Bronchoconstrictor effect of the tachykinin NK3-receptor agonists [MePhe7]-neurokinin B and senktide in the isolated guinea pig lung

To determine whether bronchoconstriction can be mediated via the tachykinin NK3 receptors, isolated guinea pig lungs were challenged with the exogenous tachykinin NK3-receptor agonists [MePhe(7)]-neurokinin B ([MePhe(7)]-NKB) and senktide. [MePhe(7)]-NKB induced bronchoconstriction (EC50 = 11.8 +/- 1.7 mu M) that was significantly inhibited by the tachykinin NK3-receptor antagonist SB 223412 at 10 mu M (EC50 = 24.4 +/- 4.5 mu M). Senktide also induced bronchoconstriction (EC50 = 96.2 +/- 20.3 mu M) and the bronchoconstriction was significantly reduced by SB 223412 at 1 and 10 mu M (EC50 = 270.8 +/- 78.9 mu M and 388.3 +/- 105.5 mu M, respectively). Although the authors demonstrated that SB 223412, [MePhe(7)]-NKB, and senktide are potent and selective for the tachykinin NK3 receptors in binding and functional (Ca2+ mobilization) assays, the tachykinin NK1-receptor antagonist CP 99,994 at 1 mu M (EC50 = 32.7 +/- 8.5 mu M) produced inhibition of [MePhe(7)]-NKB-induced bronchoconstriction, whereas the tachykinin NK2-receptor antagonist SR 48968 at 0.1 mu M (EC50 = 213.2 +/- 42.9 mu M) blocked senktide-induced bronchoconstriction. These data suggest that [MePhe(7)]-NKB and senktide caused bronchoconstriction in guinea pig through activation of the tachykinin NK3-receptors but the tachykinin NK1- and/or NK2-receptors are also involved in the response.