We have demonstrated previously that
tachykinin depletion by
capsaicin prevented the
ozone-induced
airway hyperresponsiveness and the bronchial wall oedema in guinea pigs. To further clarify the role of
neurogenic inflammation in
ozone-induced
airway hyperresponsiveness, we investigated the effects of a specific
tachykinin receptor antagonist (FK-224) in guinea pigs. Animals were anaesthetized, tracheostomized and mechanically ventilated. Total pulmonary resistance (RL) was calculated from transpulmonary pressure and box flow in a plethysmograph. Airway responsiveness was assessed by determining the provocative concentration of
histamine aerosol that increased RL to twice the baseline value (PC200). Animals were injected with either
FK-224 (10 mg/kg, dissolved in 0.2 mL/kg
DMSO) or vehicle (0.2 mL/kg
DMSO) intravenously, then pre-
ozone PC200 was determined. Following this measurement, animals were exposed to 3 ppm
ozone for 60 min. Immediately after exposure, the
histamine dose response curve was evaluated again. Bronchoalveolar lavage (BAL) was performed in animals treated with
FK-224 or vehicle. In animals treated with vehicle,
ozone exposure caused significant decrease in PC200 and moderate increase in neutrophils in BAL fluid.
FK-224 pre-treatment significantly inhibited
ozone-induced hyperresponsiveness. Neutrophils in BAL fluid did not significantly increase after
ozone exposure in animals treated with
FK-224. By contrast, the degree of epithelial desquamation did not differ significantly between the two groups. We conclude that
neurogenic inflammation caused by
tachykinin release may be responsible for
ozone-induced bronchial hyperresponsiveness, and that
tachykinins may play a role in the initiation of airway
inflammation.