KCNQ/M-channels regulate mouse vagal bronchopulmonary C-fiber excitability and cough sensitivity
Hui Sun, An-Hsuan Lin, Fei Ru, Mayur J. Patil, Sonya Meeker, Lu-Yuan Lee, Bradley J. Undem
Hui Sun, An-Hsuan Lin, Fei Ru, Mayur J. Patil, Sonya Meeker, Lu-Yuan Lee, Bradley J. Undem
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Research Article Pulmonology

KCNQ/M-channels regulate mouse vagal bronchopulmonary C-fiber excitability and cough sensitivity

Abstract

Increased airway vagal sensory C-fiber activity contributes to the symptoms of inflammatory airway diseases. The KCNQ/Kv7/M-channel is a well-known determinant of neuronal excitability, yet whether it regulates the activity of vagal bronchopulmonary C-fibers and airway reflex sensitivity remains unknown. Here we addressed this issue using single-cell RT-PCR, patch clamp technique, extracellular recording of single vagal nerve fibers innervating the mouse lungs, and telemetric recording of cough in free-moving mice. Single-cell mRNA analysis and biophysical properties of M-current (IM) suggest that KCNQ3/Kv7.3 is the major M-channel subunit in mouse nodose neurons. The M-channel opener retigabine negatively shifted the voltage-dependent activation of IM, leading to membrane hyperpolarization, increased rheobase, and suppression of both evoked and spontaneous action potential (AP) firing in nodose neurons in an M-channel inhibitor XE991–sensitive manner. Retigabine also markedly suppressed the α,β-methylene ATP–induced AP firing in nodose C-fiber terminals innervating the mouse lungs, and coughing evoked by irritant gases in awake mice. In conclusion, KCNQ/M-channels play a role in regulating the excitability of vagal airway C-fibers at both the cell soma and nerve terminals. Drugs that open M-channels in airway sensory afferents may relieve the sufferings associated with pulmonary inflammatory diseases such as chronic coughing.

Authors

Hui Sun, An-Hsuan Lin, Fei Ru, Mayur J. Patil, Sonya Meeker, Lu-Yuan Lee, Bradley J. Undem

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Figure 6

Effects of M-channel modulators on AP discharge in mouse bronchopulmonary nodose C-fibers.

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Effects of M-channel modulators on AP discharge in mouse bronchopulmonar...
(A) Image (left) and schematic representation (right) of a trachea-perfused mouse lung vagus nerve preparation. (B) Representative traces (left) and group data (right, n = 7) of α,β-MeATP–induced AP firing recorded from mouse lung nodose C-fibers before (Ctrl) and after treatment with retigabine (RTG; 10 μM for 15 minutes). The fiber shown on the left responded to α,β-Me ATP with a peak firing frequency of 4 Hz. Calibration bar: 10 seconds. In the right panel, open symbols and lines indicate the change in AP number for individual fibers. Bold X and error bars represent mean ± SEM of the group. *P = 0.004 (paired t test). (C) Recording from one of 4 C-fibers exhibiting spontaneous AP firing (<1 Hz) that was silenced by application of retigabine. Calibration bar: 2 minutes. (D) AP numbers in response to 3 μM α,β-MeATP obtained from 6 fibers in the presence of XE991 (XE; 30 μM) and XE991 (30 μM) plus retigabine (10 μM) for 15 minutes. The preparations were perfused with normal Krebs solution for 30 minutes between treatments. Open symbols and lines indicate the changes for individual fibers. Bold X and error bars represent mean ± SEM. Note: AP number in XE991 is less than control (48 ± 24 APs for this group of fibers), which may be due to the inhibition of INa, as discussed in the main text. P > 0.05 by 1-way repeated-measures ANOVA.