Smith T D, Annis S J, Ehlert F J, Leslie F M
Department of Pharmacology, College of Medicine, University of California, Irvine.
J Pharmacol Exp Ther. 1991 Mar;256(3):1173-81.
Radioligand binding and quantitative autoradiographic techniques were used to characterize the pharmacological profile and anatomical distribution of N-[3H]methylscopolamine [( 3H] NMS)-labeled sites under assay conditions in which radioligand binding to M1 and M2 muscarinic receptors was blocked by addition of pirenzepine and AF-DX 116 (11[[2-[(diethylamino)methyl]-1-piperidinyl] acetyl]-5,11-dihydro-6H-pyrido[2,3-b] [1,4]benzodiazepine-6-one) to the incubation buffer. Nonlinear regression analysis of saturation data demonstrated that a large proportion of atropine-displaceable [3H]NMS binding persisted in the presence of saturating concentrations of M1 and M2 blockers. The residual [3H]NMS [( 3H]NMSb) sites were widely distributed throughout rat brain and represented the predominant muscarinic receptor population. The autoradiographic distribution of [3H]NMSb sites did not correspond to that of [3H]pirenzepine or [3H]AF-DX 116, indicating that [3H]NMSb labeled non-M1, non-M2 muscarinic sites. Moreover, the pharmacological profile of [3H]NMSb differed from that of [3H]pirenzepine at M1 sites, and was inconsistent with that of M2 receptor binding sites. Although we were unable to pharmacologically distinguish subpopulations of non-M1, non-M2 binding sites, the anatomical distribution of [3H]NMSb sites corresponded to that of the combined mRNA distributions for m3 and m4.
在测定条件下，通过向孵育缓冲液中添加哌仑西平和AF-DX 116（11[[2-[(二乙氨基)甲基]-1-哌啶基]乙酰基]-5,11-二氢-6H-吡啶并[2,3-b][1,4]苯并二氮杂䓬-6-酮）来阻断放射性配体与M1和M2毒蕈碱受体的结合，运用放射性配体结合和定量放射自显影技术来表征N-[3H]甲基东莨菪碱[（3H]NMS）标记位点的药理学特征和解剖分布。饱和数据的非线性回归分析表明，在M1和M2阻断剂饱和浓度存在的情况下，仍有很大比例的阿托品可置换的[3H]NMS结合存在。残留的[3H]NMS[（3H]NMSb）位点广泛分布于大鼠脑内，代表了主要的毒蕈碱受体群体。[3H]NMSb位点的放射自显影分布与[3H]哌仑西平或[3H]AF-DX 116的分布不对应，表明[3H]NMSb标记的是非M1、非M2毒蕈碱位点。此外，[3H]NMSb的药理学特征在M1位点与[3H]哌仑西平不同，且与M2受体结合位点的特征不一致。尽管我们无法从药理学上区分非M1、非M2结合位点的亚群，但[3H]NMSb位点的解剖分布与m3和m4的联合mRNA分布相对应。
