Airway Responses to Tachykinins

Tachykinins transduce multiple effects in the airways, including bronchoconstriction, increased ion and water flux across the epithelium, cough, mucous secretion, increased ciliary beat frequency, increased airway blood flow and increased airway vascular permeability (Gashi et /., 1986 Borson et al., 1987, 1989 Kohrogi et /., 

In initial studies in which substance P was administered to subjects by intravenous infusion, no effect on airway caliber could be demonstrated. It is possible that potent cardiovascular side effects resulted in homeostatic reflexes with secondary effects on the airways that masked the effects of substance P (Fuller et al., 1987). However, when changes in the partial flow volume curve, a highly sensitive index of airway caliber, were used as the index of airway obstruction, inhaled NkA - and, to a lesser extent, inhaled substance P - caused airway obstruction in healthy people (Joos et al., 1987). NkA is approximately 10-100 times more potent as a bronchocon-strictor in asthmatic than in non-asthmatic subjects (Cheung et al., 1992, 1993) this ratio of potency is similar to that observed for other agonists. 

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