Respiratory Pharmacology DEMO

Bombesin is a peptide which causes long lasting bronchoconstriction in vivo via an indirect effect on the airway smooth muscle. It is known that bombesin induced bronchoconstriction is unaffected by pretreatment with antihistamines such as mepyramine, COX inhibitors, 5-LO inhibitors, PAF antagonists or 5-HT antagonists. Thus, bombesin does not cause bronchoconstriction by release of mediators such as PAF or leukotrienes and the lack of effect of capsaicin or cholinergic antagonists suggest that neural mechanisms are not involved. The substance released must be a spasmogen as the bronchdilator, epinephrine reduces the bronchoconstriction. The action of epinephrine on airways contracted with bombesin is known as a functional anatgonism - i.e. its actions are opposite to those of bombesin, but acts via a different receptor. Mepyramine has no effect on the airway responses of animals treated with bombesin as it is a H₁ receptor antagonist and not a bronchodilator.