title: Pharmacological differences between immunoisolated native brain and heterologously expressed rat alpha4beta2 nicotinic receptors.
abstract: Native brain and heterologously expressed rat alpha4beta2 nicotinic receptors (in Xenopus oocytes and CV-1 cells) were immunoisolated with the anti-alpha4 antibody mAb 299 and their pharmacological properties were compared using [3H](+/-)epibatidine, the novel N-alkylnicotinium analog N-n-octylnicotinium iodide (NONI), and the ganglionic antagonist trimethaphan (TRM). The equilibrium dissociation constant (K(d)) for [3H](+/-)epibatidine binding to the native and heterologously expressed receptors ranged from 13 to 21 pM. The Hill coefficients for [3H](+/-)epibatidine binding to the native and expressed receptors ranged from 0.8 to 1.1 and were consistent with a single high-affinity site. NONI inhibited 30 pM [3H](+/-)epibatidine binding to the native and expressed receptors with similar potency (IC(50) values of 6-7 microM). However, [3H](+/-)epibatidine dissociated 2-3 times more slowly from the native, than from the expressed receptors and TRM inhibited 30 pM [3H](+/-)epibatidine binding to the native receptors (IC(50) value of 330 microM) less potently than it did to the receptors expressed in oocytes (IC(50) value of 16 microM) or CV-1 cells (IC(50) value of 55 microM). The differences between the native and expressed [3H](+/-)epibatidine dissociation rate constants and IC(50) values for TRM were significant for both host cell types, although the values for the CV-1-expressed receptors were closer to the native ones than were those for the oocyte-expressed receptors. Thus, the epibatidine and trimethaphan binding sites in native and expressed alpha4beta2 receptors appear to have significantly different structural or chemical properties.
authors.affiliation: Division of Biomedical Sciences, University of California, Riverside, CA 92521-0121, USA.
authors.forename: A
authors.initials: A
authors.lastname: Truong
authors.forename: X
authors.initials: X
authors.lastname: Xing
authors.forename: J R
authors.initials: JR
authors.lastname: Forsayeth
authors.forename: L P
authors.initials: LP
authors.lastname: Dwoskin
authors.forename: P A
authors.initials: PA
authors.lastname: Crooks
authors.forename: B N
authors.initials: BN
authors.lastname: Cohen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001667:Binding, Competitive; D001923:Brain Chemistry; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D005260:Female; D005730:Ganglionic Blockers / Q000737:chemistry / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D009525:Niacin / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D009865:Oocytes / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011978:Receptors, Nicotinic / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D014294:Trimethaphan / Q000737:chemistry / Q000494:pharmacology; D014316:Tritium; D014982:Xenopus laevis
chemical_list: D000911:Antibodies, Monoclonal; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005730:Ganglionic Blockers; D018722:Nicotinic Agonists; D011725:Pyridines; D011978:Receptors, Nicotinic; C403531:nicotinic receptor alpha4beta2; D014316:Tritium; D009525:Niacin; D014294:Trimethaphan; C082748:epibatidine