Firing properties of medullary expiratory neurons during fictive straining in cats

Expiratory (E) neurons in the caudal nucleus retroambigualis extend descending spinal axons to the lumbar and sacral spinal cord. Discharge rates of single E neurons were recorded to examine differences in activity of E neurons projecting to the lumbar or sacral spinal cord during fictive straining induced by distention of the colon with a balloon. Firing frequencies of E neurons with descending axons in the thoracic and lumbar spinal cord increased during the repetitive rise of rectum pressure, whereas those of E neurons with descending axons in the sacral spinal cord decreased. E neurons with descending axons in the thoracic/lumbar and sacral spinal cord exhibit different firing characteristics during the repetitive rise of rectum pressure when straining during defecation. The activity of abdominal nerves during fictive straining is in phase with changes in rectum pressure, but out of phase with the activity of E neurons.

The investigation of diet recovery after distal gastrectomy

This study aims to investigate the adaptation process of the alimentary tract after distal gastrectomy and understand the impact of remnant stomach volume (RSV) on diet recovery.One year after gastrectomy, although patients' oral intake had increased, the RSV was decreased and small bowel motility was enhanced. Patients with a larger RSV showed no additional benefits regarding nutritional outcomes.We prospectively enrolled patients who underwent distal gastrectomy with Billroth II reconstruction to treat gastric cancer at a tertiary hospital cancer center between September 2009 and February 2012. Demographic data, diet questionnaires, computed tomography (CT), and contrast fluoroscopy findings were collected. Patients were divided into 2 groups according to the RSV calculated using CT gastric volume measurements (large vs small). Dietary habits and nutritional status were compared between the groups.Seventy-eight patients were enrolled. Diet volume recovered to 90% of baseline by the 36 postoperative month, and RSV was 70% of baseline at 6 months after surgery and gradually decreased over time. One year after surgery, small bowel transit time was 75% compared to the 1st postoperative month (P < .05); however, transit time in the esophagus and remnant stomach showed no change in any studied interval. Compared to patients with a small RSV, those with a large RSV showed no differences in diet volume, habits, or other nutritional benefits (P > .05).Diet recovery for distal gastrectomy patients was achieved by increased small bowel motility. The size of the remnant stomach showed no positive impact on nutritional outcomes.

Simultaneous Determination of Biliary and Intestinal Cholesterol Secretion Reveals That CETP (Cholesteryl Ester Transfer Protein) Alters Elimination Route in Mice

OBJECTIVE

Determine the impact of CETP (cholesteryl ester transfer protein) on the route of cholesterol elimination in mice. Approach and Results: We adapted our protocol for biliary cholesterol secretion with published methods for measuring transintestinal cholesterol elimination. Bile was diverted and biliary lipid secretion maintained by infusion of bile acid. The proximal small bowel was perfused with bile acid micelles. In high-fat, high-cholesterol-fed mice, the presence of a CETP transgene increased biliary cholesterol secretion at the expense of transintestinal cholesterol elimination. The increase in biliary cholesterol secretion was not associated with increases in hepatic SR-BI (scavenger receptor BI) or ABCG5 (ATP-binding cassette G5) ABCG8. The decline in intestinal cholesterol secretion was associated with an increase in intestinal Niemann-Pick disease, type C1, gene-like 1 mRNA. Finally, we followed the delivery of HDL (high-density lipoprotein) or LDL (low-density lipoprotein) cholesteryl esters (CE) from plasma to bile and intestinal perfusates. HDL-CE favored the biliary pathway. Following high-fat feeding, the presence of CETP directed HDL-CE away from the bile and towards the intestine. The presence of CETP increased LDL-CE delivery to bile, whereas the appearance of LDL-CE in intestinal perfusate was near the lower limit of detection.

CONCLUSIONS

Biliary and intestinal cholesterol secretion can be simultaneously measured in mice and used as a model to examine factors that alter cholesterol elimination. Plasma factors, such as CETP, alter the route of cholesterol elimination from the body. Intestinal and biliary cholesterol secretion rates are independent of transhepatic or transintestinal delivery of HDL-CE, whereas LDL-CE was eliminated almost exclusively in the hepatobiliary pathway.

First translational consensus on terminology and definitions of colonic motility in animals and humans studied by manometric and other techniques

Alterations in colonic motility are implicated in the pathophysiology of bowel disorders, but high-resolution manometry of human colonic motor function has revealed that our knowledge of normal motor patterns is limited. Furthermore, various terminologies and definitions have been used to describe colonic motor patterns in children, adults and animals. An example is the distinction between the high-amplitude propagating contractions in humans and giant contractions in animals. Harmonized terminology and definitions are required that are applicable to the study of colonic motility performed by basic scientists and clinicians, as well as adult and paediatric gastroenterologists. As clinical studies increasingly require adequate animal models to develop and test new therapies, there is a need for rational use of terminology to describe those motor patterns that are equivalent between animals and humans. This Consensus Statement provides the first harmonized interpretation of commonly used terminology to describe colonic motor function and delineates possible similarities between motor patterns observed in animal models and humans in vitro (ex vivo) and in vivo. The consolidated terminology can be an impetus for new research that will considerably improve our understanding of colonic motor function and will facilitate the development and testing of new therapies for colonic motility disorders.

Quantification of gastric emptying caused by impaired coordination of pyloric closure with antral contraction: a simulation study

Proper coordination of gastric motor functions is required for healthy gastric emptying. However, pyloric function may be impaired by functional disorders or surgical procedures. Here, we show how coordination between pyloric closure and antral contraction affects the emptying of liquid contents. We numerically simulated fluid dynamics using an anatomically realistic gastrointestinal geometry. Peristaltic contractions in the proximal stomach resulted in gastric emptying at a rate of 3-8 ml min-1. When the pylorus was unable to close, the emptying rate increased to 10-30 ml min-1, and instantaneous retrograde flow from the duodenum to the antrum occurred during antral relaxation. Rapid emptying occurred if the pylorus began to open during the terminal antral contraction, and the emptying rate was negative if the pylorus only opened during the antral relaxation phase. Our results showed that impaired coordination between antral contraction and pyloric closure can result in delayed gastric emptying, rapid gastric emptying and bile reflux.

Gastrointestinal motility and absorptive disorders in patients with inflammatory bowel diseases: Prevalence, diagnosis and treatment

Inflammatory bowel diseases (IBD), Crohn`s disease and ulcerative colitis, are chronic conditions associated with high morbidity and healthcare costs. The natural history of IBD is variable and marked by alternating periods of flare and remission. Even though the use of newer therapeutic targets has been associated with higher rates of mucosal healing, a great proportion of IBD patients remain symptomatic despite effective control of inflammation. These symptoms may include but not limited to abdominal pain, dyspepsia, diarrhea, urgency, fecal incontinence, constipation or bloating. In this setting, commonly there is an overlap with gastrointestinal (GI) motility and absorptive disorders. Early recognition of these conditions greatly improves patient care and may decrease the risk of mistreatment. Therefore, in this review we describe the prevalence, diagnosis and treatment of GI motility and absorptive disorders that commonly affect patients with IBD.

Interactions Between Commensal Bacteria and Enteric Neurons, via FPR1 Induction of ROS, Increase Gastrointestinal Motility in Mice

BACKGROUND & AIMS

Reduced gastrointestinal (GI) motility is a feature of disorders associated with intestinal dysbiosis and loss of beneficial microbes. It is not clear how consumption of beneficial commensal microbes, marketed as probiotics, affects the enteric nervous system (ENS). We studied the effects of the widely used probiotic and the commensal Lactobacillus rhamnosus GG (LGG) on ENS and GI motility in mice.

METHODS

Conventional and germ free C57B6 mice were gavaged with LGG and intestinal tissues were collected; changes in the enteric neuronal subtypes were assessed by real-time polymerase chain reaction, immunoblots, and immunostaining. Production of reactive oxygen species (ROS) in the jejunal myenteric plexi and phosphorylation (p) of mitogen-activated protein kinase 1 (MAPK1) in the enteric ganglia were assessed by immunoblots and immunostaining. Fluorescence in situ hybridization was performed on jejunal cryosections with probes to detect formyl peptide receptor 1 (FPR1). GI motility in conventional mice was assessed after daily gavage of LGG for 1 week.

RESULTS

Feeding of LGG to mice stimulated myenteric production of ROS, increased levels of phosphorylated MAPK1, and increased expression of choline acetyl transferase by neurons (P < .001). These effects were not observed in mice given N-acetyl cysteine (a ROS inhibitor) or LGGΩSpaC (an adhesion-mutant strain of LGG) or FPR1-knockout mice. Gavage of mice with LGG for 1 week significantly increased stool frequency, reduced total GI transit time, and increased contractions of ileal circular muscle strips in ex vivo experiments (P < .05).

CONCLUSIONS

Using mouse models, we found that LGG-mediated signaling in the ENS requires bacterial adhesion, redox mechanisms, and FPR1. This pathway might be activated to increase GI motility in patients.

The Mechanism of Action of Ghrelin and Motilin in the Pacemaker Potentials of Interstitial Cells of Cajal from the Murine Small Intestine

Interstitial cells of Cajal (ICCs) are pacemaker cells that exhibit periodic spontaneous depolarization in the gastrointestinal (GI) tract and generate pacemaker potentials. In this study, we investigated the effects of ghrelin and motilin on the pacemaker potentials of ICCs isolated from the mouse small intestine. Using the whole-cell patch-clamp configuration, we demonstrated that ghrelin depolarized pacemaker potentials of cultured ICCs in a dose-dependent manner. The ghrelin receptor antagonist [D-Lys] GHRP-6 completely inhibited this ghrelin-induced depolarization. Intracellular guanosine 5'-diphosphate-β-S and pre-treatment with Ca2+free solution or thapsigargin also blocked the ghrelin-induced depolarization. To investigate the involvement of inositol triphosphate (IP3), Rho kinase, and protein kinase C (PKC) in ghrelin-mediated pacemaker potential depolarization of ICCs, we used the IP3 receptor inhibitors 2-aminoethoxydiphenyl borate and xestospongin C, the Rho kinase inhibitor Y-27632, and the PKC inhibitors staurosporine, Go6976, and rottlerin. All inhibitors except rottlerin blocked the ghrelin-induced pacemaker potential depolarization of ICCs. In addition, motilin depolarized the pacemaker potentials of ICCs in a similar dose-dependent manner as ghrelin, and this was also completely inhibited by [D-Lys] GHRP-6. These results suggest that ghrelin induced the pacemaker potential depolarization through the ghrelin receptor in a G protein-, IP3-, Rho kinase-, and PKC-dependent manner via intracellular and extracellular Ca2+ regulation. In addition, motilin was able to depolarize the pacemaker potentials of ICCs through the ghrelin receptor. Therefore, ghrelin and its receptor may modulate GI motility by acting on ICCs in the murine small intestine.

A Deep Convolutional Neural Network Approach to Classify Normal and Abnormal Gastric Slow Wave Initiation From the High Resolution Electrogastrogram

OBJECTIVE

Gastric slow wave abnormalities have been associated with gastric motility disorders. Invasive studies in humans have described normal and abnormal propagation of the slow wave. This study aims to disambiguate the abnormally functioning wave from one of normalcy using multi-electrode abdominal waveforms of the electrogastrogram (EGG).

METHODS

Human stomach and abdominal models are extracted from computed tomography scans. Normal and abnormal slow waves are simulated along stomach surfaces. Current dipoles at the stomachs surface are propagated to virtual electrodes on the abdomen with a forward model. We establish a deep convolutional neural network (CNN) framework to classify normal and abnormal slow waves from the multi-electrode waveforms. We investigate the effects of non-idealized measurements on performance, including shifted electrode array positioning, smaller array sizes, high body mass index (BMI), and low signal-to-noise ratio (SNR). We compare the performance of our deep CNN to a linear discriminant classifier using wave propagation spatial features.

RESULTS

A deep CNN framework demonstrated robust classification, with accuracy above 90% for all SNR above 0 dB, horizontal shifts within 3 cm, vertical shifts within 6 cm, and abdominal tissue depth within 6 cm. The linear discriminant classifier was much more vulnerable to SNR, electrode placement, and BMI.

CONCLUSION

This is the first study to attempt and, moreover, succeed in using a deep CNN to disambiguate normal and abnormal gastric slow wave patterns from high-resolution EGG data.

SIGNIFICANCE

These findings suggest that multi-electrode cutaneous abdominal recordings have the potential to serve as widely deployable clinical screening tools for gastrointestinal foregut disorders.

Effects of comfort care on symptoms, gastric motility, and mental state of patients with functional dyspepsia

Functional dyspepsia (FD) is a common upper gastrointestinal disorder globally, but the current treatments for FD are still unsatisfactory. This study was aimed at investigating the effects of comfort care on symptoms, gastric motility, and mental state of patients with FD.One hundred consecutive patients with FD treated at the Wuhan Union Hospital (Wuhan, China) between 03/2016 and 02/2018 were randomized to routine nursing and comfort care on the basis of routine nursing (50 patients/group), all for 8 weeks. The primary endpoint was FD symptom score. The secondary endpoint included gastric emptying rate, gastric motility parameters, and depression and anxiety scores. The endpoints were assessed at baseline and after 8 weeks.There were no significant differences between the 2 groups for gender, age, body mass index, types of FD, and course of disease (P > .05). The symptom score in the comfort care group at week 8 was lower than in the routine nursing group (8.3 ± 2.4 vs 10.2 ± 2.4, P < .001). The gastric emptying rate in the comfort care group at week 8 was higher than in the routine nursing group (28.6 ± 5.1 vs 24.3 ± 5.5, P < .001). The fasting and postprandial dominant frequencies of electrogastrogram in the comfort care group at week 8 were higher than in the routine nursing group (1.9 ± 0.9 vs 1.8 ± 1.0, P = .004; 3.1 ± 1.0 vs 2.1 ± 0.9, P < .001). The postprandial dominant power of electrogastrogram in the comfort care group at week 8 was higher than in the routine nursing group (55.7 ± 11.5 vs 42.3 ± 12.5, P < .001). The cases of abnormal electrogastrogram rhythm in the comfort care group at week 8 were significantly less than in the routine nursing group (P = .003). The self-rating depression scale and self-rating anxiety scale in the comfort care group at week 8 were significantly lower than in the routine nursing group (42.5 ± 6.9 vs 47.3 ± 6.4, P = .001; 41.1 ± 7.2 vs 46.3 ± 6.9, P < .001).Comfort care reduces the symptoms of patients with FD, increases gastric emptying rate, improves gastric motility, relieves patient's depression and anxiety, and promotes the rehabilitation of the disease.

Electroacupuncture at ST36 modulates gastric motility via vagovagal and sympathetic reflexes in rats

BACKGROUND

Electroacupuncture (EA) at ST36 can significantly improve gastrointestinal symptoms, especially in promoting gastrointestinal motility. The automatic nervous system plays a main role in EA, but few studies exist on how vagovagal and sympathetic reflexes affect EA to regulate gastrointestinal motility.

AIM

To study the role of vagovagal and sympathetic reflexes in EA at ST36, as well as the associated receptor subtypes that are involved.

METHODS

Gastric motility was measured with a manometric balloon placed in the gastric antrum area in anesthetized animals. The peripheral nervous discharge was measured using a platinum electrode hooking the vagus or greater splanchnic nerve, and the central nervous discharge was measured with a glass microelectrode in the dorsal motor nucleus of the vagus (DMV). The effects and mechanisms of EA at ST36 were explored in male Sprague-Dawley rats which were divided in to a control group, vagotomy group, sympathectomy group, and microinjection group [including an artificial cerebrospinal fluid group, glutamate (L-Glu) group, and γ-aminobutyric acid (GABA) group] and in genetically modified male mice [β1β2 receptor-knockout (β1β2^-/-) mice, M2M3 receptor-knockout (M2M3^-/-) mice, and wild-type control mice].

RESULTS

EA at ST36 promoted gastric motility during 30-120 s. During EA, both vagus and sympathetic nerve discharges increased, with a much higher frequency of vagus nerve discharge than sympathetic discharge. The gastric motility mediated by EA at ST36 was interdicted by vagotomy. However, gastric motility mediated by EA at ST36 was increased during 0-120 s by sympathectomy, which eliminated the delay effect of EA during 0-30 s, but it was lower than the control group during 30-120 s. Using gene knockout mice and their wild-type controls to explore the receptor mechanisms, we found that EA at ST36 decreased gastric motility in M2/3^-/- mice, and promoted gastric motility in β1/2^-/- mice. Extracellular recordings showed that EA at ST36 increased spikes of the DMV. Microinjection of L-Glu into the DMV increased gastric motility, while EA at ST36 decreased gastric motility during 0-60 s, and promoted gastric motility during 60-120 s. Injection of GABA reduced or increased gastric motility, and reduced the promoting gastric motility effect of EA at ST36.

CONCLUSION

These data suggest that EA at ST36 modulates gastric motility via vagovagal and sympathetic reflexes mediated through M2/3 and β1/2 receptors, respectively. Sympathetic nerve activity mediated through β1/2 receptors is associated with an early delay in modulation of gastric motility by EA at ST36.

Motilin: from gastric motility stimulation to hunger signalling

After the discovery of motilin in 1972, motilin and the motilin receptor were studied intensely for their role in the control of gastrointestinal motility and as targets for treating hypomotility disorders. The genetic revolution - with the use of knockout models - sparked novel insights into the role of multiple peptides but contributed to a decline in interest in motilin, as this peptide and its receptor exist only as pseudogenes in rodents. The past 5 years have seen a major surge in interest in motilin, as a series of studies have shown its relevance in the control of hunger and regulation of food intake in humans in both health and disease. Luminal stimuli, such as bitter tastants, have been identified as modulators of motilin release, with effects on hunger and food intake. The current state of knowledge and potential implications for therapy are summarized in this Review.

Characterization of the gastric motility response to human motilin and erythromycin in human motilin receptor-expressing transgenic mice

Motilin is a gastrointestinal peptide hormone that stimulates gastrointestinal motility. Motilin is produced primarily in the duodenum and jejunum. Motilin receptors (MTLRs) are G protein-coupled receptors that may represent a clinically useful pharmacological target as they can be activated by erythromycin. The functions of motilin are highly species-dependent and remain poorly understood. As a functional motilin system is absent in rodents such as rats and mice, these species are not commonly used for basic studies. In this study, we examine the usefulness of human MTLR-overexpressing transgenic (hMTLR-Tg) mice by identifying the mechanisms of the gastric motor response to human motilin and erythromycin. The distribution of hMTLR was examined immunohistochemically in male wild-type (WT) and hMTLR-Tg mice. The contractile response of gastric strips was measured isometrically in an organ bath, while gastric emptying was determined using phenol red. hMTLR expression was abundant in the gastric smooth muscle layer. Interestingly, higher levels of hMTLR expression were observed in the myenteric plexus of hMTLR-Tg mice but not WT mice. hMTLR was not co-localized with vesicular acetylcholine transporter, a marker of cholinergic neurons in the myenteric plexus. Treatment with human motilin and erythromycin caused concentration-dependent contraction of gastric strips obtained from hMTLR-Tg mice but not from WT mice. The contractile response to human motilin and erythromycin in hMTLR-Tg mice was affected by neither atropine nor tetrodotoxin and was totally absent in Ca2+-free conditions. Furthermore, intraperitoneal injection of erythromycin significantly promoted gastric emptying in hMTLR-Tg mice but not in WT mice. Human motilin and erythromycin stimulate gastric smooth muscle contraction in hMTLR-Tg mice. This action is mediated by direct contraction of smooth muscle via the influx of extracellular Ca2+. Thus, hMTLR-Tg mice may be useful for the evaluation of MTLR agonists as gastric prokinetic agents.

Central control of gastrointestinal motility

PURPOSE OF REVIEW

This review summarizes the organization and structure of vagal neurocircuits controlling the upper gastrointestinal tract, and more recent studies investigating their role in the regulation of gastric motility under physiological, as well as pathophysiological, conditions.

RECENT FINDINGS

Vagal neurocircuits regulating gastric functions are highly plastic, and open to modulation by a variety of inputs, both peripheral and central. Recent research in the fields of obesity, development, stress, and neurological disorders highlight the importance of central inputs onto these brainstem neurocircuits in the regulation of gastric motility.

SUMMARY

Recognition of the pivotal role that the central nervous system exerts in the regulation, integration, and modulation of gastric motility should serve to encourage research into central mechanisms regulating peripheral motility disorders.

Intraduodenal Administration of L-Valine Has No Effect on Antropyloroduodenal Pressures, Plasma Cholecystokinin Concentrations or Energy Intake in Healthy, Lean Men

Whey protein is rich in the branched-chain amino acids, L-leucine, L-isoleucine and L-valine. Thus, branched-chain amino acids may, at least in part, mediate the effects of whey to reduce energy intake and/or blood glucose. Notably, 10 g of either L-leucine or L-isoleucine, administered intragastrically before a mixed-nutrient drink, lowered postprandial blood glucose, and intraduodenal infusion of L-leucine (at a rate of 0.45 kcal/min, total: 9.9 g) lowered fasting blood glucose and reduced energy intake from a subsequent meal. Whether L-valine affects energy intake, and the gastrointestinal functions involved in the regulation of energy intake, as well as blood glucose, in humans, is currently unknown. We investigated the effects of intraduodenally administered L-valine on antropyloroduodenal pressures, plasma cholecystokinin, blood glucose and energy intake. Twelve healthy lean men (age: 29 ± 2 years, BMI: 22.5 ± 0.7 kg/m²) were studied on 3 separate occasions in randomised, double-blind order. Antropyloroduodenal pressures, plasma cholecystokinin, blood glucose, appetite perceptions and gastrointestinal symptoms were measured during 90-min intraduodenal infusions of L-valine at 0.15 kcal/min (total: 3.3 g) or 0.45 kcal/min (total: 9.9 g), or 0.9% saline (control). Energy intake from a buffet-meal immediately after the infusions was quantified. L-valine did not affect antral, pyloric (mean number; control: 14 ± 5; L-Val-0.15: 21 ± 9; L-Val-0.45: 11 ± 4), or duodenal pressures, plasma cholecystokinin (mean concentration, pmol/L; control: 3.1 ± 0.3; L-Val-0.15: 3.2 ± 0.3; L-Val-0.45: 3.0 ± 0.3), blood glucose, appetite perceptions, symptoms or energy intake (kcal; control: 1040 ± 73; L-Val-0.15: 1040 ± 81; L-Val-0.45: 1056 ± 100), at either load (p > 0.05 for all). In conclusion, intraduodenal infusion of L-valine, at loads that are moderately (3.3 g) or substantially (9.9 g) above World Health Organization valine requirement recommendations, does not appear to have energy intake- or blood glucose-lowering effects.

Will MRI of gastrointestinal function parallel the clinical success of cine cardiac MRI?

Cine cardiac MRI is generally accepted as the "gold-standard" for functional myocardial assessment. It only took a few years after the development of commercial MRI systems for functional cardiac imaging to be developed, with electrocardiogram (ECG)-gated cine imaging first reported in 1988. The function of the gastrointestinal (GI) tract is more complex to study compared to the heart. However, the idea of having a non-invasive tool to study the GI function that also allows the concurrent assessment of different aspects of this function has become more and more attractive in the gastroenterological field. This review summarises key literature of the last 5 years to describe the current status of MRI in respect to the evaluation of GI function, highlighting the gaps and challenges and the future prospects. As the clinical application of a new technique requires that its clinical utility is confirmed by demonstration of its ability to enable clinicians to make a diagnosis and/or predict the treatment response, this review also considers whether or not this has been achieved, and how MRI has been validated against techniques currently recognised as the gold standard in clinical practice.

Quercetin promotes gastrointestinal motility and mucin secretion in loperamide-induced constipation of SD rats through regulation of the mAChRs downstream signal

CONTEXT

Quercetin (QCT) has been known as a potential therapeutic strategy for gastrointestinal diseases because it contributes to the stabilization of mast cells, the prevention of histamine release and modulation of CaCC chloride channel.

OBJECTIVE

We investigated the laxative effect and action mechanism of QCT in Lop-induced constipation model.

MATERIALS AND METHODS

Constipation of SD rats was induced by subcutaneous injection of loperamide (Lop) (4 mg/kg weight) in 0.5% Tween 20 twice a day for three days. After 24 h, the constipation group was further treated with 1× PBS (Lop + Vehicle treated group), 10 mg/kg of QCT (Lop + LQCT treated group), 20 mg/kg of QCT (Lop + MQCT treated group) or 40 mg/kg QCT (Lop + HQCT treated group) at once. At 24 h after QCT treatment, the constipation phenotypes were measured and the transverse colon was collected from SD rats.

RESULTS

The gastrointestinal motility, the number of stools and histological structures were significantly recovered in Lop + QCT treated group compared with the Lop + Vehicle treated group. Also, above activity of epithelial cells and smooth muscle cells were regulated by the mRNA expression of the muscarinic acetylcholine receptors M2 and M3 (mAChR M2 and M3) and some mediators of their downstream signalling pathway. Finally, laxative effects of QCT on mAChR signalling pathway were significantly inhibited by the treatment of mAChR antagonist in primary smooth muscle of rat intestine cells (pRISMCs).

CONCLUSIONS

This study provides the first strong evidence that QCT can be considered an important candidate for improving chronic constipation induced by Lop treatment in animal models.

Effects of burns on gut motor and mucosa functions

This review analyzed the published studies on the effects of thermal injury on gastrointestinal motility and mucosal damage. Our strategy was to integrate all available evidence to provide a complete review on the prokinetic properties of variable reagents and the potential clinical treatment of mucosal damage and gastrointestinal dysmotility after thermal injury. We classified the studies into two major groups: studies on gastrointestinal dysmotility and studies on mucosal damage. We also subclassified the studies into 3 parts: stomach, small intestine, and colon. This review shows evidence that ghrelin can recover burn-induced delay in gastric emptying and small intestinal transit, and can protect the gastric mucosa from burn-induced injury. Oxytocin and β-glucan reduced the serum inflammatory mediators, and histological change and mucosal damage indicators, but did not show evidence of having the ability to recover gastrointestinal motility. Using a combination of different reagents to protect the gastrointestinal mucosa against damage and to recover gastrointestinal motility is an alternative treatment for thermal injury.

Spasmolytic activity of Aquilariae Lignum Resinatum extract on gastrointestinal motility involves muscarinic receptors, calcium channels and NO release

CONTEXT

Aquilariae Lignum Resinatum (ALR), the dry rhizome of Aquilaria agallocha R. (Thymelaeaeeae), has been widely used to treat emesis, stomachache and gastrointestinal dysfunction.

OBJECTIVE

This study evaluates the effects of ALR methanol extract on gastrointestinal motility (GIM) and possible mechanisms of the action involved.

MATERIALS AND METHODS

In vivo, the study evaluated the effects of ALR (200-800 mg/kg) on gastric emptying and small intestinal motility in normal and neostigmine-induced adult KM mice. The in vitro effects of ALR (0.2-1.6 mg/mL) on GIM were performed on isolated jejunum of Wistar rats, pretreated with acetylcholine (ACh), KCl, CaCl₂, and pre-incubation with l-NAME (a selective inhibitor of the nitric oxide synthase).

RESULTS

In vivo, ALR (800 mg/kg) decreased gastric emptying (70.82 ± 9.81%, p < 0.01, compared with neostigmine group 91.40 ± 7.81%), small intestinal transit (42.82 ± 3.82%, p < 0.01, compared with neostigmine group 85.53 ± 5.57%). In vitro, ALR concentration dependently decreased the contractions induced by ACh (10^-5 M) and KCl (60 mM) with respective EC₅₀ values of 0.35 and 0.32 mg/mL. The Ca²⁺ concentration-response curves were shifted by ALR to the right, similar to that caused by verapamil (the positive). The spasmolytic activity of ALR was inhibited by pre-incubation with l-NAME.

DISCUSSION AND CONCLUSIONS

ALR played a spasmolytic role in GIM, which is probably mediated through inhibition of muscarinic receptors, blockade of Ca²⁺ influx and NO release. This is the first study presenting a comprehensive description of the effects of ALR on GIM.

The role of CNP-mediated PKG/PKA-PLCβ pathway in diabetes-induced gastric motility disorder

Our previous work demonstrated that the C-type natriuretic peptide (CNP)/cyclic guanosine monophosphate (cGMP)/cyclic adenosine monophosphate (cAMP) pathway in gastric antrum smooth muscle of rats with diabetes was upregulated and played an important role in the development of diabetic gastric dysmotility. Our goal for this study was to explore the downstream signaling pathways of CNP. We found that the expressions of protein kinase G (PKG) and protein kinase A (PKA) in gastric smooth muscle tissue of rats with diabetes were significantly upregulated. The expressions of β-type phospholipase C 3(PLCβ3) and β-type phospholipase C 1(PLCβ1) protein were reduced, whereas Phosphor-PLCβ3Ser1105 (P-PLCβ3Ser1105) was increased. The inhibitory effect of CNP on gastric antral smooth muscle in diabetic rats was significantly greater than in the normal group. The content of trisphosphate inositol (IP3) in the gastric antral smooth muscle of rats with diabetes was significantly lower than that of the normal group. After blocking PKA with N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H-89, a blockage PKA), the effect of CNP on the production of IP3 was decreased, while blocking PKG with KT5823 (a blockage PKG) simultaneously, and CNP can no longer reduce the IP3 production. CNP promoted the phosphorylation of PLCβ3Ser1105, thereby inhibiting the activity of PLCβ3 in gastric smooth muscle tissue of rats with diabetes; this effect can be abolished by blocking PKA and PKG. These results suggested that CNP can decrease IP3 level in gastric smooth muscle cells and thus inhibit gastric smooth muscle contraction through PKG/PKA-PLCβ pathway, which may play an important role in the development of diabetic gastroparesis.

Different distributions of interstitial cells of Cajal and platelet-derived growth factor receptor-α positive cells in colonic smooth muscle cell/interstitial cell of Cajal/platelet-derived growth factor receptor-α positive cell syncytium in mice

AIM

To investigate the distribution and function of interstitial cells of Cajal (ICCs) and platelet-derived growth factor receptor-α positive (PDGFRα⁺) cells in the proximal and distal colon.

METHODS

The comparison of colonic transit in the proximal and distal ends was performed by colonic migrating motor complexes (CMMCs). The tension of the colonic smooth muscle was examined by smooth muscle spontaneous contractile experiments with both ends of the smooth muscle strip tied with a silk thread. Intracellular recordings were used to assess electrical field stimulation (EFS)-induced inhibitory junction potentials (IJP) on the colonic smooth muscle. Western blot analysis was used to examine the expression levels of ICCs and PDGFRα in the colonic smooth muscle.

RESULTS

Treatment with NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) significantly increased the CMMC frequency and spontaneous contractions, especially in the proximal colon, while treatment with MRS2500 increased only distal CMMC activity and smooth muscle contractions. Both CMMCs and spontaneous contractions were markedly inhibited by NPPB, especially in the proximal colon. Accordingly, CyPPA sharply inhibited the distal contraction of both CMMCs and spontaneous contractions. Additionally, the amplitude of stimulation-induced nitric oxide (NO)/ICC-dependent slow IJPs (sIJPs) by intracellular recordings from the smooth muscles in the proximal colon was larger than that in the distal colon, while the amplitude of electric field stimulation-induced purinergic/PDGFRα-dependent fast IJPs (fIJPs) in the distal colon was larger than that in the proximal colon. Consistently, protein expression levels of c-Kit and anoctamin-1 (ANO1) in the proximal colon were much higher, while protein expression levels of PDGFRα and small conductance calcium-activated potassium channel 3 (SK3) in the distal colon were much higher.

CONCLUSION

The ICCs are mainly distributed in the proximal colon and there are more PDGFRα⁺ cells are in the distal colon, which generates a pressure gradient between the two ends of the colon to propel the feces to the anus.

The evolution of magnetic resonance enterography in the assessment of motility disorders in children

Gastrointestinal symptoms including constipation, diarrhoea, pain and bloating represent some of the most common clinical problems for patients. These symptoms can often be managed with cheap, widely available medication or will spontaneously resolve. However, for many patients, chronic GI symptoms persist and frequently come to dominate their lives. At one end of the spectrum there is Inflammatory Bowel Disease (IBD) with a clearly defined but expensive treatment pathway. Contrasting with this is Irritable Bowel Syndrome (IBS), likely a collection of pathologies, has a poorly standardised pathway with unsatisfactory clinical outcomes. Managing GI symptoms in adult populations is a challenge. The clinical burden of gastrointestinal disease is also prevalent in paediatric populations and perhaps even harder to treat. In this review we explore some of the recent advances in magnetic resonance imaging (MRI) to study the gastrointestinal tract. Complex in both its anatomical structure and its physiology we are likely missing key physiological markers of disease through relying on symptomatic descriptors of gut function. Using MRI we might be able to characterise previously opaque processes, such as non-propulsive contractility, that could lead to changes in how we understand even common symptoms like constipation. This review explores recent advances in the field in adult populations and examines how this safe, objective and increasingly available modality might be applied to paediatric populations.

Effect of Yikou-Sizi powder hot compress on gastrointestinal functional recovery in patients after abdominal surgery: Study protocol for a randomized controlled trial

BACKGROUND

Postoperative gastrointestinal dysfunction (PGD) is a common complication of patients who have undergone surgery. The clinical manifestations cause great discomfort to postoperative patients and can severely affect postoperative recovery. However, although various pharmacologic agents have been explored for several years, success has been limited. Because some commonly used drugs have caused adverse reactions and because abdominal surgery patients generally cannot consume food or medication during the perioperative period, we were prompted to try an external Chinese medicine treatment method. Yikou-Sizi powder hot compress is an efficient therapy in our hospital, but there is a lack of rigorous studies to certify the safety and effectiveness of its external use to improve gastrointestinal motility. This study aimed to introduce the clinical trial design and test the ability of Yikou-Sizi powder hot compress treatment to accelerate gastrointestinal functional recovery after abdominal surgery.

METHODS

This study is a randomized controlled clinical trial. The participants will undergo laparoscopic colorectal cancer surgery and laparoscopic total hysterectomy. The primary outcome measure will be the gastrointestinal functional evaluation index, including the time to first passage of flatus, first defecation, first normal bowel sounds, and first consumption of liquid/semigeneral diet foods. According to good clinical practice (GCP), we will evaluate the clinical efficacy and safety of Yikou-Sizi powder hot compress and objectively study the acting mechanism of ghrelin. This pilot trial will be a standard, scientific, and clinical study designed to evaluate the effect of Yikou-Sizi powder hot compress for the recovery of gastrointestinal function after surgery and determine its overall safety.

DISCUSSION

This is the first study to describe the use of Yikou-Sizi powder hot compress to accelerate the recovery of gastrointestinal function after abdominal surgery. The study is designed as a randomized, controlled, clinical, large sample size and pilot trial. Evaluation will consist of combining the primary outcome measures with secondary outcome measures to ensure the objectivity and scientific validity of the study. Due to the observational design and the limited follow-up period, it is not possible to evaluate to what extent the connection between the observed improvement and the interventions represents a causal relationship. Efficient comparison between groups will be analyzed by chi-square test.

Methods for High-Resolution Electrical Mapping in the Gastrointestinal Tract

Over the last two decades, high-resolution (HR) mapping has emerged as a powerful technique to study normal and abnormal bioelectrical events in the gastrointestinal (GI) tract. This technique, adapted from cardiology, involves the use of dense arrays of electrodes to track bioelectrical sequences in fine spatiotemporal detail. HR mapping has now been applied in many significant GI experimental studies informing and clarifying both normal physiology and arrhythmic behaviors in disease states. This review provides a comprehensive and critical analysis of current methodologies for HR electrical mapping in the GI tract, including extracellular measurement principles, electrode design and mapping devices, signal processing and visualization techniques, and translational research strategies. The scope of the review encompasses the broad application of GI HR methods from in vitro tissue studies to in vivo experimental studies, including in humans. Controversies and future directions for GI mapping methodologies are addressed, including emerging opportunities to better inform diagnostics and care in patients with functional gut disorders of diverse etiologies.

Computational motility models of neurogastroenterology and neuromodulation

The success of neuromodulation therapies, particularly in the brain, spinal cord, and peripheral nerves, has been greatly aided by computational, biophysical models. However, treating gastrointestinal disorders with electrical stimulation has been much less explored, partly because the mode of action of such treatments is unclear, and selection of stimulation parameters is often empirical. Progress in gut neuromodulation is limited by the comparative lack of biophysical models capable of simulating neuromodulation of gastrointestinal function. Here, we review the recently developed biophysical models of electrically-active cells in the gastrointestinal system that contribute to motility. Biophysical models are replacing phenomenologically-defined models due to advancements in electrophysiological characterization of key players in the gut: enteric neurons, smooth muscle fibers, and interstitial cells of Cajal. In this review, we explore existing biophysically-defined cellular and network models that contribute to gastrointestinal motility. We focus on recent models that are laying the groundwork for modeling electrical stimulation of the gastrointestinal system. Developing models of gut neuromodulation will improve our mechanistic understanding of these treatments, leading to better parameterization, selectivity, and efficacy of neuromodulation to treat gastrointestinal disorders. Such models may have direct clinical translation to current neuromodulation therapies, such as sacral nerve stimulation.

[Motility disorders in the elderly]

Motility disorders are frequent, especially in the elderly. They must not be ignored and require a systematic evaluation. Constipation, which many elderly people suffer from, must not be trivialised as it can impact on quality of life. Diarrhoea, the manifestation of which is more acute, requires fast and adapted treatment.

Saturated long-chain fatty acid-producing bacteria contribute to enhanced colonic motility in rats

BACKGROUND

The gut microbiota is closely associated with gastrointestinal (GI) motility disorder, but the mechanism(s) by which bacteria interact with and affect host GI motility remains unclear. In this study, through using metabolomic and metagenomic analyses, an animal model of neonatal maternal separation (NMS) characterized by accelerated colonic motility and gut dysbiosis was used to investigate the mechanism underlying microbiota-driven motility dysfunction.

RESULTS

An excess of intracolonic saturated long-chain fatty acids (SLCFAs) was associated with enhanced bowel motility in NMS rats. Heptadecanoic acid (C17:0) and stearic acid (C18:0), as the most abundant odd- and even-numbered carbon SLCFAs in the colon lumen, can promote rat colonic muscle contraction and increase stool frequency. Increase of SLCFAs was positively correlated with elevated abundances of Prevotella, Lactobacillus, and Alistipes. Functional annotation found that the level of bacterial LCFA biosynthesis was highly enriched in NMS group. Essential synthetic genes Fabs were largely identified from the genera Prevotella, Lactobacillus, and Alistipes. Pseudo germ-free (GF) rats receiving fecal microbiota from NMS donors exhibited increased defecation frequency and upregulated bacterial production of intracolonic SLCFAs. Modulation of gut dysbiosis by neomycin effectively attenuated GI motility and reduced bacterial SLCFA generation in the colon lumen of NMS rats.

CONCLUSIONS

These findings reveal a previously unknown relationship between gut bacteria, intracolonic SLCFAs, and host GI motility, suggesting the importance of SLCFA-producing bacteria in GI motility disorders. Further exploration of this relationship could lead to a precise medication targeting the gut microbiota for treating GI motility disorders.

Irritable bowel syndrome in children: Current knowledge, challenges and opportunities

Irritable bowel syndrome (IBS) is a common and troublesome disorder in children with an increasing prevalence noted during the past two decades. It has a significant effect on the lives of affected children and their families and poses a significant burden on healthcare systems. Standard symptom-based criteria for diagnosis of pediatric IBS have changed several times during the past two decades and there are some differences in interpreting symptoms between different cultures. This has posed a problem when using them to diagnose IBS in clinical practice. A number of potential patho-physiological mechanisms have been described, but so far the exact underlying etiology of IBS is unclear. A few potential therapeutic modalities have been tested in children and only a small number of them have shown some benefit. In addition, most of the described patho-physiological mechanisms and treatment options are based on adult studies. These have surfaced as challenges when dealing with pediatric IBS and they need to be overcome for effective management of children with IBS. Recently suggested top-down and bottom-up models help integrating reported patho-physiological mechanisms and will provide an opportunity for better understanding of the diseases process. Treatment trials targeting single treatment modalities are unlikely to have clinically meaningful therapeutic effects on IBS with multiple integrating patho-physiologies. Trials focusing on multiple combined pharmacological and non-pharmacological therapies are likely to yield more benefit. In addition to treatment, in the future, attention should be paid for possible prevention strategies for IBS.

Analysis of the main constituents of Changshu tablet and its spasmolysis effect against contraction induced by acetylcholine in the rat-isolated intestinal smooth muscle

The Changshu tablet (CST), one kind of Chinese patent medicine with astringent to the intestine and relieving diarrhea, was made by the root of Rose odorata Sweet var. gigantean (Coll.et Hemsl.) Rehd.et Wils. Although CST has a long history of clinical application, but the research of its chemical composition is less. So the objective of this study was to investigate the main constituents and preliminarily research its effect of the contraction of isolated intestine in vitro. The contents of total polyphenols (126.23mg/g) and total triterpenoids (132.75mg/g) in CST were determined by ultraviolet spectrophotometry. Procyanidin B3, epigallo catechin, catechin, epicatechin, (-)-fisetinidol-(4α, 8)-(-)-catechin, (4α, 8)-(-)-fisetinidol-(-)-epicatechins and (+)-guibourtinidol-(4β, 8)-epicatechin were identified and determined by high performance liquid chromatography and their contents were distributed from 0.04mg/g to 1.46 mg/g. CST showed significant inhibitory effect against acetylcholine-induced contraction on the rat-isolated intestinal smooth muscle with a dose-dependent manner from 0.06 to 0.6mg/mL. The maxim inhibition rates of CST on duodenum, jejunum, ileum and colon were 65.70±3.47%, 79.74±1.27%, 58.90±1.87% and 45.75±2.21% respectively. These results indicated that CST has a spasmolytic role in gastrointestinal motility which was probably mediated through inhibition of muscarinic receptors. All these findings promote the improvement of the quality control standard of CST and provide pharmacological foundation for clinical application of CST in gastrointestinal tract.

VIP is involved in peripheral CRF-induced stimulation of propulsive colonic motor function and diarrhea in male rats

We investigated whether vasoactive intestinal peptide (VIP) and/or prostaglandins contribute to peripheral corticotropin-releasing factor (CRF)-induced CRF1 receptor-mediated stimulation of colonic motor function and diarrhea in rats. The VIP antagonist, [4Cl-D-Phe6, Leu17]VIP injected intraperitoneally completely prevented CRF (10 µg/kg ip)-induced fecal output and diarrhea occurring within the first hour after injection, whereas pretreatment with the prostaglandins synthesis inhibitor, indomethacin, had no effect. In submucosal plexus neurons, CRF induced significant c-Fos expression most prominently in the terminal ileum compared with duodenum and jejunum, whereas no c-Fos was observed in the proximal colon. c-Fos expression in ileal submucosa was colocalized in 93.4% of VIP-positive neurons and 31.1% of non-VIP-labeled neurons. CRF1 receptor immunoreactivity was found on the VIP neurons. In myenteric neurons, CRF induced only a few c-Fos-positive neurons in the ileum and a robust expression in the proximal colon (17.5 ± 2.4 vs. 0.4 ± 0.3 cells/ganglion in vehicle). The VIP antagonist prevented intraperitoneal CRF-induced c-Fos induction in the ileal submucosal plexus and proximal colon myenteric plexus. At 60 min after injection, CRF decreased VIP levels in the terminal ileum compared with saline (0.8 ± 0.3 vs. 2.5 ± 0.7 ng/g), whereas VIP mRNA level detected by qPCR was not changed. These data indicate that intraperitoneal CRF activates intestinal submucosal VIP neurons most prominently in the ileum and myenteric neurons in the colon. It also implicates VIP signaling as part of underlying mechanisms driving the acute colonic secretomotor response to a peripheral injection of CRF, whereas prostaglandins do not play a role. NEW & NOTEWORTHY Corticotropin-releasing factor (CRF) in the gut plays a physiological role in the stimulation of lower gut secretomotor function induced by stress. We showed that vasoactive intestinal peptide (VIP)-immunoreactive neurons in the ileal submucosal plexus expressed CRF1 receptor and were prominently activated by CRF, unlike colonic submucosal neurons. VIP antagonist abrogated CRF-induced ileal submucosal and colonic myenteric activation along with functional responses (defecation and diarrhea). These data point to VIP signaling in ileum and colon as downstream effectors of CRF.

Vagally mediated gastric effects of brain stem α2-adrenoceptor activation in stressed rats

Chronic stress exerts vagally dependent effects to disrupt gastric motility; previous studies have shown that, among other nuclei, A2 neurons are involved in mediating these effects. Several studies have also shown robust in vitro and in vivo effects of α2-adrenoceptor agonists on vagal motoneurons. We have demonstrated previously that brainstem vagal neurocircuits undergo remodeling following acute stress; however, the effects following brief periods of chronic stress have not been investigated. Our aim, therefore, was to test the hypothesis that different types of chronic stress influence gastric tone and motility by inducing plasticity in the response of vagal neurocircuits to α2-adrenoreceptor agonists. In rats that underwent 5 days of either homotypic or heterotypic stress loading, we applied the α2-adrenoceptor agonist, UK14304, either by in vitro brainstem perfusion to examine its ability to modulate GABAergic synaptic inputs to vagal motoneurons or in vivo brainstem microinjection to observe actions to modulate antral tone and motility. In neurons from naïve rats, GABAergic currents were unresponsive to exogenous application of UK14304. In contrast, GABAergic currents were inhibited by UK14304 in all neurons from homotypic and, in a subpopulation of neurons, heterotypic stressed rats. In control rats, UK14304 microinjection inhibited gastric tone and motility via withdrawal of vagal cholinergic tone; in heterotypic stressed rats, the larger inhibition of antrum tone was due to a concomitant activation of peripheral nonadrenergic, noncholinergic pathways. These data suggest that stress induces plasticity in brainstem vagal neurocircuits, leading to an upregulation of α2-mediated responses. NEW & NOTEWORTHY Catecholaminergic neurons of the A2 area play a relevant role in stress-related dysfunction of the gastric antrum. Brief periods of chronic stress load induce plastic changes in the actions of adrenoceptors on vagal brainstem neurocircuits.

RUMINANT NUTRITION SYMPOSIUM: Effects of postruminal flows of protein and amino acids on small intestinal starch digestion in beef cattle

Many nutritionists adopt feeding strategies designed to increase ruminal starch fermentation because ruminal capacity for starch degradation often exceeds amounts of starch able to be digested in the small intestine of cattle. However, increases in fermentable energy supply are positively correlated with increased instances of metabolic disorders and reductions in DMI, and energy derived by cattle subsequent to fermentation is less than that derived when glucose is intestinally absorbed. Small intestinal starch digestion (SISD) appears to be limited by α-glycohydrolase secretions and a precise understanding of digestion of carbohydrates in the small intestine remains equivocal. Interestingly, small intestinal α-glycohydrolase secretions are responsive to luminal appearance of milk-specific protein (i.e., casein) in the small intestine of cattle, and SISD is increased by greater postruminal flows of individual AA (i.e., Glu). Greater flows of casein and Glu appear to augment SISD, but by apparently different mechanisms. Greater small intestinal absorption of glucose has been associated with increased omental fat accretion even though SISD can increase NE from starch by more than 42% compared to ruminal starch degradation. Nonetheless, in vitro data suggest that greater glucogenicity of diets can allow for greater intramuscular fat accretion, and if greater small intestinal absorption of glucose does not mitigate hepatic gluconeogenesis then increases in SISD may provide opportunity to increase synthesis of intramuscular fat. If duodenal metabolizable AA flow can be altered to allow for improved SISD in cattle, then diet modification may allow for large improvements in feed efficiency and beef quality. Few data are available on direct effects of increases in SISD in response to greater casein or metabolizable Glu flow. An improved understanding of effects of increased SISD in response to greater postruminal flow of Glu and casein on improvements in NE and fates of luminally assimilated glucose could allow for increased efficiency of energy use from corn and improvements in conversion of corn grain to beef. New knowledge related to effects of greater postruminal flow of Glu and casein on starch utilization by cattle will allow nutritionists to more correctly match dietary nutrients to cattle requirements, thereby allowing large improvements in nutrient utilization and efficiency of gain among cattle fed starch-based diets.

Relaxin influences ileal muscular activity through a dual signaling pathway in mice

AIM

To investigate the signaling pathways involved in the relaxin (RLX) effects on ileal preparations from mice through mechanical and electrophysiological experiments.

METHODS

For mechanical experiments, ileal preparations from female mice were mounted in organ baths containing Krebs-Henseleit solution. The mechanical activity was recorded via force-displacement transducers, which were coupled to a polygraph for continuous recording of isometric tension. Electrophysiological measurements were performed in current- and voltage-clamp conditions by a microelectrode inserted in a single smooth muscle cell (SMC) of the ileal longitudinal layer. Both the membrane passive properties and inward voltage-dependent L-type Ca²⁺ currents were recorded using suitable solutions and voltage stimulation protocols.

RESULTS

Mechanical experiments showed that RLX induced a decay of the basal tension and a reduction in amplitude of the spontaneous contractions. The effects of RLX were partially reduced by 1H-[1,2,4]oxadiazolo[4,3-a]-quinoxalin-1-one (ODQ) or 9-cyclopentyladenine mesylate (9CPA), inhibitors of guanylate cyclase (GC) and adenylate cyclase (AC), respectively, and were abolished in the concomitant presence of both drugs. Electrophysiological experiments demonstrated that RLX directly influenced the biophysical properties of ileal SMCs, decreasing the membrane conductance, hyperpolarizing the resting membrane potential, reducing the L-type calcium current amplitude and affecting its kinetics. The voltage dependence of the current activation and inactivation time constant was significantly speeded by RLX. Each electrophysiological effect of RLX was reduced by ODQ or 9CPA, and abolished in the concomitant presence of both drugs as observed in mechanical experiments.

CONCLUSION

Our new findings demonstrate that RLX influences ileal muscle through a dual mechanism involving both GC and AC.

Loss of HCN2 leads to delayed gastrointestinal motility and reduced energy intake in mice

Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels are important regulators of excitability in neural, cardiac, and other pacemaking cells, which are often altered in disease. In mice, loss of HCN2 leads to cardiac dysrhythmias, persistent spike-wave discharges similar to those seen in absence epilepsy, ataxia, tremor, reduced neuropathic and inflammatory pain, antidepressant-like behavior, infertility, and severely restricted growth. While many of these phenotypes have tissue-specific mechanisms, the cause of restricted growth in HCN2 knockout animals remains unknown. Here, we characterize a novel, 3kb insertion mutation of Hcn2 in the Tremor and Reduced Lifespan 2 (TRLS/2J) mouse that leads to complete loss of HCN2 protein, and we show that this mutation causes many phenotypes similar to other mice lacking HCN2 expression. We then demonstrate that while TRLS/2J mice have low blood glucose levels and impaired growth, dysfunction in hormonal secretion from the pancreas, pituitary, and thyroid are unlikely to lead to this phenotype. Instead, we find that homozygous TRLS/2J mice have abnormal gastrointestinal function that is characterized by less food consumption and delayed gastrointestinal transit as compared to wildtype mice. In summary, a novel mutation in HCN2 likely leads to impaired GI motility, causing the severe growth restriction seen in mice with mutations that eliminate HCN2 expression.

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.

Updates on the biology of serotonin and tryptophan hydroxylase

PURPOSE OF REVIEW

To summarize the most recent findings relevant to the biology of serotonin (5-hydroxytryptamine; 5-HT) and the enzyme tryptophan hydroxylase (TPH) in human gastrointestinal disease.

RECENT FINDINGS

Serotonin is synthesized in the central nervous system (CNS) and the gastrointestinal tract where it is secreted from enteroendocrine cells. Its biosynthesis is regulated by two isoforms of the enzyme TPH of which TPH1 is localized predominantly in gastrointestinal enteroendocrine cells. Serotonin activates the peristaltic reflexes, regulates gastrointestinal motility, and has a role in intestinal inflammation. Inhibition of TPH with novel molecules represents a new pharmacological tool in the successful management of carcinoid syndrome in patients with gastrointestinal neuroendocrine tumors (GI-NETs). Certain 5-HT receptor subtype agonists and antagonists are useful in the treatment of functional gastrointestinal disorders.

SUMMARY

The gastrointestinal tract is the largest storage organ for serotonin where its biosynthesis is regulated by TPH1. It has several important functions in gastrointestinal motility, secretion, and inflammation. Furthermore, TPH represents a target for inhibitory pharmacological therapy of serotonin access states such as the carcinoid syndrome.

Improved Visualization of Gastrointestinal Slow Wave Propagation Using a Novel Wavefront-Orientation Interpolation Technique

OBJECTIVE

High-resolution mapping of gastrointestinal (GI) slow waves is a valuable technique for research and clinical applications. Interpretation of high-resolution GI mapping data relies on animations of slow wave propagation, but current methods remain as rudimentary, pixelated electrode activation animations. This study aimed to develop improved methods of visualizing high-resolution slow wave recordings that increases ease of interpretation.

METHODS

The novel method of "wavefront-orientation" interpolation was created to account for the planar movement of the slow wave wavefront, negate any need for distance calculations, remain robust in atypical wavefronts (i.e., dysrhythmias), and produce an appropriate interpolation boundary. The wavefront-orientation method determines the orthogonal wavefront direction and calculates interpolated values as the mean slow wave activation-time (AT) of the pair of linearly adjacent electrodes along that direction. Stairstep upsampling increased smoothness and clarity.

RESULTS

Animation accuracy of 17 human high-resolution slow wave recordings (64-256 electrodes) was verified by visual comparison to the prior method showing a clear improvement in wave smoothness that enabled more accurate interpretation of propagation, as confirmed by an assessment of clinical applicability performed by eight GI clinicians. Quantitatively, the new method produced accurate interpolation values compared to experimental data (mean difference 0.02 ± 0.05 s) and was accurate when applied solely to dysrhythmic data (0.02 ± 0.06 s), both within the error in manual AT marking (mean 0.2 s). Mean interpolation processing time was 6.0 s per wave.

CONCLUSION AND SIGNIFICANCE

These novel methods provide a validated visualization platform that will improve analysis of high-resolution GI mapping in research and clinical translation.

Induction of alpha-synuclein pathology in the enteric nervous system of the rat and non-human primate results in gastrointestinal dysmotility and transient CNS pathology

Alpha-Synuclein (α-syn) is by far the most highly vetted pathogenic and therapeutic target in Parkinson's disease. Aggregated α-syn is present in sporadic Parkinson's disease, both in the central nervous system (CNS) and peripheral nervous system (PNS). The enteric division of the PNS is of particular interest because 1) gastric dysfunction is a key clinical manifestation of Parkinson's disease, and 2) Lewy pathology in myenteric and submucosal neurons of the enteric nervous system (ENS) has been referred to as stage zero in the Braak pathological staging of Parkinson's disease. The presence of Lewy pathology in the ENS and the fact that patients often experience enteric dysfunction before the onset of motor symptoms has led to the hypothesis that α-syn pathology starts in the periphery, after which it spreads to the CNS via interconnected neural pathways. Here we sought to directly test this hypothesis in rodents and non-human primates (NHP) using two distinct models of α-syn pathology: the α-syn viral overexpression model and the preformed fibril (PFF) model. Subjects (rat and NHP) received targeted enteric injections of PFFs or adeno-associated virus overexpressing the Parkinson's disease associated A53T α-syn mutant. Rats were evaluated for colonic motility monthly and sacrificed at 1, 6, or 12 months, whereas NHPs were sacrificed 12 months following inoculation, after which the time course and spread of pathology was examined in all animals. Rats exhibited a transient GI phenotype that resolved after four months. Minor α-syn pathology was observed in the brainstem (dorsal motor nucleus of the vagus and locus coeruleus) 1 month after PFF injections; however, no pathology was observed at later time points (nor in saline or monomer treated animals). Similarly, a histopathological analysis of the NHP brains revealed no pathology despite the presence of robust α-syn pathology throughout the ENS which persisted for the entirety of the study (12 months). Our study shows that induction of α-syn pathology in the ENS is sufficient to induce GI dysfunction. Moreover, our data suggest that sustained spread of α-syn pathology from the periphery to the CNS and subsequent propagation is a rare event, and that the presence of enteric α-syn pathology and dysfunction may represent an epiphenomenon.

Diabetic Enteropathy: From Molecule to Mechanism-Based Treatment

The incidence of the micro- and macrovascular complications of diabetes is rising, mirroring the increase in the worldwide prevalence. Arguably, the most common microvascular complication is neuropathy, leading to deleterious changes in both the structure and function of neurons. Amongst the various neuropathies with the highest symptom burden are those associated with alterations in the enteric nervous system, referred to as diabetic enteropathy. The primary aim of this review is to provide a contemporaneous summary of pathophysiology of diabetic enteropathy thereby allowing a "molecule to mechanism" approach to treatment, which will include 4 distinct aspects. Firstly, the aim is to provide an overview of the diabetes-induced structural remodelling, biochemical dysfunction, immune-mediated alterations, and inflammatory properties of the enteric nervous system and associated structures. Secondly, the aim is to provide a synopsis of the clinical relevance of diabetic enteropathy. Thirdly, the aim is to discuss the various patient-reported outcome measures and the objective modalities for evaluating dysmotility, and finally, the aim is to outline the clinical management and different treatment options that are available. Given the burden of disease that diabetic enteropathy causes, earlier recognition is needed allowing prompt investigation and intervention, which may lead to improvements in quality of life for sufferers.

Enteric glia regulate gut motility in health and disease

The enteric nervous system, often referred to as the second brain, is the largest assembly of neurons and glia outside the central nervous system. The enteric nervous system resides within the wall of the digestive tract and regulates local gut reflexes involved in gastrointestinal motility and fluid transport; these functions can be accomplished in the absence of the extrinsic innervation from the central nervous system. It is neurons and their circuitry within the enteric nervous system that govern the gut reflexes. However, it is becoming clear that enteric glial cells are also actively involved in this process through the bidirectional signaling with neurons and other cells in the gut wall. We synthesize the recently discovered modulatory roles of enteric gliotransmission in gut motility and provide our perspective for future lines of research.

Colonic Hypermotility in a Rat Model of Irritable Bowel Syndrome Is Associated with Upregulation of TMEM16A in Myenteric Plexus

BACKGROUND

Irritable bowel syndrome (IBS) is a common disease with intestinal dysmotility, whose mechanism remains elusive. TMEM16A is a calcium-activated chloride channel (CaCC) involved in intestinal slow-wave generation.

AIMS

To investigate whether TMEM16A is involved in colonic dysmotility in IBS.

METHODS

A rat model of IBS was established by chronic water avoidance stress (WAS). Colonic pathological alterations were evaluated histologically, and intestinal motility was assessed by intestinal transit time (ITT) and fecal water content (FWC). Visceral sensitivity was determined by visceromotor response (VMR) to colorectal distension (CRD). TMEM16A expression was evaluated by RT-PCR, Western blot, and immunofluorescence. Colonic muscle strip contractility was measured by isometric transducers, and the effect of niflumic acid (NFA), a CaCC antagonist, on colonic motility was examined.

RESULTS

After 10 days of WAS exposure, ITT was decreased and FWC was elevated. Furthermore, VMR magnitude of WAS rats in response to CRD was significantly enhanced. Protein and mRNA levels of TMEM16A in colon were considerably increased after WAS. The percentage of TMEM16A-positive neurons in myenteric plexus (MP) of WAS rats was significantly higher than controls. Pharmacological blockade of TMEM16A activity by NFA considerably enhanced ITT, with concentration-dependent declines in FWC and VMR magnitude in NFA-treated rats. Further, spontaneous contraction of colonic strips of NFA-treated rats was significantly ameliorated in a concentration-dependent manner in vitro.

CONCLUSIONS

Upregulation of TMEM16A in MP neurons may play an important role in chronic stress-induced colonic hypermotility, making CaCC-blocking drugs a putatively effective treatment method for colonic hypermotility in IBS.

Ghrelin projection from the lateral hypothalamus area to the dorsal vagal complex and its regulation of gastric motility in cisplatin-treated rats

OBJECTIVE

To investigate ghrelin projection from the lateral hypothalamus area (LHA) to the dorsal vagal complex (DVC) and its regulation of gastric motility in cisplatin-treated rats.

MATERIALS AND METHODS

In the present study, the protein and mRNA expression of ghrelin and its receptor GHSR-1a were measured by Western blot and PCR, respectively. The ghrelin fiber projections arising from the LHA and projecting to the DVC were investigated by retrograde tracing combined with fluoro-immunohistochemical staining. The effects of ghrelin in the DVC, electrical stimulation of the LHA, and electrical lesion of the DVC on gastric motility were measured in cisplatin-treated rats.

RESULTS

Ghrelin fibers originating in the LHA projected to the DVC. The protein and mRNA expression of GHSR-1a was greater in cisplatin-treated rats than in saline-treated rats. Conversely, the expression of ghrelin in the LHA and DVC was reduced in cisplatin-treated rats. Cisplatin treatment also reduced gastric contractions. Ghrelin administrated into the DVC significantly promoted gastric motility, an effect completely blocked by treatment with the ghrelin receptor antagonist [D-Lys-3]-GHRP-6. In addition, electrical stimulation of the LHA promoted gastric motility, though this effect was much weaker in cisplatin-treated rats than in control rats. The excitatory effect of electrical stimulation of the LHA on gastric motility was partially blocked by pretreatment of the DVC with [D-Lys-3]-GHRP-6. Electrical lesion of the DVC diminished the excitatory effect that was induced by electrical stimulation of the LHA.

CONCLUSIONS

DVC, especially AP, may have a role for gastric contraction induced by the stimulation of the LHA. This regulation on gastric motility was weaker in cisplatin-treated rats than in saline-treated rats, possibly due to reduced ghrelin expression in the LHA and ghrelin projection from the LHA to the DVC.

Glucagon-like peptide-2 modulates the nitrergic neurotransmission in strips from the mouse gastric fundus

AIM

To investigate whether glucagon-like peptide-2 (GLP-2) influences the neurally-induced responses in gastric strips from mice, since no data are available.

METHODS

For functional experiments, gastric fundal strips were mounted in organ baths containing Krebs-Henseleit solution. Mechanical responses were recorded via force-displacement transducers, which were coupled to a polygraph for continuous recording of isometric tension. Electrical field stimulation (EFS) was applied via two platinum wire rings through which the preparation was threaded. The effects of GLP-2 (2 and 20 nmol/L) were evaluated on the neurally-induced contractile and relaxant responses elicited by EFS. Neuronal nitric oxide synthase (nNOS) enzyme was evaluated by immunohistochemistry.

RESULTS

In the functional experiments, electrical field stimulation (EFS, 4-16 Hz) induced tetrodotoxin (TTX)-sensitive contractile responses, which were reduced in amplitude by GLP-2 (P < 0.05). In the presence of the nitric oxide (NO) synthesis inhibitor L-NNA, GLP-2 no longer influenced the neurally-evoked contractile responses (P > 0.05). The direct smooth muscle response to methacholine was not influenced by GLP-2 (P > 0.05). In the presence of guanethidine and carbachol, the addition of GLP-2 to the bath medium evoked TTX-sensitive relaxant responses that were unaffected by L-NNA (P > 0.05). EFS induced a fast NO-mediated relaxation, whose amplitude was enhanced in the presence of the hormone (P < 0.05). Immunohistochemical experiments showed a significant increase (P < 0.05) in nNOS immunoreactivity in the nerve structures after GLP-2 exposure.

CONCLUSION

The results demonstrate that in gastric fundal strips, GLP-2 influences the amplitude of neurally-induced responses through the modulation of the nitrergic neurotransmission and increases nNOS expression.

The Potential for Gut Organoid Derived Interstitial Cells of Cajal in Replacement Therapy

Effective digestion requires propagation of food along the entire length of the gastrointestinal tract. This process involves coordinated waves of peristalsis produced by enteric neural cell types, including different categories of interstitial cells of Cajal (ICC). Impaired food transport along the gastrointestinal tract, either too fast or too slow, causes a range of gut motility disorders that affect millions of people worldwide. Notably, loss of ICC has been shown to affect gut motility. Patients that suffer from gut motility disorders regularly experience diarrhoea and/or constipation, insomnia, anxiety, attention lapses, irritability, dizziness, and headaches that greatly affect both physical and mental health. Limited treatment options are available for these patients, due to the scarcity of human gut tissue for research and transplantation. Recent advances in stem cell technology suggest that large amounts of rudimentary, yet functional, human gut tissue can be generated in vitro for research applications. Intriguingly, these stem cell-derived gut organoids appear to contain functional ICC, although their frequency and functional properties are yet to be fully characterised. By reviewing methods of gut organoid generation, together with what is known of the molecular and functional characteristics of ICC, this article highlights short- and long-term goals that need to be overcome in order to develop ICC-based therapies for gut motility disorders.

Hydrogen sulphide as a signalling molecule regulating physiopathological processes in gastrointestinal motility

The biology of H₂ S is a still developing area of research and several biological functions have been recently attributed to this gaseous molecule in many physiological systems, including the cardiovascular, urogenital, respiratory, digestive and central nervous system (CNS). H₂ S exerts anti-inflammatory effects and can be considered an endogenous mediator with potential effects on gastrointestinal motility. During the last few years, we have investigated the role of H₂ S as a regulator of gastrointestinal motility using both animal and human tissues. The aim of the present work is to review published data regarding the potential role of H₂ S as a signalling molecule regulating physiopathological processes in gastrointestinal motor function. H₂ S is endogenously produced by defined enzymic pathways in different cell types of the intestinal wall including neurons and smooth muscle. Inhibition of H₂ S biosynthesis increases motility and H₂ S donors cause smooth muscle relaxation and inhibition of propulsive motor patterns. Impaired H₂ S production has been described in animal models with gastrointestinal motor dysfunction. The mechanism(s) of action underlying these effects may include several ion channels, although no specific receptor has been identified. At this time, even though there is much experimental evidence for H₂ S as a modulator of gastrointestinal motility, we still do not have conclusive experimental evidence to definitively propose H₂ S as an inhibitory neurotransmitter in the gastrointestinal tract, causing nerve-mediated relaxation.

Does motilin peptide regulate gastrointestinal motility of zebrafish? An in vitro study using isolated intestinal strips

Motilin (MOT), a 22-amino-acid peptide hormone produced in the duodenal mucosa, stimulates gastrointestinal motility in mammals and birds, and it is a mediator of interdigestive motor complexes. Recently, expression of MOT-like peptide (MOTLP) and its receptor mRNAs was identified in zebrafish. The aim of the present study was to determine whether the zebrafish MOTLP (zfMOTLP, HIAFFSPKEMRELREKE) affects zebrafish gastrointestinal motility, with comparison to the effect of human MOT, in which five amino acids are identical to zfMOTLP at positions 5, 9, 15, 16, and 17. zfMOTLP caused small contractions of the rabbit duodenum and chicken ileum but, the sensitivity was about 3000-times lower than that of human MOT. zfMOTLP-induced contraction in the rabbit duodenum was decreased by pretreatment of the MOT receptor antagonist GM109, indicating that zfMOTLP could bind to the MOT receptor. zfMOTLP (3-100nM) increased the intracellular Ca²⁺ concentration in zfMOT receptor-expressing HEK293 cells, but human MOT did not cause responses even at 100nM. In in vitro study using isolated zebrafish gastrointestinal strips, zfMOTLP caused only small contractions even at high doses (1-10μM). zfMOT receptor mRNA is detected in the gastrointestinal tract and brain to almost the same extent, and the expression level (40-70 copies/100ng total RNA) is much lower than that in the chicken gastrointestinal tract. These results suggest that the MOTLP/MOT receptor system is present in zebrafish, but its physiological role for regulation of gastrointestinal motility might be not significant due to the weak contractile activity and low expression level of the receptor.

The X/A-like cell revisited - spotlight on the peripheral effects of NUCB2/nesfatin-1 and ghrelin

The gastric X/A-like cell was long thought to be restricted to the production of acyl ghrelin. However, the subsequent years witnessed the discovery of other peptide products derived from this cell, namely desacyl ghrelin, obestatin and nesfatin-1. While the role of obestatin remains highly questionable and is very critically discussed in the literature, besides acyl ghrelin also desacyl ghrelin and nesfatin-1 have been implicated in the regulation of food intake. As observed for several other peptide hormones before, ghrelin and nesfatin-1 are not restricted to one function but rather exert pleiotropic actions including effects on gastrointestinal motility, thermogenesis, lipid and glucose homeostasis, stress mediation, cardiovascular as well as reproductive functions. These often counter-regulatory effects of nesfatin-1 and ghrelin will be discussed in the present review.

Glucose kinetics: an update and novel insights into its regulation by glucagon and GLP-1

PURPOSE OF REVIEW

Glucagon and GLP-1 share the same origin (i.e., proglucagon); primarily GLP-1 is generated from intestinal L-cells and glucagon from pancreatic α-cell, but intestinal glucagon and pancreatic GLP-1 secretion is likely. Glucose kinetics are tightly regulated by pancreatic hormones insulin and glucagon, but other hormones, including glucagon-like peptide-1 (GLP-1), also play an important role. The purpose of this review is to describe the recent findings on the mechanisms by which these two hormones regulate glucose kinetics.

RECENT FINDINGS

Recent findings showed new important mechanisms of action of glucagon and GLP-1 in the regulation of glucose metabolism. Knock out of glucagon receptors protects against hyperglycemia without causing hypoglycemia. GLP-1 not only stimulates insulin secretion, but it has also an independent effect on the liver and inhibits glucose production. Moreover, when coinfused with glucagon, GLP-1 limits the hyperglycemic effects. Both hormones have also central effects on gastric emptying (delayed), intestinal motility (reduced), and satiety (increased).

SUMMARY

The implications of these findings are very important for the management of type 2 diabetes given that GLP-1 receptor agonist are currently approved for the treatment of hyperglycemia and glucagon receptor antagonists and GLP-1/glucagon dual agonists are under development.