Abstract
The existence of two neurokinin NK-3 receptor subtypes has been suggested on the basis of results obtained in binding assays. In the present study, we have confirmed the two NK-3 receptor subtypes by using data obtained in both biological and binding assays. Experiments have been performed in the rat portal vein and in the guinea-pig ileum treated with NK-1 and NK-2 selective antagonists, namely CP 96345 and SR 48968.Orders of potency of agonists on the rat portal vein are as follows: for neurokinins, NKB > NKA > SP; for tachykinins, KAS > ELE > PHY;and for selective agonist: [Mephe7]NKB >> senktide.On the guinea-pig ileum, the agonist rank orders of potency are: NKB > SP > NKA, ELE > KAS > PHY;and for selective agonist: [MePhe7=senktide.The apparent affinity of antagonists shows differences in both biological and binding assays. In fact, on the rat portal vein, SR 48968 is almost inactive (pA2 or IC50 ≈ 4.8), while R-486 [Trp7,βAla8]NKA(4–10) shows a pA2 value of 7.45 and an IC50 of 5.6. An opposite pattern of activity is observed in the guinea-pig ileum, where SR 48968 shows a pA2 of 6.05 and an IC50 of 6.7, while R-486 has a pA2 of 6.1 and an IC50 of < 5.0. These results confirm the existence of two NK-3 sites differing pharmacologically. It is proposed to name NK-3A the receptor of the guinea-pig ileum and NK-3B the receptor of the rat portal vein.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
