsynaptic signal pathway of sympathetic neural regulation of murine colonic motility

Transcriptome data revealed α1 adrenoceptors (ARs) expression in platelet-derived growth factor receptor α⁺ cells (PDGFRα⁺ cells) in murine colonic musculature. The role of PDGFRα⁺ cells in sympathetic neural regulation of murine colonic motility was investigated. Norepinephrine (NE), via α1A ARs, activated a small conductance Ca²⁺ -activated K⁺ (SK) conductance, evoked outward currents and hyperpolarized PDGFRα⁺ cells (the α1A AR-SK channel signal pathway). α1 AR agonists increased intracellular Ca²⁺ transients in PDGFRα⁺ cells and inhibited spontaneous phasic contractions (SPCs) of colonic muscle through activation of a SK conductance. Sympathetic nerve stimulation inhibited both contractions of distal colon and propulsive contractions represented by the colonic migrating motor complexes (CMMCs) via the α1A AR-SK channel signal pathway. Postsynaptic signaling through α1A ARs in PDGFRα⁺ cells is a novel mechanism that conveys part of stress responses in the colon. PDGFRα⁺ cells appear to be a primary effector of sympathetic neural regulation of murine colonic motility.

Relationships Between Distention-, Butyrate- and Pellet-Induced Stimulation of Peristalsis in the Mouse Colon

Background/Aims

Luminal factors such as short-chain fatty acids are increasingly recognized for playing a regulatory role in peristaltic activity. Our objective was to understand the roles of butyrate and propionate in regulating peristaltic activity in relation to distention-induced activities.

Methods

Butyrate and propionate were perfused intraluminally under varying intraluminal pressures in murine colons bathed in Krebs solution. We used video recording and spatiotemporal maps to examine peristalsis induced by the intrinsic rhythmic colonic motor complex (CMC) as well as pellet-induced peristaltic reflex movements.

Results

The CMC showed several configurations at different levels of excitation, culminating in long distance contractions (LDCs) which possess a triangular shape in murine colon spatiotemporal maps. Butyrate increased the frequency of CMCs but was a much weaker stimulus than distention and only contributed to significant changes under low distention. Propionate inhibited CMCs by decreasing either their amplitudes or frequencies, but only in low distention conditions. Butyrate did not consistently counteract propionate-induced inhibition likely due to the multiple and distinct mechanisms of action for these signaling molecules in the lumen. Pellet movement occurred through ongoing CMCs as well as pellet induced peristaltic reflex movements and butyrate augmented both types of peristaltic motor patterns to decrease the amount of time required to expel each pellet.

Conclusions

Butyrate is effective in promoting peristalsis, but only when the level of colonic activity is low such as under conditions of low intraluminal pressure. This suggests that it may play a significant role in patients with poor fiber intake, where there is low mechanical stimulation in the lumen.

Associations Between Colonic Motor Patterns and Autonomic Nervous System Activity Assessed by High-Resolution Manometry and Concurrent Heart Rate Variability

Abnormal colonic motility may be associated with dysfunction of the autonomic nervous system (ANS). Our aim was to evaluate if associations between colonic motor patterns and autonomic neural activity could be demonstrated by assessing changes in heart rate variability (HRV) in healthy volunteers. A total of 145 colonic motor patterns were assessed in 11 healthy volunteers by High-Resolution Colonic Manometry (HRCM) using an 84-channel water-perfused catheter. Motor patterns were evoked by balloon distention, a meal and luminal bisacodyl. The electrocardiogram (ECG) and cardiac impedance were assessed during colonic manometry. Respiratory sinus arrhythmia (RSA) and root mean square of successive differences of beat-to-beat intervals (RMSSD) served as measures of parasympathetic reactivity while the Baevsky's Stress Index (SI) and the pre-ejection period (PEP) were used as measures of sympathetic reactivity. Taking all motor patterns into account, our data show that colonic motor patterns are accompanied by increased parasympathetic activity and decreased sympathetic activity that may occur without eliciting a significant change in heart rate. Motor Complexes (more than one motor pattern occurring in close proximity), High-Amplitude Propagating Pressure Waves followed by Simultaneous Pressure Waves (HAPW-SPWs) and HAPWs without SPWs are all associated with an increase in RSA and a decrease in SI. Hence RSA and SI may best reflect autonomic activity in the colon during these motor patterns as compared to RMSSD and PEP. SI and PEP do not measure identical sympathetic reactivity. The SPW, which is a very low amplitude pressure wave, did not significantly change the autonomic measures employed here. In conclusion, colonic motor patterns are associated with activity in the ANS which is reflected in autonomic measures of heart rate variability. These autonomic measures may serve as proxies for autonomic neural dysfunction in patients with colonic dysmotility.

Development and feasibility of an ambulatory acquisition system for fiber-optic high-resolution colonic manometry

BACKGROUND

High-resolution colonic manometry is an emerging technique that has provided new insights into the pathophysiology of functional colorectal diseases. Prior studies have been limited by bulky, non-ambulatory acquisition systems, which have prevented mobilization during prolonged recordings.

METHODS

A novel ambulatory acquisition system for fiber-optic high-resolution colonic manometry was developed. Benchtop validation against a standard non-ambulatory system was performed using standardized calibration metrics. Clinical feasibility studies were conducted in three patients undergoing right hemicolectomy.

RESULTS

Pressure profiles obtained from benchtop testing were near-identical using the ambulatory and the non-ambulatory systems. Clinical studies successfully demonstrated ambulatory data capture with patients freely mobilizing postoperatively during continuous recordings of >60 hours. The occurrence (P = .56), amplitude (P = .65), velocity (P = .10), and extent (P = .12) of colonic motor patterns were similar to those obtained in non-ambulatory studies.

CONCLUSIONS

A novel ambulatory system for high-resolution colonic manometry has been developed and validated. This technique will facilitate prolonged ambulatory recordings of colonic motor activity, assisting with investigations into the role of colonic motility in disease states.

Intraluminal prucalopride increases propulsive motor activities via luminal 5-HT4 receptors in the rabbit colon

BACKGROUND

Activating luminal 5-HT₄ receptors results in the release of 5-HT from enterochromaffin cells into the lamina propria to modulate colonic motility. Our aim was to evaluate characteristics of colonic motor patterns involved in the prokinetic effects of intraluminal prucalopride in the rabbit colon.

METHODS

Colonic motor patterns were studied ex vivo using simultaneous spatiotemporal diameter mapping and pressure sensing.

KEY RESULTS

Intraluminal prucalopride and intraluminal exogenous 5-HT strongly evoked or enhanced the colonic motor complex at all levels of excitation beginning with generation of clusters of fast propagating contractions (FPCs), then development of long-distance contractions (LDCs) within the clusters, and finally forceful LDCs as the highest level of excitation. Intraluminal prucalopride and intraluminal exogenous 5-HT stimulated propulsive motor activity in a dose-dependent and antagonist-sensitive manner by increasing the contraction amplitude, intraluminal pressure, frequency, velocity, and degree of propagation of the colonic motor complex.

CONCLUSIONS AND INFERENCES

Activating mucosal 5-HT₄ receptors via intraluminal prucalopride or 5-HT increases propulsive motor activity in a graded manner; that is, depending on starting conditions, amplitudes or frequencies of an activity may increase or a new pattern may be initiated. Our data support further studies into delivering 5-HT₄ receptor agonists via colon-targeted drug delivery systems and studies into the role of luminal 5-HT as an essential requirement for normal colon motor pattern generation.

Use of prucalopride in adults with chronic idiopathic constipation

Introduction: Prucalopride is a selective 5-HT₄ receptor agonist with colonic prokinetic activity. It was recently approved by the FDA for the treatment of chronic idiopathic constipation. Before this approval, there were limited options to improve colonic motility in the treatment of chronic idiopathic constipation. Areas covered: We systematically searched PubMed, Embase, ClinicalTrials.gov, and international conference presentations, and we reviewed all studies that evaluated prucalopride for the treatment of chronic idiopathic constipation in adults. In this review, we discuss the pharmacokinetics, pharmacodynamics, receptor interactions, phase I-IV clinical trials, and safety outcomes of prucalopride in adults, including the elderly. Expert opinion: Prucalopride is an effective agent to improve colonic motility, decrease colonic transit time, and increase complete spontaneous bowel movements in patients with chronic idiopathic constipation. Unlike previously available 5-HT₄ receptor agonists such as cisapride and tegaserod, prucalopride does not interact with the cardiac hERG potassium channels or other serotonergic receptors in blood vessels and is not associated with an increase in major adverse cardiovascular events. Additionally, prucalopride has demonstrated promise in the treatment of gastroparesis, post-operative ileus, and opioid-induced constipation. Prucalopride directly stimulates colonic motility, differentiating it from all other medications (exclusively osmotic or chloride secretagogues) approved for chronic constipation in the last decade.

Noradrenaline inhibits neurogenic propulsive motor patterns but not neurogenic segmenting haustral progression in the rabbit colon

BACKGROUND

Excessive sympathetic inhibition may be a cause of colon motor dysfunction. Our aim was to better understand the mechanisms of sympathetic inhibition on colonic motor patterns using the rabbit colon, hypothesizing that noradrenaline selectively inhibits propulsive motor patterns.

METHODS

Changes in motor patterns of the rabbit colon were studied ex vivo using noradrenaline and adrenoceptor antagonists and analyzed using spatiotemporal diameter maps.

KEY RESULTS

Noradrenaline abolished propulsive contractions: it abolished the long-distance contractions (LDCs) from a baseline frequency of 0.8 ± 0.3 and the clusters of fast propagating contractions (FPCs) at a frequency of 14.4 ± 2.8 cpm. Both motor patterns recovered after addition of the α₂ -adrenoceptor antagonist yohimbine to a frequency of 0.5 ± 0.2  and 9.9 ± 3.3 cpm, respectively. The β-adrenoceptor antagonist propranolol did not prevent the loss of propulsive motor patterns with noradrenaline. Noradrenaline did not inhibit haustral boundary contractions and increased the frequency of the myogenic ripples from 8.3 ± 1.4 to 10.5 ± 1.3 cpm which was not affected by yohimbine, propranolol nor the α₁ -adrenoceptor blocker prazosin.

CONCLUSIONS AND INFERENCES

Noradrenergic inhibition of propulsive motor patterns is mediated by the α₂ -adrenoceptor to inhibit the neurogenic LDCs and the neurogenic clustering of FPCs. The neurogenic haustral boundary contractions are not affected, suggesting that α_2- receptors are on selective neural circuits. The excitatory effect of noradrenaline on ripples may be due to the activation of adrenoceptors on interstitial cells of Cajal, but action on α_1- receptors was excluded. No role for the β-adrenoceptor was found.

Translational inhibition of α-synuclein by Posiphen normalizes distal colon motility in transgenic Parkinson mice

Parkinson disease (PD) is a neurodegenerative disease with motor as well as non-motor symptoms, including gastrointestinal dysfunction. In humans, these precede the motor symptoms by decades. Previously developed and characterized transgenic mice expressing the mutant human α-synuclein gene (SNCA) (either A53T or A30P), but not the endogenous mouse Snca, serve as models for familial PD. These animals demonstrate both robust abnormalities in enteric nervous system (ENS) function as well as synuclein-immunoreactive aggregates in ENS ganglia by 3 months of age, recapitulating early gastrointestinal abnormalities seen before the gait impairment characteristics of human and murine PD. Posiphen is a translational inhibitor of α-synuclein that targets the 5' untranslated region (UTR) of SNCA mRNA and could be a potential drug for the treatment of PD. However, its efficacy in ameliorating symptoms of PD has not yet been evaluated. Here, we used these transgenic mouse models to investigate the efficacy of Posiphen in reversing the gastrointestinal dysfunction. We show that Posiphen normalizes the colonic motility of both transgenic mouse models, although it did not affect the Whole Gut Transit Time (WGTT). Pharmacokinetics studies revealed that Posiphen is more abundant in the brain than in blood, in agreement with its lipophilicity, and the main metabolite is N⁸-NorPosiphen, a molecule with similar properties as Posiphen. The brain Posiphen levels necessary to effect optimal function were calculated and compared with efficacious brain levels from previous studies, showing that a 2-3 mM concentration of Posiphen and metabolites is sufficient for functional efficacy. Finally, 10 mg/kg Posiphen reduced α-synuclein levels in the gut of hSNCA^A53T mice treated for twenty-one weeks, while 50 and 65 mg/kg Posiphen reduced α-synuclein levels in the brain of hSNCA^A53T mice treated for twenty-one days. In conclusion, this is the first study showing the preclinical efficacy of Posiphen in normalizing the colonic motility in mouse models of gastrointestinal dysfunction in early PD. This result is in agreement with the ability of Posiphen to reach the nervous system, and its mechanism of action, the translational inhibition of α-synuclein expression. These significant findings support further development of Posiphen as a drug for the treatment of PD.

Effects of exendin-4 on colonic motility in rats and its underlying mechanism

BACKGROUND

Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists modulate gastrointestinal motility; however, the effects of GLP-1R agonists on colonic motility are still controversial, and the molecular mechanism is unclear. Exendin-4 shares 53% homology with GLP-1 and is a full agonist of GLP-1R. In this study, our aims were to explore the role and mechanism of exendin-4 in isolated rat colonic tissues and cells.

METHODS

An organ bath system was used to examine the spontaneous contractions of smooth muscle strips. The whole-cell patch-clamp technique was used to investigate the currents of L-type voltage-dependent calcium channels and large conductance Ca²⁺ -activated K⁺ (BK_Ca ) channels in smooth muscle cells.

KEY RESULTS

Exendin-4 decreased both the amplitude and frequency of spontaneous contractions of smooth muscle strips in a concentration-dependent manner. The inhibitory effect was completely blocked by exendin-4(9-39), a GLP-1R antagonist. Moreover, this effect was partially abolished by tetrodotoxin (TTX), a blocker of neuronal voltage-dependent Na⁺ channels, Nω-Nitro-l-arginine (L-NNA), a nitric oxide synthase (NOS) inhibitor, apamin, an inhibitor of small-conductance Ca²⁺ -activated K⁺ (SK) channels. Whole-cell patch-clamp recordings revealed that exendin-4 inhibited the peak current of L-type calcium channels in colonic smooth muscle cells, but did not change the shape of the current-voltage (I-V) curves. The steady-state activation and steady-state inactivation of L-type calcium channels were not affected. Likewise, BK_Ca currents were significantly inhibited by exendin-4.

CONCLUSIONS

Exendin-4 indirectly inhibits colonic muscle activity via a nitrergic and a purinergic neural pathway through NO and ATP release and inhibits L-type voltage-dependent calcium channels and BK_Ca channels in smooth muscle cells.

Targeting eotaxin-1 and CCR3 receptor alleviates enteric neuropathy and colonic dysfunction in TNBS-induced colitis in guinea pigs

BACKGROUND

The accumulation of eosinophils is mediated by the chemokine receptor-3 (CCR3)-eotaxin axis. Increased expression of eotaxin and its receptor is associated with inflammatory bowel disease (IBD). Activation of eosinophils causes the release of cationic proteins that are neurotoxic such as eosinophil-derived neurotoxin (EDN). Damage to enteric neurons alters neurally controlled functions of the gut correlated with intestinal inflammation. We hypothesized that inhibition of the CCR3-eotaxin axis will prevent inflammation-induced functional changes to the gastrointestinal tract.

METHODS

Hartley guinea pigs were administered with trinitrobenzene sulfonate (TNBS; 30 mg/kg in 30% ethanol) intrarectally to induce colitis. A CCR3 receptor antagonist (SB 328437 [SB3]) was injected intraperitoneally 1 hour postinduction of colitis. Animals were euthanized 7 days post-treatment and colon tissues were collected for ex vivo studies. The EDN-positive eosinophils in the colon, indicating eosinophil activation, were quantified by immunohistochemistry. Effects of SB3 treatment on gross morphological damage, enteric neuropathy, and colonic dysmotility were determined by histology, immunohistochemistry, and organ bath experiments.

KEY RESULTS

The number of EDN-positive eosinophils was significantly increased in the lamina propria in close proximity to myenteric ganglia in inflamed colon. The TNBS-induced inflammation caused significant damage to colonic architecture and inhibition of colonic motility. Treatment with SB3 antagonist attenuated inflammation-associated morphological damage in the colon, reduced infiltration of EDN-positive eosinophils and restored colonic motility to levels comparable to control and sham-treated guinea pigs.

CONCLUSION & INFERENCES

This is the first study demonstrating that inhibition of CCR3-eotaxin axis alleviates enteric neuropathy and restores functional changes in the gut associated with TNBS-induced colitis.

Abnormal absorptive colonic motor activity in germ-free mice is rectified by butyrate, an effect possibly mediated by mucosal serotonin

The role of short-chain fatty acids (SCFAs) in the control of colonic motility is controversial. Germ-free (GF) mice are unable to produce these metabolites and serve as a model to study how their absence affects colonic motility. GF transit is slower than controls, and colonization of these mice improves transit and serotonin [5-hydroxytryptamine (5-HT)] levels. Our aim was to determine the role SCFAs play in improving transit and whether this is dependent on mucosal 5-HT signaling. Motility was assessed in GF mice via spatiotemporal mapping. First, motor patterns in the whole colon were measured ex vivo with or without luminal SCFA, and outflow from the colon was recorded to quantify outflow caused by individual propulsive contractions. Second, artificial fecal pellet propulsion was measured. Motility was then assessed in tryptophan hydroxylase-1 (TPH1) knockout (KO) mice, devoid of mucosal 5-HT, with phosphate buffer, butyrate, or propionate intraluminal perfusion. GF mice exhibited a lower proportion of propulsive contractions, lower volume of outflow/contraction, slower velocity of contractions, and slower propulsion of fecal pellets compared with controls. SCFAs changed motility patterns to that of controls in all parameters. Butyrate administration increased the proportion of propulsive contractions in controls yet failed to in TPH1 KO mice. Propionate inhibited propulsive contractions in all mice. Our results reveal significant abnormalities in the propulsive nature of colonic motor patterns in GF mice, explaining the decreased transit time in in vivo studies. We show that butyrate but not propionate activates propulsive motility and that this may require mucosal 5-HT. NEW & NOTEWORTHY Understanding the role that the microbiota play in governing the physiology of colonic motility is lacking. Here, we offer for the first time, to our knowledge, a detailed analysis of colonic motor patterns and pellet propulsion using spatiotemporal mapping in the absence of microbiota. We show a striking difference in germ-free and control phenotypes and attribute this to a lack of fermentation-produced short-chain fatty acid. We then show that butyrate but not propionate can restore motility and that the butyrate effect likely requires mucosal 5-hydroxytryptamine.

Rasagiline, an inhibitor of MAO-B, decreases colonic motility through elevating colonic dopamine content

BACKGROUND

Dopamine (DA) is a negative modulator of gut motility. Monoamine oxidase-B (MAO-B) is an important metabolic enzyme degrading DA. Rasagiline, an irreversible MAO-B inhibitor, is used to treat Parkinson's disease because of its neuroprotective effect and increasing central DA. However, it is unclear whether MAO-B exists in the colon and rasagiline increases colonic DA, thereby affecting colonic motility.

METHODS

Immunohistochemistry, western blotting, enzyme activity assay, colonic motility recording, gut transit test, and high-performance liquid chromatography-electrochemical detection were employed in this study.

KEY RESULTS

Monoamine oxidase-B was distributed in the colonic muscular layers including neurons and glias of rat and human. When oral treatment of rats with rasagiline for 4 weeks, in vitro colonic motility was significantly reduced, but it was greatly reversed by SCH-23390, an antagonist of DA D₁ receptor. The rasagiline-treated rats also manifested decreased MAO-B activity and increased DA content in the colonic muscular layer, but no alterations were detected in the protein expressions of D₁ and D₂ receptors, and MAO-A and MAO-B, as well as in the content of 5-hydroxytryptamine and noradrenaline. Moreover, acute administration of rasagiline did not affect the colonic motility in vitro and the colonic DA level in rats, although MAO-B activity was significantly inhibited.

CONCLUSIONS & INFERENCES

Monoamine oxidase-B is abundant in the colonic muscular layer including myenteric plexus of rat and human. Long-term administration of rasagiline can increase colonic DA thereby inhibiting colonic motility, suggesting that colonic MAO-B could be a potential drug target for colonic dysmotility.

Characterization of Simultaneous Pressure Waves as Biomarkers for Colonic Motility Assessed by High-Resolution Colonic Manometry

Simultaneous pressure waves (SPWs) in manometry recordings of the human colon have been associated with gas expulsion. Our hypothesis was that the SPW might be a critical component of most colonic motor functions, and hence might act as a biomarker for healthy colon motility. To that end, we performed high-resolution colonic manometry (HRCM), for the first time using an 84-sensor (1 cm spaced) water-perfused catheter, in 17 healthy volunteers. Intraluminal pressure patterns were recorded during baseline, proximal and rectal balloon distention, after a meal and following proximal and rectal luminal bisacodyl administration. Quantification was performed using software, based on Image J, developed during this study. Gas expulsion was always associated with SPWs, furthermore, SPWs were associated with water or balloon expulsion. SPWs were prominently emerging at the termination of proximal high amplitude propagating pressure waves (HAPWs); we termed this motor pattern HAPW-SPWs; hence, SPWs were often not a pan-colonic event. SPWs and HAPW-SPWs were observed at baseline with SPW amplitudes of 12.0 ± 8.5 mmHg and 20.2 ± 7.2 mmHg respectively. The SPW occurrence and amplitude significantly increased in response to meal, balloon distention and luminal bisacodyl, associated with 50.3% anal sphincter relaxation at baseline, which significantly increased to 59.0% after a meal, and 69.1% after bisacodyl. Often, full relaxation was achieved. The SPWs associated with gas expulsion had a significantly higher amplitude compared to SPWs without gas expulsion. SPWs could be seen to consist of clusters of high frequency pressure waves, likely associated with a cluster of fast propagating, circular muscle contractions. SPWs were occasionally observed in a highly rhythmic pattern at 1.8 ± 1.2 cycles/min. Unlike HAPWs, the SPWs did not obliterate haustral boundaries thereby explaining how gas can be expelled while solid content can remain restrained by the haustral boundaries. In conclusion, the SPW may become a biomarker for normal gas transit, the gastrocolonic reflex and extrinsic neural reflexes. The SPW assessment reveals coordination of activities in the colon, rectum and anal sphincters. SPWs may become of diagnostic value in patients with colonic dysmotility.

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.

Anatomical and Functional Changes to the Colonic Neuromuscular Compartment after Experimental Spinal Cord Injury

A profound reduction in colorectal transit time accompanies spinal cord injury (SCI), yet the colonic alterations after SCI have yet to be understood fully. The loss of descending supraspinal input to lumbosacral neural circuits innervating the colon is recognized as one causal mechanism. Remodeling of the colonic enteric nervous system/smooth muscle junction in response to inflammation, however, is recognized as one factor leading to colonic dysmotility in other pathophysiological models. We investigated the alterations to the neuromuscular junction in rats with experimental high-thoracic (T3) SCI. One day to three weeks post-injury, both injured and age-matched controls underwent in vivo experimentation followed by tissue harvest for histological evaluation. Spontaneous colonic contractions were reduced significantly in the proximal and distal colon of T3-SCI rats. Histological evaluation of proximal and distal colon demonstrated significant reductions of colonic mucosal crypt depth and width. Markers of intestinal inflammation were assayed by qRT-PCR. Specifically, Icam1, Ccl2 (MCP-1), and Ccl3 (MIP-1α) mRNA was acutely elevated after T3-SCI. Smooth muscle thickness and collagen content of the colon were increased significantly in T3-SCI rats. Colonic cross sections immunohistochemically processed for the pan-neuronal marker HuC/D displayed a significant decrease in colonic enteric neuron density that became more pronounced at three weeks after injury. Our data suggest that post-SCI inflammation and remodeling of the enteric neuromuscular compartment accompanies SCI. These morphological changes may provoke the diminished colonic motility that occurs during this same period, possibly through the disruption of intrinsic neuromuscular control of the colon.

Outcomes and prognostic factors of fecal microbiota transplantation in patients with slow transit constipation: results from a prospective study with long-term follow-up

Background and aim

Gut microbiota may contribute to regulate colonic motility, which is involved in the etiology of constipation. Fecal microbiota transplantation (FMT) has been demonstrated to restore intestinal homeostasis. The aim of this study was to evaluate the clinical outcomes and prognostic factors of FMT for the treatment of slow transit constipation (STC).

Methods

Fifty-two patients with STC received standardized FMT and were followed up for 6 months. Bowel habit, colonic transit time, constipation-related symptoms (PAC-SYM score), quality of life (PAC-QOL score), treatment satisfaction scores and adverse events were monitored. The primary efficacy endpoint was the proportion of patients having on average three or more complete spontaneous bowel movements (CSBMs) per week.

Results

The primary efficacy endpoint was achieved in 50.0%, 38.5% and 32.7% of patients over week intervals 3-4, 9-12 and 21-24, respectively (P < 0.01 for all comparisons). Significant improvements were also observed in other bowel movement assessments, colonic transit time, constipation-related symptoms and quality of life; but all improvements diminished at weeks 12 and 24. Incompleteness of evacuation served as the only factor associated with efficacy. No serious treatment-related adverse events were observed.

Conclusion

This study suggested FMT was effective and safe for STC, while a late loss of efficacy was also observed. A lower degree of sensation of incompleteness predicted a better outcome.

Inhibitory action of oxytocin on spontaneous contraction of rat distal colon by nitrergic mechanism: involvement of cyclic GMP and apamin-sensitive K+ channels

AIM

The mechanisms underlying the inhibitory effects of oxytocin (OT) on colon tone are not totally understood. We explore the mechanisms of OT on spontaneous contractility in rat distal colon and identify the mediators involved in this action.

METHODS

In rat distal colon strips, mechanical activity was analysed and the production of nitric oxide (NO) in tissue loaded with the fluorochrome DAF-FM was visualized by confocal microscopy. OT receptor (OTR) expression was determined by Western blotting and immunofluorescence.

RESULTS

In rat distal colon, OT produced a concentration-dependent reduction in the spontaneous contraction, which was abolished by the OTR antagonist atosiban, the neural blocker tetrodotoxin and the inhibitor of neuronal nitric oxide synthase (nNOS) NPLA. The inhibitory effects of OT were not affected by propranolol, atropine, the nicotinic cholinoceptor blocker hexamethonium, the vasoactive intestinal peptide receptor antagonist VIPHyb, the P₂ purinoceptor antagonist PPADS, the adenosine A1 receptors antagonist DPCPX and the prostacyclin receptor antagonist Ro1138452. The soluble guanylyl cyclase (sGC) inhibitor ODQ and the small conductance Ca²⁺ -activated K⁺ (_Ca K⁺ ) channels blocker apamin significantly reduced the relaxation induced by OT, nicotine, sodium nitroprusside and the sGC activator BAY 41-2272. The neural release of NO elicited by OT was prevented by NPLA, tetrodotoxin and atosiban. The presence of the OTR and its co-localization with nNOS was detected by immunohistochemistry and Western blotting experiments.

CONCLUSION

These results demonstrate the NO release from enteric neurones induced by activation of OTR mediates distal colon relaxation. sGC and small conductance _Ca K⁺ channels are involved in this relaxation.