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Sensory receptors in the airways: neurochemical coding of smooth muscle-associated airway receptors and pulmonary neuroepithelial body innervation.
Auton Neurosci 2006; 126-127:307-19AN

Abstract

Mainly due to the lack of conclusive morphological data, correlation between functionally and morphologically defined lung receptors has so far been unsatisfactory. In the present study, multiple immunocytochemical stainings with a panel of markers for (mechanso)sensory nerve fibres were performed in order to visualise putative receptor terminals in rat intrapulmonary airways. We first focussed on determining the location, morphology and neurochemical coding of subepithelial receptor-like structures that have been sporadically reported in the wall of large diameter airways. Immunostaining with antibodies against Na+/K+-ATPase alpha3, vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 revealed branching laminar subepithelial receptor endings associated with airway smooth muscle. The latter nerve terminals appeared to further express calbindin D28k (CB), and the ATP receptor P2X3, but were calcitonin gene-related peptide (CGRP)-negative. The nerve fibres that give rise to these terminals were shown to be myelinated and have a vagal sensory origin. Because of the close association between the laminar terminals of this receptor-like structures and airway smooth muscle, we will further refer to these clearly morphologically identifiable sensory end organs as 'smooth muscle-associated airway receptors (SMARs)'. Secondly, we further explored the sensory innervation of pulmonary neuroepithelial bodies (NEBs). NEBs are intraepithelial groups of neuroendocrine cells, contacted by several nerve fibre populations, at least three of which are sensory. The spinal sensory innervation of NEBs expresses CGRP and substance P, contacts NEBs at their basal pole, and is capsaicin-sensitive. The intraepithelial vagal sensory innervation of NEBs, on the other hand, appears to be myelinated and could be labelled by antibodies against VGLUT1, VGLUT2, CB and P2X3 receptors. Na+/K+-ATPase alpha3 immunostaining additionally labelled part of the vagal sensory innervation of rat pulmonary NEBs. The neurochemical coding and receptor-like appearance of SMARs and of the complex vagal sensory innervation of NEBs appeared to be almost identical and reminiscent of mechanosensors. Both SMARs and vagal nodose nerve terminals in NEBs therefore likely represent the morphological counterparts of subgroups of the extensive population of physiologically characterised myelinated vagal airway receptors, the majority of which are mechanosensitive. Electrophysiological data based on 'local' stimuli should be interpreted with caution, because of the regular close apposition of SMARs and NEBs and the very similar characteristics of their nerve terminals.

Authors+Show Affiliations

Laboratory of Cell Biology and Histology, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

16600695

Citation

Brouns, Inge, et al. "Sensory Receptors in the Airways: Neurochemical Coding of Smooth Muscle-associated Airway Receptors and Pulmonary Neuroepithelial Body Innervation." Autonomic Neuroscience : Basic & Clinical, vol. 126-127, 2006, pp. 307-19.
Brouns I, De Proost I, Pintelon I, et al. Sensory receptors in the airways: neurochemical coding of smooth muscle-associated airway receptors and pulmonary neuroepithelial body innervation. Auton Neurosci. 2006;126-127:307-19.
Brouns, I., De Proost, I., Pintelon, I., Timmermans, J. P., & Adriaensen, D. (2006). Sensory receptors in the airways: neurochemical coding of smooth muscle-associated airway receptors and pulmonary neuroepithelial body innervation. Autonomic Neuroscience : Basic & Clinical, 126-127, pp. 307-19.
Brouns I, et al. Sensory Receptors in the Airways: Neurochemical Coding of Smooth Muscle-associated Airway Receptors and Pulmonary Neuroepithelial Body Innervation. Auton Neurosci. 2006 Jun 30;126-127:307-19. PubMed PMID: 16600695.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sensory receptors in the airways: neurochemical coding of smooth muscle-associated airway receptors and pulmonary neuroepithelial body innervation. AU - Brouns,Inge, AU - De Proost,Ian, AU - Pintelon,Isabel, AU - Timmermans,Jean-Pierre, AU - Adriaensen,Dirk, Y1 - 2006/04/05/ PY - 2005/12/02/received PY - 2006/02/03/accepted PY - 2006/4/8/pubmed PY - 2006/9/26/medline PY - 2006/4/8/entrez SP - 307 EP - 19 JF - Autonomic neuroscience : basic & clinical JO - Auton Neurosci VL - 126-127 N2 - Mainly due to the lack of conclusive morphological data, correlation between functionally and morphologically defined lung receptors has so far been unsatisfactory. In the present study, multiple immunocytochemical stainings with a panel of markers for (mechanso)sensory nerve fibres were performed in order to visualise putative receptor terminals in rat intrapulmonary airways. We first focussed on determining the location, morphology and neurochemical coding of subepithelial receptor-like structures that have been sporadically reported in the wall of large diameter airways. Immunostaining with antibodies against Na+/K+-ATPase alpha3, vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 revealed branching laminar subepithelial receptor endings associated with airway smooth muscle. The latter nerve terminals appeared to further express calbindin D28k (CB), and the ATP receptor P2X3, but were calcitonin gene-related peptide (CGRP)-negative. The nerve fibres that give rise to these terminals were shown to be myelinated and have a vagal sensory origin. Because of the close association between the laminar terminals of this receptor-like structures and airway smooth muscle, we will further refer to these clearly morphologically identifiable sensory end organs as 'smooth muscle-associated airway receptors (SMARs)'. Secondly, we further explored the sensory innervation of pulmonary neuroepithelial bodies (NEBs). NEBs are intraepithelial groups of neuroendocrine cells, contacted by several nerve fibre populations, at least three of which are sensory. The spinal sensory innervation of NEBs expresses CGRP and substance P, contacts NEBs at their basal pole, and is capsaicin-sensitive. The intraepithelial vagal sensory innervation of NEBs, on the other hand, appears to be myelinated and could be labelled by antibodies against VGLUT1, VGLUT2, CB and P2X3 receptors. Na+/K+-ATPase alpha3 immunostaining additionally labelled part of the vagal sensory innervation of rat pulmonary NEBs. The neurochemical coding and receptor-like appearance of SMARs and of the complex vagal sensory innervation of NEBs appeared to be almost identical and reminiscent of mechanosensors. Both SMARs and vagal nodose nerve terminals in NEBs therefore likely represent the morphological counterparts of subgroups of the extensive population of physiologically characterised myelinated vagal airway receptors, the majority of which are mechanosensitive. Electrophysiological data based on 'local' stimuli should be interpreted with caution, because of the regular close apposition of SMARs and NEBs and the very similar characteristics of their nerve terminals. SN - 1566-0702 UR - https://www.unboundmedicine.com/medline/citation/16600695/Sensory_receptors_in_the_airways:_neurochemical_coding_of_smooth_muscle_associated_airway_receptors_and_pulmonary_neuroepithelial_body_innervation_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1566-0702(06)00040-3 DB - PRIME DP - Unbound Medicine ER -