Platelet‐activating factor (PAF) plays an important role in the immediate asthmatic response in guinea‐pig by augmenting the response to histamine

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Abstract
1 To investigate the role of platelet activating factor (PAF) in the immediate asthmatic response, we examined the bronchial reactivity to histamine after administration of PAF to guinea-pigs or antigen challenge to passively sensitized guinea-pigs. 2 A bolus injection of PAF (20–40 ng kg−1), which did not cause a significant increase in intrathoracic pressure (ITP), augmented the bronchial response to histamine almost 8 fold. This airway hyperreactivity was observed even 1 min after PAF treatment. 3 A subthreshold dose of antigen (0.01 mg kg−1, i.v.) also provoked hyperreactivity to histamine, which became significant 6 and 11 min after the antigen treatment. 4 The specific PAF-antagonists, SM-10661 and CV-6209 (i.v.) dose-dependently inhibited both PAF-and antigen-induced airway hyperreactivities to histamine. 5 These results suggest that PAF plays an important role in antigen-induced acute airway responses by augmenting the activities of spasmogens.