ATP and P2X3 Receptor in Chronic Cough

This is a laboratory-based study that will be performed at the Clinical Research Centre at the Royal Brompton Hospital,London. The objectives are: 1. Determine whether adenosine triphosphate (ATP) is present or released in airways of idiopathic chronic cough patients 2. Determine whether there is an increase in cough sensitivity and laryngeal sensitivity to exogenous ATP 3. Examine the effects of exogenous ATP on the inflammatory response in the upper and lower airways. The participants will be: (i) Healthy subjects: non-smoker (8 subjects) and (ii) Chronic cough subjects attending Chronic Cough clinic (12 subjects). Each will be involved in: Study 1. Following recruitment, subjects will attend for a fiberoptic bronchoscopy. Study 2: Subjects will take part in a study of the effect of inhaling nebulized ATP. Subjects will be studied on 2 days separated by at least 5 days. On each day, after measurements of lung function, FeNO and cough questionnaires, the subject will inhale either saline or ATP solution from a nebulizer, following which laryngeal hypersensitivity, capsaicin cough challenge and sputum induction will be performed. Results will be expressed as mean ± standard error of the mean (SEM). Study data will be analysed by the Investigators at the completion of the study. Planned analyses will be done by comparing chronic cough patients to the healthy controls. The Spearman rank-correlation test will be used to determine correlations.