In vitro binding characteristics of [³H]AZ11637326, a novel α7-selective neuronal nicotinic receptor agonist radioligand

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• 作者：John C. Gordon ; Eifion Phillips ; David A. Gurley ; J. Richard Heys ; Lois Ann Lazor ; Herbert G. Barthlow ; Mike A. Mallamaci ; Rich A. Keith
• 关键词：Nicotinic ; Radioligand ; Alpha 7
• 刊名：European Journal of Pharmacology
• 出版年：2010
• 出版时间：25 October 2010
• 年：2010
• 卷：645
• 期：1-3
• 页码：63-69
• 全文大小：523 K

文摘

AZ11637326 (5′-(2-fluoro[3,4,5⁻³H3]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 α7 neuronal nicotinic receptor with sub-nanomolar affinity for the human and rat α7 [¹²⁵I]α-bungarotoxin binding sites. In a search for novel agonist radioligands and imaging ligands for the α7 nicotinic receptor, [³H]AZ11637326 was synthesized and its in vitro membrane binding properties were characterized. [³H]AZ11637326 bound to hα7-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 [³H]AZ11637326 strongly correlated with those determined using the classical α7 antagonist [¹²⁵I]α-bungarotoxin, indicating that [³H]AZ11637326 bound to hα7-HEK membranes with an α7 nicotinic-like pharmacology. The K_i values for the standards were on average 2.3-fold lower affinity than determined using the prototypical α7 nicotinic antagonist [¹²⁵I]α-bungarotoxin. Because [³H]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 [¹²⁵I]α-bungarotoxin. [³H]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 α7 nicotinic pharmacology. Overall, these studies indicate that [³H]AZ11637326 is a useful new in vitro probe of the α7 nicotinic receptor agonist site and support its potential utility for in vivo receptor occupancy studies.