A NEUROKININ 1-RECEPTOR ANTAGONIST IMPROVES EXERCISE-INDUCED AIRWAY NARROWING IN ASTHMATIC-PATIENTS

Recent reports suggest the involvement of vascular phenomena in exerci se-induced asthma. Sensory neuropeptides, such as substance P (SP), wh ich causes airway vascular dilatation and plasma leakage, have been de monstrated to play a role in hyperpnea-induced airway narrowing in ani mal studies. The purpose of this study was to investigate the importan ce of tachykinins in exercise-induced airway narrowing in patients wit h asthma using a selective neurokinin 1-receptor (NK1-receptor) antago nist, FK-888. In a double-blind, placebo-controlled, crossover trial, nine subjects with stable asthma were given FK-888 (2.5 mg) or placebo by inhalation 20 min before each exercise at a level previously demon strated to cause a fall of at least 40% in specific airway conduction (SGaw). Inhalation of FK-888 had no significant effect on baseline SGa w. While the recovery from exercise-induced airway narrowing was signi ficantly faster after treatment with FK-888, the area under the curve for SGaw during the 50 min after exercise was significantly reduced (p < 0.05) and the time taken for the SGaw to recover to within 65% of b aseline after exercise was also significantly shorter with FK-888 than with placebo (p < 0.05). However, treatment with FK-888 did not signi ficantly attenuate the maximal fall in SGaw. These results suggest tha t NK1-receptor-mediated mechanisms are involved in the recovery phase of exercise-induced airway narrowing. The possible mechanisms of these phenomena are discussed.