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Llorente C. The Imperative for Innovative Enteric Nervous System-Intestinal Organoid Co-Culture Models: Transforming GI Disease Modeling and Treatment. Cells 2024; 13:820. [PMID: 38786042 PMCID: PMC11119846 DOI: 10.3390/cells13100820] [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: 03/15/2024] [Revised: 04/29/2024] [Accepted: 05/08/2024] [Indexed: 05/25/2024] Open
Abstract
This review addresses the need for innovative co-culture systems integrating the enteric nervous system (ENS) with intestinal organoids. The breakthroughs achieved through these techniques will pave the way for a transformative era in gastrointestinal (GI) disease modeling and treatment strategies. This review serves as an introduction to the companion protocol paper featured in this journal. The protocol outlines the isolation and co-culture of myenteric and submucosal neurons with small intestinal organoids. This review provides an overview of the intestinal organoid culture field to establish a solid foundation for effective protocol application. Remarkably, the ENS surpasses the number of neurons in the spinal cord. Referred to as the "second brain", the ENS orchestrates pivotal roles in GI functions, including motility, blood flow, and secretion. The ENS is organized into myenteric and submucosal plexuses. These plexuses house diverse subtypes of neurons. Due to its proximity to the gut musculature and its cell type complexity, there are methodological intricacies in studying the ENS. Diverse approaches such as primary cell cultures, three-dimensional (3D) neurospheres, and induced ENS cells offer diverse insights into the multifaceted functionality of the ENS. The ENS exhibits dynamic interactions with the intestinal epithelium, the muscle layer, and the immune system, influencing epithelial physiology, motility, immune responses, and the microbiome. Neurotransmitters, including acetylcholine (ACh), serotonin (5-HT), and vasoactive intestinal peptide (VIP), play pivotal roles in these intricate interactions. Understanding these dynamics is imperative, as the ENS is implicated in various diseases, ranging from neuropathies to GI disorders and neurodegenerative diseases. The emergence of organoid technology presents an unprecedented opportunity to study ENS interactions within the complex milieu of the small and large intestines. This manuscript underscores the urgent need for standardized protocols and advanced techniques to unravel the complexities of the ENS and its dynamic relationship with the gut ecosystem. The insights gleaned from such endeavors hold the potential to revolutionize GI disease modeling and treatment paradigms.
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Affiliation(s)
- Cristina Llorente
- Department of Medicine, University of California San Diego, MC0063, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Zhao Z, Bai B, Wang S, Zhou Y, Yu P, Zhao Q, Yang B. Physical and psychological correlates of somatic symptom in patients with functional constipation: a cross-sectional study. BMC Psychiatry 2024; 24:134. [PMID: 38365647 PMCID: PMC10873943 DOI: 10.1186/s12888-024-05559-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 01/25/2024] [Indexed: 02/18/2024] Open
Abstract
BACKGROUND The symptoms of functional constipation (FC) were obviously affected by mental symptoms, which was consistent with somatic symptoms. However, the characteristics of FC patients with somatic symptom remains unexplored. METHODS Clinical characteristics including somatic symptom (SOM, PHQ-15), depression (PHQ-9), anxiety (GAD-7), quality of life (PAC-QOL), constipation (KESS), demographic variables, anatomical abnormalities and symptoms were investigated. Subsequent analyses encompassed the comparison of clinical parameters between patients with SOM + group (PHQ-15 ≥ 10) and SOM- group (PHQ-15 < 10), subgroup analysis, correlation analysis, and logistic regression. Lastly, we evaluated the somatic symptom severity (SSS) among FC patients subjected to various stressors. RESULTS Notable disparities were observed between SOM + and SOM- groups in variety of physiological and psychological variables, including gender, stressful events, sleep disorders, reduced interest, GAD-7, PHQ-15, PHQ-9, PAC-QOL, anterior rectocele, KESS, and internal anal sphincter achalasia (IASA) (P < 0.05). Subgroup analysis affirmed consistent findings across mental symptoms. Correlation analyses revealed significant associations between SSS and KESS, anterior rectocele, GAD-7, PHQ-9, and PAC-QOL (P < 0.05). Logistic regression identified PHQ-9 (OR = 7.02, CI: 2.06-27.7, P = 0.003), GAD-7 (OR = 7.18, CI: 2.00-30.7, P = 0.004), and KESS (OR = 16.8, CI: 3.09-113, P = 0.002) as independent predictors of SSS. Elevated SSS scores were significantly associated with couple, parental, and work-related stressors (P < 0.05). CONCLUSION A marked heterogeneity was observed between SOM + and SOM- patients of FC, with SOM + accompanied by more severe constipation, anxiety and depression symptoms. This finding underscores the importance of considering somatic symptoms in diagnosis and treatment of FC.
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Affiliation(s)
- Zhifeng Zhao
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China
| | - Bin Bai
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China
| | - Shiqi Wang
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China
| | - Yin Zhou
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China
| | - Pengfei Yu
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China
| | - Qingchuan Zhao
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China.
| | - Bin Yang
- State Key Laboratory of Cancer Biology & National Clinical Research Center for Digestive Diseases, Xijing Hospital of Digestive Diseases, Air Force Medical University, No.127, West Changle Road, 710032, Xi'an, Shaanxi Province, People's Republic of China.
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Akram N, Faisal Z, Irfan R, Shah YA, Batool SA, Zahid T, Zulfiqar A, Fatima A, Jahan Q, Tariq H, Saeed F, Ahmed A, Asghar A, Ateeq H, Afzaal M, Khan MR. Exploring the serotonin-probiotics-gut health axis: A review of current evidence and potential mechanisms. Food Sci Nutr 2024; 12:694-706. [PMID: 38370053 PMCID: PMC10867509 DOI: 10.1002/fsn3.3826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 10/24/2023] [Accepted: 11/01/2023] [Indexed: 02/20/2024] Open
Abstract
Modulatory effects of serotonin (5-Hydroxytryptamine [5-HT]) have been seen in hepatic, neurological/psychiatric, and gastrointestinal (GI) disorders. Probiotics are live microorganisms that confer health benefits to their host. Recent research has suggested that probiotics can promote serotonin signaling, a crucial pathway in the regulation of mood, cognition, and other physiological processes. Reviewing the literature, we find that peripheral serotonin increases nutrient uptake and storage, regulates the composition of the gut microbiota, and is involved in mediating neuronal disorders. This review explores the mechanisms underlying the probiotic-mediated increase in serotonin signaling, highlighting the role of gut microbiota in the regulation of serotonin production and the modulation of neurotransmitter receptors. Additionally, this review discusses the potential clinical implications of probiotics as a therapeutic strategy for disorders associated with altered serotonin signaling, such as GI and neurological disorders. Overall, this review demonstrates the potential of probiotics as a promising avenue for the treatment of serotonin-related disorders and signaling of serotonin.
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Affiliation(s)
- Noor Akram
- Department of Food and NutritionGovernment College University FaisalabadFaisalabadPakistan
| | - Zargham Faisal
- Department of Human NutritionBahauddin Zakariya University MultanMultanPakistan
| | - Rushba Irfan
- Faculty of Food Nutrition & Home SciencesUniversity of AgricultureFaisalabadPakistan
| | - Yasir Abbas Shah
- Natural & Medical Science Research CenterUniversity of NizwaNizwaOman
| | - Syeda Ayesha Batool
- Department of Food ScienceGovernment College University FaisalabadFaisalabadPakistan
| | - Toobaa Zahid
- Department of Food and NutritionGovernment College University FaisalabadFaisalabadPakistan
| | - Aqsa Zulfiqar
- Department of Food and NutritionGovernment College University FaisalabadFaisalabadPakistan
| | - Areeja Fatima
- National Institute of Food Science & TechnologyUniversity of AgricultureFaisalabadPakistan
| | - Qudsia Jahan
- Department of Food and NutritionGovernment College University FaisalabadFaisalabadPakistan
| | - Hira Tariq
- Department of Food and NutritionGovernment College University FaisalabadFaisalabadPakistan
| | - Farhan Saeed
- Department of Food ScienceGovernment College University FaisalabadFaisalabadPakistan
| | - Aftab Ahmed
- Department of Nutritional SciencesGovernment College University FaisalabadFaisalabadPakistan
| | - Aasma Asghar
- Department of Nutritional SciencesGovernment College University FaisalabadFaisalabadPakistan
| | - Huda Ateeq
- Department of Food ScienceGovernment College University FaisalabadFaisalabadPakistan
| | - Muhammad Afzaal
- Department of Food ScienceGovernment College University FaisalabadFaisalabadPakistan
| | - Mahbubur Rahman Khan
- Department of Food Processing and PreservationHajee Mohammad Danesh Science & Technology UniversityDinajpurBangladesh
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Suzuki M, Watanabe A, Huang J, Kobayashi Y, Sakata I. Involvement of the autonomic nervous system in colonic contractions in conscious Suncus murinus. Neurogastroenterol Motil 2024; 36:e14716. [PMID: 38031349 DOI: 10.1111/nmo.14716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 10/06/2023] [Accepted: 11/10/2023] [Indexed: 12/01/2023]
Abstract
BACKGROUND Colonic motility is regulated by various factors along the gut-brain axis; however, detailed mechanisms are unknown. This study aimed to examine the involvement of the autonomic nervous system in colonic motility. Suncus murinus (suncus) is a small laboratory mammal suitable for gastrointestinal motility studies. METHODS Colonic motility and concomitant feeding and defecation behaviors in vagotomized and reserpine-administered suncus were recorded simultaneously for 24 h. Furthermore, we performed immunohistochemistry on tyrosine hydroxylase (TH) and in situ hybridization on corticotropin-releasing hormone (CRH) in suncus brain. Additionally, we examined c-Fos expression in the brain using immunohistochemistry in conscious suncus with colorectal distension. KEY RESULTS In vagotomized suncus, clustered giant migrating contractions (GMCs), consisting of strong contractions occurring in a short time, were observed, and the percentage of GMCs without defecation increased. The frequency of GMCs in the reserpine-administered suncus increased during a light period (ZT0-4, 4-8) and decreased during a dark period (ZT16-20, 20-24) compared to a vehicle group. Additionally, the percentage of GMCs without defecation in the reserpine-administered suncus increased. Suncus TH-immunopositive neurons were found in the locus coeruleus (LC), as shown in rodents. In contrast, CRH mRNA-expressing cells were not observed in a region assumed to be the Barrington's nucleus (Bar). Furthermore, colorectal distension in conscious suncus induced c-Fos expression in LC TH neurons. CONCLUSIONS & INFERENCES Our results suggest that the vagus and sympathetic nerves are not required for induction of GMCs in vivo. However, they are likely to exert a modulatory role in control of GMC frequency in Suncus murinus.
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Affiliation(s)
- Miu Suzuki
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Ayumi Watanabe
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Jin Huang
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Yuki Kobayashi
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Ichiro Sakata
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
- Area of Research Evolutionary Molecular Design, Strategic Research Center, Saitama University, Saitama, Japan
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Li H, Lv N, Li D, Qian Y, Si X, Hua Y, Wang Y, Han X, Xu T. Tongbian decoction restores intestinal microbiota and activates 5-hydroxytryptamine signaling: implication in slow transit constipation. Front Microbiol 2024; 14:1296163. [PMID: 38287961 PMCID: PMC10822989 DOI: 10.3389/fmicb.2023.1296163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 12/01/2023] [Indexed: 01/31/2024] Open
Abstract
Introduction Slow transit constipation (STC) is a type of functional constipation. The detailed mechanism of STC, for which there is currently no effective treatment, is unknown as of yet. Tongbian decoction (TBD), a traditional Chinese medicinal formula, is commonly used to treat STC in clinical settings. However, the potential impact of TBD on the management of STC via modulation of the gut microbiota remains unclear. Methods Pseudo-germ-free rats were constructed after 6 days of treatment with bacitracin, neomycin, and streptomycin (abbreviated as ABX forthwith). Based on the successful construction of pseudo-germ-free rats, the STC model (ABX + STC) was induced using loperamide hydrochloride. After successful modeling, based on the different sources of donor rat microbiota, the ABX + STC rats were randomly divided into three groups: Control → ABX + STC, STC → ABX + STC, and STC + TBD → ABX + STC for fecal microbiota transplant (FMT). Body weight, fecal water content, and charcoal power propelling rate of the rats were recorded. Intestinal microbiota was detected by 16S rRNA sequencing, and the 5-hydroxytryptamine (5-HT) signaling pathway was examined by western blots, immunofluorescence, and immunohistochemical analysis. Results After treatment with fecal bacterial solutions derived from rats treated with Tongbian decoction (TBD), there was an increase in body weight, fecal water content, and the rate of charcoal propulsion in the rats. Additionally, activation of the 5-hydroxytryptamine (5-HT) signaling pathway was observed. The 16S rRNA sequencing results showed that the fecal bacterial solution from TBD-treated rats affected the intestinal microbiota of STC rats by increasing the proliferation of beneficial bacteria and suppressing the expansion of harmful bacteria. Conclusion Our study showed that TBD alleviated constipation in STC rats by modulating the structure of the intestinal microbiota.
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Affiliation(s)
- Hongjia Li
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Na Lv
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Dongna Li
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yunzhi Qian
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Xianghuan Si
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yuanqing Hua
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yujuan Wang
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Xiaojuan Han
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Department of Rheumatology and Immunology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Tianshu Xu
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, The Drum Tower Clinical Medical College, Nanjing University of Chinese Medicine, Nanjing, China
- Department of Traditional Chinese Medicine, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
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Lei X, Xu Z, Huang L, Huang Y, Tu S, Xu L, Liu D. The potential influence of melatonin on mitochondrial quality control: a review. Front Pharmacol 2024; 14:1332567. [PMID: 38273825 PMCID: PMC10808166 DOI: 10.3389/fphar.2023.1332567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 12/31/2023] [Indexed: 01/27/2024] Open
Abstract
Mitochondria are critical for cellular energetic metabolism, intracellular signaling orchestration and programmed death regulation. Therefore, mitochondrial dysfunction is associated with various pathogeneses. The maintenance of mitochondrial homeostasis and functional recovery after injury are coordinated by mitochondrial biogenesis, dynamics and autophagy, which are collectively referred to as mitochondrial quality control. There is increasing evidence that mitochondria are important targets for melatonin to exert protective effects under pathological conditions. Melatonin, an evolutionarily conserved tryptophan metabolite, can be synthesized, transported and metabolized in mitochondria. In this review, we summarize the important role of melatonin in the damaged mitochondria elimination and mitochondrial energy supply recovery by regulating mitochondrial quality control, which may provide new strategies for clinical treatment of mitochondria-related diseases.
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Affiliation(s)
- Xudan Lei
- Radiation Oncology Key Laboratory of Sichuan Province, Department of Experimental Research, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Center, Sichuan Cancer Hospital and Institute, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China
| | - Zhenni Xu
- Radiation Oncology Key Laboratory of Sichuan Province, Department of Experimental Research, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Center, Sichuan Cancer Hospital and Institute, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China
| | - Lingxiao Huang
- Radiation Oncology Key Laboratory of Sichuan Province, Department of Experimental Research, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Center, Sichuan Cancer Hospital and Institute, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China
| | - Yujun Huang
- College of Basic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Siyu Tu
- College of Basic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Lu Xu
- Radiation Oncology Key Laboratory of Sichuan Province, Department of Experimental Research, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Center, Sichuan Cancer Hospital and Institute, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China
| | - Dengqun Liu
- Radiation Oncology Key Laboratory of Sichuan Province, Department of Experimental Research, Sichuan Clinical Research Center for Cancer, Sichuan Cancer Center, Sichuan Cancer Hospital and Institute, Affiliated Cancer Hospital of University of Electronic Science and Technology of China, Chengdu, China
- College of Basic Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
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Kola JB, Docsa T, Uray K. Mechanosensing in the Physiology and Pathology of the Gastrointestinal Tract. Int J Mol Sci 2022; 24:ijms24010177. [PMID: 36613619 PMCID: PMC9820522 DOI: 10.3390/ijms24010177] [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] [Received: 10/02/2022] [Revised: 12/10/2022] [Accepted: 12/17/2022] [Indexed: 12/24/2022] Open
Abstract
Normal gastrointestinal function relies on sensing and transducing mechanical signals into changes in intracellular signaling pathways. Both specialized mechanosensing cells, such as certain enterochromaffin cells and enteric neurons, and non-specialized cells, such as smooth muscle cells, interstitial cells of Cajal, and resident macrophages, participate in physiological and pathological responses to mechanical signals in the gastrointestinal tract. We review the role of mechanosensors in the different cell types of the gastrointestinal tract. Then, we provide several examples of the role of mechanotransduction in normal physiology. These examples highlight the fact that, although these responses to mechanical signals have been known for decades, the mechanosensors involved in these responses to mechanical signals are largely unknown. Finally, we discuss several diseases involving the overstimulation or dysregulation of mechanotransductive pathways. Understanding these pathways and identifying the mechanosensors involved in these diseases may facilitate the identification of new drug targets to effectively treat these diseases.
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Affiliation(s)
- Job Baffin Kola
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Center of Excellence, The Hungarian Academy of Sciences, 4032 Debrecen, Hungary
| | - Tibor Docsa
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Center of Excellence, The Hungarian Academy of Sciences, 4032 Debrecen, Hungary
| | - Karen Uray
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
- Center of Excellence, The Hungarian Academy of Sciences, 4032 Debrecen, Hungary
- Correspondence:
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Spencer NJ, Keating DJ. Role of 5-HT in the enteric nervous system and enteroendocrine cells. Br J Pharmacol 2022. [PMID: 35861711 DOI: 10.1111/bph.15930] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 07/09/2022] [Accepted: 07/12/2022] [Indexed: 11/29/2022] Open
Abstract
Since the 1950s, considerable circumstantial evidence had been presented that endogenous 5-HT (serotonin) synthesized from within the wall of the gastrointestinal (GI) tract played an important role in GI motility and transit. However, identifying the precise functional role of gut-derived 5-HT has been difficult to ascertain, for a number of reasons. Over the past decade, as recording techniques have advanced significantly and access to new genetically modified animals improved, there have been major new insights and major changes in our understanding of the functional role of endogenous 5-HT in the GI tract. Data from many different laboratories have shown that major patterns of GI motility and transit still occur with minor or no, change when all endogenous 5-HT is pharmacologically or genetically ablated from the gut. Furthermore, antagonists of 5-HT3 receptors are equally, or more potent at inhibiting GI motility in segments of intestine that are completely depleted of endogenous 5-HT. Here, the most recent findings are discussed with regard to the functional role of endogenous 5-HT in enterochromaffin cells and enteric neurons in gut motility and more broadly in some major homeostatic pathways.
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Affiliation(s)
- Nick J Spencer
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Damien J Keating
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
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Wang L, Wu F, Hong Y, Shen L, Zhao L, Lin X. Research progress in the treatment of slow transit constipation by traditional Chinese medicine. JOURNAL OF ETHNOPHARMACOLOGY 2022; 290:115075. [PMID: 35134487 DOI: 10.1016/j.jep.2022.115075] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/15/2022] [Accepted: 02/02/2022] [Indexed: 06/14/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Slow transit constipation (STC) is a common gastrointestinal disorder seriously impacting patients' quality of life. At present, although conventional chemical drugs effectively control STC symptoms in the short term, the long-term effects are poor, and the side effects are significant. In this regard, traditional Chinese medicine (TCM) offers an opportunity for STC treatment. Many pharmacological and clinical studies have confirmed this efficacy of TCM with multiple targets and mechanisms. AIM OF THE STUDY This review attempted to summarize the characteristics of TCM (compound prescriptions, single Chinese herbs, and active ingredients) for STC treatment and discussed their efficacy based on analyzing the pathogenesis of STC. MATERIALS AND METHODS The information was acquired from different databases, including PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang databases. We then focused on the recent research progress in STC treatment by TCM. Finally, the future challenges and trends are proposed. RESULTS TCM has good clinical efficacy in the treatment of STC with multi-mechanisms. Based on the theory of syndrome differentiation, five kinds of dialectical treatment for STC by compound TCM prescriptions were introduced, namely: Nourishing Yin and moistening the intestines; Promoting blood circulation and removing blood stasis; Warming Yang and benefiting Qi; Soothing the liver and regulating Qi; and Benefiting Qi and strengthening the spleen. In addition, six single Chinese herbs and eight active ingredients also show good efficacy in STC treatment. CONCLUSIONS TCM, especially compound prescriptions, has bright prospects in treating STC attributed to its various holistic effects.
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Affiliation(s)
- LiangFeng Wang
- College of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China; Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Fei Wu
- Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - YanLong Hong
- Shanghai Innovation Center of Traditional Chinese Medicine Health Service, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - Lan Shen
- College of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China
| | - LiJie Zhao
- Engineering Research Center of Modern Preparation Technology of TCM of Ministry of Education, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China.
| | - Xiao Lin
- College of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, PR China.
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Naseer M, Poola S, Uraz S, Tahan V. Therapeutic Effects of Prebiotics on Constipation: A Schematic Review. ACTA ACUST UNITED AC 2021; 15:207-215. [PMID: 32048977 DOI: 10.2174/1574884715666200212125035] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/09/2020] [Accepted: 01/14/2020] [Indexed: 12/12/2022]
Abstract
Constipation is a highly prevalent functional gastrointestinal disorder that may significantly affect the quality of life and health care costs. Treatment for constipation has been broadly reviewed by cognitive therapies, medications, and surgical interventions. Gut microbiota such as Bifidobacterium, Clostridium, Bacteroidetes, and Lactobacilli have been demonstrated in functional gastrointestinal disorders and prebiotics to play a role in augmenting their presence. Prebiotics are ingredients in foods that remain undigested, stimulating the bacteria. There are a variety of prebiotics; however, there exists only a handful of studies that describe their efficacy for chronic constipation. The purpose of this study is to review the available literature on the utility of different commercially available prebiotics in patients with functional and chronic idiopathic constipation. To fulfil the objectives of the study, published articles in the English language on databases such as Pubmed, Ovid Medline, and EMBASE were searched. The terms prebiotics, constipation, chronic constipation, functional constipation were used. We reviewed and included 21 randomized controlled trials exploring the role of prebiotics in constipated adults. Prebiotics are effective treatments for chronic idiopathic constipation and showed improvement in the stool consistency, number of bowel moments and bloating. Although which prebiotic formulary would promote improved symptoms of constipation is still not clear.
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Affiliation(s)
- Maliha Naseer
- Division of Gastroenterology & Hepatology, Department of Internal Medicine, East Carolina University, Greenville, NC 27834, United States
| | - Shiva Poola
- Department of Internal and Pediatric Medicine, East Carolina University, Greenville, NC 27834, United States
| | - Suleyman Uraz
- Department of Internal Medicine, University of Missouri, Division of Gastroenterology and Hepatology, Columbia, MO 65211, United States
| | - Veysel Tahan
- Department of Internal Medicine, University of Missouri, Division of Gastroenterology and Hepatology, Columbia, MO 65211, United States
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Aikiyo S, Kishi K, Kaji N, Mikawa S, Kondo M, Shimada S, Hori M. Contribution of Serotonin 3A Receptor to Motor Function and Its Expression in the Gastrointestinal Tract. Digestion 2021; 102:516-526. [PMID: 32726781 DOI: 10.1159/000509209] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 05/31/2020] [Indexed: 02/04/2023]
Abstract
INTRODUCTION The serotonin 3A receptor (5-HT3AR) is involved in vomiting and gastrointestinal motility. However, it is not well understood the expression pattern of 5-HT3AR in the gut immunohistochemically and how much contribution of 5-HT3AR to upper or lower intestinal motility. OBJECTIVES We investigated the contribution of 5-HT3AR to gastrointestinal motor function by using 5-HT3AR KO mice and sought to identify 5-HT3AR-expressing cells via immunohistochemical staining using 5-HT3AR-GFP reporter mice. METHODS The expression of 5-HT3AR was measured in each section of the gut through real-time PCR. The motor function of the stomach and colon was assessed via the 13C-octanoic acid breath test and colonic bead expulsion test, respectively, using 5-HT3AR KO mice. 5-HT3AR-expressing cells in the muscle layer of the gut were identified by immunohistochemical staining using 5-HT3AR-GFP reporter mice. RESULTS 5-HT3AR was expressed throughout the digestive tract, and 5-HT3AR expression in the stomach and lower digestive tract was higher than that in the other sections. Motor function in the stomach and colon was lower in 5-HT3AR KO mice than in WT mice. As a result of immunohistochemical staining using GFP reporter mice, cholinergic neurons and PDGFRα+ cells were shown to express 5-HT3AR. In contrast, 5-HT3AR indicated by GFP fluorescence was rarely detected in ICC and smooth muscle cells. CONCLUSIONS These results show that 5-HT3AR is highly expressed in the stomach and large intestine and that the activation of 5-HT3AR accelerates gastric emptying and large intestine transit. Additionally, 5-HT3AR is highly expressed in cholinergic neurons and some interstitial cells, such as PDGFRα+ cells.
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Affiliation(s)
- Satoshi Aikiyo
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Kazuhisa Kishi
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Noriyuki Kaji
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo, Japan.,Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Azabu University, Kanagawa, Japan
| | - Shoma Mikawa
- Laboratory of Veterinary Clinical Pathology, Faculty of Veterinary Medicine, Okayama University of Science, Ehime, Japan
| | - Makoto Kondo
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Shoichi Shimada
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Masatoshi Hori
- Department of Veterinary Pharmacology, Graduate School of Agriculture and Life Sciences, University of Tokyo, Tokyo, Japan,
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Gut bacteria-derived 5-hydroxyindole is a potent stimulant of intestinal motility via its action on L-type calcium channels. PLoS Biol 2021; 19:e3001070. [PMID: 33481771 PMCID: PMC7857600 DOI: 10.1371/journal.pbio.3001070] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 02/03/2021] [Accepted: 12/29/2020] [Indexed: 12/24/2022] Open
Abstract
Microbial conversion of dietary or drug substrates into small bioactive molecules represents a regulatory mechanism by which the gut microbiota alters intestinal physiology. Here, we show that a wide variety of gut bacteria can metabolize the dietary supplement and antidepressant 5-hydroxytryptophan (5-HTP) to 5-hydroxyindole (5-HI) via the tryptophanase (TnaA) enzyme. Oral administration of 5-HTP results in detection of 5-HI in fecal samples of healthy volunteers with interindividual variation. The production of 5-HI is inhibited upon pH reduction in in vitro studies. When administered orally in rats, 5-HI significantly accelerates the total gut transit time (TGTT). Deciphering the underlying mechanisms of action reveals that 5-HI accelerates gut contractility via activation of L-type calcium channels located on the colonic smooth muscle cells. Moreover, 5-HI stimulation of a cell line model of intestinal enterochromaffin cells results in significant increase in serotonin production. Together, our findings support a role for bacterial metabolism in altering gut motility and lay the foundation for microbiota-targeted interventions.
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Gwynne RM, Bornstein JC. Luminal 5-HT 4 receptors-A successful target for prokinetic actions. Neurogastroenterol Motil 2019; 31:e13708. [PMID: 31524331 DOI: 10.1111/nmo.13708] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 02/08/2023]
Abstract
The prokinetic effects of 5-HT4 receptor (5-HT4 R) agonists have been utilized clinically for almost three decades to relieve symptoms of constipation. Surprisingly, the mechanism(s) of action of these compounds is still being debated. Recent studies highlight luminal 5-HT4 Rs as an alternative and effective target for these prokinetic agents. These include the study by Shokrollahi et al (2019, Neurogastroenterol Motil, e13598) published in the current issue of Neurogastroenterology and Motility, who found that activation of mucosal 5-HT4 Rs by intraluminal prucalopride, significantly enhanced propulsive motor patterns in rabbit colon. The authors highlight the idea that development of agonists targeting luminal 5-HT4 Rs in the colonic mucosa might be more effective and safer in achieving prokinetic effects on intestinal motility. The purpose of this mini-review is to discuss the evidence for luminal 5-HT4 Rs as an emerging target for prokinetic agents in facilitating propulsive motor patterns in the colon.
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Affiliation(s)
- Rachel M Gwynne
- Department of Physiology, University of Melbourne, Parkville, Vic., Australia
| | - Joel C Bornstein
- Department of Physiology, University of Melbourne, Parkville, Vic., Australia
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14
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What is the role of endogenous gut serotonin in the control of gastrointestinal motility? Pharmacol Res 2019; 140:50-55. [DOI: 10.1016/j.phrs.2018.06.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/17/2018] [Accepted: 06/18/2018] [Indexed: 12/26/2022]
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15
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Nakamori H, Naitou K, Sano Y, Shimaoka H, Shiina T, Shimizu Y. Exogenous serotonin regulates colorectal motility via the 5-HT 2 and 5-HT 3 receptors in the spinal cord of rats. Neurogastroenterol Motil 2018; 30. [PMID: 28795477 DOI: 10.1111/nmo.13183] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Accepted: 07/13/2017] [Indexed: 02/08/2023]
Abstract
BACKGROUND We previously reported that intrathecal injection of noradrenaline or dopamine causes enhancement of colorectal motility. As these monoamines are neurotransmitters of descending pain inhibitory pathways in the spinal cord, we hypothesized that serotonin, which is one of the neurotransmitters involved in descending pain inhibition, also influences the lumbosacral defecation center. Therefore, we examined whether serotonin acting on the spinal defecation center enhances colorectal motility. METHODS Colorectal intraluminal pressure and propelled liquid volume were recorded in vivo in anesthetized rats. KEY RESULTS Intrathecal injection of serotonin into the L6-S1 spinal cord elicited periodic increases in colorectal intraluminal pressure, being associated with increases in liquid output. Pharmacological experiments revealed that the effect of serotonin is mediated by both 5-HT2 and 5-HT3 receptors. The serotonin-induced enhancement of colorectal motility was unaffected even after disconnection of the defecation center from supraspinal regions by cutting the T8 spinal cord, while transection of the parasympathetic pelvic nerves prevented the colokinetic effect of serotonin. Finally, we investigated interactions among serotonin, noradrenaline and dopamine. Simultaneous administration of sub-effective doses of these monoamine neurotransmitters into the spinal cord caused propulsive colorectal motility slightly but substantially. CONCLUSIONS AND INFERENCES These results demonstrate that exogenous serotonin acts on 5-HT2 and 5-HT3 receptors in the lumbosacral defecation center and activates the parasympathetic nervous system to enhance colorectal motility in cooperation with noradrenaline and dopamine.
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Affiliation(s)
- H Nakamori
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - K Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Y Sano
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - H Shimaoka
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - T Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Y Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan.,Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University, Gifu, Japan
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Dysbiosis contributes to chronic constipation development via regulation of serotonin transporter in the intestine. Sci Rep 2017; 7:10322. [PMID: 28871143 PMCID: PMC5583244 DOI: 10.1038/s41598-017-10835-8] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 08/15/2017] [Indexed: 12/19/2022] Open
Abstract
Chronic constipation is a prevalent functional gastrointestinal disorder accompanied with intestinal dysbiosis. However, causal relationship between dysbiosis and constipation remains poorly understood. Serotonin transporter (SERT) is a transmembrane transport protein which re-uptakes excessive 5-hydroxytryptamine (5-HT) from effective location to terminate its physiological effects and involves in regulating gastrointestinal motility. In this study, fecal microbiota from patients with constipation and healthy controls were transplanted into the antibiotic depletion mice model. The mice which received fecal microbiota from patients with constipation presented a reducing in intestinal peristalsis and abnormal defecation parameters including the frequency of pellet expulsion, fecal weight and fecal water content. After fecal microbiota transplantation, the SERT expression in the colonic tissue was significantly upregulated, and the content of 5-HT was decreased which negatively correlated with the gastrointestinal transit time. Moverover, fecal microbiota from the mice which received fecal microbiota from patients with constipation also upregulated SERT in Caco-2 cells. Besides, this process accompanied with the decreased abundance of Clostridium, Lactobacillus, Desulfovibrio, and Methylobacterium and an increased tend of Bacteroides and Akkermansia, which also involved in the impairment of intestinal barrier after FMT. Taken together, intestinal dysbiosis may upregulate the SERT expression and contribute to the development of chronic constipation.
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Spencer NJ, Keating DJ. Is There a Role for Endogenous 5-HT in Gastrointestinal Motility? How Recent Studies Have Changed Our Understanding. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 891:113-22. [PMID: 27379639 DOI: 10.1007/978-3-319-27592-5_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Over the past few years, there have been dramatic changes in our understanding of the role of endogenous 5-hydroxytryptamine (5-HT) in the generation of gastrointestinal (GI) motility patterns in the small and large intestine. The idea that endogenous 5-HT played a major role in the generation of peristalsis in the small intestine was first proposed in the mid 1950s, after it was discovered that endogenous 5-HT could be released from the mucosa at a similar time that peristalsis occurred; and that exogenous 5-HT could potently stimulate peristalsis. The fact that exogenous 5-HT stimulated peristalsis and that there was a similarity in timing between the release of 5-HT from the mucosa and the onset of peristalsis led investigators to propose that release of endogenous 5-HT from the mucosa was causally related to the generation of peristalsis. In further support of this, other studies showed that selective 5-HT antagonists could inhibit or block peristalsis, and other motor patterns, such as the migrating motor complex. Taken together, based on these findings, some laboratories believed that endogenous 5-HT (synthesized in the gut wall) was an important mediator, or initiator, of different propulsive motor patterns in the lower GI tract. This notion changed dramatically in the past few years, however, after it was discovered that removal of the mucosa abolished all cyclical release of endogenous 5-HT, but did not block peristalsis, nor the cyclical migrating complex. Furthermore, other laboratories revealed that genetic deletion of the gene tryptophan hydroxylase 1 (TPH-1) (that synthesizes endogenous 5-HT in the mucosa) actually had no inhibitory effect on transit of intestinal contents in live animals. Then, perhaps one of the most startling of all observations was the discovery that selective 5-HT receptor antagonists actually have the same inhibitory effects on peristalsis and the migrating complex in segments of intestine that had been depleted of all endogenous 5-HT. Taken together, these recent findings have led to a major revision in our understanding of the functional role of endogenous 5-HT in the generation of propulsive motor patterns in the lower GI tract. This review will focus on how our understanding of endogenous 5-HT in the GI tract has changed substantially in recent times.
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Affiliation(s)
- Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia, Adelaide, SA, Australia.
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia, Adelaide, SA, Australia
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Spencer NJ, Dinning PG, Brookes SJ, Costa M. Insights into the mechanisms underlying colonic motor patterns. J Physiol 2016; 594:4099-116. [PMID: 26990133 PMCID: PMC4967752 DOI: 10.1113/jp271919] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 02/26/2016] [Indexed: 12/28/2022] Open
Abstract
In recent years there have been significant technical and methodological advances in our ability to record the movements of the gastrointestinal tract. This has led to significant changes in our understanding of the different types of motor patterns that exist in the gastrointestinal tract (particularly the large intestine) and in our understanding of the mechanisms underlying their generation. Compared with other tubular smooth muscle organs, a rich variety of motor patterns occurs in the large intestine. This reflects a relatively autonomous nervous system in the gut wall, which has its own unique population of sensory neurons. Although the enteric nervous system can function independently of central neural inputs, under physiological conditions bowel motility is influenced by the CNS: if spinal pathways are disrupted, deficits in motility occur. The combination of high resolution manometry and video imaging has improved our knowledge of the range of motor patterns and provided some insight into the neural and mechanical factors underlying propulsion of contents. The neural circuits responsible for the generation of peristalsis and colonic migrating motor complexes have now been identified to lie within the myenteric plexus and do not require inputs from the mucosa or submucosal ganglia for their generation, but can be modified by their activity. This review will discuss the recent advances in our understanding of the different patterns of propagating motor activity in the large intestine of mammals and how latest technologies have led to major changes in our understanding of the mechanisms underlying their generation.
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Affiliation(s)
- Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Phil G Dinning
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
- Departments of Gastroenterology and Surgery, Flinders Medical Centre, Adelaide, Australia
| | - Simon J Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Marcello Costa
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
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Spencer NJ, Sia TC, Brookes SJ, Costa M, Keating DJ. CrossTalk opposing view: 5-HT is not necessary for peristalsis. J Physiol 2016; 593:3229-31. [PMID: 26228548 DOI: 10.1113/jp270183] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/06/2015] [Indexed: 01/12/2023] Open
Affiliation(s)
- Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Tiong Cheng Sia
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Simon J Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Marcello Costa
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide, Australia
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20
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Electrochemical fecal pellet sensor for simultaneous real-time ex vivo detection of colonic serotonin signalling and motility. Sci Rep 2016; 6:23442. [PMID: 27000971 PMCID: PMC4802304 DOI: 10.1038/srep23442] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/07/2016] [Indexed: 12/21/2022] Open
Abstract
Various investigations have focused on understanding the relationship between mucosal serotonin (5-HT) and colonic motility, however contradictory studies have questioned the importance of this intestinal transmitter. Here we described the fabrication and use of a fecal pellet electrochemical sensor that can be used to simultaneously detect the release of luminal 5-HT and colonic motility. Fecal pellet sensor devices were fabricated using carbon nanotube composite electrodes that were housed in 3D printed components in order to generate a device that had shape and size that mimicked a natural fecal pellet. Devices were fabricated where varying regions of the pellet contained the electrode. Devices showed that they were stable and sensitive for ex vivo detection of 5-HT, and no differences in the fecal pellet velocity was observed when compared to natural fecal pellets. The onset of mucosal 5-HT was observed prior to the movement of the fecal pellet. The release of mucosal 5-HT occurred oral to the fecal pellet and was linked to the contraction of the bowel wall that drove pellet propulsion. Taken, together these findings provide new insights into the role of mucosal 5-HT and suggest that the transmitter acts as a key initiator of fecal pellet propulsion.
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21
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Spencer NJ. Constitutively Active 5-HT Receptors: An Explanation of How 5-HT Antagonists Inhibit Gut Motility in Species Where 5-HT is Not an Enteric Neurotransmitter? Front Cell Neurosci 2015; 9:487. [PMID: 26732863 PMCID: PMC4683187 DOI: 10.3389/fncel.2015.00487] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 11/30/2015] [Indexed: 11/19/2022] Open
Abstract
Antagonists of 5-Hydroxytryptamine (5-HT) receptors are well known to inhibit gastrointestinal (GI)-motility and transit in a variety of mammals, including humans. Originally, these observations had been interpreted by many investigators (including us) as evidence that endogenous 5-HT plays a major role in GI motility. This seemed a logical assumption. However, the story changed dramatically after recent studies revealed that 5-HT antagonists still blocked major GI motility patterns (peristalsis and colonic migrating motor complexes) in segments of intestine depleted of all 5-HT. Then, these results were further supported by Dr. Gershons' laboratory, which showed that genetic deletion of all genes that synthesizes 5-HT had minor, or no inhibitory effects on GI transit in vivo. If 5-HT was essential for GI motility patterns and transit, then one would expect major disruptions in motility and transit when 5-HT synthesis was genetically ablated. This does not occur. The inhibitory effects of 5-HT antagonists on GI motility clearly occur independently of any 5-HT in the gut. Evidence now suggests that 5-HT antagonists act on 5-HT receptors in the gut which are constitutively active, and don't require 5-HT for their activation. This would explain a long-standing mystery of how 5-HT antagonists inhibit gut motility in species like mice, rats, and humans where 5-HT is not an enteric neurotransmitter. Studies are now increasingly demonstrating that the presence of a neurochemical in enteric neurons does not mean they function as neurotransmitters. Caution should be exercised when interpreting any inhibitory effects of 5-HT antagonists on GI motility.
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Affiliation(s)
- Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia Adelaide, SA, Australia
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22
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Costa M, Wiklendt L, Simpson P, Spencer NJ, Brookes SJ, Dinning PG. Neuromechanical factors involved in the formation and propulsion of fecal pellets in the guinea-pig colon. Neurogastroenterol Motil 2015; 27:1466-77. [PMID: 26251321 DOI: 10.1111/nmo.12646] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 07/07/2015] [Indexed: 12/14/2022]
Abstract
BACKGROUND The neuromechanical processes involved in the formation and propulsion of fecal pellets remain incompletely understood. METHODS We analyzed motor patterns in isolated segments of the guinea-pig proximal and distal colon, using video imaging, during oral infusion of liquid, viscous material, or solid pellets. KEY RESULTS Colonic migrating motor complexes (CMMCs) in the proximal colon divided liquid or natural semisolid contents into elongated shallow boluses. At the colonic flexure these boluses were formed into shorter, pellet-shaped boluses. In the non-distended distal colon, spontaneous CMMCs produced small dilations. Both high- and low-viscosity infusions evoked a distinct motor pattern that produced pellet-shaped boluses. These were propelled at speeds proportional to their surface area. Solid pellets were propelled at a speed that increased with diameter, to a maximum that matched the diameter of natural pellets. Pellet speed was reduced by increasing resistive load. Tetrodotoxin blocked all propulsion. Hexamethonium blocked normal motor patterns, leaving irregular propagating contractions, indicating the existence of neural pathways that did not require nicotinic transmission. CONCLUSIONS & INFERENCES Colonic migrating motor complexes are responsible for the slow propulsion of the soft fecal content in the proximal colon, while the formation of pellets at the colonic flexure involves a content-dependent mechanism in combination with content-independent spontaneous CMMCs. Bolus size and consistency affects propulsion speed suggesting that propulsion is not a simple reflex but rather a more complex process involving an adaptable neuromechanical loop.
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Affiliation(s)
- M Costa
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia
| | - L Wiklendt
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia
| | - P Simpson
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia
| | - N J Spencer
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia
| | - S J Brookes
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia
| | - P G Dinning
- Disciplines of Human Physiology, Flinders University, Bedford Park, SA, Australia.,Departments of Gastroenterology and Surgery, Flinders Medical Centre, Bedford Park, SA, Australia
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Kendig DM, Grider JR. Serotonin and colonic motility. Neurogastroenterol Motil 2015; 27:899-905. [PMID: 26095115 PMCID: PMC4477275 DOI: 10.1111/nmo.12617] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 05/13/2015] [Indexed: 12/12/2022]
Abstract
The role of serotonin (5-hydroxytryptamine [5-HT]) in gastrointestinal motility has been studied for over 50 years. Most of the 5-HT in the body resides in the gut wall, where it is located in subsets of mucosal cells (enterochromaffin cells) and neurons (descending interneurons). Many studies suggest that 5-HT is important to normal and dysfunctional gut motility and drugs affecting 5-HT receptors, especially 5-HT3 and 5-HT4 receptors, have been used clinically to treat motility disorders; however, cardiovascular side effects have limited the use of these drugs. Recently studies have questioned the importance and necessity of 5-HT in general and mucosal 5-HT in particular for colonic motility. Recent evidence suggests the importance of 5-HT3 and 5-HT4 receptors for initiation and generation of one of the key colonic motility patterns, the colonic migrating motor complex (CMMC), in rat. The findings suggest that 5-HT3 and 5-HT4 receptors are differentially involved in two different types of rat CMMCs: the long distance contraction (LDC) and the rhythmic propulsive motor complex (RPMC). The understanding of the role of serotonin in colonic motility has been influenced by the specific motility pattern(s) studied, the stimulus used to initiate the motility (spontaneous vs induced), and the route of administration of drugs. All of these considerations contribute to the understanding and the controversy that continues to surround the role of serotonin in the gut.
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Affiliation(s)
- D. M. Kendig
- Virginia Commonwealth University Program in Enteric Neuromuscular Sciences; Department of Physiology and Biophysics; Virginia Commonwealth University; Richmond VA USA
| | - J. R. Grider
- Virginia Commonwealth University Program in Enteric Neuromuscular Sciences; Department of Physiology and Biophysics; Virginia Commonwealth University; Richmond VA USA
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Kendig DM, Hurst NR, Bradley ZL, Mahavadi S, Kuemmerle JF, Lyall V, DeSimone J, Murthy KS, Grider JR. Activation of the umami taste receptor (T1R1/T1R3) initiates the peristaltic reflex and pellet propulsion in the distal colon. Am J Physiol Gastrointest Liver Physiol 2014; 307:G1100-7. [PMID: 25324508 PMCID: PMC4254958 DOI: 10.1152/ajpgi.00251.2014] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Intraluminal nutrients in the gut affect the peristaltic reflex, although the mechanism is not well defined. Recent evidence supports the presence of taste receptors and their signaling components in enteroendocrine cells, although their function is unclear. This study aimed to determine if nutrients modify colonic motility through activation of taste receptors. Colonic sections were immunostained for the umami taste receptor T1R1/T1R3, which mediates the response to umami ligands, such as monosodium glutamate (MSG), in taste cells. Ascending contraction, descending relaxation, and calcitonin gene-related peptide release were measured in three-chamber flat-sheet preparations of rat colon in response to MSG alone or with inosine 5'-monophosphate (IMP). Velocity of artificial fecal pellet propulsion was measured by video recording in guinea pig distal colon. T1R1/T1R3 receptors were present in enteroendocrine cells of colonic sections from human, rat, mouse, and guinea pig. MSG initiated ascending contraction and descending relaxation components of the peristaltic reflex and calcitonin gene-related peptide release in flat-sheet preparations. IMP augmented the MSG-induced effects, suggesting activation of T1R1/T1R3 receptors. In T1R1(-/-) mice, mucosal stroking, but not MSG, elicited a peristaltic reflex. Intraluminal perfusion of MSG enhanced the velocity of artificial fecal pellet propulsion, which was also augmented by IMP. Propulsion was also increased by l-cysteine, but not l-tryptophan, supporting a role of T1R1/T1R3 receptors. We conclude that T1R1/T1R3 activation by luminal MSG or l-cysteine elicits a peristaltic reflex and CGRP release and increases the velocity of pellet propulsion in distal colon. This mechanism may explain how nutrients regulate colonic propulsion.
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Affiliation(s)
- Derek M. Kendig
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - Norman R. Hurst
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - Zachary L. Bradley
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - Sunila Mahavadi
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - John F. Kuemmerle
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and ,2Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University School of Medicine, Richmond, Virginia
| | - Vijay Lyall
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - John DeSimone
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and
| | - Karnam S. Murthy
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and ,2Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University School of Medicine, Richmond, Virginia
| | - John R. Grider
- 1Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia; and ,2Department of Medicine, VCU Program in Enteric Neuromuscular Sciences, Virginia Commonwealth University School of Medicine, Richmond, Virginia
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Smith TK, Park KJ, Hennig GW. Colonic migrating motor complexes, high amplitude propagating contractions, neural reflexes and the importance of neuronal and mucosal serotonin. J Neurogastroenterol Motil 2014; 20:423-46. [PMID: 25273115 PMCID: PMC4204412 DOI: 10.5056/jnm14092] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 09/05/2014] [Accepted: 09/08/2014] [Indexed: 12/15/2022] Open
Abstract
The colonic migrating motor complex (CMMC) is a critical neurally mediated rhythmic propulsive contraction observed in the large intestine of many mammals. It seems to be equivalent to the high amplitude propagating contractions (HAPCs) in humans. This review focuses on the probable neural mechanisms involved in producing the CMMC or HAPC, their likely dependence on mucosal and neuronal serotonin and pacemaker insterstitial cells of Cajal networks and how intrinsic neural reflexes affect them. Discussed is the possibility that myenteric 5-hydroxytryptamine (5-HT) neurons are not only involved in tonic inhibition of the colon, but are also involved in generating the CMMC and modulation of the entire enteric nervous system, including coupling motility to secretion and blood flow. Mucosal 5-HT appears to be important for the initiation and effective propagation of CMMCs, although this mechanism is a longstanding controversy since the 1950s, which we will address. We argue that the slow apparent propagation of the CMMC/HAPC down the colon is unlikely to result from a slowly conducting wave front of neural activity, but more likely because of an interaction between ascending excitatory and descending (serotonergic) inhibitory neural pathways interacting both within the myenteric plexus and at the level of the muscle. That is, CMMC/HAPC propagation appears to be similar to esophageal peristalsis. The suppression of inhibitory (neuronal nitric oxide synthase) motor neurons and mucosal 5-HT release by an upregulation of prostaglandins has important implications in a number of gastrointestinal disorders, especially slow transit constipation.
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Affiliation(s)
- Terence K Smith
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Kyu Joo Park
- Department of Surgery, School of Medicine, Seoul National University, Seoul Korea
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
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Okamoto T, Barton MJ, Hennig GW, Birch GC, Grainger N, Corrigan RD, Koh SD, Sanders KM, Smith TK. Extensive projections of myenteric serotonergic neurons suggest they comprise the central processing unit in the colon. Neurogastroenterol Motil 2014; 26:556-70. [PMID: 24460867 DOI: 10.1111/nmo.12302] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 12/12/2013] [Indexed: 01/02/2023]
Abstract
BACKGROUND 5-Hydroxytryptamine (5-HT, serotonin) is an important regulator of colonic motility and secretion; yet the role of serotonergic neurons in the colon is controversial. METHODS We used immunohistochemical techniques to examine their projections throughout the enteric nervous system and interstitial cells of Cajal (ICC) networks in the murine proximal to mid colon. KEY RESULTS Serotonergic neurons, which were mainly calbindin positive, occurred only in myenteric ganglia (1 per 3 ganglia). They were larger than nNOS neurons but similar in size to Dogiel Type II (AH) neurons. 5-HT neurons, appeared to make numerous varicose contacts with each other, most nNOS neurons, Dogiel Type II/AH neurons and glial cells. 5-HT, calbindin and nNOS nerve fibers also formed a thin perimuscular nerve plexus that was associated with ganglia, which contained both nNOS positive and negative neurons, which lay directly upon the submucosal pacemaker ICC network. Neurons in perimuscular ganglia were surrounded by 5-HT varicosities. Submucous ganglia contained nNOS positive and negative neurons, and calbindin positive neurons, which also appeared richly supplied by serotonergic nerve varicosities. Serotonergic nerve fibers ran along submucosal arterioles, but not veins. Varicosities of serotonergic nerve fibers were closely associated with pacemaker ICC networks and with intramuscular ICC (ICC-IM). 5-HT2B receptors were found on a subpopulation of non-5-HT containing myenteric neurons and their varicosities, pacemaker ICC-MY and ICC-IM. CONCLUSIONS & INFERENCES Myenteric serotonergic neurons, whose axons exhibit considerable divergence, regulate the entire enteric nervous system and are important in coordinating motility with secretion. They are not just interneurons, as regularly assumed, but possibly also motor neurons to ICC and blood vessels, and some may even be sensory neurons.
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Affiliation(s)
- T Okamoto
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
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Sia TC, Brookes SJ, Dinning PG, Wattchow DA, Spencer NJ. Peristalsis and propulsion of colonic content can occur after blockade of major neuroneuronal and neuromuscular transmitters in isolated guinea pig colon. Am J Physiol Gastrointest Liver Physiol 2013; 305:G933-9. [PMID: 24113766 DOI: 10.1152/ajpgi.00257.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We recently identified hexamethonium-resistant peristalsis in the guinea pig colon. We showed that, following acute blockade of nicotinic receptors, peristalsis recovers, leading to normal propagation velocities of fecal pellets along the colon. This raises the fundamental question: what mechanisms underlie hexamethonium-resistant peristalsis? We investigated whether blockade of the major receptors that underlie excitatory neuromuscular transmission is required for hexamethonium-resistant peristalsis. Video imaging of colonic wall movements was used to make spatiotemporal maps and determine the velocity of peristalsis. Propagation of artificial fecal pellets in the guinea pig distal colon was studied in hexamethonium, atropine, ω-conotoxin (GVIA), ibodutant (MEN-15596), and TTX. Hexamethonium and ibodutant alone did not retard peristalsis. In contrast, ω-conotoxin abolished peristalsis in some preparations and reduced the velocity of propagation in all remaining specimens. Peristalsis could still occur in some animals in the presence of hexamethonium + atropine + ibodutant + ω-conotoxin. Peristalsis never occurred in the presence of TTX. The major finding of the current study is the unexpected observation that peristalsis can occur after blockade of the major excitatory neuroneuronal and neuromuscular transmitters. Also, the colon retained an intrinsic polarity in the presence of these antagonists and was only able to expel pellets in an aboral direction. The nature of the mechanism(s)/neurotransmitter(s) that generate(s) peristalsis and facilitate(s) natural fecal pellet propulsion, after blockade of major excitatory neurotransmitters, at the neuroneuronal and neuromuscular junction remains to be identified.
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Affiliation(s)
- T C Sia
- Dept. of Human Physiology, School of Medicine, Flinders Univ., Adelaide, South Australia, Australia.
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Heredia DJ, Gershon MD, Koh SD, Corrigan RD, Okamoto T, Smith TK. Important role of mucosal serotonin in colonic propulsion and peristaltic reflexes: in vitro analyses in mice lacking tryptophan hydroxylase 1. J Physiol 2013; 591:5939-57. [PMID: 24127620 DOI: 10.1113/jphysiol.2013.256230] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Although there is general agreement that mucosal 5-hydroxytryptamine (5-HT) can initiate peristaltic reflexes in the colon, recent studies have differed as to whether or not the role of mucosal 5-HT is critical. We therefore tested the hypothesis that the secretion of 5-HT from mucosal enterochromaffin (EC) cells is essential for the manifestation of murine colonic peristaltic reflexes. To do so, we analysed the mechanisms underlying faecal pellet propulsion in isolated colons of mice lacking tryptophan hydroxylase 1 (Tph1(-/-) mice), which is the rate-limiting enzyme in the biosynthesis of mucosal but not neuronal 5-HT. We used video analysis of faecal pellet propulsion, tension transducers to record colonic migrating motor complexes (CMMCs) and intracellular microelectrodes to record circular muscle activity occurring spontaneously or following intraluminal distension. When compared with control (Tph1(+/+)) mice, Tph1(-/-) animals exhibited: (1) an elongated colon; (2) larger faecal pellets; (3) orthograde propulsion followed by retropulsion (not observed in Tph1(+/+) colon); (4) slower in vitro propulsion of larger faecal pellets (28% of Tph1(+/+)); (5) CMMCs that infrequently propagated in an oral to anal direction because of impaired descending inhibition; (6) reduced CMMCs and inhibitory responses to intraluminal balloon distension; (7) an absence of reflex activity in response to mucosal stimulation. In addition, (8) thin pellets that propagated along the control colon failed to do so in Tph1(-/-) colon; and (9) the 5-HT3 receptor antagonist ondansetron, which reduced CMMCs and blocked their propagation in Tph1(+/+) mice, failed to alter CMMCs in Tph1(-/-) animals. Our observations suggest that mucosal 5-HT is essential for reflexes driven by mucosal stimulation and is also important for normal propagation of CMMCs and propulsion of pellets in the isolated colon.
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Affiliation(s)
- Dante J Heredia
- T. K. Smith: Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Sia TC, Whiting M, Kyloh M, Nicholas SJ, Oliver J, Brookes SJ, Dinning PG, Wattchow DA, Spencer NJ. 5-HT3 and 5-HT4 antagonists inhibit peristaltic contractions in guinea-pig distal colon by mechanisms independent of endogenous 5-HT. Front Neurosci 2013; 7:136. [PMID: 23935564 PMCID: PMC3732893 DOI: 10.3389/fnins.2013.00136] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 07/15/2013] [Indexed: 11/23/2022] Open
Abstract
Recent studies have shown that endogenous serotonin is not required for colonic peristalsis in vitro, nor gastrointestinal (GI) transit in vivo. However, antagonists of 5-Hydroxytryptamine (5-HT) receptors can inhibit peristalsis and GI-transit in mammals, including humans. This raises the question of how these antagonists inhibit GI-motility and transit, if depletion of endogenous 5-HT does not cause any significant inhibitory changes to either GI-motility or transit? We investigated the mechanism by which 5-HT3 and 5-HT4 antagonists inhibit distension-evoked peristaltic contractions in guinea-pig distal colon. In control animals, repetitive peristaltic contractions of the circular muscle were evoked in response to fixed fecal pellet distension. Distension-evoked peristaltic contractions were unaffected in animals with mucosa and submucosal plexus removed, that were also treated with reserpine (to deplete neuronal 5-HT). In control animals, peristaltic contractions were blocked temporarily by ondansetron (1–10 μM) and SDZ-205–557 (1–10 μM) in many animals. Interestingly, after this temporary blockade, and whilst in the continued presence of these antagonists, peristaltic contractions recovered, with characteristics no different from controls. Surprisingly, similar effects were seen in mucosa-free preparations, which had no detectable 5-HT, as detected by mass spectrometry. In summary, distension-evoked peristaltic reflex contractions of the circular muscle layer of the guinea-pig colon can be inhibited temporarily, or permanently, in the same preparation by selective 5-HT3 and 5-HT4 antagonists, depending on the concentration of the antagonists applied. These effects also occur in preparations that lack any detectable 5-HT. We suggest caution should be exercised when interpreting the effects of 5-HT3 and 5-HT4 antagonists; and the role of endogenous 5-HT, in the generation of distension-evoked colonic peristalsis.
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Affiliation(s)
- Tiong C Sia
- Discipline of Human Physiology and Center for Neuroscience, Flinders University Adelaide, SA, Australia
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