alpha and beta-adrenoceptors in chicken airways

Isolated chicken bronchus (which had been partially contracted to carbachol) relaxes to isoproterenol and epinephrine but contracts weakly to phenylephrine. Propranolol (a beta-adrenoceptor blocker) antagonizes isoproterenol and reverses epinephrine-induced relaxations to feeble contractions. Phenylephrine-induced bronchoconstrictions and constrictions to epinephrine (in the presence of beta-blockade) were blocked by phentolamine. The results of this study showed the predominance of beta-)inhibitory) adrenoceptors and some alpha-(excitatory) adrenoceptors in the bronchus of the adult domestic fowl.