Dohanich G P, Halpain S, Lambdin L T, McEwen B S
Brain Res. 1986 Feb 26;366(1-2):338-42. doi: 10.1016/0006-8993(86)91314-4.
The binding of [3H]N-methyl scopolamine (NMS) to muscarinic binding sites in rat forebrain was compared in two types of preparations: homogenates and slide-mounted sections. Under standard assay conditions, [3H]NMS bound to the muscarinic binding site with an apparent Kd that was almost one order of magnitude lower in homogenates (Kd = 0.15 nM) than sections (Kd = 1.25 nM). In addition, the muscarinic agonist carbachol inhibited [3H]NMS binding more effectively in homogenates (Ki = 5 microM) than sections (Ki = 100 microM). The higher Kd observed in sections was dependent upon the thickness of the section since the apparent Kd decreased as the thickness of the section was reduced. A slower equilibration rate may account, in part, for the higher apparent Kd seen in thicker sections. The results support previous evidence that certain ligands exhibit different binding profiles in homogenate and section preparations.
在两种类型的制剂中比较了[3H]N-甲基东莨菪碱（NMS）与大鼠前脑毒蕈碱结合位点的结合情况：匀浆和载玻片固定切片。在标准测定条件下，[3H]NMS与毒蕈碱结合位点结合，其表观解离常数（Kd）在匀浆中（Kd = 0.15 nM）比切片中（Kd = 1.25 nM）低近一个数量级。此外，毒蕈碱激动剂卡巴胆碱在匀浆中（Ki = 5 microM）比在切片中（Ki = 100 microM）更有效地抑制[3H]NMS结合。切片中观察到的较高Kd取决于切片的厚度，因为随着切片厚度的减小，表观Kd降低。较慢的平衡速率可能部分解释了较厚切片中较高的表观Kd。这些结果支持了先前的证据，即某些配体在匀浆和切片制剂中表现出不同的结合谱。
