Kinouchi K, Pasternak G W
George Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
Eur J Pharmacol. 1991 Jun 19;207(2):135-41. doi: 10.1016/0922-4106(91)90088-y.
Both [3H]U69,593 alone and [3H]ethylketocyclazocine (EKC) in the presence of mu and delta blockers ([D-Ala2,MePhe4,Glyol5]enkephalin (DAMGO) and [D-Pen2,D-Pen5]enkephalin (DPDPE)) label kappa receptors in the guinea pig cerebellum. Dynorphin A(1-17) and nor-binaltorphimine (nor-BNI) potently competed the binding of both radioligands with Hill coefficients of approximately unity, strongly supporting a kappa classification of binding. However, saturation studies revealed that the Bmax for [3H]EKC binding was 45% greater than that for [3H]U69593, suggesting that [3H]EKC might be labeling more than one site. Although nonlinear regression analysis of dynorphin A(1-17) and nor-BNI competition of [3H]EKC binding best fit the curves with a one site model, competitions by dynorphin B, dynorphin A(1-9) and alpha-neoendorphin revealed Hill coefficients less than unity and were best fit to a two site model. Kinetic analysis also supported [3H]EKC binding heterogeneity. Together, these studies imply that under these conditions [3H]EKC labels more than one site in the guinea pig cerebellum. The sensitivity of all specific [3H]EKC binding to the selective kappa ligands dynorphin A(1-17) and nor-BNI indicates that both component are kappa while the differing sensitivities of dynorphin B, alpha-neoendorphin and dynorphin A(1-9) for these components support our previous hypothesis of kappa 1a and kappa 1b binding subtypes.
单独的[3H]U69,593以及在μ和δ受体阻断剂（[D - Ala2,MePhe4,Glyol5]脑啡肽（DAMGO）和[D - Pen2,D - Pen5]脑啡肽（DPDPE））存在的情况下的[3H]乙基酮环唑新（EKC），均可标记豚鼠小脑中的κ受体。强啡肽A(1 - 17)和去甲双丙戊啡（nor - BNI）能有效竞争两种放射性配体的结合，希尔系数约为1，有力地支持了结合的κ分类。然而，饱和研究表明，[3H]EKC结合的最大结合容量（Bmax）比[3H]U69593的大45%，这表明[3H]EKC可能标记不止一个位点。尽管强啡肽A(1 - 17)和nor - BNI对[3H]EKC结合竞争的非线性回归分析用单一位点模型能最好地拟合曲线，但强啡肽B、强啡肽A(1 - 9)和α - 新内啡肽的竞争显示希尔系数小于1，并且用双位点模型能最好地拟合。动力学分析也支持[3H]EKC结合的异质性。总之，这些研究表明在这些条件下，[3H]EKC在豚鼠小脑中标记不止一个位点。所有特异性[3H]EKC结合对选择性κ配体强啡肽A(1 - 17)和nor - BNI的敏感性表明，两个组分都是κ型，而强啡肽B、α - 新内啡肽和强啡肽A(1 - 9)对这些组分的不同敏感性支持了我们之前关于κ1a和κ1b结合亚型的假设。
