The tachykinin peptide family in mammals comprises three peptides, substance P, neurokinin A and neurokinin B, which bind to the tachykinin receptor family of GPCRs, NK1, NK2 and NK3 (Severini et al., 2002). Tachykinins have prominent activity in the GI system, in which they stimulate intestinal contraction and salivation; these effects are mediated by NK1 and NK2. Experiments with selective antagonists of NK2, SR 48,968 and MEN 10,376 indicate that NK2 mediates neurokinin- induced constriction of pulmonary artery and bronchus (Maggi et al., 1993). NK2 antagonists display efficacy in treatment of irritable bowel disorder (Lecci et al., 2004). Cloned human NK2-expressing cell line is made in the Chem-1 host, which supports high levels of recombinant NK2 expression on the cell surface and contains high levels of the promiscuous G protein Gα15 to couple the receptor to the calcium signaling pathway. Thus, the cell line is an ideal tool for screening for antagonists of interactions between NK2 and its ligands.