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Frara N, Barbe MF, Giaddui D, Porreca DS, Braverman AS, Tiwari E, Ahmad A, Brown JM, Johnston BR, Bazarek SF, Ruggieri MR. Nerve transfer for restoration of lower motor neuron-lesioned bladder, urethral, and anal sphincter function in a dog model. Part 3. nicotinic receptor characterization. Am J Physiol Regul Integr Comp Physiol 2023; 325:R344-R358. [PMID: 37458380 PMCID: PMC10642361 DOI: 10.1152/ajpregu.00273.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 06/09/2023] [Accepted: 07/05/2023] [Indexed: 09/05/2023]
Abstract
Very little is known about the physiological role of nicotinic receptors in canine bladders, although functional nicotinic receptors have been reported in bladders of many species. Utilizing in vitro methods, we evaluated nicotinic receptors mediating bladder function in dogs: control (9 female and 11 male normal controls, 5 sham operated), Decentralized (9 females, decentralized 6-21 mo), and obturator-to-pelvic nerve transfer reinnervated (ObNT-Reinn; 9 females; decentralized 9-13 mo, then reinnervated with 8-12 mo recovery). Muscle strips were collected, mucosa-denuded, and mounted in muscle baths before incubation with neurotransmitter antagonists, and contractions to the nicotinic receptor agonist epibatidine were determined. Strip response to epibatidine, expressed as percent potassium chloride, was similar (∼35% in controls, 30% in Decentralized, and 24% in ObNT-Reinn). Differentially, epibatidine responses in Decentralized and ObNT-Reinn bladder strips were lower than controls after tetrodotoxin (TTX, a sodium channel blocker that inhibits axonal action potentials). Yet, in all groups, epibatidine-induced strip contractions were similarly inhibited by mecamylamine and hexamethonium (ganglionic nicotinic receptor antagonists), SR 16584 (α3β4 neuronal nicotinic receptor antagonist), atracurium and tubocurarine (neuromuscular nicotinic receptor antagonists), and atropine (muscarinic receptor antagonist), indicating that nicotinic receptors (particularly α3β4 subtypes), neuromuscular and muscarinic receptors play roles in bladder contractility. In control bladder strips, since tetrodotoxin did not inhibit epibatidine contractions, nicotinic receptors are likely located on nerve terminals. The tetrodotoxin inhibition of epibatidine-induced contractions in Decentralized and ObNT-Reinn suggests a relocation of nicotinic receptors from nerve terminals to more distant axonal sites, perhaps as a compensatory mechanism to recover bladder function.
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Affiliation(s)
- Nagat Frara
- Center for Translational Medicine at the Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Mary F Barbe
- Center for Translational Medicine at the Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Dania Giaddui
- Center for Translational Medicine at the Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Danielle S Porreca
- Department of Neurology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, United States
| | - Alan S Braverman
- Center for Translational Medicine at the Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
| | - Ekta Tiwari
- School of Engineering, Brown University, Providence, Rhode Island, United States
| | - Attia Ahmad
- Cooper Medical School of Rowan University, Camden, New Jersey, United States
| | - Justin M Brown
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, United States
| | - Benjamin R Johnston
- Department of Neurosurgery, Brigham & Women's Hospital, Boston, Massachusetts, United States
| | - Stanley F Bazarek
- Department of Neurosurgery, Brigham & Women's Hospital, Boston, Massachusetts, United States
| | - Michael R Ruggieri
- Center for Translational Medicine at the Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania, United States
- Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts, United States
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2
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Trebesova H, Olivero G, Marchi M, Grilli M. The Anti-Aggregative Peptide KLVFF Mimics Aβ1-40 in the Modulation of Nicotinic Receptors: Implications for Peptide-Based Therapy. Biomedicines 2022; 10:biomedicines10092231. [PMID: 36140331 PMCID: PMC9496455 DOI: 10.3390/biomedicines10092231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 08/31/2022] [Accepted: 09/05/2022] [Indexed: 12/02/2022] Open
Abstract
In recent years, the inhibition of beta-amyloid (Aβ) aggregation has emerged as a potential strategy for Alzheimer’s disease. KLVFF, a small peptide corresponding to the aminoacidic sequence 16-20 of Aβ, reduces Aβ fibrillation dose dependently. Therefore, the toxic and functional characterization of its brain activity is fundamental for clarifying its potential therapeutic role. Accordingly, we studied the modulatory role of KLVFF on the cholinergic receptors regulating dopamine and noradrenaline release in rat synaptosomes. Nicotinic receptors on dopaminergic nerve terminals in the nucleus acccumbens are inhibited by KLVFF, which closely resembles full-length Aβ1-40. Moreover, KLVFF entrapped in synaptosomes does not modify the nicotinic receptor’s function, suggesting that external binding to the receptor is required for its activity. The cholinergic agent desformylflustrabromine counteracts the KLVFF effect. Remarkably, muscarinic receptors on dopaminergic terminals and nicotinic receptors regulating noradrenaline release in the hippocampus are completely insensitive to KLVFF. Based on our findings, KLVFF mimics Aβ1-40 as a negative modulator of specific nicotinic receptor subtypes affecting dopamine transmission in the rat brain. Therefore, new pharmacological strategies using the anti-aggregative properties of KLVFF need to be evaluated for potential interference with nicotinic receptor-mediated transmission.
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Alijevic O, Jaka O, Alzualde A, Maradze D, Xia W, Frentzel S, Gifford AN, Peitsch MC, Hoeng J, Koshibu K. Differentiating the Neuropharmacological Properties of Nicotinic Acetylcholine Receptor-Activating Alkaloids. Front Pharmacol 2022; 13:668065. [PMID: 35392565 PMCID: PMC8980233 DOI: 10.3389/fphar.2022.668065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 02/21/2022] [Indexed: 11/13/2022] Open
Abstract
Alkaloids that target nicotinic acetylcholine receptors (nAChR) are of great interest because of the critical role they play in mood and anxiety. However, understanding of the neuropharmacological effects of nicotinic alkaloids, such as cotinine and anatabine, is very limited. In this study, we investigated the neuropharmacological effects of three naturally occurring alkaloids-nicotine, cotinine, and anatabine-in vitro and in vivo. A single injection of nicotine induced anxiolytic-like behavioral features in mice by using the SmartCube® behavioral profiling system, while cotinine and anatabine had no detectable effect. The results were corroborated by using the zebrafish novel tank test (NTT), which showed a profound anxiolytic-like effect induced by multiple doses of nicotine after a single 20-min treatment. When the regulation of dopamine and norepinephrine release-the neurotransmitter systems relevant for anxiety-were examined in vitro, we found that nicotine stimulated the release of both norepinephrine and dopamine, while cotinine and anatabine mainly stimulated the dopamine release. The molecular targets of nicotine were confirmed to be nAChRs with its most potent activities against α4β2 and α6/3β2β3 subtypes in vitro. Anatabine was a weaker agonist for these receptors than nicotine. Cotinine was the least potent nAChR compound, only being able to activate α4β2 and α6/3β2β3 subtypes at high doses and no detectable activities against α3β4 and α7 subtypes at the concentrations tested. The observed effects were unlikely due to the off-target effect, because these alkaloids did not bind or regulate >160 other molecular targets in vitro. Thus, the present results suggest that natural nicotinic alkaloids can induce an anxiolytic-like behavior in nonclinical animal models, potency of which may depend on the activation of various nAChRs and regulation of various neurotransmitter systems. Further investigations would help understand their effects on humans, because non-clinical studies should not be taken as a direct indication for human behavior and nicotine is not risk free.
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Affiliation(s)
- Omar Alijevic
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | | | | | - Diana Maradze
- Gifford Bioscience Ltd., The BioHub Birmingham, Birmingham, United Kingdom
| | - Wenhao Xia
- PMI R&D, Philip Morris International Research Laboratories Pte. Ltd., Singapore, Singapore
| | - Stefan Frentzel
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Andrew N. Gifford
- Gifford Bioscience Ltd., The BioHub Birmingham, Birmingham, United Kingdom
| | | | - Julia Hoeng
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
| | - Kyoko Koshibu
- PMI R&D, Philip Morris Products S.A., Neuchâtel, Switzerland
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Wills L, Ables JL, Braunscheidel KM, Caligiuri SPB, Elayouby KS, Fillinger C, Ishikawa M, Moen JK, Kenny PJ. Neurobiological Mechanisms of Nicotine Reward and Aversion. Pharmacol Rev 2022; 74:271-310. [PMID: 35017179 PMCID: PMC11060337 DOI: 10.1124/pharmrev.121.000299] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 08/24/2021] [Indexed: 12/27/2022] Open
Abstract
Neuronal nicotinic acetylcholine receptors (nAChRs) regulate the rewarding actions of nicotine contained in tobacco that establish and maintain the smoking habit. nAChRs also regulate the aversive properties of nicotine, sensitivity to which decreases tobacco use and protects against tobacco use disorder. These opposing behavioral actions of nicotine reflect nAChR expression in brain reward and aversion circuits. nAChRs containing α4 and β2 subunits are responsible for the high-affinity nicotine binding sites in the brain and are densely expressed by reward-relevant neurons, most notably dopaminergic, GABAergic, and glutamatergic neurons in the ventral tegmental area. High-affinity nAChRs can incorporate additional subunits, including β3, α6, or α5 subunits, with the resulting nAChR subtypes playing discrete and dissociable roles in the stimulatory actions of nicotine on brain dopamine transmission. nAChRs in brain dopamine circuits also participate in aversive reactions to nicotine and the negative affective state experienced during nicotine withdrawal. nAChRs containing α3 and β4 subunits are responsible for the low-affinity nicotine binding sites in the brain and are enriched in brain sites involved in aversion, including the medial habenula, interpeduncular nucleus, and nucleus of the solitary tract, brain sites in which α5 nAChR subunits are also expressed. These aversion-related brain sites regulate nicotine avoidance behaviors, and genetic variation that modifies the function of nAChRs in these sites increases vulnerability to tobacco dependence and smoking-related diseases. Here, we review the molecular, cellular, and circuit-level mechanisms through which nicotine elicits reward and aversion and the adaptations in these processes that drive the development of nicotine dependence. SIGNIFICANCE STATEMENT: Tobacco use disorder in the form of habitual cigarette smoking or regular use of other tobacco-related products is a major cause of death and disease worldwide. This article reviews the actions of nicotine in the brain that contribute to tobacco use disorder.
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Affiliation(s)
- Lauren Wills
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Jessica L Ables
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Kevin M Braunscheidel
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Stephanie P B Caligiuri
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Karim S Elayouby
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Clementine Fillinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Masago Ishikawa
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Janna K Moen
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
| | - Paul J Kenny
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, New York
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Characterization of AN317, a novel selective agonist of α6β2-containing nicotinic acetylcholine receptors. Biochem Pharmacol 2020; 174:113786. [DOI: 10.1016/j.bcp.2019.113786] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Accepted: 12/23/2019] [Indexed: 11/23/2022]
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6
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Hone AJ, Fisher F, Christensen S, Gajewiak J, Larkin D, Whiteaker P, McIntosh JM. PeIA-5466: A Novel Peptide Antagonist Containing Non-natural Amino Acids That Selectively Targets α3β2 Nicotinic Acetylcholine Receptors. J Med Chem 2019; 62:6262-6275. [PMID: 31194549 DOI: 10.1021/acs.jmedchem.9b00566] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Pharmacologically distinguishing α3β2 nicotinic acetylcholine receptors (nAChRs) from closely related subtypes, particularly α6β2, has been challenging due to the lack of subtype-selective ligands. We created analogs of α-conotoxin (α-Ctx) PeIA to identify ligand-receptor interactions that could be exploited to selectively increase potency and selectivity for α3β2 nAChRs. A series of PeIA analogs were synthesized by replacing amino acid residues in the second disulfide loop with standard or nonstandard residues and assessing their activity on α3β2 and α6/α3β2β3 nAChRs heterologously expressed in Xenopus laevis oocytes. Asparagine11 was found to occupy a pivotal position, and when replaced with negatively charged amino acids, selectivity for α3β2 over α6/α3β2β3 nAChRs was substantially increased. Second generation peptides were then designed to further improve both potency and selectivity. One peptide, PeIA-5466, was ∼300-fold more potent on α3β2 than α6/α3β2β3 and is the most α3β2-selective antagonist heretofore reported.
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Affiliation(s)
| | | | | | | | | | | | - J Michael McIntosh
- George E. Whalen Veterans Affairs Medical Center , Salt Lake City , Utah 84148 , United States
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7
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Prior nicotine self-administration attenuates subsequent dopaminergic deficits of methamphetamine in rats: role of nicotinic acetylcholine receptors. Behav Pharmacol 2017; 27:422-30. [PMID: 26871405 DOI: 10.1097/fbp.0000000000000215] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Preclinical studies have demonstrated that oral nicotine exposure attenuates long-term dopaminergic damage induced by toxins, including repeated, high doses of methamphetamine. It is suggested that alterations in nicotinic acetylcholine receptor (nAChR) expression, including α4β2* and α6β2* subtypes, likely contribute to this protection. The current study extended these findings by investigating whether nicotine self-administration in male, Sprague-Dawley rats (a) attenuates short-term dopaminergic damage induced by methamphetamine and (b) causes alterations in levels of α4β2* and α6β2* nAChR subtypes. The findings indicate that nicotine self-administration (0.032 mg/kg/infusion for 14 days) per se did not alter α4β2* and α6β2* nAChR expression or dopamine transporter (DAT) expression and function. Interestingly, prior nicotine self-administration attenuated methamphetamine-induced decreases in DAT function when assessed 24 h, but not 1 h, after methamphetamine treatment (4×7.5 mg/kg/injection). The ability of nicotine to attenuate the effects of methamphetamine on DAT function corresponded with increases in α4β2*, but not α6β2*, nAChR binding density. Understanding the role of nAChRs in methamphetamine-induced damage has the potential to elucidate mechanisms underlying the etiology of disorders involving dopaminergic dysfunction, as well as to highlight potential new therapeutic strategies for prevention or reduction of dopaminergic neurodegeneration.
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8
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Dutertre S, Nicke A, Tsetlin VI. Nicotinic acetylcholine receptor inhibitors derived from snake and snail venoms. Neuropharmacology 2017. [PMID: 28623170 DOI: 10.1016/j.neuropharm.2017.06.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The nicotinic acetylcholine receptor (nAChR) represents the prototype of ligand-gated ion channels. It is vital for neuromuscular transmission and an important regulator of neurotransmission. A variety of toxic compounds derived from diverse species target this receptor and have been of elemental importance in basic and applied research. They enabled milestone discoveries in pharmacology and biochemistry ranging from the original formulation of the receptor concept, the first isolation and structural analysis of a receptor protein (the nAChR) to the identification, localization, and differentiation of its diverse subtypes and their validation as a target for therapeutic intervention. Among the venom-derived compounds, α-neurotoxins and α-conotoxins provide the largest families and still represent indispensable pharmacological tools. Application of modified α-neurotoxins provided substantial structural and functional details of the nAChR long before high resolution structures were available. α-bungarotoxin represents not only a standard pharmacological tool and label in nAChR research but also for unrelated proteins tagged with a minimal α-bungarotoxin binding motif. A major advantage of α-conotoxins is their smaller size, as well as superior selectivity for diverse nAChR subtypes that allows their development into ligands with optimized pharmacological and chemical properties and potentially novel drugs. In the following, these two groups of nAChR antagonists will be described focusing on their respective roles in the structural and functional characterization of nAChRs and their development into research tools. In addition, we provide a comparative overview of the diverse α-conotoxin selectivities that can serve as a practical guide for both structure activity studies and subtype classification. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Sébastien Dutertre
- Institut des Biomolécules Max Mousseron, UMR 5247, Université Montpellier - CNRS, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
| | - Annette Nicke
- Walther Straub Institute for Pharmacology and Toxicology, Ludwig-Maximilians-Universität, Nußbaumstr. 26, 80336 Munich, Germany.
| | - Victor I Tsetlin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya str.16/10, Moscow 117999, Russian Federation
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9
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King MD, Long T, Andersen T, McDougal OM. Genetic Algorithm Managed Peptide Mutant Screening: Optimizing Peptide Ligands for Targeted Receptor Binding. J Chem Inf Model 2016; 56:2378-2387. [PMID: 28024403 DOI: 10.1021/acs.jcim.6b00095] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
This study demonstrates the utility of genetic algorithms to search exceptionally large and otherwise intractable mutant libraries for sequences with optimal binding affinities for target receptors. The Genetic Algorithm Managed Peptide Mutant Screening (GAMPMS) program was used to search an α-conotoxin (α-CTx) MII mutant library of approximately 41 billion possible peptide sequences for those exhibiting the greatest binding affinity for the α3β2-nicotinic acetylcholine receptor (nAChR) isoform. A series of top resulting peptide ligands with high sequence homology was obtained, with each mutant having an estimated ΔGbind approximately double that of the potent native α-CTx MII ligand. A consensus sequence from the top GAMPMS results was subjected to more rigorous binding free energy calculations by molecular dynamics and compared to α-CTx MII and other related variants for binding with α3β2-nAChR. In this study, the efficiency of GAMPMS to substantially reduce the sample population size through evolutionary selection criteria to produce ligands with higher predicted binding affinity is demonstrated.
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Affiliation(s)
- Matthew D King
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Thomas Long
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Timothy Andersen
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
| | - Owen M McDougal
- Department of Chemistry and Biochemistry and ‡Department of Computer Science, Boise State University , 1910 University Drive, Boise, Idaho 83725, United States
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Deflorio C, Blanchard S, Carisì MC, Bohl D, Maskos U. Human polymorphisms in nicotinic receptors: a functional analysis in iPS-derived dopaminergic neurons. FASEB J 2016; 31:828-839. [PMID: 27856558 DOI: 10.1096/fj.201600932r] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 10/31/2016] [Indexed: 11/11/2022]
Abstract
Tobacco smoking is a public health problem, with ∼5 million deaths per year, representing a heavy burden for many countries. No effective therapeutic strategies are currently available for nicotine addiction, and it is therefore crucial to understand the etiological and pathophysiological factors contributing to this addiction. The neuronal α5 nicotinic acetylcholine receptor (nAChR) subunit is critically involved in nicotine dependence. In particular, the human polymorphism α5D398N corresponds to the strongest correlation with nicotine dependence risk found to date in occidental populations, according to meta-analysis of genome-wide association studies. To understand the specific contribution of this subunit in the context of nicotine addiction, an efficient screening system for native human nAChRs is needed. We have differentiated human induced pluripotent stem (iPS) cells into midbrain dopaminergic (DA) neurons and obtained a comprehensive characterization of these neurons by quantitative RT-PCR. The functional properties of nAChRs expressed in these human DA neurons, with or without the polymorphism in the α5 subunit, were studied with the patch-clamp electrophysiological technique. Our results in human DA neurons carrying the polymorphism in the α5 subunit showed an increase in EC50, indicating that, in the presence of the polymorphism, more nicotine or acetylcholine chloride is necessary to obtain the same effect. This human cell culturing system can now be used in drug discovery approaches to screen for compounds that interact specifically with human native and polymorphic nAChRs.-Deflorio, C., Blanchard, S., Carisì, M. C., Bohl, D., Maskos, U. Human polymorphisms in nicotinic receptors: a functional analysis in iPS-derived dopaminergic neurons.
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Affiliation(s)
- Cristina Deflorio
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Département de Neuroscience, Institut Pasteur, Paris, France
| | - Stéphane Blanchard
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Département de Neuroscience, Institut Pasteur, Paris, France
| | - Maria Carla Carisì
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Département de Neuroscience, Institut Pasteur, Paris, France
| | - Delphine Bohl
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Département de Neuroscience, Institut Pasteur, Paris, France.,Institut du Cerveau et de la Moelle Epinière, INSERM Unité 1127, CNRS, UMR 7225, Université Pierre et Marie Curie, Paris, France
| | - Uwe Maskos
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Département de Neuroscience, Institut Pasteur, Paris, France; .,Centre National de la Recherche Scientifique (CNRS), Unité Mixte de Recherche (UMR) 3731, Institut Pasteur, Paris, France; and
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11
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Beckmann JS, Meyer AC, Pivavarchyk M, Horton DB, Zheng G, Smith AM, Wooters TE, McIntosh JM, Crooks PA, Bardo MT, Dwoskin LP. r-bPiDI, an α6β2* Nicotinic Receptor Antagonist, Decreases Nicotine-Evoked Dopamine Release and Nicotine Reinforcement. Neurochem Res 2015; 40:2121-30. [PMID: 26227997 DOI: 10.1007/s11064-015-1680-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/16/2015] [Accepted: 07/22/2015] [Indexed: 01/01/2023]
Abstract
α6β2* nicotinic acetylcholine receptors (nAChRs) expressed by dopaminergic neurons mediate nicotine-evoked dopamine (DA) release and nicotine reinforcement. α6β2* antagonists inhibit these effects of nicotine, such that α6β2* receptors serve as therapeutic targets for nicotine addiction. The present research assessed the neuropharmacology of 1,10-bis(3-methyl-5,6-dihydropyridin-1(2H)-yl)decane (r-bPiDI), a novel small-molecule, tertiary amino analog of its parent compound, N,N-decane-1,10-diyl-bis-3-picolinium diiodide (bPiDI). bPiDI was previously shown to inhibit both nicotine-evoked DA release and the reinforcing effects of nicotine. In the current study, r-bPiDI inhibition of [(3)H]nicotine and [(3)H]methyllycaconitine binding sites was evaluated to assess interaction with the recognition binding sites on α4β2* and α7* nAChRs, respectively. Further, r-bPiDI inhibition of nicotine-evoked DA release in vitro in the absence and presence of α-conotoxin MII and following chronic in vivo nicotine administration were determined. The ability of r-bPiDI to decrease nicotine self-administration and food-maintained responding was also assessed. Results show that r-bPiDI did not inhibit [(3)H]nicotine or [(3)H]methyllycaconitine binding, but potently (IC50 = 37.5 nM) inhibited nicotine-evoked DA release from superfused striatal slices obtained from either drug naïve rats or from those repeatedly treated with nicotine. r-bPiDI inhibition of nicotine-evoked DA release was not different in the absence or presence of α-conotoxin MII, indicating that r-bPiDI acts as a potent, selective α6β2* nAChR antagonist. Acute systemic administration of r-bPiDI specifically decreased nicotine self-administration by 75 %, and did not alter food-maintained responding, demonstrating greater specificity relative to bPiDI and bPiDDB, as well as the tertiary amino analog r-bPiDDB. The current work describes the discovery of r-bPiDI, a tertiary amino, α-conotoxin MII-like small molecule that acts as a potent and selective antagonist at α6β2* nAChRs to specifically decrease nicotine self-administration in rats, thus, establishing r-bPiDI as a lead compound for development as a treatment for nicotine addiction.
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Affiliation(s)
- Joshua S Beckmann
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - Andrew C Meyer
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - M Pivavarchyk
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 S. Limestone St., Lexington, KY, 40536-0596, USA
| | - David B Horton
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 S. Limestone St., Lexington, KY, 40536-0596, USA
| | - Guangrong Zheng
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Andrew M Smith
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 S. Limestone St., Lexington, KY, 40536-0596, USA
| | - Thomas E Wooters
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - J Michael McIntosh
- George E. Wahlen Veterans Affairs Medical Center and Departments of Psychiatry and Biology, University of Utah, Salt Lake City, UT, USA
| | - Peter A Crooks
- Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Michael T Bardo
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - Linda P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 S. Limestone St., Lexington, KY, 40536-0596, USA.
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12
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Wang J, Kuryatov A, Lindstrom J. Expression of cloned α6* nicotinic acetylcholine receptors. Neuropharmacology 2014; 96:194-204. [PMID: 25446669 DOI: 10.1016/j.neuropharm.2014.10.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/19/2014] [Accepted: 10/07/2014] [Indexed: 10/24/2022]
Abstract
Nicotinic acetylcholine receptors (AChRs) are ACh-gated ion channels formed from five homologous subunits in subtypes defined by their subunit composition and stoichiometry. Some subtypes readily produce functional AChRs in Xenopus oocytes and transfected cell lines. α6β2β3* AChRs (subtypes formed from these subunits and perhaps others) are not easily expressed. This may be because the types of neurons in which they are expressed (typically dopaminergic neurons) have unique chaperones for assembling α6β2β3* AChRs, especially in the presence of the other AChR subtypes. Because these relatively minor brain AChR subtypes are of major importance in addiction to nicotine, it is important for drug development as well as investigation of their functional properties to be able to efficiently express human α6β2β3* AChRs. We review the issues and progress in expressing α6* AChRs. This article is part of the Special Issue entitled 'The Nicotinic Acetylcholine Receptor: From Molecular Biology to Cognition'.
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Affiliation(s)
- Jingyi Wang
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Alexander Kuryatov
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Jon Lindstrom
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
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De Biasi M, McLaughlin I, Perez EE, Crooks PA, Dwoskin LP, Bardo MT, Pentel PR, Hatsukami D. Scientific overview: 2013 BBC plenary symposium on tobacco addiction. Drug Alcohol Depend 2014; 141:107-17. [PMID: 24934691 PMCID: PMC4227301 DOI: 10.1016/j.drugalcdep.2014.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 05/12/2014] [Accepted: 05/16/2014] [Indexed: 12/13/2022]
Abstract
Nicotine dependence plays a critical role in addiction to tobacco products, and thus contributes to a variety of devastating tobacco-related diseases (SGR 2014). Annual costs associated with smoking in the US are estimated to be between $289 and $333 billion. Effective interventions for nicotine dependence, especially in smokers, are a critical barrier to the eradication of tobacco-related diseases. This overview highlights research presented at the Plenary Symposium of Behavior, Biology and Chemistry: Translational Research in Addiction Conference (BBC), hosted by the UT Health Science Center San Antonio, on March 9-10, 2013. The Plenary Symposium focused on tobacco addiction, and covered topics ranging from basic science to national policy. As in previous years, the meeting brought together globally-renowned scientists, graduate student recruits, and young scientists from underrepresented populations in Texas and other states with the goal of fostering interest in drug addiction research in young generations.
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Affiliation(s)
- M De Biasi
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
| | - I McLaughlin
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - E E Perez
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - P A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - L P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - M T Bardo
- Department of Psychology, University of Kentucky, Lexington, KY, USA
| | - P R Pentel
- Department of Medicine, Hennepin County Medical Center, University of Minnesota, Minneapolis, MN, USA
| | - D Hatsukami
- Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA
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14
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Ochi S, Abe M, Li C, Mori Y, Ishimaru T, Yoshino Y, Yamazaki K, Mori T, Fukuhara R, Tanimukai S, Matsuda S, Yoshida K, Ueno SI. The nicotinic cholinergic system is affected in rats with delayed carbon monoxide encephalopathy. Neurosci Lett 2014; 569:33-7. [DOI: 10.1016/j.neulet.2014.03.054] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 03/20/2014] [Accepted: 03/24/2014] [Indexed: 01/21/2023]
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15
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Monkey adrenal chromaffin cells express α6β4* nicotinic acetylcholine receptors. PLoS One 2014; 9:e94142. [PMID: 24727685 PMCID: PMC3984115 DOI: 10.1371/journal.pone.0094142] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 03/14/2014] [Indexed: 01/02/2023] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) that contain α6 and β4 subunits have been demonstrated functionally in human adrenal chromaffin cells, rat dorsal root ganglion neurons, and on noradrenergic terminals in the hippocampus of adolescent mice. In human adrenal chromaffin cells, α6β4* nAChRs (the asterisk denotes the possible presence of additional subunits) are the predominant subtype whereas in rodents, the predominant nAChR is the α3β4* subtype. Here we present molecular and pharmacological evidence that chromaffin cells from monkey (Macaca mulatta) also express α6β4* receptors. PCR was used to show the presence of transcripts for α6 and β4 subunits and pharmacological characterization was performed using patch-clamp electrophysiology in combination with α-conotoxins that target the α6β4* subtype. Acetylcholine-evoked currents were sensitive to inhibition by BuIA[T5A,P6O] and MII[H9A,L15A]; α-conotoxins that inhibit α6-containing nAChRs. Two additional agonists were used to probe for the expression of α7 and β2-containing nAChRs. Cells with currents evoked by acetylcholine were relatively unresponsive to the α7-selctive agonist choline but responded to the agonist 5-I-A-85380. These studies provide further insights into the properties of natively expressed α6β4* nAChRs.
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16
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Crooks PA, Bardo MT, Dwoskin LP. Nicotinic receptor antagonists as treatments for nicotine abuse. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2014; 69:513-51. [PMID: 24484986 DOI: 10.1016/b978-0-12-420118-7.00013-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite the proven efficacy of current pharmacotherapies for tobacco dependence, relapse rates continue to be high, indicating that novel medications are needed. Currently, several smoking cessation agents are available, including varenicline (Chantix®), bupropion (Zyban®), and cytisine (Tabex®). Varenicline and cytisine are partial agonists at the α4β2* nicotinic acetylcholine receptor (nAChR). Bupropion is an antidepressant but is also an antagonist at α3β2* ganglionic nAChRs. The rewarding effects of nicotine are mediated, in part, by nicotine-evoked dopamine (DA) release leading to sensitization, which is associated with repeated nicotine administration and nicotine addiction. Receptor antagonists that selectivity target central nAChR subtypes mediating nicotine-evoked DA release should have efficacy as tobacco use cessation agents with the therapeutic advantage of a limited side-effect profile. While α-conotoxin MII (α-CtxMII)-insensitive nAChRs (e.g., α4β2*) contribute to nicotine-evoked DA release, these nAChRs are widely distributed in the brain, and inhibition of these receptors may lead to nonselective and untoward effects. In contrast, α-CtxMII-sensitive nAChRs mediating nicotine-evoked DA release offer an advantage as targets for smoking cessation, due to their more restricted localization primarily to dopaminergic neurons. Small drug-like molecules that are selective antagonists at α-CtxMII-sensitive nAChR subtypes that contain α6 and β2 subunits have now been identified. Early research identified a variety of quaternary ammonium analogs that were potent and selective antagonists at nAChRs mediating nicotine-evoked DA release. More recent data have shown that novel, nonquaternary bis-1,2,5,6-tetrahydropyridine analogs potently inhibit (IC50<1nM) nicotine-evoked DA release in vitro by acting as antagonists at α-CtxMII-sensitive nAChR subtypes; these compounds also decrease NIC self-administration in rats.
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Affiliation(s)
- Peter A Crooks
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arizona, USA.
| | - Michael T Bardo
- Department of Psychology, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
| | - Linda P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky, USA
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17
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The influence of inhibiting or stimulating the expression of the α3 subunit of the nicotinic receptor in SH-SY5Y cells on levels of amyloid-β peptide and β-secretase. Neurochem Int 2013. [DOI: 10.1016/j.neuint.2012.11.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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18
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Quik M, Wonnacott S. α6β2* and α4β2* nicotinic acetylcholine receptors as drug targets for Parkinson's disease. Pharmacol Rev 2012; 63:938-66. [PMID: 21969327 DOI: 10.1124/pr.110.003269] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Parkinson's disease is a debilitating movement disorder characterized by a generalized dysfunction of the nervous system, with a particularly prominent decline in the nigrostriatal dopaminergic pathway. Although there is currently no cure, drugs targeting the dopaminergic system provide major symptomatic relief. As well, agents directed to other neurotransmitter systems are of therapeutic benefit. Such drugs may act by directly improving functional deficits in these other systems, or they may restore aberrant motor activity that arises as a result of a dopaminergic imbalance. Recent research attention has focused on a role for drugs targeting the nicotinic cholinergic systems. The rationale for such work stems from basic research findings that there is an extensive overlap in the organization and function of the nicotinic cholinergic and dopaminergic systems in the basal ganglia. In addition, nicotinic acetylcholine receptor (nAChR) drugs could have clinical potential for Parkinson's disease. Evidence for this proposition stems from studies with experimental animal models showing that nicotine protects against neurotoxin-induced nigrostriatal damage and improves motor complications associated with l-DOPA, the "gold standard" for Parkinson's disease treatment. Nicotine interacts with multiple central nervous system receptors to generate therapeutic responses but also produces side effects. It is important therefore to identify the nAChR subtypes most beneficial for treating Parkinson's disease. Here we review nAChRs with particular emphasis on the subtypes that contribute to basal ganglia function. Accumulating evidence suggests that drugs targeting α6β2* and α4β2* nAChR may prove useful in the management of Parkinson's disease.
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Affiliation(s)
- Maryka Quik
- Center for Health Sciences, SRI International, Menlo Park, CA 94025, USA.
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19
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Hauser TA, Hepler CD, Kombo DC, Grinevich VP, Kiser MN, Hooker DN, Zhang J, Mountfort D, Selwood A, Akireddy SR, Letchworth SR, Yohannes D. Comparison of acetylcholine receptor interactions of the marine toxins, 13-desmethylspirolide C and gymnodimine. Neuropharmacology 2012; 62:2239-50. [DOI: 10.1016/j.neuropharm.2012.01.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 01/04/2012] [Accepted: 01/16/2012] [Indexed: 10/14/2022]
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20
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McClure-Begley TD, Wageman CR, Grady SR, Marks MJ, McIntosh JM, Collins AC, Whiteaker P. A novel α-conotoxin MII-sensitive nicotinic acetylcholine receptor modulates [(3) H]-GABA release in the superficial layers of the mouse superior colliculus. J Neurochem 2012; 122:48-57. [PMID: 22506481 DOI: 10.1111/j.1471-4159.2012.07759.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mouse superficial superior colliculus (SuSC) contains dense GABAergic innervation and diverse nicotinic acetylcholine receptor subtypes. Pharmacological and genetic approaches were used to investigate the subunit compositions of nicotinic acetylcholine receptors (nAChR) expressed on mouse SuSC GABAergic terminals. [(125) I]-Epibatidine competition-binding studies revealed that the α3β2* and α6β2* nicotinic subtype-selective peptide α-conotoxin MII-blocked binding to 40 ± 5% of SuSC nAChRs. Acetylcholine-evoked [(3) H]-GABA release from SuSC crude synaptosomal preparations is calcium dependent, blocked by the voltage-sensitive calcium channel blocker, cadmium, and the nAChR antagonist mecamylamine, but is unaffected by muscarinic, glutamatergic, P2X and 5-HT3 receptor antagonists. Approximately 50% of nAChR-mediated SuSC [(3) H]-GABA release is inhibited by α-conotoxin MII. However, the highly α6β2*-subtype-selective α-conotoxin PIA did not affect [(3) H]-GABA release. Nicotinic subunit-null mutant mouse experiments revealed that ACh-stimulated SuSC [(3) H]-GABA release is entirely β2 subunit-dependent. α4 subunit deletion decreased total function by >90%, and eliminated α-conotoxin MII-resistant release. ACh-stimulated SuSC [(3) H]-GABA release was unaffected by β3, α5 or α6 nicotinic subunit deletions. Together, these data suggest that a significant proportion of mouse SuSC nicotinic agonist-evoked GABA-release is mediated by a novel, α-conotoxin MII-sensitive α3α4β2 nAChR. The remaining α-conotoxin MII-resistant, nAChR agonist-evoked SuSC GABA release appears to be mediated via α4β2* subtype nAChRs.
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21
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Hellier JL, Arevalo NL, Smith L, Xiong KN, Restrepo D. α7-Nicotinic acetylcholine receptor: role in early odor learning preference in mice. PLoS One 2012; 7:e35251. [PMID: 22514723 PMCID: PMC3325997 DOI: 10.1371/journal.pone.0035251] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 03/14/2012] [Indexed: 11/19/2022] Open
Abstract
Recently, we have shown that mice with decreased expression of α7-nicotinic acetylcholine receptors (α7) in the olfactory bulb were associated with a deficit in odor discrimination compared to wild-type mice. However, it is unknown if mice with decreased α7-receptor expression also show a deficit in early odor learning preference (ELP), an enhanced behavioral response to odors with attractive value observed in rats. In this study, we modified ELP methods performed in rats and implemented similar conditions in mice. From post-natal days 5–18, wild-type mice were stroked simultaneously with an odor presentation (conditioned odor) for 90 s daily. Control mice were only stroked, exposed to odor, or neither. On the day of testing (P21), mice that were stroked in concert with a conditioned odor significantly investigated the conditioned odor compared to a novel odor, as observed similarly in rats. However, mice with a decrease in α7-receptor expression that were stroked during a conditioned odor did not show a behavioral response to that odorant. These results suggest that decreased α7-receptor expression has a role in associative learning, olfactory preference, and/or sensory processing deficits.
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Affiliation(s)
- Jennifer L Hellier
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
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22
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Brunzell DH. Preclinical evidence that activation of mesolimbic alpha 6 subunit containing nicotinic acetylcholine receptors supports nicotine addiction phenotype. Nicotine Tob Res 2012; 14:1258-69. [PMID: 22492084 DOI: 10.1093/ntr/nts089] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
INTRODUCTION Nicotine is a major psychoactive ingredient in tobacco yet very few individuals quit smoking with the aid of nicotine replacement therapy. Targeted therapies with more selective action at nicotinic acetylcholine receptors (nAChRs) that contain a β2 subunit (β2*nAChRs; *denotes assembly with other subunits) have enjoyed significantly greater success, but exhibit potential for unwanted cardiac, gastrointestinal, and emotive side effects. DISCUSSION This literature review focuses on the preclinical evidence that suggests that subclasses of β2*nAChRs that assemble with the α6 subunit may provide an effective target for tobacco cessation. α6β2*nAChRs have a highly selective pattern of neuroanatomical expression in catecholaminergic nuclei including the ventral tegmental area and its projection regions. α6β2*nAChRs promote dopamine (DA) neuron activity and DA release in the mesolimbic dopamine system, a brain circuitry that is well-studied for its contributions to addiction behavior. A combination of genetic and pharmacological studies indicates that activation of α6β2*nAChRs is necessary and sufficient for nicotine psychostimulant effects and nicotine self-administration. α6β2*nAChRs support maintenance of nicotine use, support the conditioned reinforcing effects of drug-associated cues, and regulate nicotine withdrawal. CONCLUSIONS These data suggest that α6β2*nAChRs represent a critical pool of high affinity β2*nAChRs that regulates nicotine dependence phenotype and suggest that inhibition of these receptors may provide an effective strategy for tobacco cessation therapy.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA.
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23
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Nicotinic cholinergic mechanisms causing elevated dopamine release and abnormal locomotor behavior. Neuroscience 2011; 200:31-41. [PMID: 22079576 DOI: 10.1016/j.neuroscience.2011.10.047] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 10/22/2011] [Accepted: 10/24/2011] [Indexed: 11/21/2022]
Abstract
Firing rates of dopamine (DA) neurons in substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) control DA release in target structures such as striatum and prefrontal cortex. DA neuron firing in the soma and release probability at axon terminals are tightly regulated by cholinergic transmission and nicotinic acetylcholine receptors (nAChRs). To understand the role of α6* nAChRs in DA transmission, we studied several strains of mice expressing differing levels of mutant, hypersensitive (leucine 9' to serine [L9'S]) α6 subunits. α6 L9'S mice harboring six or more copies of the hypersensitive α6 gene exhibited spontaneous home-cage hyperactivity and novelty-induced locomotor activity, whereas mice with an equal number of WT and L9'S α6 genes had locomotor activity resembling that of control mice. α6-dependent, nicotine-stimulated locomotor activation was also more robust in high-copy α6 L9'S mice versus low-copy mice. In wheel-running experiments, results were also bi-modal; high-copy α6 L9'S animals exhibited blunted total wheel rotations during each day of a 9-day experiment, but low-copy α6 L9'S mice ran normally on the wheel. Reduced wheel running in hyperactive strains of α6 L9'S mice was attributable to a reduction in both overall running time and velocity. ACh and nicotine-stimulated DA release from striatal synaptosomes in α6 L9'S mice was well-correlated with behavioral phenotypes, supporting the hypothesis that augmented DA release mediates the altered behavior of α6 L9'S mice. This study highlights the precise control that the nicotinic cholinergic system exerts on DA transmission and provides further insights into the mechanisms and consequences of enhanced DA release.
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Wooters TE, Smith AM, Pivavarchyk M, Siripurapu KB, McIntosh JM, Zhang Z, Crooks PA, Bardo MT, Dwoskin LP. bPiDI: a novel selective α6β2* nicotinic receptor antagonist and preclinical candidate treatment for nicotine abuse. Br J Pharmacol 2011; 163:346-57. [PMID: 21232049 DOI: 10.1111/j.1476-5381.2011.01220.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Nicotinic acetylcholine receptors (nAChRs) containing α6β2 subunits expressed by dopamine neurons regulate nicotine-evoked dopamine release. Previous results show that the α6β2* nAChR antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB) inhibits nicotine-evoked dopamine release from dorsal striatum and decreases nicotine self-administration in rats. However, overt toxicity emerged with repeated bPiDDB treatment. The current study evaluated the preclinical pharmacology of a bPiDDB analogue. EXPERIMENTAL APPROACH The C₁₀ analogue of bPiDDB, N,N-decane-1,10-diyl-bis-3-picolinium diiodide (bPiDI), was evaluated preclinically for nAChR antagonist activity. KEY RESULTS bPiDI inhibits nicotine-evoked [³H]dopamine overflow (IC₅₀= 150 nM, I(max)=58%) from rat striatal slices. Schild analysis revealed a rightward shift in the nicotine concentration-response curve and surmountability with increasing nicotine concentration; however, the Schild regression slope differed significantly from 1.0, indicating surmountable allosteric inhibition. Co-exposure of maximally inhibitory concentrations of bPiDI (1 µM) and the α6β2* nAChR antagonist α-conotoxin MII (1 nM) produced inhibition not different from either antagonist alone, indicating that bPiDI acts at α6β2* nAChRs. Nicotine treatment (0.4 mg·kg⁻¹·da⁻¹, 10 days) increased more than 100-fold the potency of bPiDI (IC₅₀=1.45 nM) to inhibit nicotine-evoked dopamine release. Acute treatment with bPiDI (1.94-5.83 µmol·kg⁻¹, s.c.) specifically reduced nicotine self-administration relative to responding for food. Across seven daily treatments, bPiDI decreased nicotine self-administration; however, tolerance developed to the acute decrease in food-maintained responding. No observable body weight loss or lethargy was observed with repeated bPiDI. CONCLUSIONS AND IMPLICATIONS These results are consistent with the hypothesis that α6β2* nAChR antagonists have potential for development as pharmacotherapies for tobacco smoking cessation.
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Affiliation(s)
- Thomas E Wooters
- Department of Psychology, College of Arts and Sciences, University of Kentucky, Lexington, KY, USA
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25
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Dash B, Bhakta M, Chang Y, Lukas RJ. Identification of N-terminal extracellular domain determinants in nicotinic acetylcholine receptor (nAChR) α6 subunits that influence effects of wild-type or mutant β3 subunits on function of α6β2*- or α6β4*-nAChR. J Biol Chem 2011; 286:37976-37989. [PMID: 21832048 DOI: 10.1074/jbc.m111.263673] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Despite the apparent function of naturally expressed mammalian α6*-nicotinic acetylcholine receptors (α6*-nAChR; where * indicates the known or possible presence of additional subunits), their functional and heterologous expression has been difficult. Here, we report that coexpression with wild-type β3 subunits abolishes the small amount of function typically seen for all-human or all-mouse α6β4*-nAChR expressed in Xenopus oocytes. However, levels of function and agonist potencies are markedly increased, and there is atropine-sensitive blockade of spontaneous channel opening upon coexpression of α6 and β4 subunits with mutant β3 subunits harboring valine-to-serine mutations at 9'- or 13'-positions. There is no function when α6 and β2 subunits are expressed alone or in the presence of wild-type or mutant β3 subunits. Interestingly, hybrid nAChR containing mouse α6 and human (h) β4 subunits have function potentiated rather than suppressed by coexpression with wild-type hβ3 subunits and potentiated further upon coexpression with hβ3(V9'S) subunits. Studies using nAChR chimeric mouse/human α6 subunits indicated that residues involved in effects seen with hybrid nAChR are located in the α6 subunit N-terminal domain. More specifically, nAChR hα6 subunit residues Asn-143 and Met-145 are important for dominant-negative effects of nAChR hβ3 subunits on hα6hβ4-nAChR function. Asn-143 and additional residues in the N-terminal domain of nAChR hα6 subunits are involved in the gain-of-function effects of nAChR hβ3(V9'S) subunits on α6β2*-nAChR function. These studies illuminate the structural bases for effects of β3 subunits on α6*-nAChR function and suggest that unique subunit interfaces involving the complementary rather than the primary face of α6 subunits are involved.
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Affiliation(s)
- Bhagirathi Dash
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013
| | - Minoti Bhakta
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013
| | - Yongchang Chang
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013
| | - Ronald J Lukas
- Division of Neurobiology, Barrow Neurological Institute, Phoenix, Arizona 85013.
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26
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Pucci L, Grazioso G, Dallanoce C, Rizzi L, De Micheli C, Clementi F, Bertrand S, Bertrand D, Longhi R, De Amici M, Gotti C. Engineering of α-conotoxin MII-derived peptides with increased selectivity for native α6β2* nicotinic acetylcholine receptors. FASEB J 2011; 25:3775-89. [PMID: 21778325 DOI: 10.1096/fj.10-179853] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
α6β2* Nicotinic acetylcholine receptors are expressed in selected central nervous system areas, where they are involved in striatal dopamine (DA) release and its behavioral consequences, and other still uncharacterized brain activities. α6β2* receptors are selectively blocked by the α-conotoxins MII and PIA, which bear a characteristic N-terminal amino acid tail [arginine (R), aspartic acid (D), and proline (P)]. We synthesized a group of PIA-related peptides in which R1 was mutated or the RDP motif gradually removed. Binding and striatal DA release assays of native rat α6β2* receptors showed that the RDP sequence, and particularly residue R1, is essential for the activity of PIA. On the basis of molecular modeling analyses, we synthesized a hybrid peptide (RDP-MII) that had increased potency (7-fold) and affinity (13-fold) for α6β2* receptors but not for the very similar α3β2* subtype. As docking studies also suggested that E11 of MII might be a key residue engendering α6β2* vs. α3β2* selectivity, we prepared MII[E11R] and RDP-MII[E11R] peptides. Their affinity and potency for native α6β2* receptors were similar to those of their parent analogues, whereas, for the oocyte expressed rat α3β2* subtype, they showed a 31- and 14-fold lower affinity and 21- and 3.5-fold lower potency. Thus, MII[E11R] and RDP-MII[E11R] are potent antagonists showing a degree of α6β2* vs. α3β2* selectivity in vivo.
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Affiliation(s)
- Luca Pucci
- Consiglio Nazionale delle Ricerche, Istituto di Neuroscienze, Farmacologia Cellulare e Molecolare e Dipartimento di Farmacologia, Chemioterapia e Tossicologia Medica, Milan, Italy
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27
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Wu J, Lukas RJ. Naturally-expressed nicotinic acetylcholine receptor subtypes. Biochem Pharmacol 2011; 82:800-7. [PMID: 21787755 DOI: 10.1016/j.bcp.2011.07.067] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 07/01/2011] [Accepted: 07/05/2011] [Indexed: 12/31/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) warrant attention, as they play many critical roles in brain and body function and have been implicated in a number of neurological and psychiatric disorders, including nicotine dependence. nAChRs are composed as diverse subtypes containing specific combinations of genetically-distinct subunits and that have different functional properties, distributions, and pharmacological profiles. There had been confidence that the rules that define ranges of assembly partners for specific subunits were well-established, especially for the more prominent nAChR subtypes. However, we review here some newer findings indicating that nAChRs having largely the same, major subunits exist as isoforms with unexpectedly different properties. Moreover, we also summarize our own studies indicating that novel nAChR subtypes exist and/or have distributions not heretofore described. Importantly, the nAChRs that exist as new isoforms or subtypes or have interesting distributions require alteration in thinking about their roles in health and disease.
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Affiliation(s)
- Jie Wu
- Division of Neurology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013, United States.
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Progress and challenges in the study of α6-containing nicotinic acetylcholine receptors. Biochem Pharmacol 2011; 82:862-72. [PMID: 21736871 DOI: 10.1016/j.bcp.2011.06.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 06/15/2011] [Accepted: 06/15/2011] [Indexed: 11/22/2022]
Abstract
Recent progress has been made in the understanding of the anatomical distribution, composition, and physiological role of nicotinic acetylcholine receptors containing the α6 subunit. Extensive study by many researchers has indicated that a collection of α6-containing receptors representing a nicotinic sub-family is relevant in preclinical models of nicotine self-administration and locomotor activity. Due to a number of technical difficulties, the state of the art of in vitro model systems expressing α6-containing receptors has lagged behind the state of knowledge of native α6 nAChR subunit composition. Several techniques, such as the expression of chimeric and concatameric α6 subunit constructs in oocytes and mammalian cell lines have been employed to overcome these obstacles. There remains a need for other critical tools, such as selective small molecules and radioligands, to advance the field of research and to allow the discovery and development of potential therapeutics targeting α6-containing receptors for smoking cessation, Parkinson's disease and other disorders.
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Role of α6 nicotinic receptors in CNS dopaminergic function: relevance to addiction and neurological disorders. Biochem Pharmacol 2011; 82:873-82. [PMID: 21684266 DOI: 10.1016/j.bcp.2011.06.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 06/01/2011] [Accepted: 06/02/2011] [Indexed: 11/23/2022]
Abstract
Although a relative newcomer to the nicotinic acetylcholine receptor (nAChR) family, substantial evidence suggests that α6 containing nAChRs play a key role in CNS function. This subtype is unique in its relatively restricted localization to the visual system and catecholaminergic pathways. These latter include the mesolimbic and nigrostriatal dopaminergic systems, which may account for the involvement of α6 containing nAChRs in the rewarding properties of nicotine and in movement. Here, we review the literature on the role of α6 containing nAChRs with a focus on the striatum and nucleus accumbens. This includes molecular, electrophysiological and behavioral studies in control and lesioned animal models, as well as in different genetic models. Converging evidence suggest that the major α6 containing nAChRs subtypes in the nigrostriatal and mesolimbic dopamine system are the α6β2β3 and α6α4β2β3 nAChR populations. They appear to have a dominant role in regulating dopamine release, with consequent effects on nAChR-modulated dopaminergic functions such as reinforcement and motor behavior. Altogether these data suggest that drugs directed to α6 containing nAChRs may be of benefit for the treatment of addiction and for neurological disorders with locomotor deficits such as Parkinson's disease.
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Lee RHC, Liu YQ, Chen PY, Liu CH, Chen MF, Lin HW, Kuo JS, Premkumar LS, Lee TJF. Sympathetic α₃β₂-nAChRs mediate cerebral neurogenic nitrergic vasodilation in the swine. Am J Physiol Heart Circ Physiol 2011; 301:H344-54. [PMID: 21536845 DOI: 10.1152/ajpheart.00172.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The α(7)-nicotinic ACh receptor (α(7)-nAChR) on sympathetic neurons innervating basilar arteries of pigs crossed bred between Landrace and Yorkshire (LY) is known to mediate nicotine-induced, β-amyloid (Aβ)-sensitive nitrergic neurogenic vasodilation. Preliminary studies, however, demonstrated that nicotine-induced cerebral vasodilation in pigs crossbred among Landrace, Yorkshire, and Duroc (LYD) was insensitive to Aβ and α-bungarotoxin (α-BGTX). We investigated nAChR subtype on sympathetic neurons innervating LYD basilar arteries. Nicotine-induced relaxation of porcine isolated basilar arteries was examined by tissue bath myography, inward currents on nAChR-expressing oocytes by two-electrode voltage recording, and mRNA and protein expression in the superior cervical ganglion (SCG) and middle cervical ganglion (MCG) by reverse transcription PCR and Western blotting. Nicotine-induced basilar arterial relaxation was not affected by Aβ, α-BGTX, and α-conotoxin IMI (α(7)-nAChR antagonists), or α-conotoxin AuIB (α(3)β(4)-nAChR antagonist) but was inhibited by tropinone and tropane (α(3)-containing nAChR antagonists) and α-conotoxin MII (selective α(3)β(2)-nAChR antagonist). Nicotine-induced inward currents in α(3)β(2)-nAChR-expressing oocytes were inhibited by α-conotoxin MII but not by α-BGTX, Aβ, or α-conotoxin AuIB. mRNAs of α(3)-, α(7)-, β(2)-, and β(4)-subunits were expressed in both SCGs and MCGs with significantly higher mRNAs of α(3)-, β(2)-, and β(4)-subunits than that of α(7)-subunit. The Aβ-insensitive sympathetic α(3)β(2)-nAChR mediates nicotine-induced cerebral nitrergic neurogenic vasodilation in LYD pigs. The different finding from Aβ-sensitive α(7)-nAChR in basilar arteries of LY pigs may offer a partial explanation for different sensitivities of individuals to Aβ in causing diminished cerebral nitrergic vasodilation in diseases involving Aβ.
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Affiliation(s)
- Reggie Hui-Chao Lee
- Institutes of Medical Sciences, College of Medicine, Tzu Chi University, Hualien, Taiwan
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Azarn L, Maskos U, Changeux JP, Dowell CD, Christensen S, Biasi MD, McIntosh JM. α‐Conotoxin BuIA[T5A;P6O]: a novel ligand that discriminates between 06 β4 and 0:6 β2 nicotinic acetylcholine receptors and blocks nicotine‐stimulated norepinephrine release. FASEB J 2010. [DOI: 10.1096/fj.10.166272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Layla Azarn
- Department of BiologyUniversity of Utah, Salt Lake City Utah USA
| | - Uwe Maskos
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Institut Pasteur Paris France
| | - Jean-Pierre Changeux
- Unité Neurobiologie Intégrative des Systèmes Cholinergiques, Institut Pasteur Paris France
| | - Cheryl D. Dowell
- Department of BiologyUniversity of Utah, Salt Lake City Utah USA
| | - Sean Christensen
- Department of BiologyUniversity of Utah, Salt Lake City Utah USA
| | - Mariella De Biasi
- Department of Neuroscience and Graduate Program in Translational Biology and Molecular MedicineBaylor College of Medicine Houston Texas USA
| | - J. Michael McIntosh
- Department of BiologyUniversity of Utah, Salt Lake City Utah USA
- Department of PsychiatryUniversity of Utah, Salt Lake City Utah USA
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Azam L, Maskos U, Changeux JP, Dowell CD, Christensen S, De Biasi M, McIntosh JM. α-Conotoxin BuIA[T5A;P6O]: a novel ligand that discriminates between α6ß4 and α6ß2 nicotinic acetylcholine receptors and blocks nicotine-stimulated norepinephrine release. FASEB J 2010; 24:5113-23. [PMID: 20739611 DOI: 10.1096/fj.10-166272] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
α6* (asterisk indicates the presence of additional subunits) nicotinic acetylcholine receptors (nAChRs) are broadly implicated in catecholamine-dependent disorders that involve attention, motor movement, and nicotine self-administration. Different molecular forms of α6 nAChRs mediate catecholamine release, but receptor differentiation is greatly hampered by a paucity of subtype selective ligands. α-Conotoxins are nAChR-targeted peptides used by Conus species to incapacitate prey. We hypothesized that distinct conotoxin-binding kinetics could be exploited to develop a series of selective probes to enable study of native receptor subtypes. Proline6 of α-conotoxin BuIA was found to be critical for nAChR selectivity; substitution of proline6 with 4-hydroyxproline increased the IC(50) by 2800-fold at α6/α3β2β3 but only by 6-fold at α6/α3β4 nAChRs (to 1300 and 12 nM, respectively). We used conotoxin probes together with subunit-null mice to interrogate nAChR subtypes that modulate hippocampal norepinephrine release. Release was abolished in α6-null mutant mice. α-Conotoxin BuIA[T5A;P6O] partially blocked norepinephrine release in wild-type controls but failed to block release in β4(-/-) mice. In contrast, BuIA[T5A;P6O] failed to block dopamine release in the wild-type striatum known to contain α6β2* nAChRs. BuIA[T5A;P6O] is a novel ligand for distinguishing between closely related α6* nAChRs; α6β4* nAChRs modulate norepinephrine release in hippocampus but not dopamine release in striatum.
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Affiliation(s)
- Layla Azam
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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Grilli M, Patti L, Robino F, Zappettini S, Raiteri M, Marchi M. Release-enhancing pre-synaptic muscarinic and nicotinic receptors co-exist and interact on dopaminergic nerve endings of rat nucleus accumbens. J Neurochem 2010; 105:2205-13. [PMID: 18298664 DOI: 10.1111/j.1471-4159.2008.05307.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Dopaminergic nerve endings in the corpus striatum possess nicotinic (nAChRs) and muscarinic cholinergic receptors (mAChRs) mediating release of dopamine (DA). Whether nAChRs and mAChRs co-exist and interact on the same nerve endings is unknown. We here investigate on these possibilities using rat nucleus accumbens synaptosomes pre-labeled with [(3)H]DA and exposed in superfusion to cholinergic receptor ligands. The mixed nAChR-mAChR agonists acetylcholine (ACh) and carbachol provoked [(3)H]DA release partially sensitive to the mAChR antagonist atropine but totally blocked by the nAChR antagonist mecamylamine. Addition of the mAChR agonist oxotremorine at the minimally effective concentration of 30 micromol/L, together with 3, 10, or 100 micromol/L (-)nicotine provoked synergistic effect on [(3)H]DA overflow. The [(3)H]DA overflow elicited by 100 micromol/L (-)nicotine plus 30 micromol/L oxotremorine was reduced by atropine down to the release produced by (-)nicotine alone and it was abolished by mecamylamine. The ryanodine receptor blockers dantrolene or 8-bromo-cADP-ribose, but not the inositol 1,4,5-trisphosphate receptor blocker xestospongin C inhibited the (-)nicotine/oxotremorine evoked [(3)H]DA overflow similarly to atropine. This overflow was partly sensitive to 100 nmol/L methyllycaconitine which did not prevent the synergistic effect of (-)nicotine/oxotremorine. Similarly to (-)nicotine, the selective alpha4beta2 nAChR agonist RJR2403 exhibited synergism when added together with oxotremorine. To conclude, in rat nucleus accumbens, alpha4beta2 nAChRs exert a permissive role on the releasing function of reportedly M(5) mAChRs co-existing on the same dopaminergic nerve endings.
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Affiliation(s)
- Massimo Grilli
- Department of Experimental Medicine, University of Genoa, Genoa, Italy
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Brunzell DH, Boschen KE, Hendrick ES, Beardsley PM, McIntosh JM. Alpha-conotoxin MII-sensitive nicotinic acetylcholine receptors in the nucleus accumbens shell regulate progressive ratio responding maintained by nicotine. Neuropsychopharmacology 2010; 35:665-73. [PMID: 19890263 PMCID: PMC2821821 DOI: 10.1038/npp.2009.171] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Beta2 subunit containing nicotinic acetylcholine receptors (beta2(*)nAChRs; asterisk ((*)) denotes assembly with other subunits) are critical for nicotine self-administration and nicotine-associated dopamine (DA) release that supports nicotine reinforcement. The alpha6 subunit assembles with beta2 on DA neurons where alpha6beta2(*)nAChRs regulate nicotine-stimulated DA release at neuron terminals. Using local infusion of alpha-conotoxin MII (alpha-CTX MII), an antagonist with selectivity for alpha6beta2(*)nAChRs, the purpose of these experiments was to determine if alpha6beta2(*)nAChRs in the nucleus accumbens (NAc) shell are required for motivation to self-administer nicotine. Long-Evans rats lever-pressed for 0.03 mg/kg, i.v., nicotine accompanied by light+tone cues (NIC) or for light+tone cues unaccompanied by nicotine (CUEonly). Following extensive training, animals were tested under a progressive ratio (PR) schedule that required an increasing number of lever presses for each nicotine infusion and/or cue delivery. Immediately before each PR session, rats received microinfusions of alpha-CTX MII (0, 1, 5, or 10 pmol per side) into the NAc shell or the overlying anterior cingulate cortex. alpha-CTX MII dose dependently decreased break points and number of infusions earned by NIC rats following infusion into the NAc shell but not the anterior cingulate cortex. Concentrations of alpha-CTX MII that were capable of attenuating nicotine self-administration did not disrupt locomotor activity. There was no effect of infusion on lever pressing in CUEonly animals and NAc infusion alpha-CTX MII did not affect locomotor activity in an open field. These data suggest that alpha6beta2(*)nAChRs in the NAc shell regulate motivational aspects of nicotine reinforcement but not nicotine-associated locomotor activation.
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Affiliation(s)
- Darlene H Brunzell
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23298, USA.
| | - Karen E Boschen
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - Elizabeth S Hendrick
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - Patrick M Beardsley
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - J Michael McIntosh
- Department of Psychiatry, University of Utah, Salt Lake City, UT, USA,Department of Biology, University of Utah, Salt Lake City, UT, USA
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Lovinger DM. Neurotransmitter roles in synaptic modulation, plasticity and learning in the dorsal striatum. Neuropharmacology 2010; 58:951-61. [PMID: 20096294 DOI: 10.1016/j.neuropharm.2010.01.008] [Citation(s) in RCA: 372] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Revised: 01/08/2010] [Accepted: 01/12/2010] [Indexed: 02/08/2023]
Abstract
The dorsal striatum is a large forebrain region involved in action initiation, timing, control, learning and memory. Learning and remembering skilled movement sequences requires the dorsal striatum, and striatal subregions participate in both goal-directed (action-outcome) and habitual (stimulus-response) learning. Modulation of synaptic transmission plays a large part in controlling input to as well as the output from striatal medium spiny projection neurons (MSNs). Synapses in this brain region are subject to short-term modulation, including allosteric alterations in ion channel function and prominent presynaptic inhibition. Two forms of long-term synaptic plasticity have also been observed in striatum, long-term potentiation (LTP) and long-term depression (LTD). LTP at glutamatergic synapses onto MSNs involves activation of NMDA-type glutamate receptors and D1 dopamine or A2A adenosine receptors. Expression of LTP appears to involve postsynaptic mechanisms. LTD at glutamatergic synapses involves retrograde endocannabinoid signaling stimulated by activation of metabotropic glutamate receptors (mGluRs) and D2 dopamine receptors. While postsynaptic mechanisms participate in LTD induction, maintained expression involves presynaptic mechanisms. A similar form of LTD has also been observed at GABAergic synapses onto MSNs. Studies have just begun to examine the roles of synaptic plasticity in striatal-based learning. Findings to date indicate that molecules implicated in induction of plasticity participate in these forms of learning. Neurotransmitter receptors involved in LTP induction are necessary for proper skill and goal-directed instrumental learning. Interestingly, receptors involved in LTP and LTD at glutamatergic synapses onto MSNs of the "indirect pathway" appear to have important roles in habit learning. More work is needed to reveal if and when synaptic plasticity occurs during learning and if so what molecules and cellular processes, both short- and long-term, contribute to this plasticity.
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Affiliation(s)
- David M Lovinger
- Laboratory for Integrative Neuroscience, NIAAA/NIH, 5625 Fishers Lane, Rockville, MD 20852, USA.
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Dwoskin LP, Smith AM, Wooters TE, Zhang Z, Crooks PA, Bardo MT. Nicotinic receptor-based therapeutics and candidates for smoking cessation. Biochem Pharmacol 2009; 78:732-43. [PMID: 19523455 PMCID: PMC4110684 DOI: 10.1016/j.bcp.2009.06.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/29/2009] [Accepted: 06/01/2009] [Indexed: 12/29/2022]
Abstract
Tobacco dependence is the most preventable cause of death and is a chronic, relapsing disorder in which compulsive tobacco use persists despite known negative health consequences. All currently available cessation agents (nicotine, varenicline and bupropion) have limited efficacy and are associated with high relapse rates, revealing a need for more efficacious, alternative pharmacotherapies. The major alkaloid in tobacco, nicotine, activates nicotinic receptors (nAChRs) which increase brain extracellular dopamine producing nicotine reward leading to addiction. nAChRs are located primarily presynaptically and modulate synaptic activity by regulating neurotransmitter release. Subtype-selective nAChR antagonists that block reward-relevant mesocorticolimbic and nigrostriatal dopamine release induced by nicotine may offer advantages over current therapies. An innovative approach is to provide pharmacotherapies which are antagonists at nAChR subtypes mediating nicotine evoked dopamine release. In addition, providing multiple medications with a wider array of targets and mechanisms should provide more treatment options for individuals who are not responsive to the currently available pharmacotherapies. This review summarizes the currently available smoking cessation therapies and discusses emerging potential therapeutic approaches employing pharmacological agents which act as antagonists at nicotinic receptors.
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Affiliation(s)
- Linda P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536, USA.
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Anderson DJ, Malysz J, Grønlien JH, El Kouhen R, Håkerud M, Wetterstrand C, Briggs CA, Gopalakrishnan M. Stimulation of dopamine release by nicotinic acetylcholine receptor ligands in rat brain slices correlates with the profile of high, but not low, sensitivity α4β2 subunit combination. Biochem Pharmacol 2009; 78:844-51. [DOI: 10.1016/j.bcp.2009.06.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 06/12/2009] [Accepted: 06/15/2009] [Indexed: 11/15/2022]
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Differential contribution of genetic variation in multiple brain nicotinic cholinergic receptors to nicotine dependence: recent progress and emerging open questions. Mol Psychiatry 2009; 14:912-45. [PMID: 19564872 DOI: 10.1038/mp.2009.59] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Nicotine dependence (ND), a major public health challenge, is a complex, multifactorial behavior, in which both genetic and environmental factors have a role. Brain nicotinic acetylcholine receptor (nAChR)-encoding genes are among the most prominent candidate genes studied in the context of ND, because of their biological relevance as binding sites for nicotine. Until recently, most research on the role of nAChRs in ND has focused on two of these genes (encoding the alpha4- and beta2-subunits) and not much attention has been paid to the possible contribution of the other nine brain nAChR subunit genes (alpha2-alpha3, alpha5-alpha7, alpha9-alpha10, beta3-beta4) to the pathophysiology and genetics of ND. This situation has changed dramatically in the last 2 years during which intensive research had addressed the issue, mainly from the genetics perspective, and has shown the importance of the CHRNA5-CHRNA3-CHRNB4 and CHRNA6-CHRNB3 loci in ND-related phenotypes. In this review, we highlight recent findings regarding the contribution of non-alpha4/beta2-subunit containing nAChRs to ND, based on several lines of evidence: (1) human genetics studies (including linkage analysis, candidate-gene association studies and whole-genome association studies) of several ND-related phenotypes; (2) differential pharmacological and biochemical properties of receptors containing these subunits; (3) evidence from genetically manipulated mice; and (4) the contribution of nAChR genes to ND-related personality traits and neurocognitive profiles. Combining neurobiological genetic and behavioral perspectives, we suggest that genetic susceptibility to ND is not linked to one or two specific nAChR subtype genes but to several. In particular, the alpha3, alpha5-6 and beta3-4 nAChR subunit-encoding genes may play a much more pivotal role in the neurobiology and genetics of ND than was appreciated earlier. At the functional level, variants in these subunit genes (most likely regulatory) may have independent as well as interactive contributions to the ND phenotype spectrum. We address methodological challenges in the field, highlight open questions and suggest possible pathways for future research.
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Mouse striatal dopamine nerve terminals express alpha4alpha5beta2 and two stoichiometric forms of alpha4beta2*-nicotinic acetylcholine receptors. J Mol Neurosci 2009; 40:91-5. [PMID: 19693710 DOI: 10.1007/s12031-009-9263-y] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
Abstract
Wild-type and alpha5 null mutant mice were used to identify nicotinic cholinergic receptors (nAChRs) that mediate alpha-conotoxin MII (alpha-CtxMII)-resistant dopamine (DA) release from striatal synaptosomes. Concentration-effect curves for ACh-stimulated release (20 s) were monophasic when wild-type synaptosomes were assayed but biphasic with synaptosomes from the alpha5 null mutant. Deleting the alpha5 gene also resulted in decreased maximal ACh-stimulated alpha-CtxMII-resistant DA release. When a shorter perfusion time (5 s) was used, biphasic curves were detected in both wild-type and alpha5 null mutants, indicative of high- and low-sensitivity (HS and LS) activity. In addition, DHbetaE-sensitive (HS) and DHbetaE-resistant (LS) components were found in both genotypes. These results indicate that alpha-CtxMII-resistant DA release is mediated by alpha4alpha5beta2, (alpha4)(2)(beta2)(3) (HS), and (alpha4)(3)(beta2)(2) (LS) nAChRs.
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41
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Nicotine and Behavioral Sensitization. J Mol Neurosci 2009; 40:154-63. [DOI: 10.1007/s12031-009-9230-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 07/20/2009] [Indexed: 10/20/2022]
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The novel nicotinic receptor antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB), inhibits nicotine-evoked [(3)H]norepinephrine overflow from rat hippocampal slices. Biochem Pharmacol 2009; 78:889-97. [PMID: 19631612 DOI: 10.1016/j.bcp.2009.07.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 07/17/2009] [Accepted: 07/20/2009] [Indexed: 11/21/2022]
Abstract
Smoking is a significant health concern and strongly correlated with clinical depression. Depression is associated with decreased extracellular NE concentrations in brain. Smokers may be self-medicating and alleviating their depression through nicotine stimulated norepinephrine (NE) release. Several antidepressants inhibit NE transporter (NET) function, thereby augmenting extracellular NE concentrations. Antidepressants, such as bupropion, also inhibit nicotinic receptor (nAChR) function. The current study determined if a recently discovered novel nAChR antagonist, N,N'-dodecane-1,12-diyl-bis-3-picolinium dibromide (bPiDDB), inhibits nicotine-evoked NE release from superfused rat hippocampal slices. Previous studies determined that bPiDDB potently (IC(50)=2 nM) inhibits nicotine-evoked striatal [(3)H]dopamine (DA) release in vitro, nicotine-evoked DA release in nucleus accumbens in vivo, and nicotine self-administration in rats. In the current study, nicotine stimulated [(3)H]NE release from rat hippocampal slices (EC(50)=50 microM). bPiDDB inhibited (IC(50)=430 nM; I(max)=90%) [(3)H]NE release evoked by 30 microM nicotine. For comparison, the nonselective nAChR antagonist, mecamylamine, and the alpha7 antagonist, methyllycaconitine, also inhibited nicotine-evoked [(3)H]NE release (IC(50)=31 and 275 nM, respectively; I(max)=91% and 72%, respectively). Inhibition by bPiDDB and mecamylamine was not overcome by increasing nicotine concentrations; Schild regression slope was different from unity, consistent with allosteric inhibition. Thus, bPiDDB was 200-fold more potent inhibiting nAChRs mediating nicotine-evoked [(3)H]DA release from striatum than those mediating nicotine-evoked [(3)H]NE release from hippocampus.
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43
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Govind AP, Vezina P, Green WN. Nicotine-induced upregulation of nicotinic receptors: underlying mechanisms and relevance to nicotine addiction. Biochem Pharmacol 2009; 78:756-65. [PMID: 19540212 DOI: 10.1016/j.bcp.2009.06.011] [Citation(s) in RCA: 213] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 06/04/2009] [Accepted: 06/09/2009] [Indexed: 02/05/2023]
Abstract
A major hurdle in defining the molecular biology of nicotine addiction has been characterizing the different nicotinic acetylcholine receptor (nAChR) subtypes in the brain and how nicotine alters their function. Mounting evidence suggests that the addictive effects of nicotine, like other drugs of abuse, occur through interactions with its receptors in the mesolimbic dopamine system, particularly ventral tegmental area (VTA) neurons, where nicotinic receptors act to modulate the release of dopamine. The molecular identity of the nicotinic receptors responsible for drug seeking behavior, their cellular and subcellular location and the mechanisms by which these receptors initiate and maintain addiction are poorly defined. In this commentary, we review how nicotinic acetylcholine receptors (nAChRs) are upregulated by nicotine exposure, the potential posttranslational events that appear to cause it and how upregulation is linked to nicotine addiction.
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Affiliation(s)
- Anitha P Govind
- Department of Neurobiology, University of Chicago, Abbot Hall 402-MC0926, Chicago, IL 60637, USA.
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44
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Alpha-conotoxins as pharmacological probes of nicotinic acetylcholine receptors. Acta Pharmacol Sin 2009; 30:771-83. [PMID: 19448650 DOI: 10.1038/aps.2009.47] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cysteine-rich peptides from the venom of cone snails (Conus) target a wide variety of different ion channels. One family of conopeptides, the alpha-conotoxins, specifically target different isoforms of nicotinic acetylcholine receptors (nAChRs) found both in the neuromuscular junction and central nervous system. This family is further divided into subfamilies based on the number of amino acids between cysteine residues. The exquisite subtype selectivity of certain alpha-conotoxins has been key to the characterization of native nAChR isoforms involved in modulation of neurotransmitter release, the pathophysiology of Parkinson's disease and nociception. Structure/function characterization of alpha-conotoxins has led to the development of analogs with improved potency and/or subtype selectivity. Cyclization of the backbone structure and addition of lipophilic moieties has led to improved stability and bioavailability of alpha-conotoxins, thus paving the way for orally available therapeutics. The recent advances in phylogeny, exogenomics and molecular modeling promises the discovery of an even greater number of alpha-conotoxins and analogs with improved selectivity for specific subtypes of nAChRs.
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Nasiripourdori A, Ranjbar B, Naderi-Manesh H. Binding of long-chain alpha-neurotoxin would stabilize the resting state of nAChR: a comparative study with alpha-conotoxin. Theor Biol Med Model 2009; 6:3. [PMID: 19210780 PMCID: PMC2649906 DOI: 10.1186/1742-4682-6-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 02/11/2009] [Indexed: 11/27/2022] Open
Abstract
Background The details of interaction in a complex between potent antagonists such as long chain α-neurotoxins and α-conotoxins with nicotinic acetylcholine receptor (nAChR), and conformational changes induced by these antagonists, are not yet clear. Modeling In order to uncover some of these critical structural features, we conducted a docking simulation and a molecular dynamics simulation (MD) of a model of the ligand binding domain of nAChR in complex with a long-chain α-neurotoxin and an α-conotoxin. Results Our docking results confirm the claim that T.nAChR is in the basal or resting state, which favors binding to the alpha-neurotoxins. Moreover, more correct "hits" for the α/γ interface upon docking for conotoxin-nAChR confirm the preference of conotoxin GI for the α/γ interface. More importantly, upon binding of α-neurotoxin, ligand-bonded nAChR is less dynamic in certain domains than the apo form of the conotoxin-AChR complex. Some critical interactions in the binding site such as the salt bridge formed between K145/D200 in the neurotoxin-nAChR complex is further stabilized during the MD simulation, while it is obviously more labile in the apo form. Conclusion These observations could support the claim that alpha neurotoxins stabilize the nAChR resting state.
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Affiliation(s)
- Adak Nasiripourdori
- Department of Biophysics, Faculty of Science, Tarbiat Modares University, P,O, Box 14115-175, Tehran, Iran.
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Livingstone PD, Srinivasan J, Kew JN, Dawson LA, Gotti C, Moretti M, Shoaib M, Wonnacott S. α7 and non-α7 nicotinic acetylcholine receptors modulate dopamine releasein vitroandin vivoin the rat prefrontal cortex. Eur J Neurosci 2009; 29:539-50. [DOI: 10.1111/j.1460-9568.2009.06613.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Cellular events in nicotine addiction. Semin Cell Dev Biol 2009; 20:418-31. [PMID: 19560047 DOI: 10.1016/j.semcdb.2009.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 12/19/2008] [Accepted: 01/09/2009] [Indexed: 11/23/2022]
Abstract
In the 25 years since the observation that chronic exposure to nicotine could regulate the number and function of high affinity nicotine binding sites in the brain there has been a major effort to link alterations in nicotinic acetylcholine receptors (nAChRs) to nicotine-induced behaviors that drive the addiction to tobacco products. Here we review the proposed roles of various nAChR subtypes in the addiction process, with emphasis on how they are regulated by nicotine and the implications for understanding the cellular neurobiology of addiction to this drug.
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Abstract
The discovery that mammalian brain expresses the mRNAs for nine different nicotinic cholinergic receptor subunits (alpha2-alpha7, beta2-beta4) that form functional receptors when expressed in Xenopus laevis oocytes suggests that many different types of nicotinic cholinergic receptors (nAChRs) might be expressed in the mammalian brain., Using an historical approach, this chapter reviews some of the progress made in identifying the nAChR subtypes that seem to play a vital role in modulating dopaminergic function. nAChR subtypes that are expressed in dopamine neurons, as well as neurons that interact with dopamine neurons (glutamatergic, GABAergic), serve as the focus of this review. Subjects that are highlighted include the discovery of a low affinity alpha4beta2* nAChR, the identity of recently characterized alpha6* nAChRs, and the finding that these alpha6* receptors have the highest affinity for receptor activation of any of the native receptors that have been characterized to date. Topics that have been ignored in other recent reviews of this area, such as the discovery and potential importance of alternative transcripts, are presented along with a discussion of their potential importance.
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Gold AB, Keller AB, Perry DC. Prenatal exposure of rats to nicotine causes persistent alterations of nicotinic cholinergic receptors. Brain Res 2008; 1250:88-100. [PMID: 19028470 DOI: 10.1016/j.brainres.2008.10.076] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2008] [Revised: 10/29/2008] [Accepted: 10/29/2008] [Indexed: 11/30/2022]
Abstract
We examined for immediate and persistent changes in nAChRs in cerebral cortex, thalamus and striatum of male rats caused by prenatal exposure to nicotine from gestational day 3 to postnatal day 10 (PN10), and how such exposure affected the responses of adolescents to subsequent nicotine challenge. Receptor numbers were assessed by [(3)H]epibatidine binding and receptor function was measured by acetylcholine-stimulated (86)Rb efflux (cerebral cortex and thalamus) and nicotine-stimulated dopamine release (striatum). Immediate effects of prenatal nicotine, assessed in PN10 animals, were not detected for any parameter. A subsequent 14 day nicotine exposure in adolescence revealed persistent changes caused by prenatal nicotine exposure. Nicotine exposure in adolescents caused up-regulation of binding in all three regions; however, this up-regulation was lost in thalamus from animals prenatally exposed to nicotine. Nicotine exposure in adolescents caused decreased nicotine-stimulated dopamine release in striatum; this effect was lost in animals prenatally exposed to nicotine. Comparison of parameters in PN10 and PN42 rats revealed developmental changes in the CNS cholinergic system. In thalamus, binding increased with age, as did the proportion of (86)Rb efflux with high sensitivity to acetylcholine. In cortex, binding also increased with age, but there was no change in total (86)Rb efflux, and the proportion of high to low sensitivity efflux declined with age. Nicotine-stimulated striatal dopamine release (both total and alpha-conotoxin MII-resistant release) increased with age in naïve animals, but not in those prenatally exposed to nicotine. These findings demonstrate that prenatal exposure to nicotine causes alterations in nAChRs and in their regulation by nicotine that persist into adolescence. These changes may play a role in the increased risk for nicotine addiction observed in adolescent offspring of smoking mothers.
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Affiliation(s)
- Allison B Gold
- Department of Pharmacology and Physiology, George Washington University Medical Center, Washington DC 20037, USA
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Drenan RM, Grady SR, Whiteaker P, McClure-Begley T, McKinney S, Miwa JM, Bupp S, Heintz N, McIntosh JM, Bencherif M, Marks MJ, Lester HA. In vivo activation of midbrain dopamine neurons via sensitized, high-affinity alpha 6 nicotinic acetylcholine receptors. Neuron 2008; 60:123-36. [PMID: 18940593 DOI: 10.1016/j.neuron.2008.09.009] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 08/06/2008] [Accepted: 09/04/2008] [Indexed: 11/16/2022]
Abstract
Alpha6-containing (alpha6*) nicotinic ACh receptors (nAChRs) are selectively expressed in dopamine (DA) neurons and participate in cholinergic transmission. We generated and studied mice with gain-of-function alpha6* nAChRs, which isolate and amplify cholinergic control of DA transmission. In contrast to gene knockouts or pharmacological blockers, which show necessity, we show that activating alpha6* nAChRs and DA neurons is sufficient to cause locomotor hyperactivity. alpha6(L9'S) mice are hyperactive in their home cage and fail to habituate to a novel environment. Selective activation of alpha6* nAChRs with low doses of nicotine, by stimulating DA but not GABA neurons, exaggerates these phenotypes and produces a hyperdopaminergic state in vivo. Experiments with additional nicotinic drugs show that altering agonist efficacy at alpha6* provides fine tuning of DA release and locomotor responses. alpha6*-specific agonists or antagonists may, by targeting endogenous cholinergic mechanisms in midbrain or striatum, provide a method for manipulating DA transmission in neural disorders.
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Affiliation(s)
- Ryan M Drenan
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
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