PHARMACOLOGICAL CHARACTERIZATION OF TACHYKININ-INDUCED INTRACELLULAR CALCIUM RISE IN A HUMAN NK2 RECEPTOR TRANSFECTED CELL-LINE

We have examined the effect of various natural and synthetic tachykinins on the steady state Ca++-rise ([Ca++](i)) in transfected chinese hamster ovary cells expressing recombinant human Neurokinin 2 (NK2) receptors. The rank order of potency with natural tachykinins was NeurokininA > Neurokinin B> Eledoisin > Physaelamin > substance P. The selective NK2 agonist, [beta-Ala(8)]NKA(4-10) was very potent,with an EC(50) value of 4.83 x 10(-9)M whereas Senktide, MePhe(7)NKB and Sar(9), (MetO(2))(11) substance P, selective NK3 and NK1 agonists, respectively, did not have any effect on [Ca++](i) in hrNK2CHO cells, suggesting a selective and preferential recognition and activation of NK2 receptors in these cells. (+/-) SR 48968, a selective NK2 antagonist, abolished the beta-AlaNKA-induced [Ca++](i) with an IC50 value of 0.7 nM. Two other peptidic NK2 antagonists, MEN 10376 and L-658977, were less active with IC50 values of 49 nM and 5.29 mu M, respectively. In contrast, (+/-) CP-96,345 and (+/-)CP-99,994 and RP 67580, all selective NK1 antagonists, did not have any effect on the beta-AlaNKA-induced [Ca++](i) in hrNK2CHO cells (+/-) SR 140333, a potent and selective NK1 antagonist,had a 35% inhibition under similar conditions. These data demonstrate a high selectivity and sensitivity to NK2 receptor mediated [Ca++](i) in rhNK2R-CHO cells and may be of value as a rapid, selective test of drug action at the human NK2 receptors in vitro. (C) 1994 Academic Press, Inc.