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Bao L, Zhao J, Gregersen H. Association between jejunal remodeling in fasting rats and hypersensitivity of intestinal afferent nerves to mechanical stimulation. Biomech Model Mechanobiol 2024; 23:73-86. [PMID: 37548873 DOI: 10.1007/s10237-023-01758-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Accepted: 07/24/2023] [Indexed: 08/08/2023]
Abstract
Remodeling of Intestinal properties and hypersensitivity of intestinal afferents to mechanical stimulation were previously demonstrated in a fasting rat model. Other studies investigated the association between mechanical and histological remodeling during fasting. This study aimed to further explore the relationship between the jejunal remodeling and intestinal afferent hypersensitivity by combining afferent nerve recordings with histological and mechanical data. Eight male Sprague Dawley rats had no access to food for 7 days (Fasting group). Seven male rats served as controls (Control group). Jejunal segments were studied in vitro in an organ bath for analysis of afferent signaling and for analysis of mechanical and histomorphological parameters. Correlation analyses were done to analyze association between nerve activity (spike rate increase ratio, SRIR) at distension levels of 20, 40 and 80 cmH2O and mechanical stress and histomorphological changes of the jejunal segments. Compared with the Control group, the main findings in jejunal segments in the Fasting group were (1) Most histomorphometry parameters were reduced (P < 0.05-P < 0.001), (2) SRIR values were higher (P < 0.001), (3) The relative numbers of intermuscular and submucosal neurons were increased (P < 0.05-P < 0.01), and (4) SRIR was negatively correlated with intestinal wall thickness, circumferential muscle layer thickness and positively correlated with the inner residual strain, the number of neurons, and the mechanical stress. In conclusion, the fasting-induced histomorphological remodeling (reduced wall thickness and increased relative number of neurons) and biomechanical remodeling (residual strain changes and high stress level) of the intestine in fasting rats were associated with hypersensitivity of intestinal afferents. Afferent hypersensitivity appears to be dependent on stress rather than on strain.
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Affiliation(s)
- Lingxia Bao
- Chongqing University of Posts and Telecommunications, Chongqing, 400065, China
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, College of Bioengineering at Chongqing University, Chongqing, 400044, China
| | - Jingbo Zhao
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, College of Bioengineering at Chongqing University, Chongqing, 400044, China.
- Anbiping (Chongqing) Pathological Diagnosis Center, No. 8 Xiyuan North Road, Shapingba District, Chongqing, 401334, China.
| | - Hans Gregersen
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, College of Bioengineering at Chongqing University, Chongqing, 400044, China
- GIOME, California Medical Innovations Institute, San Diego, CA, USA
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Durcan C, Hossain M, Chagnon G, Perić D, Girard E. Mechanical experimentation of the gastrointestinal tract: a systematic review. Biomech Model Mechanobiol 2024; 23:23-59. [PMID: 37935880 PMCID: PMC10901955 DOI: 10.1007/s10237-023-01773-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 09/10/2023] [Indexed: 11/09/2023]
Abstract
The gastrointestinal (GI) organs of the human body are responsible for transporting and extracting nutrients from food and drink, as well as excreting solid waste. Biomechanical experimentation of the GI organs provides insight into the mechanisms involved in their normal physiological functions, as well as understanding of how diseases can cause disruption to these. Additionally, experimental findings form the basis of all finite element (FE) modelling of these organs, which have a wide array of applications within medicine and engineering. This systematic review summarises the experimental studies that are currently in the literature (n = 247) and outlines the areas in which experimentation is lacking, highlighting what is still required in order to more fully understand the mechanical behaviour of the GI organs. These include (i) more human data, allowing for more accurate modelling for applications within medicine, (ii) an increase in time-dependent studies, and (iii) more sophisticated in vivo testing methods which allow for both the layer- and direction-dependent characterisation of the GI organs. The findings of this review can also be used to identify experimental data for the readers' own constitutive or FE modelling as the experimental studies have been grouped in terms of organ (oesophagus, stomach, small intestine, large intestine or rectum), test condition (ex vivo or in vivo), number of directions studied (isotropic or anisotropic), species family (human, porcine, feline etc.), tissue condition (intact wall or layer-dependent) and the type of test performed (biaxial tension, inflation-extension, distension (pressure-diameter), etc.). Furthermore, the studies that investigated the time-dependent (viscoelastic) behaviour of the tissues have been presented.
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Affiliation(s)
- Ciara Durcan
- Zienkiewicz Centre for Modelling, Data and AI, Faculty of Science and Engineering, Swansea University, Swansea, SA1 8EN, UK
- Université Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000, Grenoble, France
| | - Mokarram Hossain
- Zienkiewicz Centre for Modelling, Data and AI, Faculty of Science and Engineering, Swansea University, Swansea, SA1 8EN, UK.
| | - Grégory Chagnon
- Université Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000, Grenoble, France
| | - Djordje Perić
- Zienkiewicz Centre for Modelling, Data and AI, Faculty of Science and Engineering, Swansea University, Swansea, SA1 8EN, UK
| | - Edouard Girard
- Université Grenoble Alpes, CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, 38000, Grenoble, France
- Laboratoire d'Anatomie des Alpes Françaises, Université Grenoble Alpes, Grenoble, France
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Park SJ, Zides CG, Beyak MJ. Mechanical activation of vagal afferents involves opposing cation and TREK1 currents and NO regulation. Can J Physiol Pharmacol 2023; 101:521-528. [PMID: 37311256 DOI: 10.1139/cjpp-2022-0345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Vagal afferents convey signals of mechanical stimulation in the gut to the brain, which is essential for the regulation of food intake. However, ion channels sensing mechanical stimuli are not fully understood. This study aimed to examine the ionic currents activated by mechanical stimulation and a possible neuro-modulatory role of nitric oxide on vagal afferents. Nodose neuronal currents and potentials, and intestinal afferent firing by mechanical stimulation were measured by whole-cell patch clamp, and in vitro afferent recording, respectively. Osmotically activated cation and two-pore domain K+ currents were identified in nodose neurons. The membrane potential displayed a biphasic change under hypotonic stimulation. Cation channel-mediated depolarization was followed by a hyperpolarization mediated by K+ channels. The latter was inhibited by l-methionine (TREK1 channel inhibitor) and l-NNA (nitric oxide synthase inhibitor). Correspondingly, mechanical stimulation activated opposing cation and TREK1 currents. NOS inhibition decreased TREK1 currents and potentiated jejunal afferent nerve firing induced by mechanical stimuli. This study suggested a novel activation mechanism of ion channels underlying adaptation under mechanical distension in vagal afferent neurons. The guts' ability to perceive mechanical stimuli is vital in determining how it responds to food intake. The mechanosensation through ion channels could initiate and control gut function.
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Affiliation(s)
- Sung Jin Park
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, K7L2V7, Canada
| | - Carter G Zides
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, K7L2V7, Canada
| | - Michael J Beyak
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, K7L2V7, Canada
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Simulations of Myenteric Neuron Dynamics in Response to Mechanical Stretch. COMPUTATIONAL INTELLIGENCE AND NEUROSCIENCE 2020; 2020:8834651. [PMID: 33123188 PMCID: PMC7582074 DOI: 10.1155/2020/8834651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/20/2020] [Accepted: 09/25/2020] [Indexed: 12/02/2022]
Abstract
Background Intestinal sensitivity to mechanical stimuli has been studied intensively in visceral pain studies. The ability to sense different stimuli in the gut and translate these to physiological outcomes relies on the mechanosensory and transductive capacity of intrinsic intestinal nerves. However, the nature of the mechanosensitive channels and principal mechanical stimulus for mechanosensitive receptors are unknown. To be able to characterize intestinal mechanoelectrical transduction, that is, the molecular basis of mechanosensation, comprehensive mathematical models to predict responses of the sensory neurons to controlled mechanical stimuli are needed. This study aims to develop a biophysically based mathematical model of the myenteric neuron with the parameters constrained by learning from existing experimental data. Findings. The conductance-based single-compartment model was selected. The parameters in the model were optimized by using a combination of hand tuning and automated estimation. Using the optimized parameters, the model successfully predicted the electrophysiological features of the myenteric neurons with and without mechanical stimulation. Conclusions The model provides a method to predict features and levels of detail of the underlying physiological system in generating myenteric neuron responses. The model could be used as building blocks in future large-scale network simulations of intrinsic primary afferent neurons and their network.
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Bao L, Zhao J, Liao D, Wang G, Gregersen H. Pressure overload changes mesenteric afferent nerve responses in a stress-dependent way in a fasting rat model. Biomech Model Mechanobiol 2020; 19:1741-1753. [PMID: 32072371 DOI: 10.1007/s10237-020-01305-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 02/06/2020] [Indexed: 12/28/2022]
Abstract
It is well known that overload changes the mechanical properties of biological tissues and fasting changes the responsiveness of intestinal afferents. This study aimed to characterize the effect of overload on mechanosensitivity in mesenteric afferent nerves in normal and fasted Sprague-Dawley rats. Food was restricted for 7 days in the Fasting group. Jejunal whole afferent nerve firing was recorded during three distensions, i.e., ramp distension to 80 cmH2O luminal pressure (D1), sustained distension to 120 cmH2O for 2 min (D2), and again to 80 cmH2O (D3). Multiunit afferent recordings were separated into low-threshold (LT) and wide-dynamic-range (WDR) single-unit activity for D1 and D3. Intestinal deformation (strain), distension load (stress), and firing frequency of mesenteric afferent nerve bundles [spike rate increase ratio (SRIR)] were compared at 20 cmH2O and 40 cmH2O and maximum pressure levels among distensions and groups. SRIR and stress changes showed the same pattern in all distensions. The SRIR and stress were larger in the Fasting group compared to the Control group (P < 0.01). SRIR was lower in D3 compared to D1 in controls (P < 0.05) and fasting rats (P < 0.01). Total single units and LT were significantly lower in Fasting group than in Controls at D3. LT was significantly higher in D3 than in D1 in Controls. Furthermore, correlation was found between SRIR with stress (R = 0.653, P < 0.001). In conclusion, overload decreased afferent mechanosensitivity in a stress-dependent way and was most pronounced in fasting rats. Fasting shifts LT to WDR and high pressure shifts WDR to LT in response to mechanical stimulation.
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Affiliation(s)
- Lingxia Bao
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; State and Local Joint Engineering Laboratory for Vascular Implants, College of Bioengineering, Chongqing University, Chongqing, 400044, China.,Department of Clinical Medicine, Giome Academia, Aarhus University, 8200, Aarhus N, Denmark
| | - Jingbo Zhao
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; State and Local Joint Engineering Laboratory for Vascular Implants, College of Bioengineering, Chongqing University, Chongqing, 400044, China.,Department of Clinical Medicine, Giome Academia, Aarhus University, 8200, Aarhus N, Denmark
| | - Donghua Liao
- Department of Clinical Medicine, Giome Academia, Aarhus University, 8200, Aarhus N, Denmark.,Department of Gastroenterology and Hepatology, Mech-Sense, Aalborg University Hospital and Clinical Institute, Faculty of Health Sciences, Aalborg University, Aalborg, Denmark
| | - Guixue Wang
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; State and Local Joint Engineering Laboratory for Vascular Implants, College of Bioengineering, Chongqing University, Chongqing, 400044, China
| | - Hans Gregersen
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; State and Local Joint Engineering Laboratory for Vascular Implants, College of Bioengineering, Chongqing University, Chongqing, 400044, China. .,Department of Surgery, GIOME, the Chinese University of Hong Kong, Pok Fu Lam, Hong Kong, SAR. .,Department of Surgery, Clinical Science Building, GIOME, Prince of Wales Hospital, Ngan Street, Shatin, Hong Kong.
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Implications of rectal preconditioning for interpretation of sensory-motor data. J Biomech 2020; 99:109541. [PMID: 31787257 DOI: 10.1016/j.jbiomech.2019.109541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 11/16/2019] [Accepted: 11/19/2019] [Indexed: 11/23/2022]
Abstract
Testing of biomechanical properties of intestine requires the tissue to be preconditioned by applying cyclic loading to obtain repeatable mechanical data. However, little is known about the mechanosensory properties during intestinal preconditioning. We aimed to study the relationship between mechanical preconditioning of the human rectum and sensory response. Three fast rectal bag distensions to the pain threshold were done in seven healthy females. A visual analog scale (VAS) was used for sensory assessment. At each distension, we determined (1) time, bag cross-sectional area (CSA), radius (r), r/r0, pressure and tension to reach VAS = 1, 3 and 5 (pain threshold); (2) the same parameters at induced contraction start; (3) CSA where the pressure started to increase (CSAP>baseline) and (4) the number of contractions. The time, CSA, r/r0 and tension to reach VAS = 1 and VAS = 3 increased from distension 1 to 3 (4.9 < F < 11.5, 0.05 > P > 0.007), primarily due to difference between the first and second distension. For VAS = 5, r/r0 was smaller in distension 3 than distension 1 (P < 0.05), whereas time, CSA and tension did not differ between distensions (P > 0.5). Compared with distension 1, CSA, r/r0 and tension at contraction start, and CSAP>baseline were bigger in distensions 2 and 3 (5.5 < F < 10.9, 0.05 > P > 0.009). The pressure to reach the VAS levels, the contraction numbers and pressure at contraction start did not differ among distensions (P > 0.6). During mechanical preconditioning, CSA, tension and deformation increased at sub-pain levels, reflecting sensory adaptation. The data point to acute remodeling of a strain-dependent mechanism in the rectal wall.
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Bao L, Zhao J, Liao D, Wang G, Gregersen H. Refeeding reverses fasting-induced remodeling of afferent nerve activity in rat small intestine. Biomech Model Mechanobiol 2019; 18:1915-1926. [DOI: 10.1007/s10237-019-01185-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 06/05/2019] [Indexed: 02/08/2023]
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Liu Y, Zhao J, Liao D, Wang G, Gregersen H. Stress-strain analysis of duodenal contractility in response to flow and ramp distension in rabbits fed low-fiber diet. Neurogastroenterol Motil 2019; 31:e13476. [PMID: 30246440 DOI: 10.1111/nmo.13476] [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: 07/06/2018] [Revised: 08/24/2018] [Accepted: 08/28/2018] [Indexed: 12/16/2022]
Abstract
BACKGROUND Previously we demonstrated that low-fiber diet in rabbits affects the passive mechanomorphological properties in the small intestine, resulting in reduced intestinal wall thickness and collagen content, as well as intestinal wall softening. The aim of the present study was to evaluate the contractility in rabbits on long-term low-fiber diet and specifically to compare the contraction threshold, the frequency, and the amplitude of flow-induced and distension-induced contractions in the duodenum between rabbits on normal diet and on long-term low-fiber diet. METHODS Ten rabbits were fed a low-fiber diet for 5 months (Intervention group), and five rabbits were fed normal diet (Control group). The duodenal segments were used for determination of mechanical parameters for analyses of contractility. The duodenal experiments were carried out in organ baths containing physiological Krebs solution. Pressure and diameter changes induced by contractions in response to flow and ramp distension were measured. The frequencies and amplitude of contractions were analyzed. Distension-induced contraction thresholds and maximum contraction amplitude of flow-induced contractions were calculated in terms of mechanical stress and strain. Multiple linear regression analyses were applied to study dependencies between contractility parameters and wall thickness, wall area, and muscle layer thickness. KEY RESULTS During distension, the pressure, stress, and strain thresholds for induction of phasic contraction were biggest in the Intervention Group (P < 0.05). In addition, the contraction frequencies during flow-induced contraction were highest in the Intervention Group (P < 0.05), whereas the maximum contraction amplitudes in terms of pressure, diameter, stress, and strain were lowest in the Intervention Group (P < 0.05). The contraction thresholds and contraction frequencies were negatively associated with the wall thickness, wall area, and muscle layer thickness, whereas maximum contraction amplitudes were positively associated with the wall thickness, wall area, and muscle layer thickness. CONCLUSIONS AND INFERENCES Duodenal contractility in rabbits fed with long-term low-fiber diet exhibited low contraction amplitudes and high contraction thresholds and frequencies. The changes were associated with the low-fiber diet-induced histomorphological remodeling. Studies on detailed structural and functional diet-induced changes in smooth muscle and intestinal nerves are needed for better understanding the remodeling mechanisms.
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Affiliation(s)
- Yue Liu
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, Bioengineering College of Chongqing University, Chongqing, China.,GIOME Academia, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark.,Zhuhai Da Hengqin Technology Development Co. Ltd., Zhuhai, China
| | - Jingbo Zhao
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, Bioengineering College of Chongqing University, Chongqing, China.,GIOME Academia, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark.,Mech-Sense, Department of Gastroenterology, Aalborg University Hospital, Aalborg, Denmark
| | - Donghua Liao
- GIOME Academia, Department of Clinical Medicine, Aarhus University, Aarhus N, Denmark
| | - Guixue Wang
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, Bioengineering College of Chongqing University, Chongqing, China
| | - Hans Gregersen
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education, Bioengineering College of Chongqing University, Chongqing, China.,GIOME, Department of Surgery, Chinese University of Hong Kong, Hong Kong SAR, China
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Zhao J, Yang J, Liao D, Gregersen H. Interdependency between mechanical parameters and afferent nerve discharge in remodeled diabetic Goto-Kakizaki rat intestine. Clin Exp Gastroenterol 2017; 10:303-314. [PMID: 29238211 PMCID: PMC5716675 DOI: 10.2147/ceg.s145016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Background Gastrointestinal disorders are very common in diabetic patients, but the pathogenesis is still not well understood. Peripheral afferent nerves may be involved due to the complex regulation of gastrointestinal function by the enteric nervous system. Objective We aimed to characterize the stimulus–response function of afferent fibers innervating the jejunum in the Goto-Kakizaki (GK) type 2 diabetic rat model. A key question is whether changes in afferent firing arise from remodeled tissue or from adaptive afferent processes. Design Seven 32-week-old male GK rats and seven age-matched normal Wistar rats were studied. Firing from mesenteric afferent nerves was recorded in excised jejunal segments of seven GK rats and seven normal Wistar rats during ramp test, stress relaxation test, and creep test. The circumferential stress–strain, spike rate increase ratio (SRIR), and single unit firing rates were calculated for evaluation of interdependency of the mechanical stimulations and the afferent nerve discharge. Results Elevated sensitivity to mechanical stimuli was found for diabetic nerve bundles and single unit activity (P<0.05). The stress relaxed less in the diabetic intestinal segment (P<0.05). Linear association between SRIR and the thickness of circumferential muscle layer was found at high stress levels as well as for SRIR and the glucose level. Conclusion Altered viscoelastic properties and elevated mechanosensitivity were found in the GK rat intestine. The altered nerve signaling is related to muscle layer remodeling and glucose levels and may contribute to gastrointestinal symptoms experienced by diabetic patients.
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Affiliation(s)
- Jingbo Zhao
- Giome Academia, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jian Yang
- Giome Academia, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Donghua Liao
- Giome Academia, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Hans Gregersen
- Giome Center, Department of Surgery, Chinese University of Hong Kong and Prince of Wales Hospital, Shatin, Hong Kong
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Yang J, Zhao J, Chen P, Nakaguchi T, Grundy D, Gregersen H. Interdependency between mechanical parameters and afferent nerve discharge in hypertrophic intestine of rats. Am J Physiol Gastrointest Liver Physiol 2016; 310:G376-86. [PMID: 26585414 DOI: 10.1152/ajpgi.00192.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 11/13/2015] [Indexed: 01/31/2023]
Abstract
Partial intestinal obstruction causes smooth muscle hypertrophy, enteric neuronal plasticity, motility disorders, and biomechanical remodeling. In this study we characterized the stimulus-response function of afferent fibers innervating the partially obstructed jejunum. A key question is whether changes in afferent firing arise from remodeled mechanical tissue properties or from adaptive afferent processes. Partial obstruction was created by placing a polyethylene ring for 2 wk in jejunum of seven rats. Sham obstruction was made in six rats and seven rats served as normal controls. Firing from mesenteric afferent nerve bundles was recorded during mechanical ramp, relaxation, and creep tests. Stress-strain, spike rate increase ratio (SRIR), and firing rate in single units were assessed for evaluation of interdependency of the mechanical stimulations, histomorphometry data, and afferent nerve discharge. Partial intestinal obstruction resulted in hypertrophy and jejunal stiffening proximal to the obstruction site. Low SRIR at low strains during fast distension and at high stresses during slow distension was found in the obstructed rats. Single unit analysis showed increased proportion of mechanosensitive units but absent high-threshold (HT) units during slow stimulation, decreased number of HT units during fast stimulation, and shift from HT sensitivity towards low threshold sensitivity in the obstructed jejunum. Biomechanical remodeling and altered afferent response to mechanical stimulations were found in the obstructed jejunum. Afferents from obstructed jejunum preserved their function in encoding ongoing mechanical stimulation but showed changes in their responsiveness. The findings support that mechanical factors rather than adaption are important for afferent remodeling.
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Affiliation(s)
- Jian Yang
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; Bioengineering College of Chongqing University, Chongqing, China
| | - Jingbo Zhao
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | | | - Toshiya Nakaguchi
- Graduate School of Advanced Integrated Science, Chiba University, Chiba, Japan; and
| | - David Grundy
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Hans Gregersen
- GIOME and the Key Laboratory for Biorheological Science and Technology of Ministry of Education; Bioengineering College of Chongqing University, Chongqing, China;
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Gregersen H, Jiang W, Liao D, Grundy D. Evidence for stress-dependent mechanoreceptors linking intestinal biomechanics and sensory signal transduction. Exp Physiol 2012; 98:123-33. [PMID: 22798401 DOI: 10.1113/expphysiol.2012.066019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sensory nerve endings are widely distributed throughout the body. Neither the nature of the mechanosensitive channels nor the principal mechanical stimulus for these receptors is known. Afferents supplying the gastrointestinal tract responding to distension and contraction are responsible for co-ordinated reflex control, feeding behaviour and sensations, including pain. Different populations of intestinal afferent fibres follow different pathways to the CNS, have different terminal fields and possess different thresholds for activation that may reflect the extent to which mechanical forces are distributed and dissipated by non-neural structures in the bowel wall. In this study, we have characterized the stimulus-response function of afferent fibres innervating the rat jejunum, correlating luminal distensions in the bowel wall with the firing frequency of mesenteric afferent nerve bundles. Combining video imaging with intraluminal pressure recordings and utilizing a strain softening protocol, we have determined whether mechanoreceptors respond primarily to stress or strain. Multiunit afferent recordings were separated using spike discrimination software into low-threshold (LT) and high-threshold (HT) single units. For multifibre afferent recordings and both LT and HT single units, we observed a linear relationship between circumferential stress and mesenteric afferent discharge that was independent of distension-induced tissue softening, with correlation coefficients >0.9. A fivefold change in the rate of applied distension did not significantly alter the magnitude of the afferent response and the linearity of the stress-dependent mechanotransduction in both multifibre preparations and the LT and HT afferent fibres (P > 0.2). Thus, the firing characteristics of intestinal mechanoreceptors are linearly associated with the input in terms of mechanical stress.
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Affiliation(s)
- Hans Gregersen
- Sino-Danish Centre for Education and Research, Aarhus Hospital, Aarhus, Denmark
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