title: Contrasting properties of α7-selective orthosteric and allosteric agonists examined on native nicotinic acetylcholine receptors.
abstract: Subtype-selective ligands are important tools for the pharmacological characterisation of neurotransmitter receptors. This is particularly the case for nicotinic acetylcholine receptors (nAChRs), given the heterogeneity of their subunit composition. In addition to agonists and antagonists that interact with the extracellular orthosteric nAChR binding site, a series of nAChR allosteric modulators have been identified that interact with a distinct transmembrane site. Here we report studies conducted with three pharmacologically distinct nicotinic ligands, an orthosteric agonist (compound B), a positive allosteric modulator (TQS) and an allosteric agonist (4BP-TQS). The primary focus of the work described in this study is to examine the suitability of these compounds for the characterisation of native neuronal receptors (both rat and human). However, initial experiments were conducted on recombinant nAChRs demonstrating the selectivity of these three compounds for α7 nAChRs. In patch-clamp recordings on rat primary hippocampal neurons we found that all these compounds displayed pharmacological properties that mimicked closely those observed on recombinant α7 nAChRs. However, it was not possible to detect functional responses with compound B, an orthosteric agonist, using a fluorescent intracellular calcium assay on either rat hippocampal neurons or with human induced pluripotent stem cell-derived neurons (iCell neurons). This is, presumably, due to the rapid desensitisation of α7 nAChR that is induced by orthosteric agonists. In contrast, clear agonist-evoked responses were observed in fluorescence-based assays with the non-desensitising allosteric agonist 4BP-TQS and also when compound B was co-applied with the non-desensitising positive allosteric modulator TQS. In summary, we have demonstrated the suitability of subtype-selective orthosteric and allosteric ligands for the pharmacological identification and characterisation of native nAChRs and the usefulness of ligands that minimise receptor desensitisation for the characterisation of α7 nAChRs in fluorescence-based assays.
authors: Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
authors: JasKiran K
authors: JK
authors: Gill
authors: Anna
authors: A
authors: Chatzidaki
authors: Daniel
authors: D
authors: Ursu
authors: Emanuele
authors: E
authors: Sher
authors: Neil S
authors: NS
authors: Millar
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000166:cytology; D057054:Molecular Imaging; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018722:Nicotinic Agonists / Q000494:pharmacology*; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579167:Chrna7 protein, human; C579165:Chrna7 protein, rat; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D002118:Calcium
references: Biochem Pharmacol. 2007 Oct 15;74(8):1092-101
references: 17662959
references: Trends Neurosci. 2004 Jun;27(6):329-36
references: 15165737
references: J Pharmacol Exp Ther. 2009 Mar;328(3):766-76
references: 19050173
references: J Neurosci. 2011 Sep 28;31(39):13870-9
references: 21957249
references: Mol Pharmacol. 2007 Feb;71(2):389-97
references: 17065235
references: J Pain. 2008 Jul;9(7):580-7
references: 18420461
references: Neuropharmacology. 2011 Dec;61(8):1306-13
references: 21820451
references: J Pharmacol Exp Ther. 2011 Feb;336(2):560-74
references: 21084390
references: Biochem Pharmacol. 2011 Oct 15;82(8):891-903
references: 21741954
references: Br J Pharmacol. 2012 Sep;167(2):421-35
references: 22536953
references: BMC Neurosci. 2012 Jun 22;13:73
references: 22727315
references: Biochem Pharmacol. 2011 Oct 15;82(8):915-30
references: 21575610
references: J Pharmacol Exp Ther. 2009 Jul;330(1):257-67
references: 19389923
references: Curr Top Med Chem. 2010;10(2):144-52
references: 20166959
references: J Neurochem. 2007 Feb;100(4):1089-96
references: 17181555
references: Mol Pharmacol. 2012 May;81(5):710-8
references: 22328718
references: J Mol Neurosci. 1996 Fall;7(3):217-28
references: 8906617
references: Mol Pharmacol. 2012 Nov;82(5):910-7
references: 22874415
references: Proc Natl Acad Sci U S A. 2011 Apr 5;108(14):5867-72
references: 21436053
references: Biochem Pharmacol. 2005 Nov 1;70(9):1267-76
references: 16043127
references: Mol Pharmacol. 2008 Aug;74(2):348-59
references: 18445710
references: J Med Chem. 2008 Feb 28;51(4):701-12
references: 18198823
references: Mol Pharmacol. 2007 Sep;72(3):715-24
references: 17565004
references: J Med Chem. 2005 Jul 28;48(15):4705-45
references: 16033252
references: J Neurosci. 2005 Apr 27;25(17):4396-405
references: 15858066
references: Neuropharmacology. 2009 Jan;56(1):237-46
references: 18723036
references: Psychopharmacology (Berl). 2005 Oct;182(2):214-9
references: 16001118
references: Biochem Pharmacol. 2007 Oct 15;74(8):1155-63
references: 17707779
references: Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14686-91
references: 18791069
references: Mol Pharmacol. 2006 Oct;70(4):1350-7
references: 16822928
references: Neurochem Int. 2000 Jun;36(7):595-645
references: 10771117
references: Brain. 2001 Jul;124(Pt 7):1362-72
references: 11408331
references: J Neurobiol. 2002 Dec;53(4):447-56
references: 12436412
references: PLoS One. 2012;7(2):e32073
references: 22359659
references: J Med Chem. 2011 Dec 8;54(23):7943-61
references: 21919481
references: J Pharmacol Exp Ther. 2007 Oct;323(1):294-307
references: 17625074
references: Neuropharmacology. 2006 Sep;51(3):506-16
references: 16814329
references: Neuron. 1990 Dec;5(6):847-56
references: 1702646