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Abstract
The α7-type nicotinic acetylcholine receptor is one of the most unique and interesting of all the members of the cys-loop superfamily of ligand-gated ion channels. Since it was first identified initially as a binding site for α-bungarotoxin in mammalian brain and later as a functional homomeric receptor with relatively high calcium permeability, it has been pursued as a potential therapeutic target for numerous indications, from Alzheimer disease to asthma. In this review, we discuss the history and state of the art for targeting α7 receptors, beginning with subtype-selective agonists and the basic pharmacophore for the selective activation of α7 receptors. A key feature of α7 receptors is their rapid desensitization by standard "orthosteric" agonist, and we discuss insights into the conformational landscape of α7 receptors that has been gained by the development of ligands binding to allosteric sites. Some of these sites are targeted by positive allosteric modulators that have a wide range of effects on the activation profile of the receptors. Other sites are targeted by direct allosteric agonist or antagonists. We include a perspective on the potential importance of α7 receptors for metabotropic as well as ionotropic signaling. We outline the challenges that exist for future development of drugs to target this important receptor and approaches that may be considered to address those challenges. SIGNIFICANCE STATEMENT: The α7-type nicotinic acetylcholine receptor (nAChR) is acknowledged as a potentially important therapeutic target with functional properties associated with both ionotropic and metabotropic signaling. The functional properties of α7 nAChR can be regulated in diverse ways with the variety of orthosteric and allosteric ligands described in this review.
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Affiliation(s)
- Roger L Papke
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
| | - Nicole A Horenstein
- Departments of Pharmacology and Therapeutics (R.L.P) and Chemistry (N.A.H.), University of Florida, Gainesville, FL
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Ouach A, Pin F, Bertrand E, Vercouillie J, Gulhan Z, Mothes C, Deloye JB, Guilloteau D, Suzenet F, Chalon S, Routier S. Design of α7 nicotinic acetylcholine receptor ligands using the (het)Aryl-1,2,3-triazole core: Synthesis, in vitro evaluation and SAR studies. Eur J Med Chem 2016; 107:153-64. [DOI: 10.1016/j.ejmech.2015.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/30/2015] [Accepted: 11/01/2015] [Indexed: 10/22/2022]
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Arunrungvichian K, Fokin VV, Vajragupta O, Taylor P. Selectivity Optimization of Substituted 1,2,3-Triazoles as α7 Nicotinic Acetylcholine Receptor Agonists. ACS Chem Neurosci 2015; 6:1317-30. [DOI: 10.1021/acschemneuro.5b00058] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Affiliation(s)
- Kuntarat Arunrungvichian
- Center
of Excellence for Innovation in Drug Design and Discovery, Faculty
of Pharmacy, Mahidol University, 447 Sri-Ayudhya Road, Bangkok 10400, Thailand
- Department
of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0650, United States
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Valery V. Fokin
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Opa Vajragupta
- Center
of Excellence for Innovation in Drug Design and Discovery, Faculty
of Pharmacy, Mahidol University, 447 Sri-Ayudhya Road, Bangkok 10400, Thailand
| | - Palmer Taylor
- Department
of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0650, United States
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Umana IC, Daniele CA, McGehee DS. Neuronal nicotinic receptors as analgesic targets: it's a winding road. Biochem Pharmacol 2013; 86:1208-14. [PMID: 23948066 DOI: 10.1016/j.bcp.2013.08.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/01/2013] [Accepted: 08/01/2013] [Indexed: 12/12/2022]
Abstract
Along with their well known role in nicotine addiction and autonomic physiology, neuronal nicotinic receptors (nAChRs) also have profound analgesic effects in animal models and humans. This is not a new idea, even in the early 1500s, soon after tobacco was introduced to the new world, its proponents listed pain relief among the beneficial properties of smoking. In recent years, analgesics that target specific nAChR subtypes have shown highly efficacious antinociceptive properties in acute and chronic pain models. To date, the side effects of these drugs have precluded their advancement to the clinic. This review summarizes the recent efforts to identify novel analgesics that target nAChRs, and outlines some of the key neural substrates that contribute to these physiological effects. There remain many unanswered mechanistic questions in this field, and there are still compelling reasons to explore neuronal nAChRs as targets for the relief of pain.
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Affiliation(s)
- Iboro C Umana
- Department of Anesthesia and Critical Care, University of Chicago, Chicago, IL, United States
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Geerts H. α7 Nicotinic receptor modulators for cognitive deficits in schizophrenia and Alzheimer's disease. Expert Opin Investig Drugs 2011; 21:59-65. [PMID: 22047592 DOI: 10.1517/13543784.2012.633510] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
INTRODUCTION Nicotinic receptors (nAChR), a class of ligand-gated ion channels, are attractive targets in a variety of CNS diseases. The low-affinity α7 nAChR modulate the levels of various neurotransmitters, their receptor density is affected in schizophrenia and a single nucleotide polymorphism in the promoter region has been associated with higher risk for schizophrenia. AREAS COVERED This article reviews the scientific rationale for α7 nAChR stimulation and presents a selection of α7-positive modulators that are in development for cognitive deficits, both in Alzheimer's disease and in cognitive impairment associated with schizophrenia. The available clinical information is reviewed and the translational difficulties are discussed. EXPERT OPINION In contrast to preclinical models, clinical proof-of-concept studies so far have not shown clear unequivocal cognitive benefit, although there are signs of clinical efficacy on specific cognitive scales and on negative symptoms. Possible problems associated with the clinical development include the impact of dosage and dosing schedule on the balance between activation and desensitization of the ion channel, the selection of comedication, robust human target engagement data and the choice of clinical readout scales. A better understanding of the human biology of α7 nAChR is essential for improving the successful clinical development of this promising target.
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Jørgensen CG, Frølund B, Kehler J, Jensen AA. Discovery of Benzamide Analogues as a Novel Class of 5-HT3 Receptor Agonists. ChemMedChem 2011; 6:725-36. [DOI: 10.1002/cmdc.201000444] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 11/24/2010] [Indexed: 11/10/2022]
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Abstract
Cys-loop receptors are membrane-spanning neurotransmitter-gated ion channels that are responsible for fast excitatory and inhibitory transmission in the peripheral and central nervous systems. The best studied members of the Cys-loop family are nACh, 5-HT3, GABAA and glycine receptors. All these receptors share a common structure of five subunits, pseudo-symmetrically arranged to form a rosette with a central ion-conducting pore. Some are cation selective (e.g. nACh and 5-HT3) and some are anion selective (e.g. GABAA and glycine). Each receptor has an extracellular domain (ECD) that contains the ligand-binding sites, a transmembrane domain (TMD) that allows ions to pass across the membrane, and an intracellular domain (ICD) that plays a role in channel conductance and receptor modulation. Cys-loop receptors are the targets for many currently used clinically relevant drugs (e.g. benzodiazepines and anaesthetics). Understanding the molecular mechanisms of these receptors could therefore provide the catalyst for further development in this field, as well as promoting the development of experimental techniques for other areas of neuroscience.In this review, we present our current understanding of Cys-loop receptor structure and function. The ECD has been extensively studied. Research in this area has been stimulated in recent years by the publication of high-resolution structures of nACh receptors and related proteins, which have permitted the creation of many Cys loop receptor homology models of this region. Here, using the 5-HT3 receptor as a typical member of the family, we describe how homology modelling and ligand docking can provide useful but not definitive information about ligand interactions. We briefly consider some of the many Cys-loop receptors modulators. We discuss the current understanding of the structure of the TMD, and how this links to the ECD to allow channel gating, and consider the roles of the ICD, whose structure is poorly understood. We also describe some of the current methods that are beginning to reveal the differences between different receptor states, and may ultimately show structural details of transitions between them.
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Peng Y, Zhang Q, Snyder GL, Zhu H, Yao W, Tomesch J, Papke RL, O'Callaghan JP, Welsh WJ, Wennogle LP. Discovery of novel alpha7 nicotinic receptor antagonists. Bioorg Med Chem Lett 2010; 20:4825-30. [PMID: 20638843 PMCID: PMC3000800 DOI: 10.1016/j.bmcl.2010.06.103] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 06/16/2010] [Accepted: 06/21/2010] [Indexed: 11/20/2022]
Abstract
Two distinct families of small molecules were discovered as novel alpha7 nicotinic acetylcholine receptor (nAChR) antagonists by pharmacophore-based virtual screening. These novel antagonists exhibited selectivity for the neuronal alpha7 subtype over other nAChRs and good brain penetration. Neuroprotection was demonstrated by representative compounds 7i and 8 in a mouse seizure-like behavior model induced by the nerve agent diisopropylfluorophosphate (DFP). These novel nAChR antagonists have potential use as antidote for organophosphorus nerve agent intoxication.
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Affiliation(s)
- Youyi Peng
- Intra-Cellular Therapies, Inc., New York, NY, 10032, United States
| | - Qiang Zhang
- Intra-Cellular Therapies, Inc., New York, NY, 10032, United States
| | | | - Hongwen Zhu
- Intra-Cellular Therapies, Inc., New York, NY, 10032, United States
| | - Wei Yao
- Intra-Cellular Therapies, Inc., New York, NY, 10032, United States
| | - John Tomesch
- Intra-Cellular Therapies, Inc., New York, NY, 10032, United States
| | - Roger L. Papke
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, United States
| | - James P. O'Callaghan
- Centers for Disease Control and Prevention-National Institute for Occupational Safety and Health, Morgantown, WV 26505, United States
| | - William J. Welsh
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, United States
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Fitch RW, Spande TF, Garraffo HM, Yeh HJC, Daly JW. Phantasmidine: an epibatidine congener from the ecuadorian poison frog Epipedobates anthonyi. JOURNAL OF NATURAL PRODUCTS 2010; 73:331-7. [PMID: 20337496 PMCID: PMC2866194 DOI: 10.1021/np900727e] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The skin of the Ecuadorian poison frog Epipedobates anthonyi contains the potent nicotinic agonists epibatidine (1) and N-methylepibatidine (3). In addition, a condensed tetracyclic epibatidine congener has been identified with activity at nicotinic acetylcholine receptors, but different selectivity than epibatidine. This rigid tetracycle has been named phantasmidine (4). Phantasmidine has a molecular formula of C(11)H(11)N(2)OCl, shares a chloropyridine moiety with 1, and also contains furan, pyrrolidine, and cyclobutane rings. A combination of GC-MS and GC-FTIR analysis with on-column derivatization, 1D NMR spectroscopy with selective irradiation, and spectral simulation, along with 2D NMR, were used to elucidate the structure from a total sample of approximately 20 microg of HPLC-purified 4 and its corresponding acetamide (5). After synthesis, this novel rigid agonist may serve as a selective probe for beta4-containing nicotinic receptors and potentially lead to useful pharmaceuticals.
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Affiliation(s)
- Richard W Fitch
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892, USA.
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Huang LT, Sherwood JL, Sun YJ, Lodge D, Wang Y. Activation of presynaptic alpha7 nicotinic receptors evokes an excitatory response in hippocampal CA3 neurones in anaesthetized rats: an in vivo iontophoretic study. Br J Pharmacol 2010; 159:554-65. [PMID: 20105181 DOI: 10.1111/j.1476-5381.2009.00529.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE alpha7 Nicotinic receptors have been suggested to play an important role in hippocampal learning and memory. However, the direct action of this receptor subtype on hippocampal pyramidal neurones in vivo has not yet been fully investigated. The availability of selective agonists for alpha7 receptors [AR-R17779 and (R)-(-)-5'-phenylspiro[1-azabicyclo[2.2.2] octane-3,2'-(3'H)furo[2,3-b]pyridine (PSAB-OFP)] has now allowed this role to be investigated. EXPERIMENTAL APPROACH Single-cell extracellular recordings were made from hippocampal CA3 pyramidal neurones in anaesthetized rats. The effects of nicotine, AR-R17779 and PSAB-OFP, applied either systemically or iontophoretically, were studied on the activity of these neurones. KEY RESULTS Intravenous injection of cumulative doses of nicotine and PSAB-OFP induced dose-related, significant increases in neuronal firing in the majority of neurones tested. This excitation could be inhibited by intravenous administration of methyllycaconitine (MLA), a selective alpha7 nicotinic receptor antagonist. Furthermore, iontophoretic application of nicotine, AR-R17779 and PSAB-OFP each evoked current-dependent excitation of most CA3 pyramidal neurones studied, and this excitation was antagonized by co-iontophoretic application of MLA. In addition, the excitation induced by iontophoretic application of nicotine, AR-R17779 or PSAB-OFP was also blocked by co-iontophoretic application of either 6,7-dinitroquinoxaline-2,3-dione (DNQX) or D(2)-2-amino-5-phosphonopentanoate (D-AP5), selective N-methyl-D-aspartic acid (NMDA) and non-NMDA receptor antagonists respectively. CONCLUSIONS AND IMPLICATIONS CA3 pyramidal neurones are modulated by activation of presynaptic alpha7 nicotinic receptors, which, at least in part, enhances glutamate release onto post-synaptic (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid and NMDA receptors on these CA3 neurones. This mechanism probably contributes to the effects of nicotine on hippocampal learning and memory.
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Affiliation(s)
- Lan-Ting Huang
- Institutes of Brain Science and State Key Laboratory for Medical Neurobiology, Fudan University, Shanghai, China
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Roncarati R, Scali C, Comery TA, Grauer SM, Aschmi S, Bothmann H, Jow B, Kowal D, Gianfriddo M, Kelley C, Zanelli U, Ghiron C, Haydar S, Dunlop J, Terstappen GC. Procognitive and neuroprotective activity of a novel alpha7 nicotinic acetylcholine receptor agonist for treatment of neurodegenerative and cognitive disorders. J Pharmacol Exp Ther 2009; 329:459-68. [PMID: 19223665 DOI: 10.1124/jpet.108.150094] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The alpha7 nicotinic acetylcholine receptor (nAChR) is a promising target for treatment of cognitive dysfunction associated with Alzheimer's disease and schizophrenia. Here, we report the pharmacological properties of 5-morpholin-4-yl-pentanoic acid (4-pyridin-3-yl-phenyl)-amide [SEN12333 (WAY-317538)], a novel selective agonist of alpha7 nAChR. SEN12333 shows high affinity for the rat alpha7 receptor expressed in GH4C1 cells (K(i) = 260 nM) and acts as full agonist in functional Ca(2+) flux studies (EC(50) = 1.6 microM). In whole-cell patch-clamp recordings, SEN12333 activated peak currents and maximal total charges similar to acetylcholine (EC(50) = 12 microM). The compound did not show agonist activity at other nicotinic receptors tested and acted as a weak antagonist at alpha3-containing receptors. SEN12333 treatment (3 mg/kg i.p.) improved episodic memory in a novel object recognition task in rats in conditions of spontaneous forgetting as well as cognitive disruptions induced via glutamatergic [5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate); MK-801] or cholinergic (scopolamine) mechanisms. This improvement was blocked by the alpha7-selective antagonist methyllycaconitine, indicating that it is mediated by alpha7 activation. SEN12333 also prevented a scopolamine-induced deficit in a passive avoidance task. In models targeting other cognitive domains, including attention and perceptual processing, SEN12333 normalized the apomorphine-induced deficit of prepulse inhibition. Neuroprotection of SEN12333 was demonstrated in quisqualate-lesioned animals in which treatment with SEN12333 (3 mg/kg/day i.p.) resulted in a significant protection of choline acetyltransferase-positive neurons in the lesioned hemisphere. Cumulatively, our results demonstrate that the novel alpha7 nAChR agonist SEN12333 has procognitive and neuroprotective properties, further demonstrating utility of alpha7 agonists for treatment of neurodegenerative and cognitive disorders.
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Sharma G, Vijayaraghavan S. Nicotinic receptors containing the alpha7 subunit: a model for rational drug design. Curr Med Chem 2009; 15:2921-32. [PMID: 19075644 DOI: 10.2174/092986708786848703] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The neuronal nicotinic receptor has gained considerable recognition as a target, not just for combating drug addiction but also for treating a number of illnesses ranging from neurodegenerative diseases to psychotic disorders like schizophrenia. This recognition has led to a burgeoning field examining the receptor at all levels. A class of nicotinic receptors that contains the alpha7 gene product, apparently as a homomer, illustrates this multidisciplinary approach. Here, we review recent progress in our understanding of this class of receptors based on data from molecular, structural, physiological and patho-physiological studies. These studies have set the stage for rational drug design to combat disorders of the central nervous system. The studies also exemplify the cautious approach needed in developing CNS therapies and the importance of physiology in tempering drug design.
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Affiliation(s)
- G Sharma
- Department of Physiology and Biophysics and Neuroscience Program, University of Colorado, Denver, School of Medicine, Aurora Colorado, USA
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Horenstein NA, Leonik FM, Papke RL. Multiple pharmacophores for the selective activation of nicotinic alpha7-type acetylcholine receptors. Mol Pharmacol 2008; 74:1496-511. [PMID: 18768388 DOI: 10.1124/mol.108.048892] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The activation of heteromeric and homomeric nicotinic acetylcholine receptors was studied in Xenopus laevis oocytes to identify key structures of putative agonist molecules associated with the selective activation of homomeric alpha7 receptors. We observed that selectivity between alpha7 and alpha4beta2 was more readily obtained than selectivity between alpha7 and alpha3beta4. Based on structural comparisons of previously characterized selective and nonselective agonists, we hypothesize at least three chemical motifs exist that, when present in molecules containing an appropriate cationic center, could be associated with the selective activation of alpha7 receptors. We identify the three distinct structural motifs based on prototypical drugs as the choline motif, the tropane motif, and the benzylidene motif. The choline motif involves the location of an oxygen-containing polar group such as a hydroxyl or carbonyl separated by two carbons from the charged nitrogen. The tropane motif provides alpha7-selectivity based on the addition of multiple small hydrophobic groups positioned away from the cationic center in specific orientations. We show that this motif can convert the nonselective agonists quinuclidine and ethyltrimethyl-ammonium to the alpha7-selective analogs methyl-quinuclidine and diethyldimethyl-ammonium, respectively. We have shown previously that the benzylidene group of 3-2,4, dimethoxy-benzylidene anabaseine (GTS-21) converts anabaseine into an alpha7-selective agonist. The benzylidene motif was also applied to quinuclidine to generate another distinct family of alpha7-selective agonists. Our results provide insight for the further development of nicotinic therapeutics and will be useful to direct future experiments with protein structure-based modeling and site-directed mutagenesis.
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Affiliation(s)
- Nicole A Horenstein
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, USA
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Drisdel RC, Sharp D, Henderson T, Hales TG, Green WN. High affinity binding of epibatidine to serotonin type 3 receptors. J Biol Chem 2008; 283:9659-65. [PMID: 17702741 PMCID: PMC2442297 DOI: 10.1074/jbc.m703672200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2007] [Revised: 08/15/2007] [Indexed: 01/22/2023] Open
Abstract
Epibatidine and mecamylamine are ligands used widely in the study of nicotinic acetylcholine receptors (nAChRs) in the central and peripheral nervous systems. In the present study, we find that nicotine blocks only 75% of (125)I-epibatidine binding to rat brain membranes, whereas ligands specific for serotonin type 3 receptors (5-HT(3)Rs) block the remaining 25%. (125)I-Epibatidine binds with a high affinity to native 5-HT(3)Rs of N1E-115 cells and to receptors composed of only 5-HT(3A) subunits expressed in HEK cells. In these cells, serotonin, the 5-HT(3)R-specific antagonist MDL72222, and the 5-HT(3)R agonist chlorophenylbiguanide readily competed with (125)I-epibatidine binding to 5-HT(3)Rs. Nicotine was a poor competitor for (125)I-epibatidine binding to 5-HT(3)Rs. However, the noncompetitive nAChR antagonist mecamylamine acted as a potent competitive inhibitor of (125)I-epibatidine binding to 5-HT(3)Rs. Epibatidine inhibited serotonin-induced currents mediated by endogenous 5-HT(3)Rs in neuroblastoma cell lines and 5-HT(3A)Rs expressed in HEK cells in a competitive manner. Our results demonstrate that 5-HT(3)Rs are previously uncharacterized high affinity epibatidine binding sites in the brain and indicate that epibatidine and mecamylamine act as 5-HT(3)R antagonists. Previous studies that depended on epibatidine and mecamylamine as nAChR-specific ligands, in particular studies of analgesic properties of epibatidine, may need to be reinterpreted with respect to the potential role of 5-HT(3)Rs.
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Affiliation(s)
- Renaldo C Drisdel
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA
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Moore C, Wang Y, Ramage AG. Cardiovascular effects of activation of central alpha7 and alpha4beta2 nAChRs: a role for vasopressin in anaesthetized rats. Br J Pharmacol 2008; 153:1728-38. [PMID: 18297099 PMCID: PMC2438263 DOI: 10.1038/bjp.2008.47] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Revised: 01/10/2008] [Accepted: 01/22/2008] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Central application of nicotine causes the release of vasopressin and affects blood pressure. Involvement of the 5 neuronal nicotinic receptor groups, alpha2(*)-alpha7(*) in these effects is unknown. The availability of selective agonists for alpha7 (PSAB-OFP) and alpha4beta2 (TC-2559) nACh receptors allowed their role to be investigated. EXPERIMENTAL APPROACH Recordings were made of arterial blood pressure, heart rate and renal sympathetic nerve activity in anaesthetized male rats with neuromuscular blockade and artificial respiration. Effects of the agonists, PSAB-OFP (1-10 micromol kg(-1)) and TC-2559 (1-10 micromol kg(-1)) on these variables given intracerebroventricularly (i.c.v.) and intracisternally (i.c.) in the presence or absence of the antagonists, DhbetaE (10 micromol kg(-1)) and MLA (0.5 micromol kg(-1)), for the appropriate nicotinic receptor subtypes, respectively, and a V(1) receptor antagonist, given i.v. or centrally, were investigated. KEY RESULTS Both agonists given i.c.v. caused a delayed rise in blood pressure and renal nerve activity which could be blocked only with the appropriate antagonist. The agonists had an earlier onset of action when given i.c., favouring the brainstem as the major site of action. The effects of these agonists were also attenuated by the V(1) receptor antagonist given i.v. and blocked when this antagonist was given centrally. Antagonists had no effect on baseline variables. CONCLUSIONS AND IMPLICATIONS Activation of alpha4beta2 and alpha7 receptors in the brainstem is mainly responsible for the cardiovascular effects of activating these receptors, which have a similar profile of action. These actions, although independent, are mediated by the central release of vasopressin.
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Affiliation(s)
- C Moore
- Department of Pharmacology, University College London, London, UK
| | - Y Wang
- Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Fudan University, Shanghai, China
| | - A G Ramage
- Department of Pharmacology, University College London, London, UK
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Tietje KR, Anderson DJ, Bitner RS, Blomme EA, Brackemeyer PJ, Briggs CA, Browman KE, Bury D, Curzon P, Drescher KU, Frost JM, Fryer RM, Fox GB, Gronlien JH, Håkerud M, Gubbins EJ, Halm S, Harris R, Helfrich RJ, Kohlhaas KL, Law D, Malysz J, Marsh KC, Martin RL, Meyer MD, Molesky AL, Nikkel AL, Otte S, Pan L, Puttfarcken PS, Radek RJ, Robb HM, Spies E, Thorin-Hagene K, Waring JF, Ween H, Xu H, Gopalakrishnan M, Bunnelle WH. Preclinical Characterization of A-582941: A Novel α7 Neuronal Nicotinic Receptor Agonist with Broad Spectrum Cognition-Enhancing Properties. CNS Neurosci Ther 2008. [DOI: 10.1111/j.1755-5949.2008.00037.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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17
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Tietje KR, Anderson DJ, Bitner RS, Blomme EA, Brackemeyer PJ, Briggs CA, Browman KE, Bury D, Curzon P, Drescher KU, Frost JM, Fryer RM, Fox GB, Gronlien JH, Håkerud M, Gubbins EJ, Halm S, Harris R, Helfrich RJ, Kohlhaas KL, Law D, Malysz J, Marsh KC, Martin RL, Meyer MD, Molesky AL, Nikkel AL, Otte S, Pan L, Puttfarcken PS, Radek RJ, Robb HM, Spies E, Thorin‐Hagene K, Waring JF, Ween H, Xu H, Gopalakrishnan M, Bunnelle WH. Preclinical characterization of A-582941: a novel alpha7 neuronal nicotinic receptor agonist with broad spectrum cognition-enhancing properties. CNS Neurosci Ther 2008; 14:65-82. [PMID: 18482100 PMCID: PMC6494002 DOI: 10.1111/j.1527-3458.2008.00037.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Among the diverse sets of nicotinic acetylcholine receptors (nAChRs), the alpha7 subtype is highly expressed in the hippocampus and cortex and is thought to play important roles in a variety of cognitive processes. In this review, we describe the properties of a novel biaryl diamine alpha7 nAChR agonist, A-582941. A-582941 was found to exhibit high-affinity binding and partial agonism at alpha7 nAChRs, with acceptable pharmacokinetic properties and excellent distribution to the central nervous system (CNS). In vitro and in vivo studies indicated that A-582941 activates signaling pathways known to be involved in cognitive function such as ERK1/2 and CREB phosphorylation. A-582941 enhanced cognitive performance in behavioral models that capture domains of working memory, short-term recognition memory, memory consolidation, and sensory gating deficit. A-582941 exhibited a benign secondary pharmacodynamic and tolerability profile as assessed in a battery of assays of cardiovascular, gastrointestinal, and CNS function. The studies summarized in this review collectively provide preclinical validation that alpha7 nAChR agonism offers a mechanism with potential to improve cognitive deficits associated with various neurodegenerative and psychiatric disorders.
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Affiliation(s)
- Karin R. Tietje
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - David J. Anderson
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - R. Scott Bitner
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Eric A. Blomme
- Department of Cellular and Molecular Toxicology, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Paul J. Brackemeyer
- Manufacturing Science and Technology, Global Pharmaceutical Operations, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Clark A. Briggs
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Kaitlin E. Browman
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Dagmar Bury
- Toxicology & Pathology, Global Pharmaceutical Research and Development, Abbott Laboratories, Ludwigshafen, Germany
| | - Peter Curzon
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Karla U. Drescher
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Ludwigshafen, Germany
| | - Jennifer M. Frost
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Ryan M. Fryer
- Department of Integrative Pharmacology, Global Pharmaceutical Research & Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Gerard B. Fox
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Jens Halvard Gronlien
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Monika Håkerud
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Earl J. Gubbins
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Sabine Halm
- Toxicology & Pathology, Global Pharmaceutical Research and Development, Abbott Laboratories, Ludwigshafen, Germany
| | - Richard Harris
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Rosalind J. Helfrich
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Kathy L. Kohlhaas
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Devalina Law
- Manufacturing Science and Technology, Global Pharmaceutical Operations, Abbott Laboratories, Abbott Park, Illinois, USA
| | - John Malysz
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Kennan C. Marsh
- Pharmacokinetics and Metabolism, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Ilinois, USA
| | - Ruth L. Martin
- Department of Integrative Pharmacology, Global Pharmaceutical Research & Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Michael D. Meyer
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Angela L. Molesky
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Arthur L. Nikkel
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Stephani Otte
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Liping Pan
- Pharmacokinetics and Metabolism, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Ilinois, USA
| | - Pamela S. Puttfarcken
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Richard J. Radek
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Holly M. Robb
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Eva Spies
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Ludwigshafen, Germany
| | - Kirsten Thorin‐Hagene
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Jeffrey F. Waring
- Department of Cellular and Molecular Toxicology, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Hilde Ween
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - Hongyu Xu
- Pharmacokinetics and Metabolism, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Ilinois, USA
| | - Murali Gopalakrishnan
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
| | - William H. Bunnelle
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois, USA
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18
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Feuerbach D, Nozulak J, Lingenhoehl K, McAllister K, Hoyer D. JN403, in vitro characterization of a novel nicotinic acetylcholine receptor alpha7 selective agonist. Neurosci Lett 2007; 416:61-5. [PMID: 17314009 DOI: 10.1016/j.neulet.2007.01.045] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2006] [Revised: 01/15/2007] [Accepted: 01/21/2007] [Indexed: 11/30/2022]
Abstract
This report describes the in vitro features of a novel selective nicotinic acetylcholine receptor (nAChR) alpha7 agonist, JN403, (S)-(1-Aza-bicyclo[2.2.2]oct-3-yl)-carbamic acid (S)-1-(2-fluoro-phenyl)-ethyl ester. JN403 was evaluated in a number of in vitro systems of different species, at recombinant receptors using radioligand binding, signal transduction and electrophysiological studies. When using [(125)I] alpha-bungarotoxin (alpha-BTX) as a radioligand, JN403 has high affinity for human recombinant nAChR alpha7 (pK(D)=6.7). Functionally, JN403 is a partial and potent agonist at human nAChR alpha7. The compound stimulates calcium influx in GH3 cells recombinantly expressing the human nAChR with an pEC(50) of 7.0 and an E(max) of 85% (compared to the full agonist epibatidine). In Xenopus oocytes expressing human nAChR alpha7 JN403 induces inward currents with an pEC(50) of 5.7 and an E(max) of 55%. In both recombinant systems JN403 is a partial agonist and the agonistic effects are blocked after pre-administration of methyllycaconitine (MLA, 100nM), a nAChR alpha7 antagonist. In functional calcium influx assays, JN403 displays a significantly lower potency for other subtypes of human nAChRs like alpha4beta2, alpha3beta4, alpha1beta1gammadelta as well as 5HT(3) receptors when tested functionally as an antagonist (pIC(50)<4.8) and is devoid of agonistic activity (pEC(50)<4). Similarly, JN403 shows low binding activity at a wide panel of neurotransmitter receptors. Thus, JN403 is a potent and selective nAChR alpha7 agonist and will be a useful tool for the characterization of nAChR alpha7 mediated effects both in vitro and in vivo.
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Affiliation(s)
- Dominik Feuerbach
- Neuroscience Research, Novartis Institutes for BioMedical Research, Basel, Switzerland.
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19
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Young GT, Broad LM, Zwart R, Astles PC, Bodkin M, Sher E, Millar NS. Species selectivity of a nicotinic acetylcholine receptor agonist is conferred by two adjacent extracellular beta4 amino acids that are implicated in the coupling of binding to channel gating. Mol Pharmacol 2006; 71:389-97. [PMID: 17065235 DOI: 10.1124/mol.106.030809] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
5-(Trifluoromethyl)-6-(1-methyl-azepan-4-yl)methyl-1H-quinolin-2-one (TMAQ) is a novel nicotinic acetylcholine receptor (nAChR) agonist with strong selectivity for beta4-containing receptors. TMAQ also exhibits remarkable species selectivity, being a potent agonist of nAChRs containing the human beta4 subunit but having no detectable agonist activity on nAChRs containing the rat beta4 subunit. With the aim of identifying subunit domains and individual amino acids, which contribute to the species selectivity of TMAQ, a series of chimeric and mutated beta4 subunits has been constructed. Recombinant receptors containing wild-type, chimeric, or mutated beta4 subunits have been examined by radioligand binding, intracellular calcium assays, and electrophysiological recording. Two adjacent amino acids located within the extracellular loop D domain of the beta4 subunit (amino acids 55 and 56) have been identified as playing a critical role in determining the agonist potency of TMAQ. Mutagenesis of these two residues within the rat beta4 subunit to the corresponding amino acids in the human beta4 subunit (S55N and I56V mutations) confers sensitivity to TMAQ. The converse mutations in the human beta4 subunit (N55S and V56I) largely abolish sensitivity to TMAQ. In contrast, these mutations have little or no effect on sensitivity to the nonselective nicotinic agonist epibatidine. Despite acting as a potent agonist of human beta4-containing nAChRs, TMAQ acts as an antagonist of rat beta4-containing receptors. Our experimental data, together with homology models of the rat and human alpha3beta4 nAChRs, suggest that amino acids 55 and 56 may be involved in the coupling of agonist binding and channel gating.
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Affiliation(s)
- Gareth T Young
- Department of Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK
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20
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Tatsumi R, Fujio M, Takanashi SI, Numata A, Katayama J, Satoh H, Shiigi Y, Maeda JI, Kuriyama M, Horikawa T, Murozono T, Hashimoto K, Tanaka H. (R)-3‘-(3-Methylbenzo[b]thiophen-5-yl)spiro[1-azabicyclo[2,2,2]octane-3,5‘-oxazolidin]-2‘-one, a Novel and Potent α7 Nicotinic Acetylcholine Receptor Partial Agonist Displays Cognitive Enhancing Properties. J Med Chem 2006; 49:4374-83. [PMID: 16821797 DOI: 10.1021/jm060249c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent studies have suggested that the alpha7 nicotinic acetylcholine receptors play important roles in learning and memory. Herein, we describe our research of the structure-activity relationships (SAR) in a series of (S)-spiro[1-azabicyclo[2.2.2]octane-3,5'-oxazolidin]-2'-ones bearing various bicyclic moieties to discover novel alpha7 receptor agonists. Through a number of SAR studies on the series, we have found out that inhibition of CYP 2D6 isozyme, which was a primary obstacle for the previously identified compound, was avoidable by the introduction of bicyclic moieties. Chemical optimization of the series led to the identification of a novel and potent alpha7 nicotinic acetylcholine receptor partial agonist 23. This compound not only possessed high binding affinity (K(i) = 3 nmol/L) toward the alpha7 receptor but also showed agonistic activity even at a concentration of 0.1 micromol/L. In addition, compound 23 improved cognition in several rat models, which might suggest the potential of the alpha7 receptor partial agonist for the treatment of neurological disorders including cognitive dysfunction.
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Affiliation(s)
- Ryo Tatsumi
- Pharmaceuticals Research Unit, Research & Development Division, Mitsubishi Pharma Corporation, Yokohama, Kanagawa 227-0033, Japan
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21
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Alexander SPH, Mathie A, Peters JA. Acetylcholine (nicotinic). Br J Pharmacol 2006. [DOI: 10.1038/sj.bjp.0706572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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22
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Wang Y, Sherwood JL, Miles CP, Whiffin G, Lodge D. TC-2559 excites dopaminergic neurones in the ventral tegmental area by stimulating alpha4beta2-like nicotinic acetylcholine receptors in anaesthetised rats. Br J Pharmacol 2006; 147:379-90. [PMID: 16402043 PMCID: PMC1616994 DOI: 10.1038/sj.bjp.0706621] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Revised: 10/14/2005] [Accepted: 11/15/2005] [Indexed: 11/09/2022] Open
Abstract
1. The in vivo effects of a selective partial agonist for neuronal nicotinic acetylcholine receptor (nAChRs) alpha4beta2 subtype, TC-2559, characterised recently in in vitro preparations, have been profiled. The brain bioavailability of TC-2559 and its effects on the spontaneous firing and bursting properties of the dopaminergic (DAergic) neurones recorded extracellularly in the ventral tegmental area (VTA) were studied following systemic administration in anaesthetised rats. 2. Cumulative doses of TC-2559 (0.021-1.36 mg kg(-1), i.v.) increased both the firing and bursting activities of VTA DA neurones. The effect of bolus doses of TC-2559 of 0.66 or 1.32 mg kg(-1), i.v., was approximately equivalent to that of 0.0665 mg kg(-1), i.v. nicotine. 3. The excitation evoked by both nicotine and TC-2559 was fully reversed by DHbetaE (0.39-0.77 mg kg(-1), i.v.), an alpha4beta2-subtype-preferring nicotinic antagonist, and application of nicotine after DHbetaE failed to evoke any excitation. MLA (0.23 mg kg(-1), i.v.), an alpha7 selective antagonist, failed to alter TC-2559-evoked excitation and bursting activities, and a novel alpha7 agonist (PSAB-OFP; 0.23 mg kg(-1), i.v.) was also without effect. 4. The present results indicated that TC-2559 fully mimics nicotine by increasing both the excitability and bursting behaviour of VTA DA neurones, effects that are predominantly due to activation of alpha4beta2-like nAChRs. 5. TC-2559 has been demonstrated to be a useful in vivo pharmacological tool for studying the alpha4beta2 subtype of nicotinic receptor.
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Affiliation(s)
- Yun Wang
- Lilly Research Centre, Eli Lilly & Co. Ltd, Erl Wood Manor, Sunninghill Road, Windlesham, Surrey GU20 6PH.
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23
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Papke RL. Estimation of both the potency and efficacy of alpha7 nAChR agonists from single-concentration responses. Life Sci 2005; 78:2812-9. [PMID: 16343553 DOI: 10.1016/j.lfs.2005.11.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Accepted: 11/02/2005] [Indexed: 11/27/2022]
Abstract
The assessment of functional properties is a crucial step in the screening of potential new drug candidates. The development of moderate to high throughput electrophysiological recording systems such as OpusXpress (Molecular Devices) has facilitated the process of testing new drugs to a large degree. However, while the simple screening of multiple drugs at a single concentration identifies "hits" and "misses", the generation of full concentration-response studies is still a bottleneck in drug development. The alpha7 nicotinic acetylcholine receptor displays a unique concentration dependence of response kinetics which permits estimates of EC50 and Imax values for experimental drugs to be generated from single-concentration responses. This method is based on the analysis of 13 different concentration-response studies utilizing either human or rat alpha7 nAChR. Each experimental response was first normalized to an ACh control, and then a transformation of the pooled data was generated which, based on the relationship between the net charge and peak current to their respective EC50 values defined the "functional concentration" (the test concentration relative to the EC50 for the given agonist). At low functional concentrations, net charge is large relative to peak current amplitude and at higher functional concentration this relationship reverses. For any single-concentration response, the ratio of net charge to peak current can be used to estimate functional concentration. Efficacy can then be estimated by comparing the observed (net charge) response to the expected value for a full agonist at the estimated functional concentration. This extended analysis, combined with automated recording methods, should greatly increase the efficiency with which promising new drug candidates can be characterized.
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Affiliation(s)
- Roger L Papke
- Pharmacology and Therapeutics 100267 JHMHSC, 1600 SW Archer Rd. University of Florida, College of Medicine Gainesville, FL 32610, USA.
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24
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25
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Baker SR, Boot J, Brunavs M, Dobson D, Green R, Hayhurst L, Keenan M, Wallace L. High affinity ligands for the α7 nicotinic receptor that show no cross-reactivity with the 5-HT3 receptor. Bioorg Med Chem Lett 2005; 15:4727-30. [PMID: 16165358 DOI: 10.1016/j.bmcl.2005.07.070] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Revised: 07/14/2005] [Accepted: 07/26/2005] [Indexed: 11/22/2022]
Abstract
Potent and selective ligands of the alpha7 nicotinic acetylcholine receptor are required to understand the pharmacological effect of alpha7 activation. A common cross-reactivity occurs with serotonergic 5-HT3 receptors with which alpha7 receptors have a high sequence homology. We demonstrate that certain quinuclidine 3-biaryl carboxamides are high affinity alpha7 ligands with an excellent binding selectivity over 5-HT3 receptors.
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Affiliation(s)
- S Richard Baker
- Eli Lilly and Company Ltd., Lilly Research Centre, Erl Wood Manor, Windlesham, Surrey, GU20 6PH, UK
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26
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Jensen AA, Frølund B, Liljefors T, Krogsgaard-Larsen P. Neuronal nicotinic acetylcholine receptors: structural revelations, target identifications, and therapeutic inspirations. J Med Chem 2005; 48:4705-45. [PMID: 16033252 DOI: 10.1021/jm040219e] [Citation(s) in RCA: 433] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anders A Jensen
- Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
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27
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Daly JW. Nicotinic Agonists, Antagonists, and Modulators From Natural Sources. Cell Mol Neurobiol 2005; 25:513-52. [PMID: 16075378 DOI: 10.1007/s10571-005-3968-4] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Accepted: 04/14/2004] [Indexed: 10/25/2022]
Abstract
1. Acetylcholine receptors were initially defined as nicotinic or muscarinic, based on selective activation by two natural products, nicotine and muscarine. Several further nicotinic agonists have been discovered from natural sources, including cytisine, anatoxin, ferruginine, anabaseine, epibatidine, and epiquinamide. These have provided lead structures for the design of a wide range of synthetic agents. 2. Natural sources have also provided competitive nicotinic antagonists, such as the Erythrina alkaloids, the tubocurarines, and methyllycaconitine. Noncompetitive antagonists, such as the histrionicotoxins, various izidines, decahydroquinolines, spiropyrrolizidine oximes, pseudophrynamines, ibogaine, strychnine, cocaine, and sparteine have come from natural sources. Finally, galanthamine, codeine, and ivermectin represent positive modulators of nicotinic function, derived from natural sources. 3. Clearly, research on acetylcholine receptors and functions has been dependent on key natural products and the synthetic agents that they inspired.
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Affiliation(s)
- John W Daly
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892, USA.
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28
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Bunnelle WH, Decker MW. Neuronal nicotinic acetylcholine receptor ligands as potential analgesics. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.13.7.1003] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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29
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Young JW, Finlayson K, Spratt C, Marston HM, Crawford N, Kelly JS, Sharkey J. Nicotine improves sustained attention in mice: evidence for involvement of the alpha7 nicotinic acetylcholine receptor. Neuropsychopharmacology 2004; 29:891-900. [PMID: 14970827 DOI: 10.1038/sj.npp.1300393] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In humans, nicotine has been shown to improve attention in both normal and impaired individuals. Observations in rats reflect some, but not all aspects of the nicotine-induced improvements in humans. To date these findings have not been replicated in mice. To examine the effect of nicotine on sustained attention in mice, we have established a version of the 5-choice serial reaction-time (5-CSR) task with graded levels of difficulty, based upon spatial displacement and a variable intertrial interval. Using this paradigm, microgram doses of nicotine produced a consistent reduction in the level of omissions and an improvement in proportion correct in normal mice. This improvement in sustained attention was made irrespectively of whether mice had previously received nicotine. In an attempt to elucidate which nicotinic acetylcholine receptor (nAChR) subtype(s) mediate this effect, we examined the performance of alpha7 nAChR knockout (KO) mice in the 5-CSR task. alpha7 nAChR KO mice not only acquired the task more slowly than their wild-type littermates, but on attaining asymptotic performance, they exhibited a higher level of omissions. In conclusion, by increasing the level of task difficulty, the performance of mice was maintained at sufficiently low levels to allow a demonstrable improvement in performance upon nicotine administration. Furthermore, as alpha7 KO mice are clearly impaired in the acquisition and asymptotic performance of this task, the alpha7 nAChR may be involved in mediating these effects of nicotine.
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Affiliation(s)
- Jared W Young
- Fujisawa Institute of Neuroscience, Division of Neuroscience, University of Edinburgh, Edinburgh, UK
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