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Gur S, Alzweri L, Yilmaz-Oral D, Kaya-Sezginer E, Abdel-Mageed AB, Sikka SC, Hellstrom WJG. Ivabradine, the hyperpolarization-activated cyclic nucleotide-gated channel blocker, elicits relaxation of the human corpus cavernosum: a potential option for erectile dysfunction treatment. Aging Male 2020; 23:1088-1097. [PMID: 31741421 DOI: 10.1080/13685538.2019.1678125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVE To evaluate the effect of the If channel inhibitor, ivabradine on human corpus cavernosum (HCC) smooth muscle tone. METHODS HCC samples were obtained from erectile dysfunction(ED) patients (n = 12) undergoing penile prosthesis surgery. Concentration-response curves for ivabradine were exposed to various inhibitory and stimulatory agents. The relaxant and contractile responses to electrical field stimulation (EFS, 10 Hz and 80 Hz) were examined in the presence or absence of ivabradine (10 μM). HCN3 and HCN4 channel expression and localization were determined by Western blot and immunohistochemical analyses of HCC tissues. RESULTS Increasing ivabradine concentrations dependently reduced the maximal contractile responses of isolated HCC strips induced by KCl (59.5 ± 2.5%) and phenylephrine (84.0 ± 9.8%), which was not affected by nitric oxide synthase and soluble guanylyl cyclase inhibitors after phenylephrine-induced contraction. Nifedipine and tetraethylammonium inhibited the maximum relaxation to ivabradine by 75% and 39.3%, respectively. Fasudil and sildenafil increased the relaxation response to ivabradine without altering the maximum response. Pre-incubation with ivabradine significantly increased relaxant responses to EFS (p < 0.01) and reduced the contractile tension evoked by EFS (72.3%) (p < 0.001). Ivabradine incubation did not affect the expression and localization of HCN3 and HCN4 channels in the HCC smooth muscle cells. CONCLUSIONS Ivabradine exhibits a relaxant effect on HCC tissues, which is likely to be attributed to the blocking of L-type Ca2+ channels and the opening of K+ channels, independent of changes in the activation of the nitric oxide/cyclic guanosine monophosphate system. Inhibition of HCN channels localized in cavernosal smooth muscle cells may offer pharmacological benefits for patients with cardiovascular risk factors.
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Affiliation(s)
- Serap Gur
- Departments of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
- Department of Pharmacology and Biochemistry, Faculty of Pharmacy, Ankara University, Ankara, Turkey
| | - Laith Alzweri
- Departments of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - Didem Yilmaz-Oral
- Department of Pharmacology, Faculty of Pharmacy, Cukurova University, Adana, Turkey
| | - Ecem Kaya-Sezginer
- Department of Pharmacology and Biochemistry, Faculty of Pharmacy, Ankara University, Ankara, Turkey
| | - Asim B Abdel-Mageed
- Departments of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - Suresh C Sikka
- Departments of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - Wayne J G Hellstrom
- Departments of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
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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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Kentish SJ, Christie S, Vincent A, Li H, Wittert GA, Page AJ. Disruption of the light cycle ablates diurnal rhythms in gastric vagal afferent mechanosensitivity. Neurogastroenterol Motil 2019; 31:e13711. [PMID: 31509314 DOI: 10.1111/nmo.13711] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 08/15/2019] [Accepted: 08/16/2019] [Indexed: 02/08/2023]
Abstract
BACKGROUND Gastric vagal afferents (GVAs) respond to mechanical stimulation, initiating satiety. These afferents exhibit diurnal fluctuations in mechanosensitivity, facilitating food intake during the dark phase in rodents. In humans, desynchrony of diurnal rhythms (eg, shift work) is associated with a higher risk of obesity. To test the hypothesis that shift work disrupts satiety signaling, the effect of a rotating light cycles on diurnal rhythms in GVA mechanosensitivity in lean and high-fat diet (HDF)-induced obese mice was determined. METHODS Male C57BL/6 mice were fed standard laboratory diet (SLD) or HFD for 12 weeks. After 4 weeks, mice were randomly allocated to a normal light (NL; 12 hour light: 12 hour dark; lights on at zeitgeber time [ZT] 0) or rotating light (RL; 3-day NL cycle, 4-day reversed light cycle [lights on: ZT12] repeated) cycle for 8 weeks. At week 12, eight mice from each group were housed in metabolic cages. After 12 weeks, ex vivo GVA recordings were taken at 3 hour intervals starting at ZT0. KEY RESULTS SLD-RL and HFD-RL gained more weight compared to SLD-NL and HFD-NL mice, respectively. Gonadal fat pad mass was higher in SLD-RL compared to SLD-NL mice. In SLD-NL mice, tension and mucosal receptor mechanosensitivity exhibited diurnal rhythms with a peak at ZT9. These rhythms were lost in SLD-RL, HFD-NL, and HFD-RL mice and associated with dampened diurnal rhythms in food intake. CONCLUSIONS & INFERENCES GVA diurnal rhythms are susceptible to disturbances in the light cycle and/or the obese state. This may underpin the observed changes in feeding behavior.
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Affiliation(s)
- Stephen J Kentish
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Stewart Christie
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
| | - Andrew Vincent
- Nutrition, Diabetes & Metabolism, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.,Freemasons Foundation Centre for Men's Health, The University of Adelaide, Adelaide, South Australia, Australia
| | - Hui Li
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia.,Nutrition, Diabetes & Metabolism, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
| | - Gary A Wittert
- Nutrition, Diabetes & Metabolism, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.,Freemasons Foundation Centre for Men's Health, The University of Adelaide, Adelaide, South Australia, Australia
| | - Amanda J Page
- Vagal Afferent Research Group, Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia.,Nutrition, Diabetes & Metabolism, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia
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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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Affiliation(s)
- Amanda J Page
- Vagal Afferent Research Group, Centre for Nutrition and Gastrointestinal Disease, Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia.,Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, SA, 5000, Australia
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Yu Y, Park SJ, Beyak MJ. Inducible nitric oxide synthase-derived nitric oxide reduces vagal satiety signalling in obese mice. J Physiol 2018; 597:1487-1502. [PMID: 30565225 DOI: 10.1113/jp276894] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/19/2018] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Obesity is associated with disrupted satiety regulation. Mice with diet-induced obesity have reduced vagal afferent neuronal excitability and a decreased afferent response to satiety signals. A low grade inflammation occurs in obesity with increased expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS in diet-induced obese mice restored vagal afferent neuronal excitability, increased the afferent response to satiety mediators and distention of the gut, and reduced short-term energy intake. A prolonged inhibition of iNOS reduced energy intake and body weight gain during the first week, and reduced amounts of epididymal fat after 3 weeks. We identified a novel pathway underlying disrupted satiety regulation in obesity. Blocking of this pathway might be clinically useful for the management of obesity. ABSTRACT Vagal afferents regulate feeding by transmitting satiety signals to the brain. Mice with diet-induced obesity have reduced vagal afferent sensitivity to satiety signals. We investigated whether inducible nitric oxide synthase (iNOS)-derived NO contributed to this reduction. C57BL/6J mice were fed a high- or low-fat diet for 6-8 weeks. Nodose ganglia and jejunum were analysed by immunoblotting for iNOS expression; NO production was measured using a fluorometric assay. Nodose neuron excitability and intestinal afferent sensitivity were evaluated by whole-cell patch clamp and in vitro afferent recording, respectively. Expression of iNOS and production of NO were increased in nodose ganglia and the small intestine in obese mice. Inhibition of iNOS in obese mice by pre-treatment with an iNOS inhibitor increased nodose neuron excitability via 2-pore-domain K+ channel leak currents, restored afferent sensitivity to satiety signals and reduced short-term energy intake. Obese mice given the iNOS inhibitor daily for 3 weeks had reduced energy intake and decreased body weight gain during the first week, compared to mice given saline, and lower amounts of epididymal fat at the end of 3 weeks. Inhibition of iNOS or blocking the action of iNOS-derived NO on vagal afferent pathways might comprise therapeutic strategies for hyperphagia and obesity.
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Affiliation(s)
- Yang Yu
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
| | - Sung Jin Park
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
| | - Michael J Beyak
- Gastrointestinal Disease Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada
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Page AJ, Kentish SJ. Plasticity of gastrointestinal vagal afferent satiety signals. Neurogastroenterol Motil 2017; 29. [PMID: 27781333 DOI: 10.1111/nmo.12973] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022]
Abstract
The vagal link between the gastrointestinal tract and the central nervous system (CNS) has numerous vital functions for maintaining homeostasis. The regulation of energy balance is one which is attracting more and more attention due to the potential for exploiting peripheral hormonal targets as treatments for conditions such as obesity. While physiologically, this system is well tuned and demonstrated to be effective in the regulation of both local function and promoting/terminating food intake the neural connection represents a susceptible pathway for disruption in various disease states. Numerous studies have revealed that obesity in particularly is associated with an array of modifications in vagal afferent function from changes in expression of signaling molecules to altered activation mechanics. In general, these changes in vagal afferent function in obesity further promote food intake instead of the more desirable reduction in food intake. It is essential to gain a comprehensive understanding of the mechanisms responsible for these detrimental effects before we can establish more effective pharmacotherapies or lifestyle strategies for the treatment of obesity and the maintenance of weight loss.
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Affiliation(s)
- A J Page
- Centre for Nutrition and Gastrointestinal Disease, Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia.,Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, SA, Australia.,Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - S J Kentish
- Centre for Nutrition and Gastrointestinal Disease, Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia.,Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, SA, Australia.,School of Medicine, University of Queensland, St Lucia, QLD, Australia
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de Lartigue G, Diepenbroek C. Novel developments in vagal afferent nutrient sensing and its role in energy homeostasis. Curr Opin Pharmacol 2016; 31:38-43. [PMID: 27591963 DOI: 10.1016/j.coph.2016.08.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 07/01/2016] [Accepted: 08/11/2016] [Indexed: 12/16/2022]
Abstract
Vagal afferent neurons (VANs) play an important role in the control of food intake by signaling nutrient type and quantity to the brain. Recent findings are broadening our view of how VANs impact not only food intake but also energy homeostasis. This review focuses exclusively on studies of the vagus nerve from the past 2 years that highlight major new advancements in the field. We firstly discuss evidence that VANs can directly sense nutrients, and we consider new insights into mechanisms affecting sensing of gastric distension and signaling by gastrointestinal hormones ghrelin and GLP1. We discuss evidence that disrupting vagal afferent signaling increases long-term control of food intake and body weight management, and the importance of this gut-brain pathway in mediating beneficial effects of bariatric surgery. We conclude by highlighting novel roles for vagal afferent neurons in circadian rhythm, thermogenesis, and reward that may provide insight into mechanisms by which VAN nutrient sensing controls long-term control of energy homeostasis.
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Affiliation(s)
- Guillaume de Lartigue
- The John B. Pierce Laboratory, New Haven, CT, USA; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA.
| | - Charlene Diepenbroek
- The John B. Pierce Laboratory, New Haven, CT, USA; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT, USA
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Taylor-Clark TE. Role of reactive oxygen species and TRP channels in the cough reflex. Cell Calcium 2016; 60:155-62. [PMID: 27016063 DOI: 10.1016/j.ceca.2016.03.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 12/15/2022]
Abstract
The cough reflex is evoked by noxious stimuli in the airways. Although this reflex is essential for health, it can be triggered chronically in inflammatory and infectious airway disease. Neuronal transient receptor potential (TRP) channels such as ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) are polymodal receptors expressed on airway nociceptive afferent nerves. Reactive oxygen species (ROS) and other reactive compounds are associated with inflammation, from either NADPH oxidase or mitochondria. These reactive compounds cause activation and hyperexcitability of nociceptive afferents innervating the airways, and evidence suggests key contributions of TRPA1 and TRPV1.
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Affiliation(s)
- Thomas E Taylor-Clark
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612, USA.
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10
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Sun Y, Lau CW, Jia Y, Li Y, Wang W, Ran J, Li F, Huang Y, Zhou H, Yang B. Functional inhibition of urea transporter UT-B enhances endothelial-dependent vasodilatation and lowers blood pressure via L-arginine-endothelial nitric oxide synthase-nitric oxide pathway. Sci Rep 2016; 6:18697. [PMID: 26739766 PMCID: PMC4703984 DOI: 10.1038/srep18697] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 11/23/2015] [Indexed: 12/25/2022] Open
Abstract
Mammalian urea transporters (UTs), UT-A and UT-B, are best known for their role in urine concentration. UT-B is especially distributed in multiple extrarenal tissues with abundant expression in vascular endothelium, but little is known about its role in vascular function. The present study investigated the physiological significance of UT-B in regulating vasorelaxations and blood pressure. UT-B deletion in mice or treatment with UT-B inhibitor PU-14 in Wistar-Kyoto rats (WKYs) and spontaneous hypertensive rats (SHRs) reduced blood pressure. Acetylcholine-induced vasorelaxation was significantly augmented in aortas from UT-B null mice. PU-14 concentration-dependently produced endothelium-dependent relaxations in thoracic aortas and mesenteric arteries from both mice and rats and the relaxations were abolished by N(ω)-nitro-L-arginine methyl ester. Both expression and phosphorylation of endothelial nitric oxide synthase (eNOS) were up-regulated and expression of arginase I was down-regulated when UT-B was inhibited both in vivo and in vitro. PU-14 induced endothelium-dependent relaxations to a similar degree in aortas from 12 weeks old SHRs or WKYs. In summary, here we report for the first time that inhibition of UT-B plays an important role in regulating vasorelaxations and blood pressure via up-regulation of L-arginine-eNOS-NO pathway, and it may become another potential therapeutic target for the treatment of hypertension.
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Affiliation(s)
- Yi Sun
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Chi-Wai Lau
- Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China
| | - Yingli Jia
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Yingjie Li
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Weiling Wang
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Jianhua Ran
- Department of Anatomy and Neuroscience Center, Chongqing Medical University, Chongqing, China
| | - Fei Li
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Yu Huang
- Institute of Vascular Medicine and Li Ka Shing Institute of Health Sciences, Chinese University of Hong Kong, Hong Kong, China
| | - Hong Zhou
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
| | - Baoxue Yang
- State Key Laboratory of Natural and Biomimetic Drugs, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Department of Pharmacology, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
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Browning KN. Role of central vagal 5-HT3 receptors in gastrointestinal physiology and pathophysiology. Front Neurosci 2015; 9:413. [PMID: 26578870 PMCID: PMC4625078 DOI: 10.3389/fnins.2015.00413] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 10/15/2015] [Indexed: 12/21/2022] Open
Abstract
Vagal neurocircuits are vitally important in the co-ordination and modulation of GI reflexes and homeostatic functions. 5-hydroxytryptamine (5-HT; serotonin) is critically important in the regulation of several of these autonomic gastrointestinal (GI) functions including motility, secretion and visceral sensitivity. While several 5-HT receptors are involved in these physiological responses, the ligand-gated 5-HT3 receptor appears intimately involved in gut-brain signaling, particularly via the afferent (sensory) vagus nerve. 5-HT is released from enterochromaffin cells in response to mechanical or chemical stimulation of the GI tract which leads to activation of 5-HT3 receptors on the terminals of vagal afferents. 5-HT3 receptors are also present on the soma of vagal afferent neurons, including GI vagal afferent neurons, where they can be activated by circulating 5-HT. The central terminals of vagal afferents also exhibit 5-HT3 receptors that function to increase glutamatergic synaptic transmission to second order neurons of the nucleus tractus solitarius within the brainstem. While activation of central brainstem 5-HT3 receptors modulates visceral functions, it is still unclear whether central vagal neurons, i.e., nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) neurons themselves also display functional 5-HT3 receptors. Thus, activation of 5-HT3 receptors may modulate the excitability and activity of gastrointestinal vagal afferents at multiple sites and may be involved in several physiological and pathophysiological conditions, including distention- and chemical-evoked vagal reflexes, nausea, and vomiting, as well as visceral hypersensitivity.
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Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine Hershey, PA, USA
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12
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Browning KN. Excited by fasting? NO. J Physiol 2014; 592:3175-6. [PMID: 25085972 DOI: 10.1113/jphysiol.2014.278663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Kirsteen N Browning
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, 17033, USA
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