Differential effects of airway afferent nerve subtypes on cough and respiration in anesthetized guinea pigs

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2008-11, Vol.295 (5), p.R1572-R1584
• Main Authors: Chou, Yang-Ling, Scarupa, Mark D, Mori, Nanako, Canning, Brendan J
• Format: Article
• Language: English
• Subjects: Administration, Inhalation; Airway management; Anesthesia; Animals; Capsaicin; Citric Acid; Cough - physiopathology; Exercise and Respiratory Physiology; Guinea Pigs; Histamine; Hypertonic Solutions; Injections, Intra-Arterial; Injections, Intravenous; Larynx - physiology; Lung - innervation; Lung - physiopathology; Male; Nasal Mucosa - physiology; Neurology; Neurons; Neurons, Afferent - physiology; Reflex - physiology; Respiratory Mechanics - physiology; Respiratory System - innervation; Respiratory System - physiopathology; Rodents; Sleep disorders; Trachea - physiology; Vagotomy; Whooping cough
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.90382.2008

Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland Submitted 23 April 2008 ; accepted in final form 2 September 2008 The hypothesis that respiratory reflexes, such as cough, reflect the net and often opposing effects of activation of multiple afferent nerve subpopulations throughout the airways was evaluated. Laryngeal and tracheal mucosal challenge with either citric acid or mechanical probing reliably evoked coughing in anesthetized guinea pigs. No other stimulus reliably evoked coughing in these animals, regardless of route of administration and despite some profound effects on respiration. Selectively activating vagal C-fibers arising from the nodose ganglia with either adenosine or 2-methyl-5-HT evoked only tachypnea. Selectively activating vagal afferents arising from the jugular ganglia induced respiratory slowing and apnea. Nasal afferent nerve activation by capsaicin, citric acid, hypertonic saline, or histamine evoked only respiratory slowing. Histamine, which activates intrapulmonary rapidly adapting receptors but not airway or lung C-fibers or tracheal bronchial cough receptors induced bronchospasm and tachypnea, but no coughing. The results indicate that the reflexes initiated by stimuli thought to be selective for some afferent nerve subtypes will likely depend on the net and potentially opposing effects of multiple afferent nerve subpopulations throughout the airways. The data also provide further evidence that the afferent nerves regulating cough in anesthetized guinea pigs are distinct from either C-fibers or intrapulmonary rapidly adapting receptors. vagal; capsaicin; apnea; trigeminal; laryngeal Address for reprint requests and other correspondence: B. J. Canning, Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224 (e-mail: bjc{at}jhmi.edu )