CNS Discovery, AstraZeneca, Wilmington, Delaware 19850-5437, USA.
Eur J Pharmacol. 2010 Oct 25;645(1-3):63-9. doi: 10.1016/j.ejphar.2010.07.035. Epub 2010 Jul 30.
AZ11637326 (5'-(2-fluoro[3,4,5(-3)H3]phenyl)-spiro[1-azabicyclo [2.2.2]octane-3,2'(3'H)-furo[2,3-b]pyridine) is a potent partial agonist at the human alpha7 neuronal nicotinic receptor with sub-nanomolar affinity for the human and rat alpha7 [(125)I]alpha-bungarotoxin binding sites. In a search for novel agonist radioligands and imaging ligands for the alpha7 nicotinic receptor, [(3)H]AZ11637326 was synthesized and its in vitro membrane binding properties were characterized. [(3)H]AZ11637326 bound to halpha7-HEK membranes with high specificity (>95%), high affinity (230 pM) and a B(max) of 460 fmol/mg. The rank order of affinity of nicotinic standards determined with [(3)H]AZ11637326 strongly correlated with those determined using the classical alpha7 antagonist [(125)I]alpha-bungarotoxin, indicating that [(3)H]AZ11637326 bound to halpha7-HEK membranes with an alpha7 nicotinic-like pharmacology. The K(i) values for the standards were on average 2.3-fold lower affinity than determined using the prototypical alpha7 nicotinic antagonist [(125)I]alpha-bungarotoxin. Because [(3)H]AZ11637326 specific binding is rapid and reversible, the K(i) values determined using this ligand are more accurate estimates of affinity than those determined using the kinetically sluggish [(125)I]alpha-bungarotoxin. [(3)H]AZ11637326 also bound to a high affinity (510 pM), nicotine-sensitive site on rat hippocampal membranes with an average B(max) of 55 fmol/mg. With rat hippocampal membranes, the nicotine-sensitive fraction of total binding was sub-optimal for a radioligand (~50%), yet the potencies and rank order of the K(i) values for standards were consistent with an alpha7 nicotinic pharmacology. Overall, these studies indicate that [(3)H]AZ11637326 is a useful new in vitro probe of the alpha7 nicotinic receptor agonist site and support its potential utility for in vivo receptor occupancy studies.
AZ11637326（5'-(2-氟[3,4,5(-3)H3]苯基）-螺[1-氮杂双环[2.2.2]辛烷-3,2'-(3'H)-呋喃[2,3-b]吡啶）是一种有效的人类α7 神经元烟碱受体部分激动剂，对人和大鼠α7[（125）I]α-银环蛇毒素结合位点具有亚纳摩尔亲和力。在寻找新型激动剂放射性配体和α7 烟碱受体成像配体的过程中，合成了[（3）H]AZ11637326 并对其体外膜结合特性进行了表征。[（3）H]AZ11637326 与 halpha7-HEK 膜结合具有高度特异性（>95%）、高亲和力（230 pM）和 Bmax 为 460 fmol/mg。用[（3）H]AZ11637326 确定的烟碱标准品的亲和力顺序与用经典的α7 拮抗剂[（125）I]α-银环蛇毒素确定的亲和力顺序密切相关，表明[（3）H]AZ11637326 与 halpha7-HEK 膜结合具有α7 烟碱样药理学。标准品的 K i 值平均比使用原型α7 烟碱拮抗剂[（125）I]α-银环蛇毒素确定的 K i 值低 2.3 倍。由于[（3）H]AZ11637326 的特异性结合快速且可逆，因此使用该配体确定的 K i 值比使用动力学缓慢的[（125）I]α-银环蛇毒素确定的 K i 值更准确地反映亲和力。[（3）H]AZ11637326 还与大鼠海马膜上高亲和力（510 pM）、尼古丁敏感位点结合，平均 Bmax 为 55 fmol/mg。用大鼠海马膜，总结合的尼古丁敏感部分对放射性配体来说并不理想（~50%），但标准品的 K i 值的效价和顺序与α7 烟碱药理学一致。总体而言，这些研究表明[（3）H]AZ11637326 是一种有用的新型α7 烟碱受体激动剂位点的体外探针，并支持其在体内受体占有率研究中的潜在应用。
