1
|
Sharkey KA, Mawe GM. The enteric nervous system. Physiol Rev 2023; 103:1487-1564. [PMID: 36521049 PMCID: PMC9970663 DOI: 10.1152/physrev.00018.2022] [Citation(s) in RCA: 51] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/12/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.
Collapse
Affiliation(s)
- Keith A Sharkey
- Hotchkiss Brain Institute and Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Gary M Mawe
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, Vermont
| |
Collapse
|
2
|
Athavale ON, Avci R, Cheng LK, Du P. Computational models of autonomic regulation in gastric motility: Progress, challenges, and future directions. Front Neurosci 2023; 17:1146097. [PMID: 37008202 PMCID: PMC10050371 DOI: 10.3389/fnins.2023.1146097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 02/27/2023] [Indexed: 03/17/2023] Open
Abstract
The stomach is extensively innervated by the vagus nerve and the enteric nervous system. The mechanisms through which this innervation affects gastric motility are being unraveled, motivating the first concerted steps towards the incorporation autonomic regulation into computational models of gastric motility. Computational modeling has been valuable in advancing clinical treatment of other organs, such as the heart. However, to date, computational models of gastric motility have made simplifying assumptions about the link between gastric electrophysiology and motility. Advances in experimental neuroscience mean that these assumptions can be reviewed, and detailed models of autonomic regulation can be incorporated into computational models. This review covers these advances, as well as a vision for the utility of computational models of gastric motility. Diseases of the nervous system, such as Parkinson’s disease, can originate from the brain-gut axis and result in pathological gastric motility. Computational models are a valuable tool for understanding the mechanisms of disease and how treatment may affect gastric motility. This review also covers recent advances in experimental neuroscience that are fundamental to the development of physiology-driven computational models. A vision for the future of computational modeling of gastric motility is proposed and modeling approaches employed for existing mathematical models of autonomic regulation of other gastrointestinal organs and other organ systems are discussed.
Collapse
|
3
|
Barth BB, Henriquez CS, Grill WM, Shen X. Electrical stimulation of gut motility guided by an in silico model. J Neural Eng 2018; 14:066010. [PMID: 28816177 DOI: 10.1088/1741-2552/aa86c8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Neuromodulation of the central and peripheral nervous systems is becoming increasingly important for treating a diverse set of diseases-ranging from Parkinson's Disease and epilepsy to chronic pain. However, neuromodulation of the gastrointestinal (GI) tract has achieved relatively limited success in treating functional GI disorders, which affect a significant population, because the effects of stimulation on the enteric nervous system (ENS) and gut motility are not well understood. Here we develop an integrated neuromechanical model of the ENS and assess neurostimulation strategies for enhancing gut motility, validated by in vivo experiments. APPROACH The computational model included a network of enteric neurons, smooth muscle fibers, and interstitial cells of Cajal, which regulated propulsion of a virtual pellet in a model of gut motility. MAIN RESULTS Simulated extracellular stimulation of ENS-mediated motility revealed that sinusoidal current at 0.5 Hz was more effective at increasing intrinsic peristalsis and reducing colon transit time than conventional higher frequency rectangular current pulses, as commonly used for neuromodulation therapy. Further analysis of the model revealed that the 0.5 Hz sinusoidal currents were more effective at modulating the pacemaker frequency of interstitial cells of Cajal. To test the predictions of the model, we conducted in vivo electrical stimulation of the distal colon while measuring bead propulsion in awake rats. Experimental results confirmed that 0.5 Hz sinusoidal currents were more effective than higher frequency pulses at enhancing gut motility. SIGNIFICANCE This work demonstrates an in silico GI neuromuscular model to enable GI neuromodulation parameter optimization and suggests that low frequency sinusoidal currents may improve the efficacy of GI pacing.
Collapse
Affiliation(s)
- Bradley B Barth
- Department of Biomedical Engineering, Duke University, Durham, NC, United States of America
| | | | | | | |
Collapse
|
4
|
Marega P, Liberti EA, Freitas JJS, Kietzer KS. Walker-256 tumor alters morphology of intestinal myenteric plexus in rats. Neurogastroenterol Motil 2018; 30. [PMID: 29542845 DOI: 10.1111/nmo.13322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/30/2018] [Indexed: 12/20/2022]
Abstract
BACKGROUND Gastrointestinal (GI) dysmotility is common in patients with cancer. There are a few studies about the myenteric plexus in the presence of anatomically remote tumors. METHODS Forty-eight male Wistar rats were divided into a control (CT) or Walker-256 (TW) group. Tumor cells were subcutaneously injected and saline was injected in the CT group. After 14 days, the small and large intestines were removed for histochemical analysis. The macroscopic morphology of the intestines and the fecal excretion were also observed. KEY RESULTS The upper GI transit and weight of fecal pellets were reduced and the walls of the large intestine in tumor-bearing rats showed multiple constrictions. In the capsules' constitution of the myenteric plexus of the TW group, there were type III collagen fibers in addition to type I fibers, and the thin septa inside the capsule were absent. The large intestine in the TW group exhibited smaller neurons and the number of nitrergic-positive neurons was also reduced in the myenteric plexus, compared to the CT group. In the TW group, the neuronal numbers and the staining intensity of acetylcholinesterase (AChE) were reduced in the large intestine. Staining was not different in the small intestine. CONCLUSIONS AND INFERENCES This study showed that the Walker-256 tumor induced alterations in the morphology of nitrergic and cholinergic neurons in the myenteric plexus and decreased the upper GI transit with the presence of multiple constrictions in the colon. Therefore, these alterations can interfere on neurotransmission and can be related to the intestinal motility alterations observed in tumor-bearing rats.
Collapse
Affiliation(s)
- P Marega
- Federal University of Santa Maria, Santa Maria, RS, Brazil
| | - E A Liberti
- University of São Paulo, Sao Paulo, SP, Brazil
| | | | - K S Kietzer
- University of Pará State, Belem, Pará, Brazil
| |
Collapse
|
5
|
West C, Wu RY, Wong A, Stanisz AM, Yan R, Min KK, Pasyk M, McVey Neufeld KA, Karamat MI, Foster JA, Bienenstock J, Forsythe P, Kunze WA. Lactobacillus rhamnosus strain JB-1 reverses restraint stress-induced gut dysmotility. Neurogastroenterol Motil 2017; 29. [PMID: 27381257 DOI: 10.1111/nmo.12903] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 06/15/2016] [Indexed: 12/11/2022]
Abstract
BACKGROUND Environmental stress affects the gut with dysmotility being a common consequence. Although a variety of microbes or molecules may prevent the dysmotility, none reverse the dysmotility. METHODS We have used a 1 hour restraint stress mouse model to test for treatment effects of the neuroactive microbe, L. rhamnosus JB-1™ . Motility of fluid-filled ex vivo gut segments in a perfusion organ bath was recorded by video and migrating motor complexes measured using spatiotemporal maps of diameter changes. KEY RESULTS Stress reduced jejunal and increased colonic propagating contractile cluster velocities and frequencies, while increasing contraction amplitudes for both. Luminal application of 10E8 cfu/mL JB-1 restored motor complex variables to unstressed levels within minutes of application. L. salivarius or Na.acetate had no treatment effects, while Na.butyrate partially reversed stress effects on colonic frequency and amplitude. Na.propionate reversed the stress effects for jejunum and colon except on jejunal amplitude. CONCLUSIONS & INFERENCES Our findings demonstrate, for the first time, a potential for certain beneficial microbes as treatment of stress-induced intestinal dysmotility and that the mechanism for restoration of function occurs within the intestine via a rapid drug-like action on the enteric nervous system.
Collapse
Affiliation(s)
- C West
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - R Y Wu
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - A Wong
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - A M Stanisz
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - R Yan
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - K K Min
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - M Pasyk
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - K-A McVey Neufeld
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - M I Karamat
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - J A Foster
- Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada
| | - J Bienenstock
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.,Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - P Forsythe
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Medicine, McMaster University, Hamilton, ON, Canada.,Firestone Institute for Respiratory Health, St. Joseph's Healthcare, Hamilton, ON, Canada
| | - W A Kunze
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada.,Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton, ON, Canada.,Department of Biology, McMaster University, Hamilton, ON, Canada
| |
Collapse
|
6
|
Swaminathan M, Hill-Yardin E, Ellis M, Zygorodimos M, Johnston LA, Gwynne RM, Bornstein JC. Video Imaging and Spatiotemporal Maps to Analyze Gastrointestinal Motility in Mice. J Vis Exp 2016:53828. [PMID: 26862815 DOI: 10.3791/53828] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The enteric nervous system (ENS) plays an important role in regulating gastrointestinal (GI) motility and can function independently of the central nervous system. Changes in ENS function are a major cause of GI symptoms and disease and may contribute to GI symptoms reported in neuropsychiatric disorders including autism. It is well established that isolated colon segments generate spontaneous, rhythmic contractions known as Colonic Migrating Motor Complexes (CMMCs). A procedure to analyze the enteric neural regulation of CMMCs in ex vivo preparations of mouse colon is described. The colon is dissected from the animal and flushed to remove fecal content prior to being cannulated in an organ bath. Data is acquired via a video camera positioned above the organ bath and converted to high-resolution spatiotemporal maps via an in-house software package. Using this technique, baseline contractile patterns and pharmacological effects on ENS function in colon segments can be compared over 3-4 hr. In addition, propagation length and speed of CMMCs can be recorded as well as changes in gut diameter and contraction frequency. This technique is useful for characterizing gastrointestinal motility patterns in transgenic mouse models (and in other species including rat and guinea pig). In this way, pharmacologically induced changes in CMMCs are recorded in wild type mice and in the Neuroligin-3(R451C) mouse model of autism. Furthermore, this technique can be applied to other regions of the GI tract including the duodenum, jejunum and ileum and at different developmental ages in mice.
Collapse
Affiliation(s)
| | | | - Melina Ellis
- Department of Physiology, The University of Melbourne
| | | | - Leigh A Johnston
- Department of Electrical and Electronic Engineering, The University of Melbourne
| | | | | |
Collapse
|
7
|
Al-Saffar A, Nogueira da Costa A, Delaunois A, Leishman DJ, Marks L, Rosseels ML, Valentin JP. Gastrointestinal Safety Pharmacology in Drug Discovery and Development. Handb Exp Pharmacol 2015; 229:291-321. [PMID: 26091645 DOI: 10.1007/978-3-662-46943-9_12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although the basic structure of the gastrointestinal tract (GIT) is similar across species, there are significant differences in the anatomy, physiology, and biochemistry between humans and laboratory animals, which should be taken into account when conducting a gastrointestinal (GI) assessment. Historically, the percentage of cases of drug attrition associated with GI-related adverse effects is small; however, this incidence has increased over the last few years. Drug-related GI effects are very diverse, usually functional in nature, and not limited to a single pharmacological class. The most common GI signs are nausea and vomiting, diarrhea, constipation, and gastric ulceration. Despite being generally not life-threatening, they can greatly affect patient compliance and quality of life. There is therefore a real need for improved and/or more extensive GI screening of candidate drugs in preclinical development, which may help to better predict clinical effects. Models to identify drug effects on GI function cover GI motility, nausea and emesis liability, secretory function (mainly gastric secretion), and absorption aspects. Both in vitro and in vivo assessments are described in this chapter. Drug-induced effects on GI function can be assessed in stand-alone safety pharmacology studies or as endpoints integrated into toxicology studies. In silico approaches are also being developed, such as the gut-on-a-chip model, but await further optimization and validation before routine use in drug development. GI injuries are still in their infancy with regard to biomarkers, probably due to their greater diversity. Nevertheless, several potential blood, stool, and breath biomarkers have been investigated. However, additional validation studies are necessary to assess the relevance of these biomarkers and their predictive value for GI injuries.
Collapse
Affiliation(s)
- Ahmad Al-Saffar
- Faculty of Medicine, Department of Medical Sciences, Uppsala University, 751 85, Uppsala, Sweden
| | | | | | | | | | | | | |
Collapse
|
8
|
Huizinga JD, Parsons SP, Chen JH, Pawelka A, Pistilli M, Li C, Yu Y, Ye P, Liu Q, Tong M, Zhu YF, Wei D. Motor patterns of the small intestine explained by phase-amplitude coupling of two pacemaker activities: the critical importance of propagation velocity. Am J Physiol Cell Physiol 2015; 309:C403-14. [PMID: 26135802 DOI: 10.1152/ajpcell.00414.2014] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 06/26/2015] [Indexed: 12/23/2022]
Abstract
Phase-amplitude coupling of two pacemaker activities of the small intestine, the omnipresent slow wave activity generated by interstitial cells of Cajal of the myenteric plexus (ICC-MP) and the stimulus-dependent rhythmic transient depolarizations generated by ICC of the deep muscular plexus (ICC-DMP), was recently hypothesized to underlie the orchestration of the segmentation motor pattern. The aim of the present study was to increase our understanding of phase-amplitude coupling through modeling. In particular the importance of propagation velocity of the ICC-DMP component was investigated. The outcome of the modeling was compared with motor patterns recorded from the rat or mouse intestine from which propagation velocities within the different patterns were measured. The results show that the classical segmentation motor pattern occurs when the ICC-DMP component has a low propagation velocity (<0.05 cm/s). When the ICC-DMP component has a propagation velocity in the same order of magnitude as that of the slow wave activity (∼1 cm/s), cluster type propulsive activity occurs which is in fact the dominant propulsive activity of the intestine. Hence, the only difference between the generation of propagating cluster contractions and the Cannon-type segmentation motor pattern is the propagation velocity of the low-frequency component, the rhythmic transient depolarizations originating from the ICC-DMP. Importantly, the proposed mechanism explains why both motor patterns have distinct rhythmic waxing and waning of the amplitude of contractions. The hypothesis is brought forward that the velocity is modulated by neural regulation of gap junction conductance within the ICC-DMP network.
Collapse
Affiliation(s)
- Jan D Huizinga
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Sean P Parsons
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and
| | - Ji-Hong Chen
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Andrew Pawelka
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and
| | - Marc Pistilli
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and
| | - Chunpei Li
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Yuanjie Yu
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Pengfei Ye
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Qing Liu
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Mengting Tong
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| | - Yong Fang Zhu
- Farncombe Family Digestive Health Research Institute, Department of Medicine, McMaster University, Hamilton, Canada; and
| | - Defei Wei
- Department of Gastroenterology and Hepatology, Renmin Hospital of Wuhan University, Wuhan University Institute of Digestive and Liver Diseases, Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China
| |
Collapse
|
9
|
Chambers JD, Thomas EA, Bornstein JC. Mathematical modelling of enteric neural motor patterns. Clin Exp Pharmacol Physiol 2014; 41:155-64. [PMID: 24471867 DOI: 10.1111/1440-1681.12209] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 01/07/2023]
Abstract
1. The enteric nervous system modulates intestinal behaviours, such as motor patterns and secretion. Although much is known about different types of neurons and simple reflexes in the intestine, it remains unclear how complex behaviours are generated. 2. Mathematical modelling is an important tool for assisting the understanding of how the neurons and reflexes can be pieced together to generate intestinal behaviours. 3. Models have identified a functional role for slow excitatory post-synaptic potentials (EPSPs) by distinguishing between fast and slow EPSPs in the ascending excitation reflex. These models also discovered coordinated firing of similarly located neurons as emergent properties of feed-forward networks of interneurons in the intestine. A model of the recurrent network of intrinsic sensory neurons identified important control mechanisms to prevent uncontrolled firing due to positive feedback and that the interaction between these control mechanisms and slow EPSPs is necessary for the networks to encode ongoing sensory stimuli. This model also showed that such networks may mediate migrating motor complexes. 4. A network model of vasoactive intestinal peptide neurons in the submucosal plexus found this relatively sparse recurrent network could produce uncontrolled firing under conditions that appear to be related to cholera toxin-induced hypersecretion. 5. Abstract modelling of the intestinal fed-state motor patterns has identified how stationary contractions can arise from a polarized network. 6. These models have also helped predict and/or explained pharmacological evidence for two rhythm generators and the requirement of feedback from contractions in the circular muscle.
Collapse
Affiliation(s)
- Jordan D Chambers
- Department of Physiology, University of Melbourne, Victoria, Australia
| | | | | |
Collapse
|
10
|
Ramakrishnan S, Arnett B, Murphy AD. Contextual modulation of a multifunctional central pattern generator. J Exp Biol 2014; 217:3935-44. [PMID: 25189372 DOI: 10.1242/jeb.086751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The multifunctional buccal central pattern generator in snails, which controls different oral behaviors, has been well characterized. In this work we propose a role for the group of about 40 electrotonically coupled buccal A cluster cells as a context-dependant switch for the buccal central pattern generator, modulating motor patterns that elicit different oral behaviors. We characterize these cells based on location and morphology, and provide evidence for their selective activation under two different stimuli - Listerine perfusion and intestinal nerve stimulation - triggering buccal motor patterns putatively underlying egestion and substrate cleaning. A new role for these electrotonically coupled buccal A cluster neurons is shown. They serve as a context-dependant switch that alters buccal motor patterns depending on input stimuli, thereby eliciting the appropriate behavioral response.
Collapse
Affiliation(s)
| | | | - A Don Murphy
- Department of Biological Sciences, University of Illinois, Chicago, IL-60607, USA
| |
Collapse
|
11
|
Janssen PWM, Lentle RG, Chambers P, Reynolds GW, De Loubens C, Hulls CM. Spatiotemporal organization of standing postprandial contractions in the distal ileum of the anesthetized pig. Neurogastroenterol Motil 2014; 26:1651-62. [PMID: 25251369 DOI: 10.1111/nmo.12447] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 08/30/2014] [Indexed: 02/08/2023]
Abstract
BACKGROUND Spatiotemporal (ST) mapping has mainly been applied to ex vivo preparations of the gut. We report the results of ST mapping of the spontaneous and remifentanil-induced motility of circular and longitudinal muscles of the distal ileum in the postprandial anaesthetized pig. METHODS Spatiotemporal maps of strain rate were derived from image sequences of an exteriorized loop of ileum on a superfusion tray at laparotomy. Parameters were obtained by direct measurement from these maps, and by auto- and cross-correlation of map segments. KEY RESULTS Localized domains of standing longitudinal and circular activity that alternated between neighboring domains occurred spontaneously and both were promptly extinguished following intraluminal dosage with lidocaine. Longitudinal or circular contractions within a domain typically occurred at times that would coincide with every second or third cycle of the slow wave but propagated within the domain at a rate consistent with that reported within spike patches. Shortly after intravenous administration of remifentanil, longitudinal and circular contractions at the reported slow wave frequency propagated over longer distances at a high speed before slowing to a rate similar to that reported for slow waves. CONCLUSIONS & INFERENCES ST mapping based on cross-correlation is a robust tool for the analysis of intestinal movement and minimizing movement artefacts. We propose that the ST pattern of standing longitudinal and circular contractions arises from variation in the refractory period of smooth muscle, and hence, in its response to successive slow waves with neural stimuli influencing the former and having a mainly permissive role.
Collapse
Affiliation(s)
- P W M Janssen
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand
| | | | | | | | | | | |
Collapse
|
12
|
Gwynne RM, Clarke AJ, Furness JB, Bornstein JC. Both exogenous 5-HT and endogenous 5-HT, released by fluoxetine, enhance distension evoked propulsion in guinea-pig ileum in vitro. Front Neurosci 2014; 8:301. [PMID: 25285066 PMCID: PMC4168689 DOI: 10.3389/fnins.2014.00301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/03/2014] [Indexed: 12/11/2022] Open
Abstract
The roles of 5-HT3 and 5-HT4 receptors in the modulation of intestinal propulsion by luminal application of 5-HT and augmentation of endogenous 5-HT effects were studied in segments of guinea-pig ileum in vitro. Persistent propulsive contractions evoked by saline distension were examined using a modified Trendelenburg method. When 5-HT (30 nM), fluoxetine (selective serotonin reuptake inhibitor; 1 nM), 2-methyl-5-HT (5-HT3 receptor agonist; 1 mM), or RS 67506 (5-HT4 receptor agonist, 1 μM) was infused into the lumen, the pressure needed to initiate persistent propulsive activity fell significantly. A specific 5-HT4 receptor antagonist, SB 207266 (10 nM in lumen), abolished the effects of 5-HT, fluoxetine, and RS 67506, but not those of 2-methyl-5-HT. Granisetron (5-HT3 receptor antagonist; 1 μM in lumen) abolished the effect of 5-HT, fluoxetine, RS 67506, and 2-methyl-5-HT. The NK3 receptor antagonist SR 142801 (100 nM in lumen) blocked the effects of 5-HT, fluoxetine, and 2-methyl-5-HT. SB 207266, granisetron, and SR 142801 had no effect by themselves. Higher concentrations of fluoxetine (100 and 300 nM) and RS 67506 (3 and 10 μM) had no effect on the distension threshold for propulsive contractions. These results indicate that luminal application of exogenous 5-HT, or increased release of endogenous mucosal 5-HT above basal levels, acts to lower the threshold for propulsive contractions in the guinea-pig ileum via activation of 5-HT3 and 5-HT4 receptors and the release of tachykinins. The results further indicate that basal release of 5-HT is insufficient to alter the threshold for propulsive motor activity.
Collapse
Affiliation(s)
- Rachel M Gwynne
- Department of Physiology, University of Melbourne Parkville, VIC, Australia
| | - Amanda J Clarke
- Department of Physiology, University of Melbourne Parkville, VIC, Australia
| | - John B Furness
- Departments of Anatomy and Cell Biology, University of Melbourne Parkville, VIC, Australia
| | - Joel C Bornstein
- Department of Physiology, University of Melbourne Parkville, VIC, Australia
| |
Collapse
|
13
|
Wang K, Bertrand RL, Senadheera S, Polglaze KE, Murphy TV, Sandow SL, Liu L, Bornstein JC, Bertrand PP. Motility changes induced by intraluminal FeSO4 in guinea pig jejunum. Neurogastroenterol Motil 2014; 26:385-96. [PMID: 24330033 DOI: 10.1111/nmo.12276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 11/14/2013] [Indexed: 12/21/2022]
Abstract
BACKGROUND Dietary iron supplementation is associated with gastrointestinal (GI) side effects including vomiting, nausea, and diarrhea. Although inorganic iron in high concentrations may be damaging to the intestinal mucosa, we hypothesize that there are physiological effects on the GI tract that occur at concentrations achieved by supplementation. Thus, our aim was to investigate the effect of intraluminal ferrous sulfate (FeSO4 ) on jejunal motility. METHODS Segments of guinea pig jejunum were cannulated and the intraluminal pressure recorded with a transducer, while movements were recorded with a video camera. Peristaltic threshold was the oral pressure that evoked four consecutive propulsive contractions. The nutrients decanoic acid (1 mM), l-phenylalanine (50 mM), or the micronutrient FeSO4 (1 mM) were infused intraluminally. We also tested the effect of FeSO4 on electrochemically detected serotonin (5-HT, 5-hydroxytryptamine) released from in vitro tissues, both at rest and following mechanical stimulation. KEY RESULTS The jejuna peristaltic threshold was significantly decreased by all three nutrients: FeSO4 : 31 ± 2-23 ± 3 mmH2 O; decanoic acid: 27 ± 2-14 ± 2 mmH2 O; and l-phenylalanine: 30 ± 3-14 ± 3mmH2 O. Of the three, only decanoic acid induced segmentation, while FeSO4 inhibited decanoic acid-induced segmentation. Resting 5-HT release was increased by FeSO4 (128% of control), but mechanically evoked 5-HT release was reduced (70% of control). CONCLUSIONS & INFERENCES These data suggest that some luminal effects of inorganic iron on jejunal motility could be mediated through a pathway involving altered release of 5-HT. A better understanding of the interaction between luminal iron and 5-HT containing enterochromaffin cells could improve iron supplementation strategies, thus reducing side effects.
Collapse
Affiliation(s)
- K Wang
- Department of Physiology, School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Kano T, Kawakatsu T, Ishiguro A. Generating Situation-Dependent Behavior: Decentralized Control of Multi-Functional Intestine-Like Robot that can Transport and Mix Contents. JOURNAL OF ROBOTICS AND MECHATRONICS 2013. [DOI: 10.20965/jrm.2013.p0871] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most robots are designed to perform a specific task in a predefined environment and have difficulty in producing situation-dependent behavior. To tackle this problem, we focus here on a mammal intestine that either transports or mixes the contents depending on the encountered circumstances. We propose a simple model for the intestinal movement and design an autonomous decentralized control scheme for an intestine-like robot by using coupled oscillators with local sensory feedback. Simulation results show that different types of motions are generated depending on the the physical conditions of the intestine and its contents. Our simulated robot does not require any input from a higher center to switch between different types of motions but determines autonomously which motion to generate. This study thus paves the way for developing “multi-functional robots” whose behavior is changed flexibly and spontaneously depending on circumstances.
Collapse
|
15
|
Mao YK, Kasper DL, Wang B, Forsythe P, Bienenstock J, Kunze WA. Bacteroides fragilis polysaccharide A is necessary and sufficient for acute activation of intestinal sensory neurons. Nat Commun 2013; 4:1465. [PMID: 23403566 DOI: 10.1038/ncomms2478] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 01/11/2013] [Indexed: 02/08/2023] Open
Abstract
Symbionts or probiotics are known to affect the nervous system. To understand the mechanisms involved, it is important to measure sensory neuron responses and identify molecules responsible for this interaction. Here we test the effects of adding Lactobacillus rhamnosus (JB-1) and Bacteroides fragilis to the epithelium while making voltage recordings from intestinal primary afferent neurons. Sensory responses are recorded within 8 s of applying JB-1 and excitability facilitated within 15 min. Bacteroides fragilis produces similar results, as does its isolated, capsular exopolysaccharide, polysaccharide A. Lipopolysaccharide-free polysaccharide A completely mimics the neuronal effects of the parent organism. Experiments with a mutant Bacteroides fragilis devoid of polysaccharide A shows that polysaccharide A is necessary and sufficient for the neuronal effects. Complex carbohydrates have not been reported before as candidates for such signalling between symbionts and the host. These observations indicate new neuronal targets and invite further study of bacterial carbohydrates as inter-kingdom signalling molecules between beneficial bacteria and sensory neurons.
Collapse
Affiliation(s)
- Yu-Kang Mao
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, Ontario, Canada L8N 4A6
| | | | | | | | | | | |
Collapse
|
16
|
Linden DR. Enhanced excitability of guinea pig ileum myenteric AH neurons during and following recovery from chemical colitis. Neurosci Lett 2013; 545:91-5. [PMID: 23628671 DOI: 10.1016/j.neulet.2013.04.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 04/02/2013] [Accepted: 04/06/2013] [Indexed: 11/26/2022]
Abstract
Inflammation of the colon changes motor function of more proximal regions of the gastrointestinal tract. Colitis alters the neurophysiology of enteric neurons within the region of inflammation, which may contribute to altered colonic motor and secretory function. This study seeks to test the hypothesis that colitis alters the neurophysiology of myenteric neurons in the non-inflamed ileum, and that altered neurophysiology coincides with altered small bowel motor function. Trinitrobenzene sulfonic acid (TNBS)-induced colitis was associated with hyperexcitability of AH neurons in the ileum myenteric plexus, demonstrated by depolarized neurons and increased numbers of action potentials, but without changes in the action potential duration or afterhyperpolarization typical of plasticity in these cells. There were no changes in synaptic transmission of either AH neurons or S neurons observed in the current study. The onset of AH neuron hyperexcitability occurred 24 h following administration of TNBS, and persisted to eight weeks, a time point following the resolution of colitis. Small bowel transit was reduced as early as 12 h after TNBS and resolved by 48 h after TNBS. While AH neurons play a central role in coordinating motor function of the ileum, changes in excitability of these neurons did not coincide with changes in small bowel transit.
Collapse
Affiliation(s)
- David R Linden
- Department of Physiology and Biomedical Engineering and Enteric NeuroScience Program, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
| |
Collapse
|
17
|
Ellis M, Chambers JD, Gwynne RM, Bornstein JC. Serotonin and cholecystokinin mediate nutrient-induced segmentation in guinea pig small intestine. Am J Physiol Gastrointest Liver Physiol 2013; 304:G749-61. [PMID: 23392236 DOI: 10.1152/ajpgi.00358.2012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Segmentation is an important process in nutrient mixing and absorption; however, the mechanisms underlying this motility pattern are poorly understood. Segmentation can be induced by luminal perfusion of fatty acid in guinea pig small intestine in vitro and mimicked by the serotonin (5-HT) reuptake inhibitor fluoxetine (300 nM) and by cholecystokinin (CCK). Serotonergic and CCK-related mechanisms underlying nutrient-induced segmentation were investigated using selective 5-HT and CCK receptor antagonists on isolated segments of small intestine luminally perfused with 1 mM decanoic acid. Motility patterns were analyzed using video imaging and spatiotemporal maps. Segmenting activity mediated by decanoic acid was depressed following luminal application of the 5-HT receptor antagonists granisetron (5-HT(3), 1 μM) and SB-207266 (5-HT(4), 10 nM) and the CCK receptor antagonists devazepide (CCK-1, 300 nM) and L-365260 (CCK-2, 300 nM), but these antagonists did not further depress segmentation when combined. The P2 receptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonate (10 μM) had no effect on activity. Serosal application of 5-HT antagonists had little effect on segmentation in the duodenum but reduced activity in the jejunum when granisetron and SB-207266 were applied together. These results reveal that 5-HT(3) and 5-HT(4) receptors, as well as CCK-1 and CCK-2 receptors, are critical in regulating decanoic acid-induced segmentation. Computational simulation indicated that these data are consistent with decanoic acid activating two pathways in the mucosa that converge within the enteric neural circuitry, while contraction-induced release of 5-HT from the mucosa provides feedback into the neural circuit to set the time course of the overall contractile activity.
Collapse
Affiliation(s)
- Melina Ellis
- Department of Physiology, University of Melbourne, Parkville, Victoria, Australia.
| | | | | | | |
Collapse
|
18
|
Du P, O'Grady G, Gao J, Sathar S, Cheng LK. Toward the virtual stomach: progress in multiscale modeling of gastric electrophysiology and motility. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2013; 5:481-93. [PMID: 23463750 DOI: 10.1002/wsbm.1218] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Experimental progress in investigating normal and disordered gastric motility is increasingly being complimented by sophisticated multiscale modeling studies. Mathematical modeling has become a valuable tool in this effort, as there is an ever-increasing need to gain an integrative and quantitative understanding of how physiological mechanisms achieve coordinated functions across multiple biophysical scales. These interdisciplinary efforts have been particularly notable in the area of gastric electrophysiology, where they are beginning to yield a comprehensive and integrated in silico organ modeling framework, or 'virtual stomach'. At the cellular level, a number of biophysically based mathematical cell models have been developed, and these are now being applied in areas including investigations of gastric electrical pacemaker mechanisms, smooth muscle electrophysiology, and electromechanical coupling. At the tissue level, micro-structural models are being creatively developed and employed to investigate clinically significant questions, such as the functional effects of ICC degradation on gastrointestinal (GI) electrical activation. At the organ level, high-resolution electrical mapping and modeling studies are combined to provide improved insights into normal and dysrhythmic gastric electrical activation. These efforts are also enabling detailed forward and inverse modeling studies at the 'whole body' level, with implications for diagnostic techniques for gastric dysrhythmias. These recent advances, together with several others highlighted in this review, collectively demonstrate a powerful trend toward applying mathematical models to effectively investigate structure-function relationships and overcome multiscale challenges in basic and clinical GI research.
Collapse
Affiliation(s)
- Peng Du
- The Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.
| | | | | | | | | |
Collapse
|
19
|
Wu RY, Pasyk M, Wang B, Forsythe P, Bienenstock J, Mao YK, Sharma P, Stanisz AM, Kunze WA. Spatiotemporal maps reveal regional differences in the effects on gut motility for Lactobacillus reuteri and rhamnosus strains. Neurogastroenterol Motil 2013; 25:e205-14. [PMID: 23316914 DOI: 10.1111/nmo.12072] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Commensal bacteria such as probiotics that are neuroactive acutely affect the amplitudes of intestinal migrating motor complexes (MMCs). What is lacking for an improved understanding of these motility effects are region specific measurements of velocity and frequency. We have combined intraluminal pressure recordings with spatiotemporal diameter maps to analyze more completely effects of different strains of beneficial bacteria on motility. METHODS Intraluminal peak pressure (PPr) was measured and video recordings made of mouse ex vivo jejunum and colon segments before and after intraluminal applications of Lactobacillus rhamnosus (JB-1) or Lactobacillus reuteri (DSM 17938). Migrating motor complex frequency and velocity were calculated. KEY RESULTS JB-1 decreased jejunal frequencies by 56% and 34% in colon. Jejunal velocities increased 171%, but decreased 31% in colon. Jejunal PPr decreased by 55% and in colon by 21%. DSM 17938 increased jejunal frequencies 63% and in colon 75%; jejunal velocity decreased 57%, but increased in colon 146%; jejunal PPr was reduced 26% and 12% in colon. TRAM-34 decreased frequency by 71% and increased velocity 200% for jejunum, but increased frequency 46% and velocity 50% for colon; PPr was decreased 59% for jejunum and 39% for colon. CONCLUSIONS & INFERENCES The results show that probiotics and other beneficial bacteria have strain and region-specific actions on gut motility that can be successfully discriminated using spatiotemporal mapping of diameter changes. Effects are not necessarily the same in colon and jejunum. Further research is needed on the detailed effects of the strains on enteric neuron currents for each gut region.
Collapse
Affiliation(s)
- R Y Wu
- McMaster Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Abstract
Neural activity is integral to the development of the enteric nervous system (ENS). A subpopulation of neural crest-derived cells expresses pan-neuronal markers at early stages of ENS development (at E10.5 in the mouse). However, the electrical activity of these cells has not been previously characterized, and it is not known whether all cells expressing neuronal markers are capable of firing action potentials (APs). In this study, we examined the activity of "neuron"-like cells (expressing pan-neuronal markers or with neuronal morphology) in the gut of E11.5 and E12.5 mice using whole-cell patch-clamp electrophysiology and compared them to the activity of neonatal and adult enteric neurons. Around 30-40% of neuron-like cells at E11.5 and E12.5 fired APs, some of which were very similar to those of adult enteric neurons. All APs were sensitive to tetrodotoxin (TTX), indicating that they were driven by voltage-gated Na+ currents. Expression of mRNA encoding several voltage-gated Na+ channels by the E11.5 gut was detected using RT-PCR. The density of voltage-gated Na+ currents increased from E11.5 to neonates. Immature active responses, mediated in part by TTX- and lidocaine-insensitive channels, were observed in most cells at E11.5 and E12.5, but not in P0/P1 or adult neurons. However, some cells expressing neuronal markers at E11.5 or E12.5 did not exhibit an active response to depolarization. Spontaneous depolarizations resembling excitatory postsynaptic potentials were observed at E12.5. The ENS is one of the earliest parts of the developing nervous system to exhibit mature forms of electrical activity.
Collapse
|
21
|
Che T, Sun H, Li J, Yu X, Zhu D, Xue B, Liu K, Zhang M, Kunze W, Liu C. Oxytocin hyperpolarizes cultured duodenum myenteric intrinsic primary afferent neurons by opening BK(Ca) channels through IP₃ pathway. J Neurochem 2012; 121:516-25. [PMID: 22356163 DOI: 10.1111/j.1471-4159.2012.07702.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Oxytocin (OT) is clinically important in gut motility and constitutively reduces duodenum contractility. Intrinsic primary afferent neurons (IPANs), whose physiological classification is as AH cells, are the 1st neurons of the peristaltic reflex pathway. We set out to investigate if this inhibitory effect is mediated by IPANs and to identify the ion channel(s) and intracellular signal transduction pathway that are involved in this effect. Myenteric neurons were isolated from the longitudinal muscle myenteric plexus (LMMP) preparation of rat duodenum and cultured for 16-24 h before electrophysiological recording in whole cell mode and AH cells identified by their electrophysiological characteristics. The cytoplasmic Ca²⁺ concentration ([Ca²⁺](i) ) of isolated neurons was measured using calcium imaging. The concentration of IP(3) in the LMMP and the OT secreted from the LMMP were measured using ELISA. The oxytocin receptor (OTR) and large-conductance calcium-activated potassium (BK(Ca)) channels, as well as the expression of OT and the IPAN marker calbindin 28 K, on the myenteric plexus neurons were localized using double-immunostaining techniques. We found that administration of OT (10⁻⁷ to 10⁻⁵ M) dose dependently hyperpolarized the resting membrane potential and increased the total outward current. The OTR antagonist atosiban or the BK(Ca) channel blocker iberiotoxin (IbTX) blocked the effects of OT suggesting that the increased outward current resulted from BK(Ca) channel opening. OTR and the BK(Ca) α subunit were co-expressed on a subset of myenteric neurons at the LMMP. NS1619 (10⁻⁵ M, a BK(Ca) channel activator) increased the outward current similar to the effect of OT. OT administration also increased [Ca²⁺](i) and the OT-evoked outward current was significantly attenuated by thapsigargin (10⁻⁶ M) or CdCl₂. The effect of OT on the BK(Ca) current was also blocked by pre-treatment with the IP₃ receptor antagonist 2-APB (10⁻⁴ M) or the PLC inhibitor U73122 (10⁻⁵ M). OT (10⁻⁶ M) also increased the IP₃ concentration within the LMMP. Both of the spontaneous and KCl-induced secretion of OT was enhanced by atosiban. Most of OT-immunoreactive cells are also immunoreactive for calbindin 28 K. In summary, we concluded that OT hyperpolarized myenteric IPANs by activating BK(Ca) channels via the OTR-PLC-IP₃-Ca²⁺ signal pathway. OT might modulate IPANs mediated ENS reflex by an autocrine and negative feedback manner.
Collapse
Affiliation(s)
- Tongtong Che
- Department of Physiology, Shandong Provincial Key Laboratory of Mental Disorders, Shandong University School of Medicine, Jinan, China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Du P, Poh YC, Lim JL, Gajendiran V, O'Grady G, Buist ML, Pullan AJ, Cheng LK. A preliminary model of gastrointestinal electromechanical coupling. IEEE Trans Biomed Eng 2011; 58:3491-5. [PMID: 21878406 DOI: 10.1109/tbme.2011.2166155] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Gastrointestinal (GI) motility is coordinated by several cooperating mechanisms, including electrical slow wave activity, the enteric nervous system (ENS), and other factors. Slow waves generated in interstitial cells of Cajal (ICC) depolarize smooth muscle cells (SMC), generating basic GI contractions. This unique electrical coupling presents an added layer of complexity to GI electromechanical models, and a current barrier to further progress is the lack of a framework for ICC-SMC-contraction coupling. In this study, an initial framework for the electromechanical coupling was developed in a 2-D model. At each solution step, the slow wave propagation was solved first and [Ca(2+)](i) in the SMC model was related to a Ca(2+)-tension-extension relationship to simulate active contraction. With identification of more GI-specific constitutive laws and material parameters, the ICC-SMC-contraction approach may underpin future GI electromechanical models of health and disease states.
Collapse
Affiliation(s)
- Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland 1010, New Zealand.
| | | | | | | | | | | | | | | |
Collapse
|