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Jayaprakash N, Song W, Toth V, Vardhan A, Levy T, Tomaio J, Qanud K, Mughrabi I, Chang YC, Rob M, Daytz A, Abbas A, Nassrallah Z, Volpe BT, Tracey KJ, Al-Abed Y, Datta-Chaudhuri T, Miller L, Barbe MF, Lee SC, Zanos TP, Zanos S. Organ- and function-specific anatomical organization of vagal fibers supports fascicular vagus nerve stimulation. Brain Stimul 2023; 16:484-506. [PMID: 36773779 DOI: 10.1016/j.brs.2023.02.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Revised: 02/03/2023] [Accepted: 02/03/2023] [Indexed: 02/11/2023] Open
Abstract
Vagal fibers travel inside fascicles and form branches to innervate organs and regulate organ functions. Existing vagus nerve stimulation (VNS) therapies activate vagal fibers non-selectively, often resulting in reduced efficacy and side effects from non-targeted organs. The transverse and longitudinal arrangement of fibers inside the vagal trunk with respect to the functions they mediate and organs they innervate is unknown, however it is crucial for selective VNS. Using micro-computed tomography imaging, we tracked fascicular trajectories and found that, in swine, sensory and motor fascicles are spatially separated cephalad, close to the nodose ganglion, and merge caudad, towards the lower cervical and upper thoracic region; larynx-, heart- and lung-specific fascicles are separated caudad and progressively merge cephalad. Using quantified immunohistochemistry at single fiber level, we identified and characterized all vagal fibers and found that fibers of different morphological types are differentially distributed in fascicles: myelinated afferents and efferents occupy separate fascicles, myelinated and unmyelinated efferents also occupy separate fascicles, and small unmyelinated afferents are widely distributed within most fascicles. We developed a multi-contact cuff electrode to accommodate the fascicular structure of the vagal trunk and used it to deliver fascicle-selective cervical VNS in anesthetized and awake swine. Compound action potentials from distinct fiber types, and physiological responses from different organs, including laryngeal muscle, cough, breathing, and heart rate responses are elicited in a radially asymmetric manner, with consistent angular separations that agree with the documented fascicular organization. These results indicate that fibers in the trunk of the vagus nerve are anatomically organized according to functions they mediate and organs they innervate and can be asymmetrically activated by fascicular cervical VNS.
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Affiliation(s)
| | - Weiguo Song
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Viktor Toth
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Todd Levy
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Khaled Qanud
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Yao-Chuan Chang
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Moontahinaz Rob
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Anna Daytz
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Adam Abbas
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Zeinab Nassrallah
- Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA
| | - Bruce T Volpe
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Kevin J Tracey
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | - Yousef Al-Abed
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Larry Miller
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Sunhee C Lee
- Feinstein Institutes for Medical Research, Manhasset, NY, USA
| | | | - Stavros Zanos
- Feinstein Institutes for Medical Research, Manhasset, NY, USA; Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, USA; Elmezzi Graduate School of Molecular Medicine, Manhasset, NY, USA.
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Morishita R, Yoshimura R, Sakamoto H, Kuramoto H. Localization of substance P (SP)-immunoreactivity in the myenteric plexus of the rat esophagus. Histochem Cell Biol 2023; 159:7-21. [PMID: 35507035 DOI: 10.1007/s00418-022-02104-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2022] [Indexed: 02/07/2023]
Abstract
The present immunohistochemical study was performed to examine the number, distribution, and chemical coding of intrinsic substance P (SP) neurons and nerve fibers within the esophagus and discuss their functional roles. Many SP neurons and nerve fibers were found in the myenteric plexus, and the SP neurons gradually decreased from the oral side toward the aboral side of the esophagus. Double-immunolabeling showed that most SP neurons were cholinergic (positive for choline acetyltransferase), and few were nitrergic (positive for nitric oxide synthase). Some cholinergic SP nerve terminals surrounded cell bodies of several myenteric neurons. In the muscularis mucosa and lower esophageal sphincter, and around blood vessels, numerous SP nerve endings were present, and many of them were cholinergic. Also, SP nerve endings were found on only a few motor endplates of the striated muscles, and most of them were calcitonin gene-related peptide (CGRP)-positive. Retrograde tracing using Fast Blue (FB) showed that numerous sensory neurons in the dorsal root ganglia (DRGs) and nodose ganglion (NG) projected to the esophagus, and most FB-labeled SP neurons were CGRP-positive. These results suggest that the intrinsic SP neurons in the rat esophagus may play roles as, at least, motor neurons, interneurons, and vasomotor neurons, which are involved in local regulation of smooth muscle motility, neuronal transmission, and blood circulation, respectively. Moreover, SP nerve endings on only a minority of motor endplates may be extrinsic, derived from DRGs or NG, and possibly detect chemical circumstances within motor endplates to modulate esophageal motility.
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Affiliation(s)
- Ryo Morishita
- Cell Function Division, Department of Applied Biology, Kyoto Institute of Technology, Kyoto, Japan
| | - Ryoichi Yoshimura
- Cell Function Division, Department of Applied Biology, Kyoto Institute of Technology, Kyoto, Japan
| | - Hiroshi Sakamoto
- Department of Physical Therapy, Health Science University, Yamanashi, Japan
| | - Hirofumi Kuramoto
- Cell Function Division, Department of Applied Biology, Kyoto Institute of Technology, Kyoto, Japan.
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Stefanidis A, Forrest N, Brown WA, Dixon JB, O’Brien PB, Juliane Kampe, Oldfield BJ. An investigation of the neural mechanisms underlying the efficacy of the adjustable gastric band. Surg Obes Relat Dis 2016; 12:828-838. [DOI: 10.1016/j.soard.2015.11.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 10/19/2015] [Accepted: 11/19/2015] [Indexed: 02/08/2023]
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Brain-derived neurotrophic factor immunoreactive vagal sensory neurons innervating the gastrointestinal tract of the rat. J Chem Neuroanat 2014; 61-62:83-7. [PMID: 25128629 DOI: 10.1016/j.jchemneu.2014.07.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Revised: 07/30/2014] [Accepted: 07/30/2014] [Indexed: 01/01/2023]
Abstract
We have determined whether brain-derived neurotrophic factor immunoreactive (BDNF-ir) neurons in the vagal ganglia innervate the gastrointestinal tract. Many BDNF-ir neurons were medium in size and located throughout the jugular and nodose ganglia. When Fluorogold was injected into the wall of the cervical esophagus, many retrogradely Fluorogold-labeled neurons were found in both the jugular ganglion and the nodose ganglion. When Fluorogold was injected into the body of the stomach or applied to the cut end of the subdiaphragmatic vagus nerve, numerous Fluorogold-labeled neurons were found mostly in the nodose ganglion. Double-labeling combining immunohistochemistry for BDNF and retrograde tracing with Fluorogold showed that more than 90% of the neurons in the jugular ganglion and the nodose ganglion projecting to the cervical esophagus contained BDNF-like immunoreactivity. In the cases of both Fluorogold injection into the stomach and Fluorogold application to the subdiaphragmatic vagus nerve, almost all Fluorogold-labeled neurons in the nodose ganglion contained BDNF-like immunoreactivity. These results indicated that almost all vagal sensory neurons located in either the jugular ganglion or the nodose ganglion that innervate the gastrointestinal tract are BDNF-ir neurons.
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Hayakawa T, Kuwahara-Otani S, Maeda S, Tanaka K, Seki M. Calcitonin gene-related peptide immunoreactive sensory neurons in the vagal and glossopharyngeal ganglia innervating the larynx of the rat. J Chem Neuroanat 2014; 55:18-23. [DOI: 10.1016/j.jchemneu.2013.11.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 11/06/2013] [Accepted: 11/08/2013] [Indexed: 10/26/2022]
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Localization of receptors for calcitonin-gene-related peptide to intraganglionic laminar endings of the mouse esophagus: peripheral interaction between vagal and spinal afferents? Histochem Cell Biol 2013; 141:321-35. [PMID: 24203088 DOI: 10.1007/s00418-013-1162-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/23/2013] [Indexed: 12/11/2022]
Abstract
The calcitonin-gene-related peptide (CGRP) receptor is a heterodimer of calcitonin-receptor-like receptor (CLR) and receptor-activity-modifying protein 1 (RAMP1). Despite the importance of CGRP in regulating gastrointestinal functions, nothing is known about the distribution and function of CLR/RAMP1 in the esophagus, where up to 90 % of spinal afferent neurons contain CGRP. We detected CLR/RAMP1 in the mouse esophagus using immunofluorescence and confocal laser scanning microscopy and examined their relationship with neuronal elements of the myenteric plexus. Immunoreactivity for CLR and RAMP1 colocalized with VGLUT2-positive intraganglionic laminar endings (IGLEs), which were contacted by CGRP-positive varicose axons presumably of spinal afferent origin, typically at sites of CRL/RAMP1 immunoreactivity. This provides an anatomical basis for interaction between spinal afferent fibers and IGLEs. Immunoreactive CLR and RAMP1 also colocalized in myenteric neurons. Thus, CGRP-containing spinal afferents may interact with both vagal IGLEs and myenteric neurons in the mouse esophagus, possibly modulating motility reflexes and inflammatory hypersensitivity.
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Hübsch M, Neuhuber WL, Raab M. Muscarinic acetylcholine receptors in the mouse esophagus: focus on intraganglionic laminar endings (IGLEs). Neurogastroenterol Motil 2013; 25:e560-73. [PMID: 23742744 DOI: 10.1111/nmo.12161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 05/04/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND IGLEs represent the only low-threshold vagal mechanosensory terminals in the tunica muscularis of the esophagus. Previously, close relationships of vesicular glutamate transporter 2 (VGLUT2) immunopositive IGLEs and cholinergic varicosities suggestive for direct contacts were described in almost all mouse esophageal myenteric ganglia. Possible cholinergic influence on IGLEs requires specific acetylcholine receptors. In particular, the occurrence and location of neuronal muscarinic acetylcholine receptors (mAChR) in the esophagus were not yet characterized. METHODS This study aimed at specifying relationships of VGLUT2 immunopositive IGLEs and vesicular acetylcholine transporter (VAChT)-immunopositive varicosities using pre-embedding electron microscopy and the location of mAChR1-3 (M1-3) within esophagus and nodose ganglia using multilabel immunofluorescence and retrograde tracing. KEY RESULTS Electron microscopy confirmed synaptic contacts between cholinergic varicosities and IGLEs. M1- and M2-immunoreactivities (-iry; -iries) were colocalized with VGLUT2-iry in subpopulations of IGLEs. Retrograde Fast Blue tracing from the esophagus showed nodose ganglion neurons colocalizing tracer and M2-iry. M1-3-iries were detected in about 80% of myenteric ganglia and in about 67% of myenteric neurons. M1- and M2-iry were present in many fibers and varicosities within myenteric ganglia. Presynaptic M2-iry was detected in all, presynaptic M3-iry in one-fifth of motor endplates of striated esophageal muscles. M1-iry could not be detected in motor endplates of the esophagus, but in sternomastoid muscle. CONCLUSIONS & INFERENCES Acetylcholine probably released from varicosities of both extrinsic and intrinsic origin may influence a subpopulation of esophageal IGLEs via M2 and M1-receptors.
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Affiliation(s)
- M Hübsch
- Institute of Anatomy I, University of Erlangen-Nuremberg, Erlangen, Germany
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Hayakawa T, Kuwahara-Otani S, Maeda S, Tanaka K, Seki M. Localization in the vagal ganglia of calcitonin gene-related peptide- and calretinin-immunoreactive neurons that innervate the cervical and the subdiaphragmatic esophagus of the rat. J Chem Neuroanat 2012; 43:34-42. [DOI: 10.1016/j.jchemneu.2011.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 10/11/2011] [Accepted: 10/11/2011] [Indexed: 11/24/2022]
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Immunohistochemical characteristics of neurons in nodose ganglia projecting to the different chambers of the rat heart. Auton Neurosci 2010; 155:33-8. [DOI: 10.1016/j.autneu.2010.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 12/31/2009] [Accepted: 01/06/2010] [Indexed: 12/26/2022]
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Mazzone SB, McGovern AE. Innervation of tracheal parasympathetic ganglia by esophageal cholinergic neurons: evidence from anatomic and functional studies in guinea pigs. Am J Physiol Lung Cell Mol Physiol 2010; 298:L404-16. [PMID: 20061441 DOI: 10.1152/ajplung.00166.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the present study, we describe a subset of nerve fibers, characterized by their immunoreactivity for the calcium-binding protein calretinin, that are densely and selectively associated with cholinergic postganglionic neurons in the guinea pig tracheal ganglia. Retrograde neuronal tracing with cholera toxin B, combined with immunohistochemical analyses, showed that these nerve fibers do not originate from sensory neurons in the nodose, jugular, or dorsal root ganglia or from motor neurons in the nucleus ambiguus, dorsal motor nucleus of the vagus nerve, spinal cord, stellate ganglia, or superior cervical ganglia. Calretinin-immunoreactive nerve fibers disappeared from tracheal segments after 48 h in organotypic culture, indicating that the fibers were of extrinsic origin. However, calretinin-positive nerve fibers persisted in tracheal ganglia when tracheae were cocultured with the adjacent esophagus intact. Immunohistochemical analysis of the esophagus revealed a population of cholinergic neurons in the esophageal myenteric plexus that coexpressed calretinin. In functional studies, electrical stimulation of the esophagus in vitro evoked measurable contractions of the trachea. These contractions were not altered by prior organotypic culture of the trachea and esophagus to remove the extrinsic innervation to the airways but were significantly (P < 0.05) inhibited by the ganglionic blocker hexamethonium or by physical disruption of the tissue connecting the trachea and esophagus. These data suggest that a subset of esophageal neurons, characterized by the expression of calretinin and acetylcholine, provide a previously unrecognized excitatory input to tracheal cholinergic ganglia in guinea pigs.
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Affiliation(s)
- Stuart B Mazzone
- School of Biomedical Sciences, University of Queensland, St. Lucia, QLD 4072, Australia.
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Guić MM, Košta V, Aljinović J, Sapunar D, Grković I. Characterization of spinal afferent neurons projecting to different chambers of the rat heart. Neurosci Lett 2010; 469:314-8. [DOI: 10.1016/j.neulet.2009.12.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 12/09/2009] [Accepted: 12/10/2009] [Indexed: 11/24/2022]
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Kestler C, Neuhuber WL, Raab M. Distribution of P2X(3) receptor immunoreactivity in myenteric ganglia of the mouse esophagus. Histochem Cell Biol 2008; 131:13-27. [PMID: 18810483 DOI: 10.1007/s00418-008-0498-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2008] [Indexed: 02/07/2023]
Abstract
Intraganglionic laminar endings (IGLEs) represent the major vagal afferent terminals throughout the gut. Electrophysiological experiments revealed a modulatory role of ATP in the IGLE-mechanotransduction process and the P2X(2)-receptor has been described in IGLEs of mouse, rat and guinea pig. Another purinoceptor, the P2X(3)-receptor, was found in IGLEs of the rat esophagus. These findings prompted us to investigate occurrence and distribution of the P2X(3)-receptor in the mouse esophagus. Using multichannel immunofluorescence and confocal microscopy, P2X(3)-immunoreactivity (-iry) was found colocalized with the vesicular glutamate transporter 2 (VGLUT2), a specific marker for IGLEs, on average in three-fourths of esophageal IGLEs. The distribution of P2X(3) immunoreactive (-ir) IGLEs was similar to that of P2X(2)-iry and showed increasing numbers towards the abdominal esophagus. P2X(3)/P2X(2)-colocalization within IGLEs suggested the occurrence of heteromeric P2X(2/3) receptors. In contrast to the rat, where only a few P2X(3)-ir perikarya were described, P2X(3) stained perikarya in ~80% of myenteric ganglia in the mouse. Detailed analysis revealed P2X(3)-iry in subpopulations of nitrergic (nNOS) and cholinergic (ChAT) myenteric neurons and ganglionic neuropil of the mouse esophagus. We conclude that ATP might act as a neuromodulator in IGLEs via a (P2X(2))-P2X(3) receptor-mediated pathway especially in the abdominal portion of the mouse esophagus.
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Affiliation(s)
- Christine Kestler
- Institut für Anatomie, Lehrstuhl I, Universität Erlangen-Nürnberg, Krankenhausstr. 9, 91054 Erlangen, Germany
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Li K, Zheng S, Xiao X, Wang Q, Zhou Y, Chen L. The structural characteristics and expression of neuropeptides in the esophagus of patients with congenital esophageal atresia and tracheoesophageal fistula. J Pediatr Surg 2007; 42:1433-8. [PMID: 17706510 DOI: 10.1016/j.jpedsurg.2007.03.050] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE The aim of this study was to investigate the structural characteristics and the expression of a group of neuropeptides in the esophagus of patients with congenital esophageal atresia and tracheoesophageal fistula (EA-TEF), as well to elucidate the roles of these neuropeptides in the pathogenesis of postoperative incoordination of esophagus after successful surgical repair of EA-TEF. METHODS Twenty-four specimens from distal tracheoesophageal fistulas of patients with EA-TEF (EA-TEF group) and 10 esophageal specimens from neonates who died of nonesophageal diseases (control group) were studied. All of the specimens were subjected to routine pathologic study, ultrastructural observation, and immunohistochemical staining for neuron-specific enolase, substance P, vasoactive intestinal polypeptide, and nitric oxide synthase. RESULTS In the EA-TEF group, mitochondria were distributed along the membrane of smooth muscle cell, whereas mitochondria in the control group were distributed along the karyotheca of the smooth muscle cells. The ratio of granulated vesicles to clear vesicles in the varicosity of the intramuscular motor nerve ending of the EA-TEF group (0.520 +/- 0.137) was much higher than that in the control group (0.192 +/- 0.020, P < .05). The percentages of specimens shown to have positive expression of neuron-specific enolase and substance P in the EA-TEF group (20.8% and 12.5%, respectively) were significantly lower than those in the control group (90% and 80% respectively, P < .05). The percentages of specimens shown to have positive expression of vasoactive intestinal polypeptide and nitric oxide synthase in the EA-TEF group (83.3% and 75%, respectively) were significantly higher than that in the control group (30% and 10% respectively, P < .05). CONCLUSION Imbalance of neurotransmitters excretion in nerve vesicle, abnormal intrinsic dysplasia of nerve plexus and increased expression of certain neuropeptides were the main characteristics of esophagus with abnormal intrinsic innervation, which may be responsible for the postoperative esophageal dysfunction of EA-TEF.
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Affiliation(s)
- Kai Li
- Department of Surgery, Children's Hospital, Medical Center of Fudan University (Former Shanghai Medical University), Shanghai 200032, PR China
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Kraus T, Neuhuber WL, Raab M. Distribution of vesicular glutamate transporter 1 (VGLUT1) in the mouse esophagus. Cell Tissue Res 2007; 329:205-19. [PMID: 17508221 DOI: 10.1007/s00441-007-0392-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Accepted: 12/12/2006] [Indexed: 01/22/2023]
Abstract
In rat and mouse esophagus, vesicular glutamate transporter 2 (VGLUT2) has been demonstrated to identify vagal intraganglionic laminar endings (IGLEs); this has recently also been shown for VGLUT1 in rat esophagus. In this study, we have investigated the distribution of VGLUT1 in the mouse esophagus and compared these results with the recently published data from the rat esophagus. Unexpectedly, we have discovered that VGLUT1 mostly fails to identify IGLEs in the mouse esophagus. This is surprising, since the distribution of VGLUT2 shows comparable results in both species. Confocal imaging has revealed substantial colocalization of VGLUT1 immunoreactivity (-ir) with cholinergic and nitrergic/peptidergic markers within the myenteric neuropil and in both cholinergic and nitrergic myenteric neuronal cell bodies. VGLUT1 and cholinergic markers have also been colocalized in fibers of the muscularis mucosae, whereas VGLUT1 and nitrergic markers have never been colocalized in fibers of the muscularis mucosae, although this does occur in fibers of the muscularis running to motor endplates. Thus, VGLUT1 is contained in the nitrergic innervation of mouse esophageal motor endplates, another difference from the rat esophagus. VGLUT1-ir is therefore present in extrinsic and intrinsic innervation of the mouse esophagus, but the significant differences from the rat indicate species variations concerning the distribution of VGLUTs in the peripheral nervous system.
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Affiliation(s)
- T Kraus
- Department of Anatomy I, University of Erlangen-Nuremberg, Erlangen, Germany
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Raab M, Neuhuber WL. Glutamatergic functions of primary afferent neurons with special emphasis on vagal afferents. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 256:223-75. [PMID: 17241909 DOI: 10.1016/s0074-7696(07)56007-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Glutamate has been identified as the main transmitter of primary afferent neurons. This was established based on biochemical, electrophysiological, and immunohistochemical data from studies on glutamatergic receptors and their agonists/antagonists. The availability of specific antibodies directed against glutamate and, more recently, vesicular glutamate transporters corroborated this and led to significant new discoveries. In particular, peripheral endings of various classes of afferents contain vesicular glutamate transporters, suggesting vesicular storage in and exocytotic release of glutamate from peripheral afferent endings. This suggests that autocrine mechanisms regulate sensory transduction processes. However, glutamate release from peripheral sensory terminals could also enable afferent neurons to influence various cells associated with them. This may be particularly relevant for vagal intraganglionic laminar endings, which could represent glutamatergic sensor-effector components of intramural reflex arcs in the gastrointestinal tract. Thus, morphological analysis of the relationships of putative glutamatergic primary afferents with associated tissues may direct forthcoming studies on their functions.
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Affiliation(s)
- Marion Raab
- Institut für Anatomie, Universität Erlangen-Nürnberg, Erlangen, Germany
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Neuhuber WL, Raab M, Berthoud HR, Wörl J. Innervation of the mammalian esophagus. ADVANCES IN ANATOMY EMBRYOLOGY AND CELL BIOLOGY 2006. [PMID: 16573241 DOI: 10.1007/978-3-540-32948-0_1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Understanding the innervation of the esophagus is a prerequisite for successful treatment of a variety of disorders, e.g., dysphagia, achalasia, gastroesophageal reflux disease (GERD) and non-cardiac chest pain. Although, at first glance, functions of the esophagus are relatively simple, their neuronal control is considerably complex. Vagal motor neurons of the nucleus ambiguus and preganglionic neurons of the dorsal motor nucleus innervate striated and smooth muscle, respectively. Myenteric neurons represent the interface between the dorsal motor nucleus and smooth muscle but they are also involved in striated muscle innervation. Intraganglionic laminar endings (IGLEs) represent mechanosensory vagal afferent terminals. They also establish intricate connections with enteric neurons. Afferent information is implemented by the swallowing central pattern generator in the brainstem, which generates and coordinates deglutitive activity in both striated and smooth esophageal muscle and orchestrates esophageal sphincters as well as gastric adaptive relaxation. Disturbed excitation/inhibition balance in the lower esophageal sphincter results in motility disorders, e.g., achalasia and GERD. Loss of mechanosensory afferents disrupts adaptation of deglutitive motor programs to bolus variables, eventually leading to megaesophagus. Both spinal and vagal afferents appear to contribute to painful sensations, e.g., non-cardiac chest pain. Extrinsic and intrinsic neurons may be involved in intramural reflexes using acetylcholine, nitric oxide, substance P, CGRP and glutamate as main transmitters. In addition, other molecules, e.g., ATP, GABA and probably also inflammatory cytokines, may modulate these neuronal functions.
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Kuramoto H, Kadowaki M. Vagus nerve stimulation preferentially induces Fos expression in nitrergic neurons of rat esophagus. Cell Tissue Res 2006; 324:361-7. [PMID: 16450125 DOI: 10.1007/s00441-005-0124-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Accepted: 10/31/2005] [Indexed: 11/30/2022]
Abstract
To identify neurochemical phenotypes of esophageal myenteric neurons synaptically activated by vagal preganglionic efferents, we immunohistochemically detected the expression of Fos, an immediate early gene product, in whole-mount preparations of the entire esophagus of rats following electrical stimulation of the vagus nerves. When electrical stimulation was applied to either the cervical left (LVN) or right vagus nerve (RVN), neurons with nuclei showing Fos immunoreactivity (IR) were found to comprise approximately 10% of the total myenteric neurons in the entire esophagus. These neurons increased from the oral toward the gastric end of the esophagus, with the highest frequency in the abdominal portion of the esophagus. A significant difference was not found in the number of Fos neurons between the LVN-stimulated and RVN-stimulated esophagus. Double-immunolabeling showed that nitric oxide synthase (NOS)-IR occurred in most (86% and 84% in the LVN-stimulated and RVN-stimulated esophagus, respectively) of the Fos neurons in the entire esophagus. Furthermore, the stimulation of either of the vagus nerves resulted in high proportions (71%-90%) of Fos neurons with NOS-IR, with respect to the total Fos neurons in each segment, in the entire esophagus. However, a small proportion (8% and 7% in the LVN-stimulated and RVN-stimulated esophagus, respectively) of the Fos neurons in the esophagus exhibited choline acetyltransferase (ChAT)-IR. The occurrence-frequency of Fos neurons with ChAT-IR was less than 4% of the total Fos neurons in any segment of the LVN-stimulated and RVN-stimulated esophagus. Some of the Fos neurons with ChAT-IR appeared to be innervated by numerous varicose ChAT-positive nerve terminals. The present results showing that electrical stimulation of the vagus nerves induces a high proportion of Fos neurons with NOS-IR suggests the preferential activation of NOS neurons in the esophagus by vagal preganglionic efferents. This connectivity between the vagal efferents and intrinsic nitrergic neurons might be involved in inhibitory actions on esophageal motility.
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Affiliation(s)
- Hirofumi Kuramoto
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto, 606-8585, Japan.
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Ewald P, Neuhuber WL, Raab M. Vesicular glutamate transporter 1 immunoreactivity in extrinsic and intrinsic innervation of the rat esophagus. Histochem Cell Biol 2005; 125:377-95. [PMID: 16231188 DOI: 10.1007/s00418-005-0083-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2005] [Indexed: 01/19/2023]
Abstract
Encouraged by the recent finding of vesicular glutamate transporter 2 (VGLUT2) immunoreactivity (-ir) in intraganglionic laminar endings (IGLEs) of the rat esophagus, we investigated also the distribution and co-localization patterns of VGLUT1. Confocal imaging revealed substantial co-localization of VGLUT1-ir with selective markers of IGLEs, i.e., calretinin and VGLUT2, indicating that IGLEs contain both VGLUT1 and VGLUT2 within their synaptic vesicles. Besides IGLEs, we found VGLUT1-ir in both cholinergic and nitrergic myenteric neuronal cell bodies, in fibers of the muscularis mucosae, and in esophageal motor endplates. Skeletal neuromuscular junctions, in contrast, showed no VGLUT1-ir. We also tested for probable co-localization of VGLUT1-ir with markers of extrinsic and intrinsic esophageal innervation and glia. Within the myenteric neuropil we found, besides co-localization of VGLUT1 and substance P, no further co-localization of VGLUT1-ir with any of these markers. In the muscularis mucosae some VGLUT1-ir fibers were shown to contain neuronal nitric oxide synthase (nNOS)-ir. VGLUT1-ir in esophageal motor endplates was partly co-localized with vesicular acetylcholine transporter (VAChT)/choline acetyltransferase (ChAT)-ir, but VGLUT1-ir was also demonstrated in separately terminating fibers at motor endplates co-localized neither with ChAT/VAChT-ir nor with nNOS-ir, suggesting a hitherto unknown glutamatergic enteric co-innervation. Thus, VGLUT1-ir was found in extrinsic as well as intrinsic innervation of the rat esophagus.
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Affiliation(s)
- P Ewald
- Department of Anatomy I, University of Erlangen-Nuremberg, Krankenhausstr. 9, 91054, Erlangen, Germany
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Raab M, Neuhuber WL. Number and distribution of intraganglionic laminar endings in the mouse esophagus as demonstrated with two different immunohistochemical markers. J Histochem Cytochem 2005; 53:1023-31. [PMID: 15923367 DOI: 10.1369/jhc.4a6582.2005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Intraganglionic laminar endings (IGLEs) represent the only vagal mechanosensory terminals in the tunica muscularis of the esophagus. Two specific markers for IGLEs were recently described in mouse: the purinergic P2 x 2 receptor and the vesicular glutamate transporter 2 (VGLUT2). This study aimed at comparing both markers with respect to their suitability for quantitative analysis. We counted IGLEs immunostained for VGLUT2 and P2 x 2, respectively, and mapped their distribution in esophageal wholemounts of C57Bl/6 mice. Numbers and distribution of IGLEs were compared with those of myenteric ganglia as demonstrated by cuprolinic blue histochemistry. Whereas the distribution of VGLUT2-immunopositive IGLEs closely matched that of myenteric ganglia, P2 x 2-immunopositive IGLEs were rarely found in upper and middle esophagus but increasingly in its lower parts. P2 x 2 stained only half the number of IGLEs found with VGLUT2 immunostaining. We also investigated the correlation between anterograde tracing and immunohistochemistry for identifying IGLEs. Confocal microscopy revealed colocalization of all three markers in approximately 50% of IGLEs. The remaining IGLEs showed only tracer and VGLUT2 labeling but no P2 x 2 immunoreactivity. Thus, VGLUT2 and P2 x 2 represent two specific markers for qualitative demonstration of esophageal IGLEs. However, VGLUT2 may be superior to P2 x 2 as a quantitative marker for IGLEs in the esophagus of C57Bl/6 mice.
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Affiliation(s)
- M Raab
- Department of Anatomy I, University of Erlangen-Nuremberg, Erlangen, Germany.
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Wörl J, Neuhuber WL. Enteric co-innervation of motor endplates in the esophagus: state of the art ten years after. Histochem Cell Biol 2005; 123:117-30. [PMID: 15729553 DOI: 10.1007/s00418-005-0764-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2004] [Indexed: 01/26/2023]
Abstract
The existence of a distinct ganglionated myenteric plexus between the two layers of the striated tunica muscularis of the mammalian esophagus represented an enigma for quite a while. Although an enteric co-innervation of vagally innervated motor endplates in the esophagus has been repeatedly suggested, it was not possible until recently to demonstrate this dual innervation. Ten years ago, we were able to demonstrate that motor endplates in the rat esophagus receive a dual innervation from both vagal nerve fibers originating in the brain stem and from varicose enteric nerve fibers originating in the myenteric plexus. Since then, a considerable amount of data could be raised on enteric co-innervation and its occurrence in a variety of species, including humans, its neurochemistry, spatial relationships on motor endplates, ontogeny, and possible roles during esophageal peristalsis. These data underline the significance of this newly discovered innervation component, although its function is still largely unknown. The aim of this review is to summarize current knowledge about enteric co-innervation of esophageal striated muscle and to provide some hints as to its functional significance.
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Affiliation(s)
- Jürgen Wörl
- Anatomy Institute, University of Erlangen-Nuremberg, Krankenhausstrasse 9, D-91054, Erlangen, Germany.
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Raab M, Neuhuber WL. Intraganglionic laminar endings and their relationships with neuronal and glial structures of myenteric ganglia in the esophagus of rat and mouse. Histochem Cell Biol 2004; 122:445-59. [PMID: 15378379 DOI: 10.1007/s00418-004-0703-z] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2004] [Indexed: 12/15/2022]
Abstract
Intraganglionic laminar endings (IGLEs) represent the only vagal mechanosensory terminals in the tunica muscularis of the esophagus and may be involved in local reflex control. We recently detected extensive though not complete colocalization of the vesicular glutamate transporter 2 (VGLUT2) with markers for IGLEs. To elucidate this colocalization mismatch, this study aimed at identifying markers for nitrergic, cholinergic, peptidergic, and adrenergic neurons and glial cells, which may colocalize with VGLUT2 outside of IGLEs. Confocal imaging revealed, besides substantial colocalization of VGLUT2 and substance P (SP), no other significant colocalizations of VGLUT2 and immunoreactivity for any of these markers within the same varicosities. However, we found close contacts of VGLUT2-positive structures to vesicular acetylcholine transporter, choline acetyltransferase, neuronal nitric oxide synthase, galanin, neuropeptide Y, and vasoactive intestinal peptide immunoreactive cell bodies and varicosities, as well as to glial cells. Neuronal perikarya were never positive for VGLUT2. Thus, VGLUT2 was almost exclusively found in IGLEs and may serve as a specific marker for them. In addition, many IGLEs also contained SP. The close contacts established by IGLEs to myenteric cell bodies, dendrites, and varicose fibers suggest that IGLEs modulate various types of enteric neurons and vice versa.
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Affiliation(s)
- M Raab
- Department of Anatomy I, University of Erlangen-Nuremberg, Lehrstuhl I, Krankenhausstrasse 9, 91054, Erlangen, Germany.
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Raab M, Wörl J, Brehmer A, Neuhuber WL. Reduction of NT-3 or TrkC results in fewer putative vagal mechanoreceptors in the mouse esophagus. Auton Neurosci 2003; 108:22-31. [PMID: 14614961 DOI: 10.1016/j.autneu.2003.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Intraganglionic laminar endings (IGLEs) represent major vagal afferent structures throughout the gastrointestinal tract. Both morphological and functional data suggested a mechanosensory role. Elucidation of their functional significance in a particular organ would be facilitated by the availability of animal models with significantly altered numbers of IGLEs. The present study was aimed at searching for mouse strains fulfilling this criterion in the esophagus. Anterograde wheat germ agglutinin-horseradish peroxidase tracing (WGA-HRP) from nodose ganglion was used in order to label esophageal IGLEs in mice deficient for neurotrophin-3 (NT-3) or tyrosine kinase C-receptor (TrkC) and in control littermates. This approach was feasible only in heterozygous mutants which are viable. IGLEs were counted in tetramethylbenzidine (TMB) processed wholemounts using a standardised protocol. Quantification of myenteric neurons was done in cuprolinic blue-stained specimens. Nodose neuron counts were performed in cryostat sections stained with cresyl violet. Numbers of IGLEs in the esophagus were significantly reduced in both heterozygous NT-3 (NT-3+/-) and heterozygous TrkC (TrkC+/-) mutants (65% and 40% reduction, respectively). Numbers of nodose neurons were also significantly reduced in NT-3+/- mice (48% reduction), while their reduction in TrkC+/- mutants was insignificant (11% reduction). There was no reduction of myenteric neurons in the esophagus of either mutant strain. The numeric deficiency of IGLEs was unlikely to be secondary to reduction of myenteric neurons. Although only heterozygous mutants could be studied, these results suggest that esophageal IGLEs share neurotrophin dependence on NT-3/TrkC with spinal proprioceptors and some cutaneous mechanosensors. This concurs with their proposed function as vagal mechanosensors crucial for reflex peristalsis.
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Affiliation(s)
- Marion Raab
- Department of Anatomy I, University of Erlangen-Nuremberg, Erlangen, Germany
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Raab M, Neuhuber WL. Vesicular glutamate transporter 2 immunoreactivity in putative vagal mechanosensor terminals of mouse and rat esophagus: indication of a local effector function? Cell Tissue Res 2003; 312:141-8. [PMID: 12698357 DOI: 10.1007/s00441-003-0721-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Accepted: 03/18/2003] [Indexed: 11/27/2022]
Abstract
Intraganglionic laminar endings (IGLEs) represent the major vagal afferent structures throughout the gastrointestinal tract. Previous ultrastructural investigations have revealed synaptic contacts of IGLEs on myenteric neurons. Thus, in addtion to functioning probably as mechanosensors, IGLEs may also synaptically influence myenteric neurons. In search of clues for potential transmitters in IGLEs, we investigated, by combined neuronal tracing and immunocytochemistry in the esophagus, the correlation between IGLEs and vesicular glutamate transporter 2 (VGLUT2), which is considered a reliable marker for glutamatergic neurons. In rat esophagus, IGLEs were immunostained with calretinin. In the mouse, anterograde wheat germ agglutinin/horseradish peroxidase (WGA-HRP) tracing from nodose ganglion was used in order to label esophageal IGLEs. Confocal laser scanning microscopy demonstrated that VGLUT2 immunoreactivity was highly colocalized with synaptophysin and that both calretinin and tyramide amplified WGA-HRP in rat and mouse esophagus, respectively. No colocalization was found with calcitonin gene-related peptide, a marker for spinal primary afferents. Thus, VGLUT2 is found in vagal afferent endings in the esophagus, suggesting that glutamate is contained in, and probably released from, synaptic vesicles previously described in IGLEs. Functional evidence pending, this finding is in favor of a local effector function of IGLEs onto myenteric neurons.
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Affiliation(s)
- M Raab
- Institut für Anatomie, Lehrstuhl I, Universität Erlangen-Nürnberg, Krankenhausstrasse 9, 91054 Erlangen, Germany
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Kohrogi H, Hamamoto J, Kawano O, Iwagoe H, Fujii K, Hirata N, Ando M. The role of substance P release in the lung with esophageal acid. Am J Med 2001; 111 Suppl 8A:25S-30S. [PMID: 11749920 DOI: 10.1016/s0002-9343(01)00859-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To investigate whether tachykinins are released in the airways by stimulating the esophagus, airway plasma extravasation induced by intraesophageal hydrochloric acid (HCl) in the presence or absence of the neutral endopeptidase (NEP) inhibitor phosphoramidon and the neurokinin-1-receptor antagonist FK888 was studied in anesthetized guinea pigs. Airway plasma extravasation also was studied in the presence of the NEP inhibitor in guinea pigs pretreated with capsaicin or bilateral vagotomy. Propranolol and atropine were used in all animals to block adrenergic and cholinergic nerve effects. Airway plasma leakage was evaluated by measuring extravasated Evans blue dye. One normal HCl infusion into the esophagus significantly increased plasma extravasation in the trachea. Phosphoramidon significantly potentiated plasma extravasation induced by HCl infusion into the esophagus in the trachea and main bronchi, and FK888 significantly inhibited extravasation in a dose-related manner. In capsaicin-treated animals, airway plasma extravasation was completely inhibited even in the presence of phosphoramidon. Tracheal plasma extravasation potentiated by phosphoramidon was significantly inhibited in the bilaterally vagotomized animals. These results suggest that locally acting substances are released by intraesophageal HCl stimulation that cause airway plasma extravasation. These substances are generated through activation of neural pathways, including some that traffic through the vagus nerves that link the esophagus or airways.
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Affiliation(s)
- H Kohrogi
- First Department of Internal Medicine, Kumamoto University School of Medicine, 1-1-1 Honjo Kumamoto 860-8556, Japan
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Dong H, Loomis CW, Bieger D. Vagal afferent input determines the volume dependence of rat esophageal motility patterns. Am J Physiol Gastrointest Liver Physiol 2001; 281:G44-53. [PMID: 11408254 DOI: 10.1152/ajpgi.2001.281.1.g44] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The volume dependence of balloon distension-evoked esophageal rhythmic motor responses and their neural correlates was investigated in 72 urethane-anesthetized rats. With increasing balloon volume (75--200 microl), distal esophageal rhythmic contractions decreased in rate and became tonic in the range of 150--250 microl. This change in motor pattern involved only the striated musculature of the esophageal body and persisted after acute transection of the spinal cord at C(2). Impulse frequency in single vagal afferents of the distal esophagus increased with intraluminal pressure over the entire range of balloon volumes tested (50--300 microl). Distension-responsive neurons in the nucleus tractus solitarii showed rhythmic burst activity (type I), tonic excitation (type II), or inhibition followed by off bursts (type III). Increasing strength of stimulation changed type I responses to nonrhythmic but intensified type II and III responses. We conclude that load-dependent changes in distal esophagus motility pattern are encoded by vagal afferents alone and do not involve a spinal afferent input even at near-noxious stimulus strengths.
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Affiliation(s)
- H Dong
- Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3V6
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27
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Zagorodnyuk VP, Chen BN, Brookes SJ. Intraganglionic laminar endings are mechano-transduction sites of vagal tension receptors in the guinea-pig stomach. J Physiol 2001; 534:255-68. [PMID: 11433006 PMCID: PMC2278677 DOI: 10.1111/j.1469-7793.2001.00255.x] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
1. Distension-sensitive vagal afferent fibres from the cardiac region of the guinea-pig stomach were recorded extracellularly, then filled with biotinamide, using an anterograde tracing technique. 2. Most of the stretch-sensitive units of the guinea-pig stomach (41 out of 47; number of animals N = 26) had low thresholds (less than 1 mm) to circumferential stretch and showed slow adaptation. Twenty of these units fired spontaneously under resting conditions (mean: 1.9 +/- 0.3 Hz, n = 20, N = 14). 3. Adaptation of firing during slow or maintained stretch correlated closely with accommodation of intramural tension, but tension-independent adaptation was also present. 4. Nicardipine (3 microM) with hyoscine (3 microM) reduced stretch-evoked firing of gastric vagal afferents, by inhibiting smooth muscle contraction. Gadolinium (1 mM) blocked distension-evoked firing. 5. Focal stimulation of the stomach muscle wall with a von Frey hair (0.4 mN) identified one to six punctate receptive fields in each low threshold vagal distension-sensitive afferent. These were marked on the serosal surface of the stomach wall. 6. Anterograde filling of recorded nerve trunks revealed intraganglionic laminar endings (IGLEs) within 142 +/- 34 microm (n = 38; N = 10) of marked receptive fields. The mean distance from randomly generated sites to the nearest IGLE was significantly greater (1500 +/- 48 microm, n = 380, N = 10, P < 0.0001). Viscerofugal nerve cell bodies, intramuscular arrays and varicose axons were not associated with receptive fields. The results indicate that IGLEs are the mechanotransduction sites of low threshold, slowly adapting vagal tension receptors in the guinea-pig upper stomach.
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Affiliation(s)
- V P Zagorodnyuk
- Department of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia.
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Abstract
Neuroanatomical tracing techniques, and retrograde labelling in particular, are widely used tools for the analysis of neuronal pathways in the central and peripheral nervous system. Over the last 10 years, these techniques have been used extensively to identify enteric neuronal pathways. In combination with multiple-labelling immunohistochemistry, quantitative data about the projections and neurochemical profile of many functional classes of cells have been acquired. These data have revealed a high degree of organization of the neuronal plexuses, even though the different classes of nerve cell bodies appear to be randomly assorted in ganglia. Each class of neurone has a predictable target, length and polarity of axonal projection, a particular combination of neurochemicals in its cell body and distinctive morphological characteristics. The combination of retrograde labelling with targeted intracellular recording has made it possible to target small populations of cells that would rarely be sampled during random impalements. These neuroanatomical techniques have also been applied successfully to human tissue and are gradually unravelling the complexity of the human enteric nervous system.
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Affiliation(s)
- S Brookes
- Department of Human Physiology and Centre for Neuroscience, Flinders University, South Australia.
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Wank M, Neuhuber WL. Local differences in vagal afferent innervation of the rat esophagus are reflected by neurochemical differences at the level of the sensory ganglia and by different brainstem projections. J Comp Neurol 2001; 435:41-59. [PMID: 11370010 DOI: 10.1002/cne.1192] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The objective of the present study was to characterize further the vagal afferent fibers in the rat esophagus, particularly those in its uppermost part, their cell bodies in vagal sensory ganglia, and their central projections. We applied immunohistochemistry for calretinin, calbindin, and calcitonin gene-related peptide (CGRP); retrograde tracing with FluoroGold; and transganglionic tracing with wheat germ agglutinin-horseradish peroxidase in combination with neurectomies. Vagal terminal structures in the muscularis propria of the whole esophagus consisted of calretinin-immunoreactive intraganglionic laminar endings that were linked to cervical vagal and recurrent laryngeal nerve pathways. The mucosa of the uppermost esophagus was innervated by a very dense net of longitudinally arranged, calretinin-positive fibers that were depleted by section of the superior laryngeal nerve. Distal to this area, the mucosa was virtually devoid of calretinin-immunoreactive vagal afferents. Calretinin-positive mucosal fibers in the upper cervical esophagus were classified into four types. One type, the finger-like endings, was sometimes immunoreactive also for CGRP. About one-third of cell bodies in vagal sensory ganglia retrogradely labeled from the upper cervical esophagus expressed CGRP, whereas two-thirds coexpressed calretinin and calbindin but not CGRP. In addition to the central subnucleus of the nucleus of the solitary tract, vagal afferents from the upper cervical esophagus also projected heavily to the interstitial subnucleus. This additional projection was attributed to mucosal afferents traveling through the superior laryngeal nerve. The present study provides a possible morphological basis for bronchopulmonary and aversive reflexes elicited upon stimulation of the esophagus.
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Affiliation(s)
- M Wank
- Anatomisches Institut I, Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
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Abstract
The results of neural tracing studies suggest that vagal afferent fibers in cervical and thoracic branches innervate the esophagus, lower airways, heart, aorta, and possibly the thymus, and via abdominal branches the entire gastrointestinal tract, liver, portal vein, billiary system, pancreas, but not the spleen. In addition, vagal afferents innervate numerous thoracic and abdominal paraganglia associated with the vagus nerves. Specific terminal structures such as flower basket terminals, intraganglionic laminar endings and intramuscular arrays have been identified in the various organs and organ compartments, suggesting functional specializations. Electrophysiological recording studies have identified mechano- and chemo-receptors, as well as temperature- and osmo-sensors. In the rat and several other species, mostly polymodal units, while in the cat more specialized units have been reported. Few details of the peripheral transduction cascades and the transmitters for signal propagation in the CNS are known. Glutamate and its various receptors are likely to play an important role at the level of primary afferent signaling to the solitary nucleus. The vagal afferent system is thus in an excellent position to detect immune-related events in the periphery and generate appropriate autonomic, endocrine, and behavioral responses via central reflex pathways. There is also good evidence for a role of vagal afferents in nociception, as manifested by affective-emotional responses such as increased blood pressure and tachycardia, typically associated with the perception of pain, and mediated via central reflex pathways involving the amygdala and other parts of the limbic system. The massive central projections are likely to be responsible for the antiepileptic properties of afferent vagal stimulation in humans. Furthermore, these functions are in line with a general defensive character ascribed to the vagal afferent, paraventricular system in lower vertebrates.
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Affiliation(s)
- H R Berthoud
- Neurobiology of Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge 70808, USA.
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Phillips RJ, Powley TL. Tension and stretch receptors in gastrointestinal smooth muscle: re-evaluating vagal mechanoreceptor electrophysiology. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2000; 34:1-26. [PMID: 11086184 DOI: 10.1016/s0165-0173(00)00036-9] [Citation(s) in RCA: 198] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Electrophysiological and morphological analyses of vagal mechanoreceptors in the gut wall suggest conflicting conclusions. Electrophysiology has distinguished a single general class of ending in smooth muscle, one characterized as an 'in series' tension receptor. Morphology, in contrast, has characterized two distinct specializations of vagal afferent endings in the muscle wall of the gastrointestinal (GI) tract. These two structures differ in terms of their target tissues, terminal architectures and regional distributions; they also develop on different ontogenetic timetables and depend on different trophic support in the muscle wall. On the basis of these features, we have proposed that one of the putative mechanoreceptors, the intraganglionic laminar ending (IGLE), has characteristics of a tension receptor and the other, the intramuscular array (IMA), has features of a stretch or length receptor. In a functional analogy with striated muscle proprioceptors, IGLEs should have similarities to Golgi tendon organs, whereas IMAs should have equivalencies with muscle spindle afferents. The present survey re-examines the recording analyses in light of the structural observations. This review indicates that previous electrophysiological studies are too inconclusive to refute the inference that the vagus supplies two distinct types of mechanoreceptors to the muscle wall of the GI tract. Multiple methodological constraints and sources of variance have limited the resolution of electrophysiological experiments. Specifically, these experiments have conventionally used distension stimuli that confound tension and stretch. In addition, sampling strategies have biased recording experiments towards a focus on one type of ending, the IGLE. Furthermore, putative functional properties (e.g., broad tuning) of vagal mechanoreceptors suggest that distinguishing two recording patterns will require exacting protocols. Combining a recognition of the methodological difficulties that have limited electrophysiological analyses with an understanding of the structural features of the endings, however, suggests several critical electrophysiological experiments with the resolution to distinguish two classes of response profiles. Until such experiments can be conducted, sensory physiology's axiom that 'function varies with form', taken together with a re-assessment of the existing data, suggests that the vagus nerve supplies stretch receptors as well as tension receptors to the wall of the GI tract.
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Affiliation(s)
- R J Phillips
- Department of Psychological Sciences, Purdue University, 165 Peirce Hall, West Lafayette, IN 47907, USA
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Dong H, Loomis CW, Bieger D. Effects of vagal cooling on esophageal cardiovascular reflex responses in the rat. Neurosci Lett 2000; 287:89-92. [PMID: 10854719 DOI: 10.1016/s0304-3940(00)01139-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Distension of the distal esophagus in the anesthetized rat causes a vagally-mediated arterial pressor and tachycardia response. To investigate the nature of viscerosensory fibers in the afferent limb of this reflex, the present study was carried out in urethane-anesthetized rats that were subjected to graded cooling of both cervical vagal trunks in situ. Distal esophageal distension was applied for 20 s by means of a water-filled high compliance balloon. Vagal cooling to 9 degrees C abolished pressor responses and unmasked a depressor component during maximal distension. Cooling to 7.5 degrees C blocked this inhibitory component, well above the temperature known to block C-fibers. We conclude that the cardiovascular response to esophageal distension is triggered via at least two subpopulations of A(delta) type vagal afferents that project to brain stem nuclei regulating central vasomotor tone.
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Affiliation(s)
- H Dong
- Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Canada
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