The Effect of Exposure of Guinea Pig to Cigarette Smoke and their Sensitization in Tracheal Responsiveness to Histamine and Histamine Receptor (H1) Blockade by Chlorpheniramine

Airway responsiveness to histamine and histamine H(1) receptor blockade by chlorpheniramine (CR-1) on guinea pig trachea were examined. Chronic obstructive pulmonary disease (COPD) and asthma were induced in guinea pigs by exposing them to cigarette smoke for 3 months and by sensitization with injection and inhalation of ovalbumin (OA). The responses of tracheal chains of COPD (n=8), COPD+asthma (n=6) and control animals (n=8) to histamine (EC(50) H) and (CR-1) were measured. The in vitro histamine responses of COPD and COPD+asthmatic guinea pigs in tracheal chains were significantly higher than those of control animals (p<0.001 and p<0.01, respectively). The CR-1 blockade was also significantly greater in trachea of COPD and COPD+asthma compared to that of controls (p<0.01 and p<0.05, respectively). There were significant correlations between EC(50) H and (CR-1) (r=-0.542, p<0.01). The hematocrit in COPD and COPD+asthma groups was also significantly higher than in controls (p<0.001 for both groups). The contractility of tracheal chains to histamine in COPD+asthma animals was significantly greater than those of control and COPD groups (p<0.05 for both cases). The differences in contractility between COPD and COPD+asthmatic groups, however, suggests different basic mechanisms for AHR in COPD and asthma.