EFFECTS OF AIRWAY INFLAMMATION ON COUGH RESPONSE IN THE GUINEA-PIG

We have developed a guinea pig model for cough related to allergic air way inflammation. Unanesthetized animals were exposed to capsaicin aer osols for 10 min, and cough frequency was counted during this period. The cough evaluation was performed by the following three methods: vis ual observation, acoustic analysis, and monitoring of pressure changes in the body chamber. These analyses clearly differentiated a cough fr om a sneeze. To elucidate the relationship between cough response and airway inflammation, animals were immunosensitized and multiple challe nged. Sensitized guinea pigs presented no specific changes microscopic ally, but multiple-challenged animals showed an increased infiltration of inflammatory cells into the airway. Cough number in response to ca psaicin increased significantly from 4.7 +/- 1.4 coughs/10 min in norm al animals to 10.6 +/- 2.0 coughs/10 min in sensitized animals and fur ther to 22.8 +/- 1.3 coughs/10 min in multiple-challenged animals. Thi s augmented cough frequency was significantly inhibited by the inhalat ion of tachykinin-receptor antagonists and by oral ingestion, but not inhalation, of codeine phosphate. The results suggest that airway infl ammation potentiates an elevation of cough sensitivity in this model.