title: Structure-activity relationship of ibogaine analogs interacting with nicotinic acetylcholine receptors in different conformational states.
abstract: The interaction of ibogaine analogs with nicotinic acetylcholine receptors (AChRs) in different conformational states was studied by functional and structural approaches. The results established that ibogaine analogs: (a) inhibit (±)-epibatidine-induced Ca²⁺ influx in human embryonic muscle AChRs with the following potency sequence (IC(50) in μM): (±)-18-methylaminocoronaridine (5.9±0.3)∼(±)-18-methoxycoronaridine (18-MC) (6.8±0.8)>(-)-ibogaine (17±3)∼(+)-catharanthine (20±1)>(±)-albifloranine (46±13), (b) bind to the [³H]TCP binding site with higher affinity when the Torpedo AChR is in the desensitized state compared to that in the resting state. Similar results were obtained using [³H]18-MC. These and docking results suggest a steric interaction between TCP and ibogaine analogs for the same site, (c) enhance [³H]cytisine binding to resting but not to desensitized AChRs, with desensitizing potencies (apparent EC₅₀) that correlate very well with the pK(i) values in the desensitized state, and (d) there are good bilinear correlations between the ligand molecular volumes and their affinities in the desensitized and resting states, with an optimal volume of ∼345 Å³ for the ibogaine site. These results indicate that the size of the binding sites for ibogaine analogs, located between the serine and nonpolar rings and shared with TCP, is an important structural feature for binding and for inducing desensitization.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, Midwestern University, 19555 N. 59th Ave., Glendale, AZ 85308, USA. harias@midwestern.edu
authors.forename: Hugo R
authors.initials: HR
authors.lastname: Arias
authors.forename: Dominik
authors.initials: D
authors.lastname: Feuerbach
authors.forename: Katarzyna M
authors.initials: KM
authors.lastname: Targowska-Duda
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Jozwiak
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D001392:Azocines / Q000494:pharmacology; D001667:Binding, Competitive; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D003198:Computer Simulation; D004557:Electric Organ / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007050:Ibogaine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016014:Linear Models; D008958:Models, Molecular; D009538:Nicotine / Q000037:antagonists & inhibitors; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology*; D011487:Protein Conformation; D011725:Pyridines / Q000494:pharmacology; D011807:Quinolizines / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014101:Torpedo; D000093843:Quinolizidine Alkaloids
chemical_list: D000470:Alkaloids; D001392:Azocines; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007050:Ibogaine; D009538:Nicotine; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011725:Pyridines; D011807:Quinolizines; D011978:Receptors, Nicotinic; C004712:cytisine; D000093843:Quinolizidine Alkaloids; C082748:epibatidine