Colonic Contractions Research Articles

A porcine model of opioid-induced constipation: colon motility characterization and evidence for intestinal opioid receptor modulation

Background: About 41-81% of non-cancer patients receiving opioid analgesics for chronic pain develop opioid induced constipation (OIC). Response of OIC to currently available first line therapies is inadequate and prescription drugs come with side effects. Knowledge on the specific effects of chronic opioids on gut motility mechanisms involved isincomplete. Goal: Develop OIC model and characterize gut motility and colonic opioid receptor (OR) modulation in a high translational value porcine model. Methods: The influence of loperamide, a preferential m-OR agonist, on colon motility, intestinal transit, fecal water content (FWC) and colonic OR expression was studied in Yucatan pigs (adult, male and female) naïve or fitted with a chronic cecal cannula. Loperamide was given orally at 0.2, 0.4, and 3 mg/kg/day for 15-30 days in regular diet mixed with palatants (bananas, marshmallows or yogurt mixed with honey). Manometry recordings of the proximal (pc) and distal (dc) colon motility were done using Millar pressure probes placed in each region (4-5 probes, sensors 3cms apart) in awake pigs with chronic cecal cannulas (n=3). In the same pigs, we tested the effect of the luminal stimulator VibrabotTM (30 min or 18 h) on colon motility and FWC under control and loperamide-induced constipation (1, 2 or 3 days). VibrabotTM was inserted into the proximal colon through the cecal cannula. Colonic tissues were collected and mOR expression was assessed using RNAscope. Results: Colon contraction frequency analysis shows region-specific differential effects of loperamide with an increased activity in the proximal and reduced activity in the distal colon. At the highest dose, it causes selective suppression of 5 cpm peak frequency while inducing 3 cpm peak. Loperamide (0.4mg/kg/day) reduces FWC (69.5±0.9 vs 75.9±0.9, p<0.001), and VibrabotTM stimulation (18-hours) reverses the loperamide-induced decreased FWC (74.7±3.3 vs 69.5±0.0.9). ORs are expressed differentially in the proximal vs distal colon (3.5±0.5 vs 4.6±0.8 dot/cell). Loperamide (0.4 or 3mg/kg/day, 30 days) induces an upregulation of colonic mOR expression (3.1±0.8 vs 4.4±1.2 & 4.3±0.6 dot/cell,). Conclusions: Loperamide in pigs causes constipation as shown by decreased FWC, differential effects on proximal vs distal colon contraction frequency power, with an overall inhibition of motility, while increasing m OR expression in both proximal and distal colon. Whether the differential expression of m OR in the different regions and layers of the colon contribute to the regional differences in motility needs further studies. Prolonged luminal stimulation of the colon with VibrabotTM reverses loperamide-induced decreased FWC. We established a model of OIC in pigs that has high face and construct validity as it is characterized by decreased FWC and alterations of colonic motility patterns akin to that reported in some chronic constipation patients. Supported by NIH SPARC OT2-OD024899. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A novel model of adenine-induced chronic kidney disease-associated gastrointestinal dysfunction in mice: The gut-kidney axis

Although constipation is a common complication of chronic kidney disease (CKD), there is no animal model that can be used to study the association between renal impairment and gastrointestinal function without interfering with the gastrointestinal tract of the model. Therefore, we determined whether adenine could induce CKD in association with gastrointestinal dysfunction. Six-week-old ICR mice were intraperitoneally injected with saline, 25, 50, or 75 mg adenine/kg body weight for 21 days. Blood urea nitrogen (BUN), plasma creatinine, and renal histopathology were evaluated. Defecation status was evaluated from defecation frequency and fecal water content. Colonic smooth muscle contraction was measured by the organ bath technique, and transepithelial electrical resistance (TEER) was measured using an Ussing chamber. In the 50 mg/kg treatment group, BUN and creatinine were significantly increased compared with control, and inflammatory cell infiltration, glomerular necrosis, tubular dilatation, and interstitial fibrosis were observed in renal tissues. Mice in this group also showed a significant decrease in defecation frequency, fecal water content, colonic motility index, and TEER. Overall, 50 mg/kg of adenine was the best dose to induce CKD with associated constipation and intestinal barrier impairment. Therefore, this adenine administration model can be recommended for CKD-associated gastrointestinal dysfunction research.

Intravenous Immunoglobulin Therapy for Autoimmune Dysautonomia in children: A Case Series (P10-5.013)

<h3>Objective:</h3> To assess the efficacy of intravenous immunoglobulin (IVIG) therapy in Autoimmune Dysautonomia <h3>Background:</h3> IVIG has been successfully used in the past for pain management and Autoimmune Gastric Dysmotility Disorder (AGID) of adult patients with suspected autoimmune etiology. However, the literature on efficacy of IVIG in children is scarce. <h3>Design/Methods:</h3> A retrospective review of AGID patients treated with IVIG was conducted. All symptoms were reviewed. <h3>Results:</h3> Patient 1 was positive for IgM TS-HDS Ab. Patients 2 and 3 were positive for Neuronal Acetylcholine Receptor Ganglionic (alpha-3) Ab. Patients 1 and 2 had Small Fiber Neuropathy diagnosis. Age at diagnosis of patients 1, 2, and 3 were 14, 17.25, and 16.5 years, respectively. Duration of treatment for patient 3 was 6 months, and 1 year for patients 1 and 2. Post treatment, patient 1 did not require venting of J tube; though still dependent on Total Parenteral Nutrition (TPN). Patient 1 is no longer dependent on enemas, as distal colonic and antroduodenal contractions have normalized. Esophageal dysmotility remains unchanged. Abdominal pain and distention, Postural Orthostatic Tachycardia Syndrome (POTS), and neuropathic pain improved. Patient 2 presented with intractable vomiting and POTS. She was dependent on Nasogastric tube (NG) feedings due to vomiting and was on cyproheptadine, erythromycin, bethanechol, amitriptyline, and prucalopride. Post treatment, vomiting resolved and all but prucalopride were discontinued. Colonic motility has not been re-assessed, however constipation, abdominal distention, and pain resolved. Polyethylene glycol and Bisacodyl were discontinued. Likewise, her POTS resolved. Patient 3 had hyperadrenergic POTS, persistent vomiting, and constipation, suffering a 4 kg weight loss. Following treatment, her vomiting and constipation improved, regaining 3.5 kg. Activity levels and orthostatic dizziness improved, and midodrine and fludrocortisone were discontinued. <h3>Conclusions:</h3> IVIG is an effective treatment for autoimmune dysautonomia in patients with positive IgM TS-HDS Ab and N-AchR Ganglionic (alpha-3) Ab. <b>Disclosure:</b> Mr. Bolufer has nothing to disclose. Dr. Prakash has nothing to disclose.

Colonic motility adjustments in acute and chronic DSS-induced colitis

AimsInflammatory bowel disease is recurrent inflammation that affects the gastrointestinal tract causing changes in intestinal motility. The evolution of these changes is not completely understood. The aim of this study was to evaluate anatomical and functional changes in the colon during the development of acute and chronic DSS-induced ulcerative colitis (UC) in C57Bl/6 mice. Materials and methodsMice were relocated into 5 groups: control (GC) and groups exposed to DSS 3 % for 2 (DSS2d), 5 (DSS5d) and 7 DSS7d) days (acute UC) or 3 cycles (DSS3C; Chronic UC). Mice were monitored daily. After euthanasia, colonic tissue was assessed with histological, immunofluorescence and colon manometry methods. Key findingsUlcerative Colitis is a chronic disease characterized by overt inflammation of the colon. Here we investigate whether the morphological changes caused by UC in the colonic wall, in tuft cells and in enteric neurons also promote any alteration in colonic motility patterns. UC Promotes thickening in the colonic wall, fibrosis, reduction in the number of tuft cells and consequently goblet cells also, without promoting neuronal death however there is a change in the chemical code of myenteric neurons. All of these morphological changes were responsible for causing a change in colonic contractions, colonic migration motor complex, total time of gastrointestinal transit and therefore promoting dysmotility. Further studies stimulating a hyperplasia of tuft cells may be the way to try to keep the colonic epithelium healthy, reducing the damage caused by UC. SignificanceIncreasing disease pathology of DSS-induced UC induces structural and neuroanatomical changes and driven damage to cholinergic neurons causes colonic dysmotility, including increase of cholinergic myenteric neurons, followed by variations in the motility pattern of different regions of the colon that taking together characterize colonic dysmotility.

Effects and underlying mechanisms of L-arginine on spontaneous muscle contraction of rat colon.

Arginine (Arg), as a basic amino acid, has been reported to be involved in regulation of gut motility. However, the evidence is limited and the underlying mechanism is not fully understood. Our study was conducted to investigate the effects of L-Arg on spontaneous contraction of the longitudinal muscle strip (LMS) of the rat colon and the relevant mechanisms. An organ bath system was used to detect the contractile force of the LMS. Whole-cell voltage-clamp techniques were applied to observe alterations in the currents of large conductance Ca2+-activated K+ (KCa) channels, voltage-dependent potassium (KV) channels, and L-type Ca2+ channels (LTCCs) in smooth muscle cells (SMCs) of the colon. We found that L-Arg within the physiological concentration had no effect on contraction of LMS, while 1mM L-Arg significantly increased both the amplitude and frequency of LMS contractility. And the increase in force was mucosa-dependent, whereas changes in frequency as well as in amplitude were inhibited by atropine. In addition, L-Arg (1mM) activated the LTTCs and inhibited both KCa channels and KV channels on SMCs. Thus, L-Arg above the physiological concentration exerted an excitatory effect on colonic LM contraction, and stimulation by L-Arg was mediated by ACh. In addition, LTCCs, KCa channels, and KV channels on SMCs were involved in the action of L-Arg.

Effects of PAR2 Gene Knockout on Visceral Sensitivity, Stress Behaviors, and Colonic Electrical Activities in Irritable Bowel Syndrome.

Irritable bowel syndrome (IBS) could seriously affect the patient's health quality by its recurrence. There is a great medical and social need to explore the mechanisms and new treatment strategies of IBS. To explore the influence of protease-activated receptor 2 (PAR2) gene knockout on IBS visceral sensitivity, stress behaviors, and colonic electrical activities. The PAR2 gene knockout and IBS model rats were generated and divided into PAR2+/+ wild control (WC) group, PAR2+/+ wild IBS model (WM) group, PAR2-/- knockout control (KC) group and PAR2-/- knockout IBS model (KM) group. The stress behaviors scores, minimum rectal fluid injection capacity threshold value of abdominal withdrawal reflex (AWR) = 3, and the colonic electrical activities indexes were recorded and the experimental results were analyzed statistically. (1) PAR2 gene deletion and IBS models were successfully generated. (2) The scores of aggressive and exploratory behaviors in WM and KM groups were higher than WC and KC groups (p < 0.05). The grooming behavior scores in WC and KC groups were higher than the WM and KM groups (p < 0.05). WM group had the highest aggressive and exploratory behavior scores; WC group had the highest grooming behavior scores. (3) The minimum rectal fluid injection capacity threshold value of AWR = 3 in WM and KM groups were lower than WC and KC groups (p < 0.05); WM group had the lowest value. (4) The maximum amplitude and wave frequency of colonic fast and slow waves in WM and WC groups were greater than in the KM and KC groups, respectively (p < 0.05). The amplitude index and number of colonic contraction waves in WM and KM groups were greater than the WC and KC groups (p < 0.05). Colonic electrical activity indexes were highest in the WM group. The PAR2 gene deletion could have a beneficial effect on visceral sensitivity, stress behaviors and colonic electrical activities in rats with IBS.

Stimulatory Effect of Lactobacillus Metabolites on Colonic Contractions in Newborn Rats.

Microbiota are known to play an important role in gastrointestinal physiology and pathophysiology. Microbiota and their metabolites can affect gut motility, neural regulation and the enteric endocrine systems and immune systems of the gut. The use of fermented/hydrolyzed products may be a promising new avenue for stimulating gastrointestinal motility. The purpose of this study was to investigate the effect of lactobacillus metabolites (PP), produced using a U.S.-patented fermentation method, on rat colon motility in vitro. The distal colon was incised from newborn male Wistar rats. A sensitive tensometric method for the study of colon contractions was used. The [Ca2+]i in colon tissue was registered using a computerized ratiometric system for an intracellular ion content assay (Intracellular Imaging and Photometry System, Intracellular imaging, Inc. Cincinnati, OH, USA). The cumulative addition of PP induced contraction with sigmoid dose responses with ED50 = 0.13 ± 0.02% (n = 4), where 10% PP was accepted as a maximal dose. This contraction was accompanied by an increase in the concentration of [Ca2+]i. It was shown that introducing Lactobacillus metabolites produced using a U.S.-patented fermentation method quickly stimulates dose-dependent colon contractions and an increase in intracellular calcium. The direct application of PP via enema to the colon could stimulate colon motility and suppress pathogenic microbiota, owing to the antagonistic property of PP on pathogens.

Mechanistic Study of Coffee Effects on Gut Microbiota and Motility in Rats.

Consumption of coffee has benefits in postoperative ileus. We tested the hypothesis that the benefits may be related to the effects of coffee on gut microbiota and motility and studied the mechanisms of action in rats. The in vitro and in vivo effects of regular and decaffeinated (decaf) coffee on gut microbiota of the ileum and colon were determined by bacterial culture and quantitative RT-PCR. Ileal and colonic smooth muscle contractility was determined in a muscle bath. In the in vivo studies, coffee solution (1 g/kg) was administered by oral gavage daily for 3 days. Compared to regular LB agar, the growth of microbiota in the colon and ileal contents was significantly suppressed in LB agar containing coffee or decaf (1.5% or 3%). Treatment with coffee or decaf in vivo for 3 days suppressed gut microbiota but did not significantly affect gut motility or smooth muscle contractility. However, coffee or decaf dose-dependently caused ileal and colonic muscle contractions in vitro. A mechanistic study found that compound(s) other than caffeine contracted gut smooth muscle in a muscarinic receptor-dependent manner. In conclusion, coffee stimulates gut smooth muscle contractions via a muscarinic receptor-dependent mechanism and inhibits microbiota in a caffeine-independent manner.

Dysregulated cystathionine-β-synthase/hydrogen sulfide signaling promotes chronic stress-induced colonic hypermotility in rats.

Hydrogen sulfide (H2 S), an important endogenous gasotransmitter, is involved in the modulation of gastrointestinal motility, but whether it mediates the intestinal dysmotility in irritable bowel syndrome (IBS) is not known. This study explored the significance of cystathionine-β-synthase (CBS)/H2 S signaling in stress-induced colonic dysmotility. A rat model of IBS was established using chronic water avoidance stress (WAS). Colonic pathological alterations were detected histologically. Intestinal motility was determined by intestinal transit time (ITT) and fecal water content (FWC). Visceral sensitivity was assessed using the visceromotor response (VMR) to colorectal distension (CRD). Real-time PCR, Western blotting, and immunostaining were performed to identify the expression of CBS in the colon. The contractions of distal colon were studied in an organ bath system and H2 S content was measured by ELISA. The effects of SAM, a selective CBS activator, on colonic dysmotility were examined. MEK1 was tested as a potential upstream effector of CBS/H2 S loss. After 10 days of WAS, the ITT was decreased and FWC was increased, and the VMR magnitude in response to CRD was enhanced. The colonic CBS expression and H2 S levels were significantly declined in WAS-exposed rats, and the density of CBS-positive enteric neurons in the myenteric plexus in WAS-treated rats was lower than that in controls. SAM treatment relieved WAS-induced colonic hypermotility via increased H2 S production. AZD6244, a selective inhibitor of MEK1, partially reversed CBS downregulation and colonic hypermotility in WAS-treated rats. Decreased CBS/H2 S signaling through increased MEK1 signaling might be important in the pathogenesis of chronic stress-induced colonic hypermotility. SAM could be administered for disorders associated with intestinal hypermotility.

Role of Hydrogen Sulfide in the Development of Colonic Hypomotility in a Diabetic Mouse Model Induced by Streptozocin.

Hydrogen sulfide (H2S), a novel gasotransmitter, is involved in the regulation of gut motility. Alterations in the balance of H2S play an important role in the pathogenesis of diabetes. This study was conducted to investigate the role of H2S in the colonic hypomotility of mice with streptozotocin (STZ)-induced diabetes. A single intraperitoneal injection of STZ was used to induce the type 1 diabetes model. Male C57BL/6 mice were randomized into a control group and an STZ-treated group. Immunohistochemistry, Western blotting, H2S generation, organ bath studies and whole-cell patch clamp techniques were carried out in single smooth muscle cells (SMCs) of the colon. We found that STZ-induced diabetic mice showed decreased stool output, impaired colonic contractility, and increased endogenous generation of H2S (p < 0.05). H2S-producing enzymes were upregulated in the colon tissues of diabetic mice (p < 0.05). The exogenous H2S donor sodium hydrosulfide (NaHS) elicited a biphasic action on colonic muscle contraction with excitation at lower concentrations and inhibition at higher concentrations. NaHS (0.1 mM) increased the currents of voltage-dependent calcium channels (VDCCs), while NaHS at 0.5 mM and 1.5 mM induced inhibition. Furthermore, NaHS reduced the currents of both voltage-dependent potassium (KV) channels and large conductance calcium-activated potassium (BK) channels in a dose-dependent manner. These results show that spontaneous contraction of colonic muscle strips from diabetic mice induced by STZ was significantly decreased, which may underlie the constipation associated with diabetes mellitus (DM). H2S overproduction with subsequent suppression of muscle contraction via VDCCs on SMCs may contribute in part to the pathogenesis of colonic hypomotility in DM. SIGNIFICANCE STATEMENT: Hydrogen sulfide may exhibit a biphasic effect on colonic motility in mice by regulating the activities of voltage-dependent calcium channels and voltage-dependent and large conductance calcium activated potassium channels. H2S overproduction with subsequent suppression of muscle contraction via VDCCs may contribute to the pathogenesis of colonic hypomotility in diabetes mellitus.

Chronic jetlag reprograms gene expression in the colonic smooth muscle layer inducing diurnal rhythmicity in the effect of bile acids on colonic contractility.

Secondary bile acids entrain peripheral circadian clocks and inhibit colonic motility via the bile acid receptor GPBAR1. We aimed to investigate whether chronodisruption affected the rhythm in serum bile acid levels and whether this was associated with alterations in clock gene and Gpbar1 mRNA expression in the colonic smooth muscle layer. We hypothesized that this in turn may affect the rhythm in the inhibitory effect of secondary bile acids on colonic contractility. Mice were exposed to 4 weeks of chronic jetlag induction. The expression of Gpbar1 and clock genes was measured in colonic smooth muscle tissue using RT-qPCR over 24 h (4h time interval). The effect of secondary bile acids on electrical field-induced neural contractions was measured isometrically in colonic smooth muscle strips. Chronic jetlag abolished the rhythmicity in serum bile acid levels. This was associated with a phase-shift in diurnal clock gene mRNA fluctuations in smooth muscle tissue. Chronic jetlag induced a rhythm in Gpbar1 expression in the colonic smooth muscle layer. In parallel, a rhythm was induced in the inhibitory effect of taurodeoxycholic acid (TDCA), but not deoxycholic acid, on neural colonic contractions that peaked together with Gpbar1 expression. Chronodisruption abolished the rhythm in bile acid levels which might contribute to a shift in smooth muscle clock gene expression. Our findings suggest that chronodisruption caused a transcriptional reprogramming in the colonic smooth layer thereby inducing a rhythm in the expression of Gpbar1 and in the inhibitory effect of TDCA on colonic contractility.

Elucidation of a Novel Mechanism of Perioperative and Postoperative Ileus: Microvascular Leak of Serum Immunoglobulins Directly Activates Inhibitory Nitrergic Neuromuscular Transmission, Causing Ileus

INTRODUCTION: Postoperative ileus delays enteral feeding, increases morbidity, prolongs hospitalization, and increases cost. Prevailing hypotheses are that anesthesia plays a major role in perioperative ileus and inflammation causes postoperative ileus. However, the direct causative mechanism of ileus is still unknown. Our goal was to delineate the components of an abdominal operative procedure on ileus and elucidate a major causative mechanism. METHODS: Five groups of C57Bl/6 were used: control, anesthesia, incision, laparotomy, and intestinal manipulation (IM), (N = 4 each). Gastrointestinal transit (GIT) with geometric center (GC) calculation was assessed immediately after resuscitation and after 24 hours. IM consisted of “running the bowel”. Circular muscle contractility assessed using an organ bath. Jejunal and colonic segments with fluorophore illuminated microvasculature were imaged by confocal microscopy. RESULTS: GIT for each component of the immediate perioperative ileus response was: anesthesia 25.7%, incision 13.6%, laparotomy 15.2% and IM 45.5%. Anesthesia decreased GIT, which rapidly waned. Only IM 24-hour postoperative GIT remained delayed (GC = 4.2 ± 0.52). Contractility was only significantly suppressed in IM 24-hour group. Imaging of control jejunal and colonic segments demonstrated illuminated microvasculature fluorophore containment. Vascular leak was prominent in IM immediate and IM 24-hour groups. Intraperitoneal serum injection (250µl) caused an immediate transit delay. Jejunal and colonic muscle spontaneous contraction was significantly inhibited by 1% serum, which was blocked with L-nitro-arginine (100µM). L-protein Ig elution and exogenous IgG abolished contractions. CONCLUSION: The data demonstrate that perioperative and postoperative ileus is mechanistically caused by the microvascular leak of serum immunoglobulin triggering a nitrergic neuromuscular suppression of motility.

Altered functional responses by PAR1 agonist in murine dextran sodium sulphate-treated colon

Protease-activated receptor-1 (PAR1) is highly expressed in murine colonic smooth muscles. Responses to PAR1 activation are complex and result from responses in multiple cell types. We investigated whether PAR1 responses are altered in inflamed colon induced by dextran sodium sulfate (DSS)-treatment. Colitis was induced in C57BL/6 mice by administration of 3% DSS in drinking water for 7 days. Measurements of isometric force, transmembrane potentials from impaled smooth muscle cells, quantitative PCR and Western blots were performed. Thrombin, an activator of PAR1, caused transient hyperpolarization and relaxation of untreated colons, but these responses decreased in DSS-treated colons. Apamin caused depolarization and increased contractions of muscles from untreated mice. This response was decreased in DSS-treated colons. Expression of Kcnn3 and Pdgfra also decreased in DSS-treated muscles. A second phase of thrombin responses is depolarization and increased contractions in untreated muscles. However, thrombin did cause depolarization in DSS-treated colon, yet it increased colonic contractions. The latter effect was associated with enhanced expression of MYPT1 and CPI-17. The propagation velocity and frequency of colonic migrating motor complexes in DSS-treated colon was significantly higher compared to control colons. In summary, DSS treatment causes loss of transient relaxations due to downregulation of SK3 channels in PDGFRα+ cells and may increase contractile responses due to increased Ca2+ sensitization of smooth muscle cells via PAR1 activation.

Bio-impedance method to monitor colon motility response to direct distal colon stimulation in anesthetized pigs

Electrical stimulation has been demonstrated as an alternative approach to alleviate intractable colonic motor disorders, whose effectiveness can be evaluated through colonic motility assessment. Various methods have been proposed to monitor the colonic motility and while each has contributed towards better understanding of colon motility, a significant limitation has been the spatial and temporal low-resolution colon motility data acquisition and analysis. This paper presents the study of employing bio-impedance characterization to monitor colonic motor activity. Direct distal colon stimulation was undertaken in anesthetized pigs to validate the bio-impedance scheme simultaneous with luminal manometry monitoring. The results indicated that the significant decreases of bio-impedance corresponded to strong colonic contraction in response to the electrical stimulation in the distal colon. The magnitude/power of the dominant frequencies of phasic colonic contractions identified at baseline (in the range 2–3 cycles per minute (cpm)) were increased after the stimulation. In addition, positive correlations have been found between bio-impedance and manometry. The proposed bio-impedance-based method can be a viable candidate for monitoring colonic motor pattern with high spatial and temporal resolution. The presented technique can be integrated into a closed-loop therapeutic device in order to optimize its stimulation protocol in real-time.

Effect of electroacupuncture on colonic motility and RhoA and ROCK protein expression in IBS-D rats

To observe the effect of electroacupuncture (EA) of "Tianshu"(ST25) and "Shangjuxu"(ST37)on gastrointestinal motility, psychological abnormality and expression of RhoA and ROCK protein in rats with diarrhea predominant irritable bowel syndrome (IBS-D), so as to explore its underlying mechanism in improving IBS-D. Thirty-six male rats were randomly and equally divided into control, model, EA and medication groups (n=9 in each group). The IBS-D model with psychological abnormality was established by gavage of dinitrobenzene sulfonic acid (DNBS) + chronic restraint stress. EA (2 Hz/100 Hz, 0.3 mA) was applied to bilateral ST25 and ST37 for 20 min, once a day for 7 days. Rats of the medication group received gavage of pinaverium bromide solution (15 mg/kg), once a day for 7 days. The rats' food intake in 24 h, body mass and colonic contraction waves were recorded. The anhedonia-related behavior was measured using the sucrose consumption test. The elevated plus maze test (the open-arm residence time ratio) was used to assess the anxiety-like behavior. The small intestinal propulsion rate test was used to assess the intestinal motility. The expression levels of RhoA and ROCK proteins in the colonic tissue were measured by Western blot. After modeling, the body mass, food consumption, sucrose preference index, the open-arm residence time ratio andlatency of colonic contraction waves were significantly decreased (P<0.05), and the number of contraction waves, intestinal propulsive rate, and the expression levels of RhoA and ROCK proteins considerably increased (P<0.01，P<0.05) in the model group relevant to the control group. Following the interventions, the decrease of body mass, food consumption, sucrose preference index, open-arm residence time ratio and latency of contraction waves, and the increase of the contraction waves, intestinal propulsive rate, and the expression levels of RhoA and ROCK proteins were all reversed by both EA and medication (P<0.05，P<0.01). The effect of EA was significantly superior to that of medication in increasing the sucrose pre-ference index (P<0.05). EA can improve both colonic motility and psychological disorders in IBS-D rats with psychological disorder, which may be related to its function in down-regulating the expression of colonic RhoA and ROCK proteins.

Faecal incontinence is associated with an impaired rectosigmoid brake and improved by sacral neuromodulation.

The rectosigmoid brake, characterised by retrograde cyclic motor patterns on high-resolution colonic manometry, has been postulated as a contributor to the maintenance of bowel continence. Sacral neuromodulation (SNM) is an effective therapy for faecal incontinence, but its mechanism of action is unclear. This study aims to investigate the colonic motility patterns in the distal colon of patients with faecal incontinence, and how these are modulated by SNM. A high-resolution fibreoptic colonic manometry catheter, containing 36 sensors spaced at 1-cm intervals, was positioned in patients with faecal incontinence undergoing stage 1 SNM. One hour of pre- and post meal recordings were obtained followed by pre- and post meal recordings with suprasensory SNM. A 700-kcal meal was given. Data were analysed to identify propagating contractions. Fifteen patients with faecal incontinence were analysed. Patients had an abnormal meal response (fewer retrograde propagating contractions compared to controls; p= 0.027) and failed to show a post meal increase in propagating contractions (mean 17 ± 6/h premeal vs. 22 ± 9/h post meal, p= 0.438). Compared to baseline, SNM significantly increased the number of retrograde propagating contractions in the distal colon (8± 3/h premeal vs. 14 ± 3/h premeal with SNM, p= 0.028). Consuming a meal did not further increase the number of propagating contractions beyond the baseline upregulating effect of SNM. The rectosigmoid brake was suppressed in this cohort of patients with faecal incontinence. SNM may exert a therapeutic effect by modulating this rectosigmoid brake.

The excitatory effect of hydrogen sulfide on rat colonic muscle contraction and the underlying mechanism

H2S is a well-known relaxant regulator in muscle contraction but little attention has been paid to its excitatory effect on colonic motility. To investigate the excitation of H2S on rat colonic contraction and the underlying mechanism, the muscle contractile activity was assessed by an organ bath system, the level of substance P (SP) in the colon was detected using enzyme immunoassay kits, L-type Ca2+ channel currents (ICa,L) and large conductance Ca2+-activated K+ channel currents (IBK) in smooth muscle cells (SMCs) were measured by patch-clamp electrophysiology. The results show that the H2S donor NaHS (100 μM) reversed the relaxation of the NO donor SNP on colonic muscle contraction. Pretreatment with the TRPV1 antagonist and the neurokinin receptor antagonists attenuated the NaHS-induced excitation. Incubation of colon with NaHS increased the SP level. In freshly isolated SMCs, NaHS exerted a biphasic effect on ICa,L and concentration-dependently inhibited the IBK. And 100 μM NaHS partially reversed the SNP-induced changes in ICa,L and IBK. We concluded that exogenous H2S exerts a potential excitatory effect on colonic motility, which may be achieved by activating SP release from afferent nerves in combination with a direct activation of ICa,L and suppression of IBK in SMCs.

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.

Microbiome biomarkers associated with the gut contraction response elicited by the Japanese traditional medicine daikenchuto

Objective biomarkers are crucial in the development of personalized medicines, such as Japanese traditional medicine (Kampo). To date, some objective markers to predict the response of Kampo medicines have been reported, but the information is somewhat limited. The aim of this study was to search for objective markers and combinations thereof to estimate the effect of the Japanese traditional medicine daikenchuto (DKT) on colon contraction intensity in guinea pigs. Specifically, the microbiome biomarkers were employed as candidate, using the Fisher ratio and the nearest neighbor classifier for statistical pattern recognition. The combination of the ratio between gut microbes of family Ruminococcaceae/Rikenellaceae, Ruminococcaceae/Paraprevotellaceae, and genus Ruminococcus/unknown genus in family Rikenellaceae of guinea pig gut microbes was found to influence the activity of DKT with 0.8 accuracy for test samples. These findings suggest that statistical pattern recognition can contribute to identifying target markers of multi-target drugs such as Kampo.

Gastrocolic Reflex Is Delayed and Diminished in Adults with Type 1 Diabetes.

Constipation is a prevalent gastrointestinal complication in diabetes. The pathophysiology may include neural dysfunction and impaired gastrocolic reflex; however, investigation of the latter has been limited in diabetes. Using the wireless motility capsule, we investigated whether the gastrocolic reflex was impaired in adults with type 1 diabetes compared to healthy. One hundred and four adults with type 1 diabetes underwent investigation with the wireless motility capsule and recorded sleep cycle, eating habits, and bowel movements in a diary. Colonic motility index, contraction amplitudes, time-to-peak, peak motility, and colonic transit time were investigated directly in response to a meal. Diagnosis of peripheral (nerve conduction) and autonomic (orthostatic hypotension) polyneuropathy was verified. In comparison with health, people with diabetes had at the time of ingestion decreased motility index and contraction amplitudes (p < 0.001), prolonged time-to-peak (p = 0.01), and borderline decreased peak motility (p = 0.06), which taken together indicate impaired coordination of the gastrocolic reflex. These features were most prominent in those with concomitant peripheral or autonomic neuropathy. Additionally, they were associated with prolonged colonic transit time (p > 0.01). In type 1 diabetes, the gastrocolic reflex was delayed and diminished and further associated with the presence of neuropathy and constipation. These results suggest that impaired reflex is part of the underlying pathogenesis in the development of constipation.