Degradation of Tachykinins

The route of delivery of substance P to the lung appears to be of critical importance in determining which peptidase is likely to be responsible for degradation of the peptide. When substance P is administered intravenously to 

Although tachykinins are important in the airway response to certain interventions, there appears to be little or no tachykinin tone in the absence of intervention. In non-asthmatic or stable asthmatic human airways, neither the NEP inhibitor thiorphan (Cheung et /., 1992, 1993) nor the combined Nkl/Nk2 receptor antagonist FK224 (Ichinose et al., 1992) has any effect on baseline specific airways resistance. Likewise, alterations in NEP activity do not contribute to the enhanced bronchoconstrictive responses to NkA observed in patients with mild asthma. Asthmatic patients respond to inhaled thiorphan with an increase in NkA-induced bronchoconstriction similar in magnitude to that documented in non-asthmatic subjects (Cheung et al., 1992, 1993). 

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