Experimental allergic rhinitis-related cough and airway eosinophilia in sensitized guinea pigs

Allergic rhinitis is one of the most common causes of chronic cough. The characteristic feature of allergic rhinitis is eosinophilic nasal inflammation. This study was determined to find the relation between airway eosinophils and chemically-induced cough in guinea pigs with antigen-induced rhinitis at the early and late allergic phases. Forty animals were sensitized with ovalbumin (OVA) and divided into four separated groups. Four weeks later, the sensitized animals were either once or repeatedly (6 times at 7-day intervals) intranasally challenged with OVA to develop experimental allergic rhinitis. The control group was given saline. Cough was elicited by inhalation of citric acid aerosols and evaluated at 30 min (early phase) or 24 h (late phase) after the 1st or 6th nasal challenge (NC) in the sensitized animals. The citric acid-induced cough was significantly increased in the sensitized animals in the early allergic phase after the first and repeated NC compared with the control values [14(9-19) vs. 16(10-17) vs. 8(6-10); P=0.049], whereas there was no significant increase in the cough response tested in the late allergic phase. A correlation between the cough intensity and the number of eosinophils from nasal mucosa only (P=0.008) was found.