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Capsaicin‐sensitive and ‐insensitive vagal bronchopulmonary C‐fibres in the mouse
Author(s) -
Kollarik Marian,
Dinh Q. Thai,
Fischer Axel,
Undem Bradley J.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2003.00869.x
Subject(s) - peristalsis , pacemaker potential , anatomy , chemistry , electrophysiology , ion channel , medicine , neuroscience , biology , receptor
We developed an isolated tracheally perfused (35‐37 °C) nerve‐lung preparation for the study of bronchopulmonary afferent nerve activity in the mouse. Extracellular recordings were made from the vagal sensory neurons located in the jugular‐nodose ganglia complex (JNC) with identified receptive fields in the lungs. Analysis of the vagal compound action potential revealed that the mouse vagal C‐fibre conduction velocities range from 0.3 to 1.5 m s −1 . A total of 83 bronchopulmonary C‐fibres were studied. The sensitivity of the bronchopulmonary C‐fibres to the vanilloid receptor 1 (VR1) agonist capsaicin was dependent on conduction velocity. Thus C‐fibres with conduction velocities between 0.3 and 0.7 m s −1 responded to capsaicin (1 μM) while C‐fibres with conduction velocities between 0.7 and 1.5 m s −1 were capsaicin insensitive. Similarly, bradykinin (1 μM) excited only those C‐fibres with conduction velocities < 0.7 m s −1 . The response to bradykinin was not mimicked by the B 1 receptor agonist [des‐Arg 9 ]bradykinin (1 μM) and was abolished by the bradykinin B 2 receptor antagonist HOE 140 (1 μM). Adenosine 5′‐triphosphate (ATP, 30 μM) activated the C‐fibres irrespective of the conduction velocities. This response was mimicked by the selective P2X agonist α,β‐methylene‐adenosine 5′‐triphosphate (30 μM). Consistent with the electrophysiology, morphological analysis revealed that only ˜40 % of the lung‐specific small diameter (< 20 μm) JNC neurons consistent with the C‐fibre cell bodies display VR1 immunoreactivity. This study describes a convenient in vitro method for the study of mouse bronchopulmonary C‐fibres. The results indicate that C‐fibres in the mouse lungs are not homogeneous, but can be subclassified into capsaicin‐sensitive and capsaicin‐insensitive phenotypes.