Goodwin B P, Anderson G F, Barraco R A
Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Neurosci Lett. 1995 May 19;191(1-2):131-5. doi: 10.1016/0304-3940(95)11563-3.
Crude membrane preparations from the dorsomedial medulla and whole heart of adult rats were used to characterize muscarinic receptors (mChRs) in the nucleus tractus solitarius (NTS). Isotherm binding assays with [3H]quinuclidinyl benzilate ([3H]QNB) indicated a uniform population of muscarinic cholinergic receptors in both tissues with a Kd of 60.3 pM and a Bmax of 401 fmol/mg protein for NTS membranes while heart membranes had a Kd of 56.6 pM and a Bmax of 193 fmol/mg protein. Competitive binding assays with selective muscarinic antagonists on NTS membranes using 80 pM [3H]QNB showed the following relative Ki values consistent with M2 mChRs: atropine, 1.9 nM; methoctramine, 7.7 nM; 4-diphenylacetoxy-N-methylpiperidine methobromide, 9.4 nM; AF-DX 116, 87.6 nM; and pirenzepine, 657 nM. Similarly, two agonists, carbachol and oxotremorine, showed Ki values of 1.82 microM and 0.379 microM, respectively. All of the competitive binding assays exhibited Hill coefficients close to 1.0 and InPlot analysis showed a single binding site for each agonist and antagonist examined.
使用成年大鼠背内侧延髓和全心的粗制膜制剂来表征孤束核（NTS）中的毒蕈碱受体（mChRs）。用[3H]喹核醇基苯甲酸酯（[3H]QNB）进行的等温结合试验表明，两种组织中毒蕈碱胆碱能受体的群体均一，NTS膜的解离常数（Kd）为60.3 pM，最大结合容量（Bmax）为401 fmol/mg蛋白质，而心脏膜的Kd为56.6 pM，Bmax为193 fmol/mg蛋白质。在NTS膜上使用80 pM [3H]QNB，用选择性毒蕈碱拮抗剂进行的竞争性结合试验显示出与M2 mChRs一致的以下相对抑制常数（Ki）值：阿托品，1.9 nM；甲氧基氨甲酰胆碱，7.7 nM；4-二苯基乙酰氧基-N-甲基哌啶甲溴化物，9.4 nM；AF-DX 116，87.6 nM；以及哌仑西平，657 nM。同样，两种激动剂，卡巴胆碱和氧化震颤素，分别显示出Ki值为1.82 microM和0.379 microM。所有竞争性结合试验的希尔系数均接近1.0，InPlot分析表明所检测的每种激动剂和拮抗剂均有单一结合位点。
