Elsevier

Brain Research

Volume 1044, Issue 2, 24 May 2005, Pages 133-143
Brain Research

Research report
Airway-related vagal preganglionic neurons express brain-derived neurotrophic factor and TrkB receptors: Implications for neuronal plasticity

https://doi.org/10.1016/j.brainres.2005.02.037Get rights and content

Abstract

Recent evidence indicates that brain-derived neurotrophic factor (BDNF) is present in neurons and may affect neurotransmitter release, cell excitability, and synaptic plasticity via activation of tyrosine kinase B (TrkB) receptors. However, whether airway-related vagal preganglionic neurons (AVPNs) produce BDNF and contain TrkB receptors is not known. Hence, in ferrets, we examined BDNF and TrkB receptor expression in identified AVPNs using in situ hybridization and immunohistochemistry. BDNF protein levels were measured within the rostral nucleus ambiguus (rNA) region by ELISA. We observed that the subpopulation of AVPNs, identified by neuroanatomical tract tracing, within the rNA region express BDNF mRNA, BDNF protein, as well as TrkB receptor. In addition, brain tissue from the rNA region contained measurable amounts of BDNF that were comparable to the hippocampal region of the brain. These data indicate, for the first time, that the BDNF–TrkB system is expressed by AVPNs and may play a significant role in regulating cholinergic outflow to the airways.

Introduction

In the last decade, enormous progress has been made in understanding the role that neurotrophins, including brain derived neurotrophic factor (BDNF), play in development, neuronal survival, differentiation, synapse formation and stabilization, and structural and functional neuronal plasticity in many networks [10], [11], [35], [41], [44], [47], [55], [56], [57], [58], [59], including the brainstem and spinal cord respiratory related pathways [3], [4], [54]. For example, intermittent hypoxia provokes a serotonin-dependent increase in the BDNF protein synthesis that is necessary and sufficient for spinal respiratory plasticity following intermittent hypoxic stress [3].

Recent findings, obtained through an array of techniques in normal and transgenic animals, provide insight into the modulatory mechanisms of BDNF at central synapses [7], [8], [13]. BDNF signaling evokes both short- and long-term periods of enhanced synaptic transmission, acting pre- and postsynaptically [57]. Results indicate that BDNF-producing neurons respond to stimulation with increased synthesis and elevated release of BDNF [3], [5], [56], [61] that in turn enhances quantal neurotransmitter release [55], [56] such as glutamate [12], [22], [45], [49]. The elevated levels of BDNF increase expression and activity of glutamatergic receptors [37], [43], facilitate glutamatergic synaptic transmission [13], [42], and unmask the silent synapses [36]. Furthermore, it has been shown that a positive feedback between acetylcholine and the BDNF exists in the rat hippocampus [40]. BDNF released may cause rapid excitation of neurons via activation of high-affinity tyrosine kinase B (TrkB) receptors [38], producing postsynaptic long-term potentiation [3], [41], [48], [57]. Therefore, BDNF–TrkB receptors could participate in centrally induced increase in cholinergic outflow to the airways.

In order to define the role of BDNF in the plasticity of the neuronal network linked to regulation of cholinergic outflow to the airways, first it should be shown that BDNF and TrkB receptors are present in the network regulating cholinergic outflow to the airways. Therefore, the aim of the present study was to test our hypothesis that the BDNF and/or TrkB receptors are expressed by airway-related vagal preganglionic neurons (AVPNs) at the mRNA and protein levels.

In these studies, we characterized BDNF and TrkB receptor expression by parasympathetic premotor cells that innervate extrathoracic trachea using neuroanatomical and molecular techniques. Results showed for the first time that AVPNs innervating the airways produce BDNF and express TrkB receptors, suggesting that BDNF–TrkB receptor signaling pathway may play a role in neuronal plasticity, modulating AVPN discharge and cholinergic outflow to the airways.

Section snippets

Animals

Experimental protocols were approved by the Institutional Animal Care and Use Committees at Case Western Reserve and Howard University. To minimize gender-related differences, all experiments were performed in male European ferrets, Mustella putorius furo (600–900 g). In the present study, six healthy male ferrets were used.

Injection of CT-b into the extrathoracic trachea

Under pentobarbital anesthesia (50 mg/kg, ip), the tracheas of ferrets were injected with cholera toxin β subunit (CT-b) as previously described [27], [29]. CT-b was

Expression of BDNF mRNA and BDNF protein within the rNA region

In situ hybridization studies with rat BDNF probe showed that in normal adult male ferrets, neurons located within the rNA region express BDNF mRNA. The signal was considered BDNF-specific for the ferret, since signals with the sense probe could not be detected, as demonstrated in Fig. 1. The results showed that 34.5% of the retrogradely labeled AVPNs express robust BDNF mRNA (Fig. 2). BDNF immunoreactivity was found in fibers and neurons in the rNA region that expressed BDNF mRNA. A

Discussion

In this study, we used in situ hybridization and immunohistochemistry to detect the location of endogenous BDNF and TrkB receptors within the rNA. A double labeling technique was used to define whether identified AVPNs produce BDNF and/or express TrkB receptors. BDNF is a secretory protein known to be transported to and accumulated at target sites. Therefore, to identify whether AVPNs are the BDNF-producing cells, we used BDNF mRNA in situ hybridization. In addition, in situ hybridization was

Acknowledgments

We thank Drs. Martha J. Miller and Serdia O. Mack for reading the manuscript and Ms. Lisa Leighty for outstanding technical assistance.

This study was supported by National Heart, Lung, and Blood Institute Grants HL-50527 and HL 56470. National Institute of Neurological Disorders and Stroke and National Center for Research Resources 1U54-NS-39407.

References (67)

  • N.L. Ward et al.

    BDNF is needed for postnatal maturation of basal forebrain and neostriatum cholinergic neurons in vivo

    Exp. Neurol.

    (2000)
  • Q. Yan et al.

    Expression of brain-derived neurotrophic factor protein in the adult rat central nervous system

    Neuroscience

    (1997)
  • C.A. Altar et al.

    Anterograde transport of brain-derived neurotrophic factor and its role in the brain

    Nature

    (1997)
  • M.P. Armanini et al.

    Truncated and catalytic isoforms of trkB are co-expressed in neurons of rat and mouse CNS

    Eur. J. Neurosci.

    (1995)
  • T.L. Baker-Herman et al.

    BDNF is necessary and sufficient for spinal respiratory plasticity following intermittent hypoxia

    Nat. Neurosci.

    (2004)
  • A. Balkowiec et al.

    Brain-derived neurotrophic factor is required for normal development of the central respiratory rhythm in mice

    J. Physiol. (London)

    (1998)
  • A. Balkowiec et al.

    Activity-dependent release of endogenous brain-derived neurotrophic factor from primary sensory neurons detected by ELISA in situ

    J. Neurosci.

    (2000)
  • M. Barbacid

    The Trk family of neurotrophin receptors

    J. Neurobiol.

    (1994)
  • B. Berninger et al.

    Fast actions of neurotrophic factors

    Curr. Opin. Neurobiol.

    (1994)
  • R. Blum et al.

    Neurotrophin-evoked depolarization requires the sodium channel Na(V)1.9

    Nature

    (2002)
  • M. Bothwell

    Functional interactions of neurotrophins and neurotrophin receptors

    Annu. Rev. Neurosci.

    (1995)
  • R. Brady et al.

    BDNF is a target-derived survival factor for arterial baroreceptor and chemoafferent primary sensory neurons

    J. Neurosci.

    (1999)
  • C. Brodski et al.

    Neurotrophin-3 promotes the cholinergic differentiation of sympathetic neurons

    Proc. Natl. Acad. Sci. U. S. A.

    (2000)
  • G. Carmignoto et al.

    Brain derived neurotrophic factor and nerve growth factor potentiate excitatory synaptic transmission in the rat visual cortex

    J. Physiol.

    (1997)
  • T.W. Carver et al.

    Increased type I procollagen mRNA in airways and pulmonary vessels after vagal denervation in rats

    Am. J. Respir. Cell Mol. Biol.

    (1997)
  • S. Ceccatelli et al.

    Expanded distribution of mRNA for nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3 in the rat brain after colchicine treatment

    Proc. Natl. Acad. Sci. U. S. A.

    (1991)
  • A. Cellerino et al.

    Brain-derived neurotrophic factor regulates expression of vasoactive intestinal polypeptide in retinal amacrine cells

    J. Comp. Neurol.

    (2003)
  • M.V. Chao

    Neurotrophins and their receptors: a convergence point for many signaling pathways

    Nat. Rev., Neurosci.

    (2003)
  • Q. Cheng et al.

    Brain-derived neurotrophic factor attenuates mouse cerebellar granule cell GABAA receptor-mediated responses via postsynaptic mechanisms

    J. Physiol.

    (2003)
  • J.M. Conner et al.

    Distribution of brain-derived neurotrophic factor (BDNF) protein and mRNA in the normal adult rat CNS: evidence for anterograde axonal transport

    J. Neurosci.

    (1997)
  • J.M. Conner et al.

    Anterograde transport of neurotrophin proteins in the CNS—a reassessment of the neurotrophic hypothesis

    Rev. Neurosci.

    (1998)
  • G.G. Haddad et al.

    Congenital failure of automatic control of ventilation, gastrointestinal motility and heart rate

    Medicine (Baltimore)

    (1978)
  • J.R. Haselton et al.

    Bronchomotor vagalpreganglionic cell bodies in the dog: an anatomic and functional study

    J. Appl. Physiol.

    (1992)

    • Cited by (27)

    • Neurotrophic factors and their receptors in lung development and implications in lung diseases

      2021, Cytokine and Growth Factor Reviews
      Citation Excerpt :

      These findings suggests a role of neurotrophins in the local control of lung vascular responses [96]. Neurotrophins and their receptors have been localized to airway innervation (reviewed in [97,98]), with BDNF expressed in brain stem airway preganglionic neurons [59]. They can increase the substance P content of sensory nerves [90] and of vagal afferents [99].

    • Regulation of Lower Airway Function

      2017, Fetal and Neonatal Physiology, 2-Volume Set

    • Respiratory function after selective respiratory motor neuron death from intrapleural CTB-saporin injections

      2015, Experimental Neurology
      Citation Excerpt :

      There were no apparent effects of CTB–SAP treatment in other brainstem areas, including the lateral reticular nucleus, gigantocellular reticular nucleus and the lateral paragigantocellular nucleus (data not shown; areas located based on diagrams from The Spinal Cord by Watson et al., 2009). The “trace” staining patterns observed are consistent with reports after CTB injections into the upper lung lobe, or pseudorabies virus injections into the lung or trachea (Dehkordi et al., 2006; Fontan et al., 2000; Hadziefendic and Haxhiu, 1999; Haxhiu et al., 1993; Zaidi et al., 2005). Spinal microglial number increases with disease progression in SOD1G93A rats (Nikodemova et al., 2013).

    • Brain-derived neurotrophic factor in the airways

      2014, Pharmacology and Therapeutics
      Citation Excerpt :

      These findings raise the possibility that upregulation of BDNF and its autocrine signaling may result in enhanced airway reactivity in neonates, thus contributing to neonatal/pediatric asthma, and other inflammatory airway disease in infants and children (Yao et al., 2006). This scenario is also consistent with the finding that BDNF is expressed in airway preganglionic neurons (Zaidi et al., 2005), and additionally that hyperoxia substantially increases ACh content in the lung: an effect inhibited by tyrosine kinase inhibitors. These findings, albeit in animals, suggest that BDNF/TrkB signaling increases neuronal ACh production and resultant cholinergic outflow to the airways under conditions of hyperoxia (Sopi et al., 2008).

    • Regulation of Lower Airway Function

      2011, Fetal and Neonatal Physiology E-Book, Fourth Edition

    • Role of central neurotransmission and chemoreception on airway control

      2010, Respiratory Physiology and Neurobiology
    View all citing articles on Scopus
    View full text
    Copyright © 2005 Elsevier B.V. All rights reserved.