A novel bioassay for the NK-2 neurokinin receptor: the guinea pig gallbladder.
Although three neurokinin receptors (NK-1, NK-2, NK-3) have been identified by radioligand binding assays, only the NK-1 and NK-3 types have been found in smooth muscle bioassays. In this study, evidence is presented demonstrating functional NK-2 type receptors in the guinea pig gallbladder (GPGB). The potencies of the following neurokinins were determined in the GPGB and the guinea pig ileum (GPI): substance P (SP), physalaemin (PH), eledoisin (EL), substance K (SK) and kassinin (KA). ED50 values were determined by linear regression analysis of the dose-related increases in the force generated by each peptide. In the GPI, the rank order of potency was SP = PH = EL greater than SK = KA, indicating NK-1 selectivity. In the GPGB, the relative potencies were SK greater than KA greater than EL much greater than PH greater than SP, which is similar to that reported for the NK-2 receptor in radioligand binding assays. These findings demonstrate the NK-2 receptor tissue selectivity of the GPGB.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001681:Biological Assay / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004600:Eledoisin / Q000378:metabolism; D005704:Gallbladder / Q000032:analysis*; D006168:Guinea Pigs; D015286:Kassinin; D015288:Neurokinin A; D009479:Neuropeptides / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010803:Physalaemin / Q000378:metabolism; D011377:Proglumide / Q000494:pharmacology; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter / Q000032:analysis*; D012844:Sincalide / Q000378:metabolism; D013373:Substance P / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D009479:Neuropeptides; D009842:Oligopeptides; D018041:Receptors, Neurokinin-2; D017981:Receptors, Neurotransmitter; D010803:Physalaemin; D013373:Substance P; D013779:Tetrodotoxin; D015286:Kassinin; D004600:Eledoisin; D001285:Atropine; D015288:Neurokinin A; D011377:Proglumide; D012844:Sincalide