title: 2-Fluoro-3-(4-nitro-phenyl)deschloroepibatidine is a novel potent competitive antagonist of human neuronal alpha4beta2 nAChRs.
abstract: A patch-clamp technique in a whole-cell configuration was used to examine the functional activity of recently developed 2-fluoro-3-(substituted phenyl)deschloroepibatidine analogs on two major subtypes of neuronal nicotinic acetylcholine receptors (nAChRs), alpha4beta2 and alpha3beta4, that predominate in the central and peripheral nervous systems, respectively. These epibatidine analogs have been shown previously to possess high binding affinity to alpha4beta2 but not to alpha7 nAChRs and to inhibit nicotine-induced analgesia in behavioral pain tests. The 2-fluoro-3-(4-nitro-phenyl)deschloroepibatidine (4-nitro-PFEB) exhibited the most pronounced antagonist activity among these analogs when tested electrophysiologically on alpha4beta2 nAChRs. It inhibited acetylcholine (ACh)-induced currents in a concentration-dependent manner with an IC(50) value of 0.1 microM and produced complete inhibition at approximately 1 microM concentration. 4-Nitro-PFEB at 0.1 microM concentration produced a 4-fold rightward shift in the ACh concentration-response curve without altering maximum ACh-induced response. This inhibitory effect of 4-nitro-PFEB was voltage- and use-independent and was partially reversible at its 1 microM concentration. The rise and decay kinetics of ACh-induced currents was not altered in the presence of 4-nitro-PFEB. In contrast to alpha4beta2 nAChRs, this compound did not affect alpha3beta4 nAChR-mediated currents at < or =1 microM (IC(50) approximately 63.9 microM). Overall, these functional data agree with previous binding and behavioral findings and suggest collectively that 4-nitro-PFEB is the most effective and selective antagonist of alpha4beta2 versus alpha3beta4 and alpha7 nAChRs among the tested analogs, acting on alpha4beta2 nAChR through a competitive mechanism with a potency 17-fold higher than that of dihydro-beta-erythroidine.
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, 1112 E. Clay Street, P.O. Box 980524, Richmond, VA 23298, USA. gabdrakhmano@mail1.vcu.edu
authors.forename: Galya R
authors.initials: GR
authors.lastname: Abdrakhmanova
authors.forename: M Imad
authors.initials: MI
authors.lastname: Damaj
authors.forename: F Ivy
authors.initials: FI
authors.lastname: Carroll
authors.forename: Billy R
authors.initials: BR
authors.lastname: Martin
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D002478:Cells, Cultured; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D009474:Neurons / Q000187:drug effects*; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000235:genetics
chemical_list: C511623:2-fluoro-3-(4-nitrophenyl)deschloroepibatidine; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018733:Nicotinic Antagonists; D011725:Pyridines; D011978:Receptors, Nicotinic; C403530:nicotinic receptor alpha3beta4; C403531:nicotinic receptor alpha4beta2