TACHYKININS MEDIATE THE POTENTIATION OF ANTIGEN-INDUCED BRONCHOCONSTRICTION BY COLD-AIR IN GUINEA-PIGS

The role of tachykinins in the potentiation of antigen-evoked bronchoc onstriction induced by inhalation of cold air was studied in guinea pi gs. Cold air was delivered through a tracheal cannula to anethetized, artificially ventilated guinea pigs sensitized with ovalbumin and pret reated with atropine (1.4 mu mol/kg). Inhalation of cold air increased total pulmonary resistance (R(L)) in a time-dependent manner; inhalat ion of cold air for 10 or 15 minutes, but not for 5 minutes, produced a significant increase in R(L). Aerosolized ovalbumin (5 breaths) incr eased R(L) in a dose-dependent manner (0.5% to 5%). Inhalation of cold air for 5 minutes significantly enhanced both the peak and the durati on of the increased in R(L) induced by 0.5% ovalbumin. The tachykinin neurokinin 2-receptor antagonist, SR 48968 (0.3 mu mol/kg intravenousl y) inhibited both the peak and the duration of the bronchoconstriction induced by 5-minute inhibited of cold air and ovalbumin (0.5%), where as it did not affect the response to ovalbumin (0.5%) alone. These fin dings suggest that exposure to cold air potentiates the bronchoconstri ction response to antigen and that this potentiation is mediated by ta chykinin release from sensory nerves.