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Na^sup +^-K^sup +^-2CI- cotransporters and Cl^sup -^ channels regulate citric acid cough in guinea pigs
Ist Teil von
Journal of applied physiology (1985), 2006-08, Vol.101 (2), p.635
Ort / Verlag
Bethesda: American Physiological Society
Erscheinungsjahr
2006
Link zum Volltext
Quelle
Free E-Journal (出版社公開部分のみ）
Beschreibungen/Notizen
Loop diuretics have been shown to inhibit cough and other airway defensive reflexes via poorly defined mechanisms. We test the hypothesis that the furosemide-sensitive Na^sup +^-K^sup +^-2Cl^sup -^ cotransporter (NKCCl) is expressed by sensory nerve fibers innervating the airways where it plays an important role in regulating sensory neural activity. NKCCl immunoreactivity was present on the cell membranes of most nodose and jugular ganglia neurons projecting to the trachea, and it was present on the peripheral terminals of putative mechanosensory nerve fibers in the airways. In urethane-anesthetized, spontaneously breathing guinea pigs, bolus application of citric acid (1 mM to 2 M) to an isolated and perfused segment of the tracheal mucosa evoked coughing and respiratory slowing. Removal of Cl^sup -^ from the tracheal perfusate evoked spontaneous coughing and significantly potentiated cough and respiratory slowing reflexes evoked by citric acid. The NKCCl inhibitor furosemide (10-100 µM) significantly reduced both the number of coughs evoked by citric acid and the degree of acid-evoked respiratory slowing (P < 0.05). Localized tracheal pretreatment with the Cl^sup -^ channel inhibitors DIDS or niflumic acid (100 µM) also significantly reduced cough, whereas the GABA^sub A^ receptor agonist muscimol potentiated acid-evoked responses. These data suggest that vagal sensory neurons may accumulate Cl^sup -^ due to the expression of the furosemide-sensitive Cl^sup -^ transporter, NKCCl. Efflux of intracellular Cl^sup -^, in part through calcium-activated Cl^sup -^ channels, may play an important role in regulating airway afferent neuron activity. [PUBLICATION ABSTRACT]