PHARMACOLOGICAL EVIDENCE FOR NEUROKININ RECEPTORS IN MURINE NEUROBLASTOMA C1300 CELLS

We found that neurokinin A (NKA) and neurokinin B (NKB) induce an incr ease in the concentration of intracellular free Ca2+ ([Ca2+](i)) in mu rine neuroblastoma C1300 cells (EC(50): NKA 87 +/- 13 nM, NKB 97 +/- 1 5 nM). Substance P (SP) also caused a transient Ca2+ increase, althoug h the potency of SP was much less than that of NKA and NKB. The increa se in [Ca2+](i) induced by NKA and NKB was inhibited by SR 48,968, a s elective antagonist for NK2, and [beta Ala(8)]NKA(4-10), a selective a gonist for NK2, did not stimulate the increase in [Ca2+](i). NKA- and NKB-induced Ca2+ mobilization was not inhibited by CP-96,345 and [Trp( 7),beta Ala(8)]NKA(4-10), selective antagonists for NK1 and NK3, respe ctively. These results suggested that C1300 cells express endogenous N K2 neurokinin receptors that have different: features from known NK2 r eceptors.