Dual Sensory Innervation of Pulmonary Neuroepithelial Bodies (original) (raw)

Neurochemical pattern of the complex innervation of neuroepithelial bodies in mouse lungs

Histochemistry and Cell Biology, 2009

As best characterized for rats, it is clear that pulmonary neuroepithelial bodies (NEBs) are contacted by a plethora of nerve Wber populations, suggesting that they represent an extensive group of multifunctional intraepithelial airway receptors. Because of the importance of genetically modiWed mice for functional studies, and the current lack of data, the main aim of the present study was to achieve a detailed analysis of the origin and neurochemical properties of nerve terminals associated with NEBs in mouse lungs. Antibodies against known selective markers for sensory and motor nerve terminals in rat lungs were used on lungs from control and vagotomized mice of two diVerent strains, i.e., Swiss and C57-Bl6. NEB cells were visualized by antibodies against either the general neuroendocrine marker protein gene-product 9.5 (PGP9.5) or calcitonin gene-related peptide (CGRP). Thorough immunohistochemical examination of NEB cells showed that some of these NEB cells also exhibit calbindin D-28 k (CB) and vesicular acetylcholine transporter (VAChT) immunoreactivity (IR). Mouse pulmonary NEBs were found to receive intraepithelial nerve terminals of at least two diVerent populations of myelinated vagal aVerents: (1) Immunoreactive (ir) for vesicular glutamate transporters (VGLUTs) and CB; (2) expressing P2X 2 and P2X 3 ATP receptors. CGRP IR was seen in varicose vagal nerve Wbers and in delicate non-vagal Wbers, both in close proximity to NEBs. VAChT immunostaining showed very weak IR in the NEB-related intraepithelial vagal sensory nerve terminals. nNOS-or VIP-ir nerve terminals could be observed at the base of pulmonary NEBs. While a single NEB can be contacted by multiple nerve Wber populations, it was clear that none of the so far characterized nerve Wber populations contacts all pulmonary NEBs. The present study revealed that mouse lungs harbor several populations of nerve terminals that may selectively contact NEBs. Although at present the physiological signiWcance of the innervation pattern of NEBs remains enigmatic, it is likely that NEBs are receptor-eVector end-organs that may host complex and/or multiple functional properties in normal airways. The neurochemical information on the innervation of NEBs in mouse lungs gathered in the present study will be essential for the interpretation of upcoming functional data and for the study of transgenic mice.

Functional morphology of pulmonary neuroepithelial bodies: Extremely complex airway receptors

The Anatomical Record, 2002

Innervated groups of neuroendocrine cells, called neuroepithelial bodies (NEBs), are diffusely spread in the epithelium of intrapulmonary airways in many species. Our present understanding of the morphology of NEBs in mammalian lungs is comprehensive, but none of the proposed functional hypotheses have been proven conclusively. In recent reviews on airway innervation, NEBs have been added to the list of presumed physiological lung receptors. Microscopic data on the innervation of NEBs, however, have given rise to conflicting interpretations. Using neuronal tracing, denervation, and immunostaining, we recently demonstrated that the innervation of NEBs is much more complex than the almost unique vagal nodose sensory innervation suggested by other authors. The aim of the present work is to summarize our present understanding about the origin and chemical coding of the profuse nerve terminals that selectively contact pulmonary NEBs. A thorough knowledge of the complex interactions between the neuroendocrine cells and at least five different nerve fiber populations is essential for defining the position(s) of NEBs among the many pulmonary receptors characterized by lung physiologists. Anat Rec Part A 270A: 25-40, 2003.

Intraepithelial Vagal Sensory Nerve Terminals in Rat Pulmonary Neuroepithelial Bodies Express P2X 3 Receptors

American Journal of Respiratory Cell and Molecular Biology, 2000

The neurotransmitters/modulators involved in the interaction between pulmonary neuroepithelial bodies (NEBs) and the vagal sensory component of their innervation have not yet been elucidated. Because P2X 3 purinoreceptors are known to be strongly expressed in peripheral sensory neurons, the aim of the present study was to examine the localization of nerve endings expressing P2X 3 purinoreceptors in the rat lung in general and those contacting pulmonary NEBs in particular. Most striking were intraepithelial arborizations of P2X 3 purinoceptor-immunoreactive (IR) nerve terminals, which in all cases appeared to ramify between calcitonin gene-related peptide (CGRP)-or calbindin D28k (CB)-labeled NEB cells. However, not all NEBs received nerve endings expressing P2X 3 receptors. Using CGRP and CB staining as markers for two different sensory components of the innervation of NEBs, it was revealed that P2X 3 receptor and CB immunoreactivity were colocalized, whereas CGRP-IR fibers clearly formed a different population. The disappearance of characteristic P2X 3 receptor-positive nerve fibers in contact with NEBs after infranodosal vagal crush and colocalization of tracer and P2X 3 receptor immunoreactivity in vagal nodose neuronal cell bodies in retrograde tracing experiments further supports our hypothesis that the P2X 3 receptor-IR nerve fibers contacting NEBs have their origin in the vagal sensory nodose ganglia. Combination of quinacrine accumulation in NEBs, suggestive of the presence of high concentrations of adenosine triphosphate (ATP) in their secretory vesicles, and P2X 3 receptor staining showed that the branching intraepithelial P2X 3 receptor-IR nerve terminals in rat lungs were exclusively associated with quinacrine-stained NEBs. We conclude that ATP might act as a neurotransmitter/neuromodulator in the vagal sensory innervation of NEBs via a P2X 3 receptor-mediated pathway. Further studies are necessary to determine whether the P2X 3 receptor-expressing neurons, specifically innervating NEBs in the rat lung, belong to a population of P2X 3 receptor-IR nociceptive vagal nodose neurons.

Evidence for a role of neuroepithelial bodies as complex airway sensors: comparison with smooth muscle-associated airway receptors

Journal of Applied Physiology, 2006

The epithelium of intrapulmonary airways in many species harbors diffusely spread innervated groups of neuroendocrine cells, called neuroepithelial bodies (NEBs). Data on the location, morphology and chemical coding of NEBs in mammalian lungs are abundant, but none of the proposed functions has so far been fully established. Besides C-fiber afferents, slowly adapting stretch receptors and rapidly adapting stretch receptors, recent reviews have added NEBs to the list of presumed sensory receptors in intrapulmonary airways. Physiologically the innervation of NEBs, however, remains enigmatic.

Quantification of Neuroepithelial Bodies and Their Innervation in Fawn-Hooded and Wistar Rat Lungs

2003

The Fawn-Hooded rat (FHR), a model for primary pulmonary hypertension, shows an unexplained hypersensitivity to airway hypoxia. Because pulmonary neuroepithelial bodies (NEBs) ap- pear to express a functional oxygen-sensing mechanism and an extensive sensory innervation, possible changes in this system should be taken into consideration. In the present study a com- parative analysis of NEBs and their selective innervation was

Voltage-gated sodium channels in nociceptive versus non-nociceptive nodose vagal sensory neurons innervating guinea pig lungs

The Journal of Physiology, 2008

Lung vagal sensory fibres are broadly categorized as C fibres (nociceptors) and A fibres (non-nociceptive; rapidly and slowly adapting low-threshold stretch receptors). These afferent fibre types differ in degree of myelination, conduction velocity, neuropeptide content, sensitivity to chemical and mechanical stimuli, as well as evoked reflex responses. Recent studies in nociceptive fibres of the somatosensory system indicated that the tetrodotoxin-resistant (TTX-R) voltage-gated sodium channels (VGSC) are preferentially expressed in the nociceptive fibres of the somatosensory system (dorsal root ganglia). Whereas TTX-R sodium currents have been documented in lung vagal sensory nerves fibres, a rigorous comparison of their expression in nociceptive versus non-nociceptive vagal sensory neurons has not been carried out. Using multiple approaches including patch clamp electrophysiology, immunohistochemistry, and single-cell gene expression analysis in the guinea pig, we obtained data supporting the hypothesis that the TTX-R sodium currents are similarly distributed between nodose ganglion A-fibres and C-fibres innervating the lung. Moreover, mRNA and immunoreactivity for the TTX-R VGSC molecules Na V 1.8 and Na V 1.9 were present in nearly all neurons. We conclude that contrary to findings in the somatosensory neurons, TTX-R VGSCs are not preferentially expressed in the nociceptive C-fibre population innervating the lungs.

Afferent nerve endings in the tracheal muscle of guinea-pigs and rats

Anatomy and Embryology, 1991

The trachea of guinea-pigs was stained as a whole-mount preparation with the zinc iodide-osmium technique. A distinct class of nerve endings was observed associated with the tracheal muscle. The endings, issued from myelinated fibres of the vagus nerve via the recurrent laryngeal nerve, are distributed on either side of the midline and ventral to the tips of cartilages. They are interpreted as afferent nerve endings that may correspond to slow adapting stretch receptors identified by physiological studies. Each nerve contributes predominantly, but not exclusively, to the receptors of the ipsilateral side. There are 120–180 receptors along the full length of the guinea-pig trachea, their density being higher at the cranial end. The receptors are variable in size and structural complexity, and, to some extent, also in spatial orientation, but distinct subtypes are not recognizable. Receptors of similar morphology and distribution are found also in the rat trachea. The receptors can also be visualized with a cytochrome oxidase method for nerve endings, but they do not stain with immunohistochemistry for the neuropeptides substance P, calcitonin gene-related peptide, vasointestinal polypeptide and neurotensin.

Identification of vagal sensory receptors in the rat lung: are there subtypes of slowly adapting receptors?

The Journal of Physiology, 1993

We studied the characteristics of pulmonary sensory receptors whose afferent fibres are in the left vagus nerve of opened-chest rats. The activity of these receptors was recorded during mechanical ventilation approximating eupnoea, as well as during deflation, stepwise inflations and constant-pressure inflations of the lungs. Data were also collected from closed-chest rats and analysed separately. 2. Ninety-four per cent of receptors were located in the ipsilateral lung or airways with the remainder in the contralateral lung. 3. Not only were slowly adapting receptors (SARs) the most abundant pulmonary receptors but 21 % of them were either exclusively or predominantly active during the deflationary phase of the ventilatory cycle. Deflationary units were found in openedand closed-chest rats. The average conduction velocity for all fibres innervating SARs averaged 29-7 m s-'. 4. We found rapidly adapting receptors (RARs) to be extremely rare in the rat. Their activity was sparse and irregular. The conduction velocities of fibres innervating RARs averaged 12 3 m s-'. 5. Far more abundant than RARs in the remaining population of pulmonary fibres were C fibres. They were observed to have an average conduction velocity of 2-1 m s-1, base-level activity which was irregular and a high pressure threshold of activation and were stimulated by intravenous capsaicin injection. 6. Notable differences exist between pulmonary receptors in rats and those reported in other species. The variations include the abundant existence of intrapulmonary SARs with exclusively deflationary modulation and the rarity of RARs. We also encountered C fibres which have not previously been described systematically in the rat.

Distribution of vasoactives intestinal peptide- and substance P-containing nerves originating from neurons of airway ganglia in cat bronchi

The Journal of Comparative Neurology, 1991

This study examined the possibility that vasoactive intestinal peptide (VIP)-and substance P (SP)-containing nerve fibers in bronchial smooth muscle, glands, epithelium, and blood vessels originate from neurons of airway ganglia. Explants of airway walls were maintained in culture with the expectation that nerve fibers from neurons of airway ganglia would remain viable, whereas fibers originating from neurons not present in the airway walls would degenerate. Airways were dissected and placed into culture dishes containing CMRL 1066 medium for 3,5, and 7 days. In controls (noncultured), VIP-and SP-like immunoreactivity was observed in nerve fibers associated with bronchial smooth muscle, glands, and blood vessel walls and in nerve cell bodies of airway ganglia. Nerve fibers containing SP were also observed within the bronchial epithelium. After 3,5, and 7 days in culture, VIP-and SP-containing fibers were identified in all of the same locations except in the airway epithelium where SP-containing fibers could not be demonstrated. VIP and SP were frequently colocalized in the same nerve fibers of bronchial smooth muscle and glands in controls and cultured airways. There were no statistically significant differences in nerve fiber density for either VIPor SP-containing fibers in bronchial smooth muscle between controlled and cultured airways. VIP concentrations in cultured airways were significantly less than in controls. The results suggest that a large proportion of VIP-and SP-containing nerve fibers supplying bronchial smooth muscle, glands, and blood vessels in the airways originate from neurons of airway ganglia.

Vagal nerve endings in visceral pleura and triangular ligaments of the rat lung

Journal of Anatomy, 2016

The inner thoracic cavity is lined by the parietal pleura, and the lung lobes are covered by the visceral pleura. The parietal and visceral plurae form the pleural cavity that has negative pressure within to enable normal respiration. The lung tissues are bilaterally innervated by vagal and spinal nerves, including sensory and motor components. This complicated innervation pattern has made it difficult to discern the vagal vs. spinal processes in the pulmonary visceral pleura. With and without vagotomy, we identified vagal nerve fibres and endings distributed extensively in the visceral pleura ('P'-type nerve endings) and triangular ligaments ('L'-type nerve endings) by injecting wheat germ agglutinin-horseradish peroxidase as a tracer into the nucleus of solitary tract or nodose ganglion of male Sprague-Dawley rats. We found the hilar and non-hilar vagal pulmonary pleural innervation pathways. In the hilar pathway, vagal sub-branches enter the hilum and follow the pleural sheet to give off the terminal arborizations. In the non-hilar pathway, vagal sub-branches run caudally along the oesophagus and either directly enter the ventral-middle-mediastinal left lobe or follow the triangular ligaments to enter the left and inferior lobe. Both vagi innervate: (i) the superior, middle and accessory lobes on the ventral surfaces that face the heart; (ii) the dorsal-rostral superior lobe; (iii) the dorsal-caudal left lobe; and (iv) the left triangular ligament. Innervated only by the left vagus is: (i) the ventral-rostral and dorsal-rostral left lobe via the hilar pathway; (ii) the ventral-middle-mediastinal left lobe and the dorsal accessory lobe that face the left lobe via the non-hilar pathway; and (iii) the ventral-rostral inferior lobe that faces the heart. Innervated only by the right vagus, via the non-hilar pathway, is: (i) the inferior (ventral and dorsal) and left (ventral only) lobe in the area near the triangular ligament; (ii) the dorsal-middle-mediastinal left lobe; and (iii) the right triangular ligament. Other regions innervated with unknown vagal pathways include: (i) the middle lobe that faces the superior and inferior lobe; (ii) the rostral-mediastinal inferior lobe that faces the middle lobe; and (iii) the ventral accessory lobe that faces the diaphragm. Our study demonstrated that most areas that face the dorsal thoracic cavity have no vagal innervation, whereas the interlobar and heart-facing areas are bilaterally or unilaterally innervated with a left-rostral vs. right-caudal lateralized innervation pattern. This innervation pattern may account for the fact that the respiratory regulation in rats has a lateralized right-side dominant pattern.