CHARACTERIZATION OF TACHYKININ RECEPTORS IN FERRET TRACHEA BY PEPTIDE AGONISTS AND NONPEPTIDE ANTAGONISTS

The tachykinin receptors mediating mucus secretion and smooth muscle contraction were studied in the ferret trachea in vitro. Substance P (SP) and the selective agonist for NK, receptor ([Sar9,Met(O2)11]SP), but not selective agonists for NK2 {[Ala5,beta-Ala8]neurokinin A-(4-10)) and NK3 ([MePhe7]neurokinin B) receptors, induced secretion of macromolecules in a concentration-dependent fashion. The nonpeptide NK, receptor antagonist, CP-96,345, but not the nonpeptide NK2 receptor antagonist, SR-48968, inhibited SP-induced secretion. Both neurokinin A (NKA) and [Ala5,beta-Ala8]NKA-(4-10), but not NK, and NK3 selective agonists, evoked a concentration-dependent smooth muscle contraction. SR-48968, but not CP-96,345, inhibited in a concentration-dependent manner the response to NKA. CP-96,345 and SR-48968 did not affect the concentration-dependent increase in macromolecule secretion or smooth muscle contraction by carbachol. These findings indicate that NK, receptors mediate secretion of macromolecules and NK2 receptors mediate smooth muscle contraction, in response to tachykinins in the ferret trachea in vitro.