Na+-K+-2Cl- cotransporters and Cl- channels regulate citric acid cough in guinea pigs

• Published in: Journal of applied physiology (1985) Vol. 101; no. 2; pp. 635 - 643
• Main Authors: Mazzone, Stuart B, McGovern, Alice E
• Format: Journal Article
• Language: English
• Published: United States Am Physiological Soc 01.08.2006
• Subjects: 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid - pharmacology; Animals; Chloride Channels - antagonists & inhibitors; Chloride Channels - physiology; Chlorides - pharmacology; Citric Acid; Cough - chemically induced; Cough - physiopathology; Furosemide - pharmacology; GABA-A Receptor Agonists; Guinea Pigs - physiology; Immunohistochemistry; Male; Muscimol - pharmacology; Neurons, Afferent - chemistry; Neurons, Afferent - drug effects; Neurons, Afferent - physiology; Niflumic Acid - pharmacology; Reflex - physiology; Respiration - drug effects; Respiratory Mechanics - physiology; Respiratory Physiological Phenomena; Respiratory System - innervation; Sodium Potassium Chloride Symporter Inhibitors - pharmacology; Sodium-Potassium-Chloride Symporters - analysis; Sodium-Potassium-Chloride Symporters - physiology
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00106.2006

Howard Florey Institute, University of Melbourne, Parkville, Victoria, Australia Submitted 20 January 2006 ; accepted in final form 6 April 2006 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 + -K + -2Cl – cotransporter (NKCC1) is expressed by sensory nerve fibers innervating the airways where it plays an important role in regulating sensory neural activity. NKCC1 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 – from the tracheal perfusate evoked spontaneous coughing and significantly potentiated cough and respiratory slowing reflexes evoked by citric acid. The NKCC1 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 – channel inhibitors DIDS or niflumic acid (100 µM) also significantly reduced cough, whereas the GABA A receptor agonist muscimol potentiated acid-evoked responses. These data suggest that vagal sensory neurons may accumulate Cl – due to the expression of the furosemide-sensitive Cl – transporter, NKCC1. Efflux of intracellular Cl – , in part through calcium-activated Cl – channels, may play an important role in regulating airway afferent neuron activity. airway; cough receptor; furosemide; sensory nerves; apnea Address for reprint requests and other correspondence: S. B. Mazzone, Howard Florey Institute, University of Melbourne, Parkville 3010, Victoria, Australia (e-mail: s.mazzone{at}hfi.unimelb.edu.au )