In vitro binding characteristics of [3H]AZ11637326, a novel alpha7-selective neuronal nicotinic receptor agonist radioligand.

Autor: Gordon JC; CNS Discovery, AstraZeneca, Wilmington, Delaware 19850-5437, USA. john.gordon@astrazeneca.com, Phillips E, Gurley DA, Heys JR, Lazor LA, Barthlow HG, Mallamaci MA, Keith RA
Jazyk: angličtina
Zdroj: European journal of pharmacology [Eur J Pharmacol] 2010 Oct 25; Vol. 645 (1-3), pp. 63-9. Date of Electronic Publication: 2010 Jul 30.
DOI: 10.1016/j.ejphar.2010.07.035
Abstrakt: 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.
(Copyright © 2010 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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