Relationship between endoscopic gastroesophageal valve grading and mean nocturnal baseline impedance and postreflux swallow-induced peristaltic wave index in patients with gastroesophageal reflux disease.

This study aimed to investigate the relationship between endoscopic gastroesophageal valve grading and mean nocturnal baseline impedance (MNBI) and postreflux swallow-induced peristaltic wave index (PSPWI) in patients with gastroesophageal reflux disease (GERD). A total of 120 patients diagnosed with GERD disease were included in the study. According to the classification of endoscopic gastroesophageal valves, the patients were divided into 5 groups, group 1 as baseline group, and Group 2-4 as Hill grade I-IV. Basic information about the patients was collected, including age and gender. The mean nocturnal baseline impedance and creep wave index induced by swallowing after rumination were measured by high resolution creep measurement technique. Through statistical analysis, the relationship between valve classification and observation index was discussed. In terms of MNBI, impedance values gradually decreased with increasing valve classification. The average impedance of the Grade 1 group was 23.5 mm Hg/cm2, while the average impedance of the Grade 5 group was 15.2 mm Hg/cm2. This reduction showed a significant decreasing trend (P < .001). In addition, in terms of the peristaltic wave index caused by swallowing after regurgitation, the peristaltic wave index gradually increased with the increase of valve classification. The mean index in the Grade 1 group was 1.8 beats/min, while the mean index in the Grade 5 group was 3.6 beats/min. This increase showed a significant positive relationship (P < .001). Endoscopic gastroesophageal valve grading was significantly correlated with MNBI and PSPWI in patients with GERD. These observations can serve as useful tools for assessing the severity of GERD and monitoring disease progression.

Resistance model of an active capsule endoscope in a peristaltic intestine.

In the past studies, the resistance of magnetically controlled capsules running through the small intestine has been modeled assuming that the small intestine was a circular tube with a constant diameter. Peristalsis is an important character of the human gastrointestinal system, and it would result in some changes in the diameter of the intestine, meaning that the existing resistance models would no longer be applicable. In this paper, based on the assumption that intestinal peristalsis is actually a sinusoidal wave, a resistance model of the capsule running in the peristaltic intestine is established, and then it is validated experimentally. The model provides a realistic foundation for the optimization and control of the magnetically controlled endoscopy.

Peristalsis prevents ureteral dilation.

PURPOSE: The etiology of ureteral dilation in primary nonrefluxing, nonobstructing megaureters is still not well understood. Impaired ureteral peristalsis has been theorized as one of the contributing factors. However, ureteral peristalsis and its "normal" function is not well defined. In this study, using mathematical modeling techniques, we aim to better understand how ureteral peristalsis works. This is the first model to consider clinically observed, back-and-forth, cyclic wall longitudinal motion during peristalsis. We hypothesize that dysfunctional ureteral peristalsis, caused by insufficient peristaltic amplitudes (e.g., circular muscle dysfunction) and/or lack of ureteral wall longitudinal motion (e.g., longitudinal muscle dysfunction), promotes peristaltic reflux (i.e., retrograde flow of urine during an episode of peristalsis) and may result in urinary stasis, urine accumulation, and consequent dilation. METHODS: Based on lubrication theory in fluid mechanics, we developed a two-dimensional (planar) model of ureteral peristalsis. In doing so, we treated ureteral peristalsis as an infinite train of sinusoidal waves. We then analyzed antegrade and retrograde flows in the ureter under different bladder-kidney differential pressure and peristalsis conditions. RESULTS: There is a minimum peristaltic amplitude required to prevent peristaltic reflux. Ureteral wall longitudinal motion decreases this minimum required amplitude, increasing the nonrefluxing range of peristaltic amplitudes. As an example, for a normal bladder-kidney differential pressure of 5 cmH2 O, ureteral wall longitudinal motion increases nonrefluxing range of peristaltic amplitude by 65%. Additionally, ureteral wall longitudinal motion decreases refluxing volumetric flow rates. For a similar normal bladder pressure example of 5 cmH2 O, refluxing volumetric flow rate decreases by a factor of 18. Finally, elevated bladder pressure, not only increases the required peristaltic amplitude for reflux prevention but it increases maximum refluxing volumetric flow rates. For the case without wall longitudinal motion, as bladder-kidney differential pressure increases from 5 to 40 cmH2 O, minimum required peristaltic amplitude to prevent reflux increases by 40% while the maximum refluxing volumetric flow rate increases by approximately 100%. CONCLUSION: The results presented in this study show how abnormal ureteral peristalsis, caused by the absence of wall longitudinal motion and/or lack of sufficient peristaltic amplitudes, facilitates peristaltic reflux and retrograde flow. We theorize that this retrograde flow can lead to urinary stasis and urine accumulation in the ureters, resulting in ureteral dilation seen on imaging studies and elevated infection risk. Our results also show how chronically elevated bladder pressures are more susceptible to such refluxing conditions that could lead to ureteral dilation.

Advancing peristalsis deciphering in mouse small intestine by multi-parameter tracking.

Assessing gastrointestinal motility lacks simultaneous evaluation of intraluminal pressure (ILP), circular muscle (CM) and longitudinal muscle (LM) contraction, and lumen emptying. In this study, a sophisticated machine was developed that synchronized real-time recordings to quantify the intricate interplay between CM and LM contractions, and their timings for volume changes using high-resolution cameras with machine learning capability, the ILP using pressure transducers and droplet discharge (DD) using droplet counters. Results revealed four distinct phases, BPhase, NPhase, DPhase, and APhase, distinguished by pressure wave amplitudes. Fluid filling impacted LM strength and contraction frequency initially, followed by CM contraction affecting ILP, volume, and the extent of anterograde, retrograde, and segmental contractions during these phases that result in short or long duration DD. This comprehensive analysis sheds light on peristalsis mechanisms, understand their sequence and how one parameter influenced the other, offering insights for managing peristalsis by regulating smooth muscle contractions.

Neural targets of the enteric dopaminergic system in regulating motility of rat proximal colon.

In isolated segments of the rat proximal colon, the dopamine reuptake inhibitor GBR 12909 (GBR) causes a dilatation, while the D1-like receptor antagonist SCH 23390 (SCH) induces a tonic constriction, suggesting that neurally released dopamine tonically stimulates enteric inhibitory efferent neurons. Here, the targets of the enteric dopaminergic neurons were investigated. Cannulated segments of rat proximal colon were bathed in physiological salt solution and luminally perfused with 0.9% saline, while all drugs were applied to the bath. Spatio-temporal maps of colonic motility were constructed from video recordings of peristaltic contractions, and the maximum diameter was measured as an index of colonic contractility. GBR (1 µM)-induced dilatations of colonic segments were prevented by SCH (5 µM), L-nitro arginine (L-NA; 100 µM), a nitric oxide synthase inhibitor, or tetrodotoxin (0.6 µM). In contrast, constrictions induced by a higher concentration of SCH (20 µM) were unaffected by either L-NA or tetrodotoxin. The vasoactive intestinal peptide (VIP) receptor antagonist VIP10-28 (3 µM) or P2Y1 receptor antagonist MRS 2500 (1 µM) had no effect on either the GBR-induced dilatation or the SCH-induced constriction. In colonic segments that had been pretreated with 6-hydroxydopamine (100 µM, 3 h) to deplete enteric dopamine, GBR failed to increase the colonic diameter, while SCH was still capable of constricting colonic segments. Enteric dopaminergic neurons appear to project to nitrergic neurons to dilate the proximal colon by activating neuronal D1-like receptors. In addition, constitutively activated D1-like receptors expressed in cells yet to be determined may provide a tonic inhibition on colonic constrictions.

Effect of inter-swallow interval on striated esophagus peristalsis; a comparative study with smooth muscle esophagus.

BACKGROUND: Effect of inter-swallow interval on the contractility of smooth muscle esophagus is well-documented. However, the effects on peristalsis of the striated esophagus have not been systematically studied. A better understanding of striated esophagus motor function in health and disease may enhance the interpretation of manometric studies and inform clinical care. The aim of this study was to assess the effect of inter-swallow interval on striated esophagus compared to findings with that of the smooth muscle esophagus. METHODS: We performed two sets of studies to (1) determine the effect of various inter-swallow interval in 20 healthy volunteers and (2) assess the effect of ultra-short swallow intervals facilitated by straw drinking in 28 volunteers. We analyzed variables using ANOVA with Tukey's pairwise comparison and paired t-test. KEY RESULTS: Unlike smooth muscle esophagus, the striated esophagus contractile integral did not change significantly for swallow intervals ranging from 30 to 5 s. On the contrary, striated esophagus demonstrated absent or reduced peristalsis in response to ultra-short (<2 s) intervals during straw-facilitated multiple rapid swallows. CONCLUSIONS AND INFERENCES: Striated esophagus peristalsis is subject to manometrically observed inhibition during swallows with ultra-short intervals. Inter-swallow intervals as short as 5 s that inhibit smooth muscle esophagus peristalsis do not inhibit striated muscle peristalsis. The mechanisms of these observations are unknown but may relate to central or myenteric nervous system influences or the effects of pharyngeal biomechanics.

Response to Letter to the Editor.

It is crucial to consider the possible influence of anesthetic agents on esophageal function testing. Dexmedetomidine has been shown to affect primary peristalsis during esophageal manometry. In the two case reports presented by Toaz et al., secondary peristalsis during FLIP panometry was also affected. This may be attributed to an alternate pharmacodynamic effect, with a transient direct α2-mediated effect on esophageal smooth muscle, associated with a high plasma concentration following bolus injection, prior to the onset of sympathetic inhibition.

Acute transcutaneous electrical stimulation (TES) augments esophageal contractility in patients with weak peristalsis.

BACKGROUND: Lung transplantation (LTx) remains controversial in patients with absent peristalsis (AP) given the increased risk for gastroesophageal reflux (GER), and chronic lung allograft dysfunction. Furthermore, specific treatments to facilitate LTx in those with AP have not been widely described. Transcutaneous Electrical Stimulation (TES) has been reported to improve foregut contractility in LTx patients and therefore we hypothesize that TES may augment the esophageal motility of patients with ineffective esophageal motility (IEM). METHODS: We included 49 patients, 14 with IEM, 5 with AP, and 30 with normal motility. All subjects underwent standard high-resolution manometry and intraluminal impedance (HRIM) with additional swallows as TES was delivered. RESULTS: TES induced a universal impedance change observable in real-time by a characteristic spike activity. TES significantly augmented the contractile vigor of the esophagus measured by the distal contractile integral (DCI) in patients with IEM [median DCI (IQR) 0 (238) mmHg-cm-s off TES vs. 333 (858) mmHg-cm-s on TES; p = .01] and normal peristalsis [median DCI (IQR) 1545 (1840) mmHg-cm-s off TES vs. 2109 (2082) mmHg-cm-s on TES; p = .01]. Interestingly, TES induced measurable contractile activity (DCI > 100 mmHg-cm-s) in three out of five patients with AP [median DCI (IQR) 0 (0) mmHg-cm-s off TES vs. 0 (182) mmHg-cm-s on TES; p < .001]. CONCLUSION: TES acutely augmented contractile vigor in patients with normal and weak/ AP. The use of TES may positively impact LTx candidacy, and outcomes for patients with IEM/AP. Nevertheless, further studies are needed to determine the long-term effects of TES in this patient population.

Numerical simulation of peristalsis to study co-localization and intestinal distribution of a macromolecular drug and permeation enhancer.

In this work, simulations of intestinal peristalsis are performed to investigate the intraluminal transport of macromolecules (MMs) and permeation enhancers (PEs). Properties of insulin and sodium caprate (C10) are used to represent the general class of MM and PE molecules. Nuclear magnetic resonance spectroscopy was used to obtain the diffusivity of C10, and coarse-grain molecular dynamics simulations were carried out to estimate the concentration-dependent diffusivity of C10. A segment of the small intestine with the length of 29.75 cm was modeled. Peristaltic speed, pocket size, release location, and occlusion ratio of the peristaltic wave were varied to study the effect on drug transport. It was observed that the maximum concentration at the epithelial surface for the PE and the MM increased by 397 % and 380 %, respectively, when the peristaltic wave speed was decreased from 1.5 to 0.5 cm s-1. At this wave speed, physiologically relevant concentrations of PE were found at the epithelial surface. However, when the occlusion ratio is increased from 0.3 to 0.7, the concentration approaches zero. These results suggest that a slower-moving and more contracted peristaltic wave leads to higher efficiency in transporting mass to the epithelial wall during the peristalsis phases of the migrating motor complex.

Peristaltic transfer of nanofluid with motile gyrotactic microorganisms with nonlinear thermic radiation.

In situated theoretical article, a study of peristaltic transition of Jeffery nanofluid comprising motile gyrotactic microorganisms is exposed. The movement floods due to anisotropically stenosed endoscope influenced by Hall current, Joule heating during Darcy-Forchheimer feature. Influences of nonlinear thermic radiation, chemical interactions as well as Soret and Dufour scheme are exhibited. To ameliorate the competence of this article, activation energy has been appended to concentration of nano-particles due to the amended Arrhenius scheme and Buongiorno type. The slip stipulation is deemed relative to the speed scheme. Meanwhile, convective stipulation is reckoned for temperature. The proposition of protracted wavelength besides subdued Reynolds numeral is regulated to transit the manner of partial differential formulations that judges the fluid movement to ordinary one. Homotopy perturbation manner is tackled to manage the traditional solutions of generated neutralizations. Influences of assorted factors of the issue are debated and schematically showed with a class of charts. The situated study grants a medication for the malign cells and clogged arteries of the heart by manner of penetrating a slender tube (catheter). Also, this study may represent the depiction of the gastric juice movement in small intestine when an endoscope is permeating across it.

Global dynamic modes of peristaltic-ciliary flow of a Phan-Thien-Tanner hybrid nanofluid model.

In this paper, the tools of dynamical systems theory are applied to examine the streamline patterns and their local and global bifurcations for ciliary-induced peristalsis of non-Newtonian fluid (blood) with the suspension of hybrid nanoparticles (Cu-Ag/Phan-Thien-Tanner based fluid) in a tube with heat source effect. The thermodynamics of this model are recently described by Ali et al. (Biomech Model Mechanobiol 20:2393-2412, 2021), where the fluid flows through a tube whose inner walls are considered to be ciliated with small hair-like structures. However, our novel approach allows us to create a complete picture of the model's overall dynamic behavior in terms of bifurcation point analysis exhibiting qualitatively different flow modes. Special attention is paid to the computing, analysis and simulation of equilibrium points in terms of capturing the global dynamics, such as evaluating the heteroclinic bifurcation, which is used to identify trapping phenomena in response to biological characteristics such as wave amplitude, Weissenberg and wave numbers. The main novelty here is the ability to control the position of the equilibrium points in the domain of interest, allowing one to identify global bifurcations that reflect key dynamic properties of the model. Based on the advantages of this technique, the maximum trapping volume and symmetric trapping zones adjacent to the walls are determined as a novel result. We also show that as the solid volume fraction of copper and the Brinkman number increases, the isotherm patterns become more distorted. Our findings highlight a novel class of complex behavior that governs transitions between qualitatively different modes and trapping phenomena.

An earthworm-like modular soft robot for locomotion in multi-terrain environments.

Robotic locomotion in subterranean environments is still unsolved, and it requires innovative designs and strategies to overcome the challenges of burrowing and moving in unstructured conditions with high pressure and friction at depths of a few centimeters. Inspired by antagonistic muscle contractions and constant volume coelomic chambers observed in earthworms, we designed and developed a modular soft robot based on a peristaltic soft actuator (PSA). The PSA demonstrates two active configurations from a neutral state by switching the input source between positive and negative pressure. PSA generates a longitudinal force for axial penetration and a radial force for anchorage, through bidirectional deformation of the central bellows-like structure, which demonstrates its versatility and ease of control. The performance of PSA depends on the amount and type of fluid confined in an elastomer chamber, generating different forces and displacements. The assembled robot with five PSA modules enabled to perform peristaltic locomotion in different media. The role of friction was also investigated during experimental locomotion tests by attaching passive scales like earthworm setae to the ventral side of the robot. This study proposes a new method for developing a peristaltic earthworm-like soft robot and provides a better understanding of locomotion in different environments.

Peristaltic regimes in esophageal transport.

A FLIP device gives cross-sectional area along the length of the esophagus and one pressure measurement, both as a function of time. Deducing mechanical properties of the esophagus including wall material properties, contraction strength, and wall relaxation from these data are a challenging inverse problem. Knowing mechanical properties can change how clinical decisions are made because of its potential for in-vivo mechanistic insights. To obtain such information, we conducted a parametric study to identify peristaltic regimes by using a 1D model of peristaltic flow through an elastic tube closed on both ends and also applied it to interpret clinical data. The results gave insightful information about the effect of tube stiffness, fluid/bolus density and contraction strength on the resulting esophagus shape through quantitive representations of the peristaltic regimes. Our analysis also revealed the mechanics of the opening of the contraction area as a function of bolus flow resistance. Lastly, we concluded that peristaltic driven flow displays three modes of peristaltic geometries, but all physiologically relevant flows fall into two peristaltic regimes characterized by a tight contraction.

Rapid Prototypable Biomimetic Peristalsis Bioreactor Capable of Concurrent Shear and Multi-Axial Strain.

Peristalsis is a nuanced mechanical stimulus comprised of multi-axial strain (radial and axial strain) and shear stress. Forces associated with peristalsis regulate diverse biological functions including digestion, reproductive function, and urine dynamics. Given the central role peristalsis plays in physiology and pathophysiology, we were motivated to design a bioreactor capable of holistically mimicking peristalsis. We engineered a novel rotating screw-drive based design combined with a peristaltic pump, in order to deliver multi-axial strain and concurrent shear stress to a biocompatible polydimethylsiloxane (PDMS) membrane "wall." Radial indentation and rotation of the screw drive against the wall demonstrated multi-axial strain evaluated via finite element modeling. Experimental measurements of strain using piezoelectric strain resistors were in close alignment with model-predicted values (15.9 ± 4.2% vs. 15.2% predicted). Modeling of shear stress on the "wall" indicated a uniform velocity profile and a moderate shear stress of 0.4 Pa. Human mesenchymal stem cells (hMSCs) seeded on the PDMS "wall" and stimulated with peristalsis demonstrated dramatic changes in actin filament alignment, proliferation, and nuclear morphology compared to static controls, perfusion, or strain, indicating that hMSCs sensed and responded to peristalsis uniquely. Lastly, significant differences were observed in gene expression patterns of calponin, caldesmon, smooth muscle actin, and transgelin, corroborating the propensity of hMSCs toward myogenic differentiation in response to peristalsis. Collectively, our data suggest that the peristalsis bioreactor is capable of generating concurrent multi-axial strain and shear stress on a "wall." hMSCs experience peristalsis differently than perfusion or strain, resulting in changes in proliferation, actin fiber organization, smooth muscle actin expression, and genetic markers of differentiation. The peristalsis bioreactor device has broad utility in the study of development and disease in several organ systems.

Propagation of Pacemaker Activity and Peristaltic Contractions in the Mouse Renal Pelvis Rely on Ca2+-activated Cl- Channels and T-Type Ca2+ Channels.

The process of urine removal from the kidney occurs via the renal pelvis (RP). The RP demarcates the beginning of the upper urinary tract and is endowed with smooth muscle cells. Along the RP, organized contraction of smooth muscle cells generates the force required to move urine boluses toward the ureters and bladder. This process is mediated by specialized pacemaker cells that are highly expressed in the proximal RP that generate spontaneous rhythmic electrical activity to drive smooth muscle depolarization. The mechanisms by which peristaltic contractions propagate from the proximal to distal RP are not fully understood. In this study, we utilized a transgenic mouse that expresses the genetically encoded Ca2+ indicator, GCaMP3, under a myosin heavy chain promotor to visualize spreading peristaltic contractions in high spatial detail. Using this approach, we discovered variable effects of L-type Ca2+ channel antagonists on contraction parameters. Inhibition of T-type Ca2+ channels reduced the frequency and propagation distance of contractions. Similarly, antagonizing Ca2+-activated Cl- channels or altering the transmembrane Cl- gradient decreased contractile frequency and significantly inhibited peristaltic propagation. These data suggest that voltage-gated Ca2+ channels are important determinants of contraction initiation and maintain the fidelity of peristalsis as the spreading contraction moves further toward the ureter. Recruitment of Ca2+-activated Cl- channels, likely Anoctamin-1, and T-type Ca2+ channels are required for efficiently conducting the depolarizing current throughout the length of the RP. These mechanisms are necessary for the efficient removal of urine from the kidney.

Distension contraction plots of pharyngeal/esophageal peristalsis: next frontier in the assessment of esophageal motor function.

Esophageal peristalsis consists of initial inhibition (relaxation) followed by excitation (contraction), both of which move sequentially in the aboral direction. Initial inhibition results in receptive relaxation and bolus-induced luminal distension, which allows propulsion by the contraction with minimal resistance to flow. Similar to the contraction wave, luminal distension has unique waveform characteristics in normal subjects; both are modulated by bolus volume, bolus viscosity, and posture, suggesting a possible cause-and-effect relationship between the two. Distension contraction plots in patients with dysphagia with normal bolus clearance [high-amplitude esophageal contractions (HAECs), esophagogastric junction outflow obstruction (EGJOO), and functional dysphagia (FD)] reveal two major findings: 1) unlike normal subjects, there is luminal occlusion distal to bolus during peristalsis in certain patients, i.e., with type 3 achalasia and nonobstructive dysphagia; and 2) bolus travels through a narrow lumen esophagus during peristalsis in patients with HAECs, EGJOO, and FD. Aforementioned findings indicate a relative dynamic obstruction to the bolus flow during peristalsis and reduced distensibility of esophageal wall in the bolus segment of the esophagus. We speculate that a normal or supernormal contraction wave pushing bolus against resistance is the mechanism of dysphagia sensation in significant number of patients. Representations of distension and contraction, combined with objective measures of flow timing and distensibility are complementary to the current scheme of classifying esophageal motility disorders based solely on the characteristics of contraction phase of peristalsis. Better understanding of the distensibility of the bolus-containing segment of the esophagus during peristalsis will lead to the development of novel medical and surgical therapies in the treatment of dysphagia in significant number of patients.

Effect of Joule heating and entropy generation on multi-slip condition of peristaltic flow of Casson nanofluid in an asymmetric channel.

In the present investigation, the effect of multi-slip condition on peristaltic flow through asymmetric channel with Joule heating effect is considered. We also considered the incompressible non-Newtonian Casson nanofluid model for blood, which is electrically conducting. Second law of thermodynamics is used to examine the entropy generation. Multi-slip condition is used at the boundary of the wall and the analysis is also restricted under the low Reynolds number and long wavelength assumption. The governing equations were transformed into a non-dimensional form by using suitable terms. The reduced non-dimensional highly nonlinear partial differential equations are solved by using the Homotopy Perturbation Sumudu transformation method (HPSTM). The influence of different physical parameters on dimensionless velocity, pressure gradient, temperature, concentration and nanoparticle is graphically presented. From the results, one can understand that the Joule heating effect controls the heat transfer in the system and as the magnetic parameter is increased, there will be decay in the velocity of fluid. The outcomes of the present investigation can be applicable in examining the chyme motion in the gastrointestinal tract and controlling the blood flow during surgery. Present study shows an excellent agreement with the previously available studies in the limiting case.

Biomechanical characterization of the small intestine to simulate gastrointestinal tract chyme propulsion.

Regular intestinal motility is essential to guarantee complete digestive function. The coordinative action and integrity of the smooth muscle layers in the small intestine's wall are critical for mixing and propelling the luminal content. However, some patients present gastrointestinal limitations which may negatively impact the normal motility of the intestine. These patients have altered mechanical and muscle properties that likely impact chyme propulsion and may pose a daily scenario for long-term complications. To better understand how mechanics affect chyme propulsion, the propulsive capability of the small intestine was examined during a peristaltic wave along the distal direction of the tract. It was assumed that such a wave works as an activation signal, inducing peristaltic contractions in a transversely isotropic hyperelastic model. In this work, the effect on the propulsion mechanics, from an impairment on the muscle contractile ability, typical from patients with systemic sclerosis, and the presence of sores resultant from ulcers was evaluated. The passive properties of the constitutive model were obtained from uniaxial tensile tests from a porcine small intestine, along with both longitudinal and circumferential directions. Our experiments show decreased stiffness in the circumferential direction. Our simulations show decreased propulsion forces in patients in systemic sclerosis and ulcer patients. As these patients may likely need medical intervention, establishing action concerning the impaired propulsion can help to ease the evaluation and treatment of future complications.

Ca2+-imaging and photo-manipulation of the simple gut of zebrafish larvae in vivo.

Zebrafish larval gut could be considered as an excellent model to study functions of vertebrate digestive organs, by virtue of its simplicity and transparency as well as the availability of mutants. However, there has been scant investigation of the detailed behavior of muscular and enteric nervous systems to convey bolus, an aggregate of digested food. Here we visualized peristalsis using transgenic lines expressing a genetically encoded Ca2+ sensor in the circular smooth muscles. An intermittent Ca2+ signal cycle was observed at the oral side of the bolus, with Ca2+ waves descending and ascending from there. We also identified a regular cycle of weaker movement that occurs regardless of the presence or absence of bolus, corresponding likely to slow waves. Direct photo-stimulation of circular smooth muscles expressing ChR2 could cause local constriction of the gut, while the stimulation of a single or a few neurons could cause the local induction or arrest of gut movements. These results indicate that the larval gut of zebrafish has basic features found in adult mammals despite the small number of enteric neurons, providing a foundation for the study, at the single-cell level in vivo, in controlling the gut behaviors in vertebrates.