Calcitonin Gene‐related Peptide Antagonizes the Protective Effect of Adrenomedullin on Histamine‐induced Bronchction

In the present study the possible relationship between adrenomedullin (AM) and calcitonin gene-related peptide (CGRP) in the regulation of airway functions in anaesthetized guinea-pigs was examined in vivo. 2. We found that AM significantly inhibited histamine-induced bronchoconstriction in a dose-dependent manner. CGRP or the CGRP receptor antagonist (CGRP [8-37]) alone did not affect pulmonary resistance and pretreatment with CGRP or CGRP [8-37] did not significantly affect histamine-induced bronchoconstriction. However, AM-induced bronchoprotection was significantly inhibited by pretreatment with CGRP or CGRP [8-37] in a dose-dependent manner. 3. It is therefore possible that CGRP may be competitive, at least in part, with binding sites of AM in the guinea-pig airway. Exogenous AM may be useful for the management of bronchial asthma, not only as a potent bronchodilator, but also as a functional antagonist of CGRP.