Broadhurst A M, Wyllie M G
Neuropharmacology. 1986 Mar;25(3):287-95. doi: 10.1016/0028-3908(86)90254-6.
In order to fully resolve the binding profile of [3H]rauwolscine to membranes from the cortex of the rat, saturation, competition and association-dissociation data were analysed by means of computerised curve-fitting techniques. The binding isotherm for [3H]rauwolscine was best fitted to a two-component model consisting of a high-affinity, saturable site (approx. Kd 1.8 nM) and a low-affinity, apparently non-saturable, component. Displacement experiments revealed shallow inhibition curves for both antagonist and agonist ligands with a rank order of potency indicative of an interaction at the alpha 2-adrenoceptor. Inclusion of spiroperidol, but not prazosin, markedly steepened the antagonist, but not the agonist inhibition curves. In addition, spiroperidol attenuated, but did not eliminate, the low-affinity component in saturation experiments. Dissociation and association data revealed a biphasic paradigm, the more slowly-associating/dissociating component of which was sensitive to spiroperidol. It was concluded that [3H]rauwolscine binds to two sites on membranes of the rat cortex; a high-affinity site corresponding to alpha 2-adrenoceptors and a low-affinity, spiroperidol-sensitive component. The possible identity of the low-affinity site is discussed with particular emphasis on displacement data for [3H]rauwolscine and the interaction with rauwolscine in isolated organs.
为了全面解析[3H]萝芙木碱与大鼠皮层膜的结合情况，采用计算机曲线拟合技术对饱和、竞争及结合-解离数据进行了分析。[3H]萝芙木碱的结合等温线最适合由一个高亲和力、可饱和位点（约Kd 1.8 nM）和一个低亲和力、明显不饱和组分组成的双组分模型。置换实验显示，拮抗剂和激动剂配体的抑制曲线较平缓，其效价顺序表明在α2-肾上腺素受体处存在相互作用。加入螺哌啶醇而非哌唑嗪，可显著使拮抗剂而非激动剂的抑制曲线变陡。此外，在饱和实验中，螺哌啶醇减弱但未消除低亲和力组分。解离和结合数据显示出双相模式，其中结合/解离较慢的组分对螺哌啶醇敏感。得出的结论是，[3H]萝芙木碱与大鼠皮层膜上的两个位点结合；一个对应于α2-肾上腺素受体的高亲和力位点和一个低亲和力、对螺哌啶醇敏感的组分。讨论了低亲和力位点可能的性质，特别强调了[3H]萝芙木碱的置换数据以及在离体器官中与萝芙木碱的相互作用。
