Calcitonin gene-related peptide relates to cough sensitivity in children with chronic cough

Airway neuropeptides, in particular calcitonin gene-related peptide (CGRP), are likely to be important in the pathogenesis of chronic cough. The present authors evaluated the following: 1) the relationship between cough sensitivity and bronchoalveolar lavage (BAL) neuropeptides; and 2) the effect of reflux oesophagitis (RO) on cough, cough sensitivity and BAL neuropeptides in children not selected for cough. It was hypothesised that CGRP would be increased in children with chronic cough and would relate to cough sensitivity. Capsaicin cough sensitivity was performed in children undergoing gastro-duodenal endoscopy. CGRP, substance P and neurokinin A were measured in BAL obtained nonbronchoscopically. Children were defined as "coughers" if chronic cough was present. Coughers (n=21) had significantly reduced cough sensitivity but were just as likely as noncoughers (n=19) to have RO. The median CGRP was significantly higher in coughers with oesophagitis than in noncoughers with oesophagitis. CGRP significantly negatively correlated to cough sensitivity in coughers but not in noncoughers. Elevated calcitonin gene-related peptide, but not substance P or neurokinin A, is only associated with chronic cough in children when oesophagitis coexists. Calcitonin gene-related peptide in bronchoalveolar lavage relates to cough sensitivity and is likely to be important in the pathophysiology of chronic cough.