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Walker NB, Tucker BR, Thomas LN, Tapp AE, Drenan DR, Drenan RM. Expression of sensitized β2 nAChR subunits in VTA neurons enhances intravenous nicotine self-administration in male rats. Neuropharmacology 2024; 261:110161. [PMID: 39299573 PMCID: PMC11486559 DOI: 10.1016/j.neuropharm.2024.110161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2024] [Revised: 09/12/2024] [Accepted: 09/13/2024] [Indexed: 09/22/2024]
Abstract
Ventral tegmental area (VTA) nicotinic acetylcholine receptors (nAChRs) are important for nicotine reinforcement. To determine whether and to what extent these receptors are sufficient for nicotine reinforcement, we expressed β2Leu9'Ser (i.e. sensitized) nAChR subunits in the VTA of adult male rats and assessed the nicotine dose-response relationship in intravenous self-administration (SA). β2Leu9'Ser rats self-administered nicotine doses 50-100 fold lower than the lowest doses that control rats would respond for. Expression of WT β2 subunits confirmed that this enhanced sensitivity to nicotine was due to the Leu9'Ser mutation in β2. Higher unit doses were associated with strong escalation in β2Leu9'Ser rats over 17 fixed ratio sessions. Escalation was minimal or absent in control rats at the same unit doses. In progressive ratio SA, β2Leu9'Ser rats exhibited higher breakpoints than control rats when the nicotine unit dose was 1.5 μg/kg/inf or higher. In intermittent access SA, β2Leu9'Ser rats exhibited response patterns very similar to control rats. By adding nicotine dose-response data, progressive ratio assays, and intermittent access results that rule out stereotypy, these data significantly extend our previous finding that nicotine activation of the mesolimbic dopamine pathway is sufficient for nicotine reinforcement.
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Affiliation(s)
- Noah B Walker
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Brenton R Tucker
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Leanne N Thomas
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Andrew E Tapp
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Dylan R Drenan
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA
| | - Ryan M Drenan
- Department of Translational Neuroscience, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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2
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O’Brien BCV, Thao S, Weber L, Danielson HL, Boldt AD, Hueffer K, Weltzin MM. The human alpha7 nicotinic acetylcholine receptor is a host target for the rabies virus glycoprotein. Front Cell Infect Microbiol 2024; 14:1394713. [PMID: 38836054 PMCID: PMC11148329 DOI: 10.3389/fcimb.2024.1394713] [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: 03/02/2024] [Accepted: 04/29/2024] [Indexed: 06/06/2024] Open
Abstract
The rabies virus enters the nervous system by interacting with several molecular targets on host cells to modify behavior and trigger receptor-mediated endocytosis of the virion by poorly understood mechanisms. The rabies virus glycoprotein (RVG) interacts with the muscle acetylcholine receptor and the neuronal α4β2 subtype of the nicotinic acetylcholine receptor (nAChR) family by the putative neurotoxin-like motif. Given that the neurotoxin-like motif is highly homologous to the α7 nAChR subtype selective snake toxin α-bungarotoxin (αBTX), other nAChR subtypes are likely involved. The purpose of this study is to determine the activity of the RVG neurotoxin-like motif on nAChR subtypes that are expressed in brain regions involved in rabid animal behavior. nAChRs were expressed in Xenopus laevis oocytes, and two-electrode voltage clamp electrophysiology was used to collect concentration-response data to measure the functional effects. The RVG peptide preferentially and completely inhibits α7 nAChR ACh-induced currents by a competitive antagonist mechanism. Tested heteromeric nAChRs are also inhibited, but to a lesser extent than the α7 subtype. Residues of the RVG peptide with high sequence homology to αBTX and other neurotoxins were substituted with alanine. Altered RVG neurotoxin-like peptides showed that residues phenylalanine 192, arginine 196, and arginine 199 are important determinants of RVG peptide apparent potency on α7 nAChRs, while serine 195 is not. The evaluation of the rabies ectodomain reaffirmed the observations made with the RVG peptide, illustrating a significant inhibitory impact on α7 nAChR with potency in the nanomolar range. In a mammalian cell culture model of neurons, we confirm that the RVG peptide binds preferentially to cells expressing the α7 nAChR. Defining the activity of the RVG peptide on nAChRs expands our understanding of basic mechanisms in host-pathogen interactions that result in neurological disorders.
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Affiliation(s)
- Brittany C. V. O’Brien
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Shelly Thao
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Lahra Weber
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Helen L. Danielson
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Agatha D. Boldt
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Karsten Hueffer
- Department of Veterinary Medicine, University of Alaska Fairbanks, Fairbanks, AK, United States
| | - Maegan M. Weltzin
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, United States
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3
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Papke RL. The many enigmas of nicotine. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2023; 99:327-354. [PMID: 38467485 DOI: 10.1016/bs.apha.2023.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
This review discusses the diverse effects of nicotine on the various nicotinic acetylcholine receptors of the central and peripheral nervous system and how those effects may promote the usage and addiction to tobacco products.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, United States.
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4
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Adolescent nicotine potentiates the inhibitory effect of raclopride, a D2R antagonist, on phencyclidine-sensitized psychotic-like behavior in mice. Toxicol Appl Pharmacol 2022; 456:116282. [DOI: 10.1016/j.taap.2022.116282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 10/03/2022] [Accepted: 10/11/2022] [Indexed: 01/01/2023]
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5
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Quijano Cardé NA, Shaw J, Carter C, Kim S, Stitzel JA, Venkatesh SK, Ramchandani VA, De Biasi M. Mutation of the α5 nicotinic acetylcholine receptor subunit increases ethanol and nicotine consumption in adolescence and impacts adult drug consumption. Neuropharmacology 2022; 216:109170. [PMID: 35752273 PMCID: PMC9308728 DOI: 10.1016/j.neuropharm.2022.109170] [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: 01/10/2022] [Revised: 06/16/2022] [Accepted: 06/19/2022] [Indexed: 10/17/2022]
Abstract
Alcohol and nicotine are commonly used during adolescence, establishing long-lasting neuroplastic alterations that influence subsequent drug use and abuse. Drinking- and smoking-related traits have been extensively associated with variation in CHRNA5 - the gene that encodes the α5 subunit of neuronal nicotinic acetylcholine receptors (nAChRs). The single nucleotide polymorphism (SNP) rs16969968 in CHRNA5 encodes an amino acid substitution (D398N) that alters the function and pharmacokinetics of α5-containing nAChR. When expressed in rodents, this variant results in increased ethanol and nicotine operant self-administration. How disruption of α5-containing nAChRs influences adolescent ethanol and nicotine intake, and how it modulates interactions between these drugs has not been previously explored. In the present study, we examined volitional ethanol and nicotine consumption in adolescent mice (post-natal day 30-43) of both sexes with mutated (SNP) or lacking (KO) the α5 nAChR subunit. The effect of adolescent alcohol or nicotine exposure on home cage consumption of the opposite drug in adulthood and its modulation by Chrna5 mutation and sex were examined. During adolescence, we found that α5 nAChR disruption increases nicotine intake in mice of both sexes, but the effect on alcohol intake was only observed in females. The sex-specific increase in alcohol consumption in α5 SNP and KO was replicated in adulthood. The effect of adolescent alcohol or nicotine exposure on subsequent intake of the opposite drug in adulthood is modulated by sex and Chrna5 mutation. These observations suggest sex differences in the genetic architecture of alcohol dependence, and modulators of alcohol and nicotine interactions.
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Affiliation(s)
- Natalia A Quijano Cardé
- Pharmacology Graduate Group, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Jessica Shaw
- Department of Psychiatry, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Christina Carter
- Department of Psychiatry, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
| | - Seung Kim
- Neuroscience Program, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
| | - Jerry A Stitzel
- Institute for Behavioral Genetics, University of Colorado Boulder, Boulder, CO, USA
| | - Shyamala K Venkatesh
- Department of Psychiatry, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA; Laboratory of Human Psychopharmacology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Vijay A Ramchandani
- Laboratory of Human Psychopharmacology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA
| | - Mariella De Biasi
- Pharmacology Graduate Group, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA; Department of Psychiatry, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA.
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6
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Lian M, Hueffer K, Weltzin MM. Interactions between the rabies virus and nicotinic acetylcholine receptors: A potential role in rabies virus induced behavior modifications. Heliyon 2022; 8:e10434. [PMID: 36091963 PMCID: PMC9450143 DOI: 10.1016/j.heliyon.2022.e10434] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 04/06/2022] [Accepted: 08/19/2022] [Indexed: 11/15/2022] Open
Affiliation(s)
- Marianne Lian
- University of Alaska Fairbanks, Department of Veterinary Medicine, 2141 Koyukuk Drive, Fairbanks, AK, 99775, USA
- Inland Norway University of Applied Sciences, Department of Forestry and Wildlife Management, Koppang, NO-2480, Norway
| | - Karsten Hueffer
- University of Alaska Fairbanks, Department of Veterinary Medicine, 2141 Koyukuk Drive, Fairbanks, AK, 99775, USA
| | - Maegan M. Weltzin
- University of Alaska Fairbanks, Department of Chemistry and Biochemistry, 1930 Yukon Dr. Fairbanks, AK, 99775, USA
- Corresponding author.
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7
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Grinevich VP, Zakirov AN, Berseneva UV, Gerasimova EV, Gainetdinov RR, Budygin EA. Applying a Fast-Scan Cyclic Voltammetry to Explore Dopamine Dynamics in Animal Models of Neuropsychiatric Disorders. Cells 2022; 11:cells11091533. [PMID: 35563838 PMCID: PMC9100021 DOI: 10.3390/cells11091533] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/29/2022] [Accepted: 04/30/2022] [Indexed: 02/07/2023] Open
Abstract
Progress in the development of technologies for the real-time monitoring of neurotransmitter dynamics has provided researchers with effective tools for the exploration of etiology and molecular mechanisms of neuropsychiatric disorders. One of these powerful tools is fast-scan cyclic voltammetry (FSCV), a technique which has progressively been used in animal models of diverse pathological conditions associated with alterations in dopamine transmission. Indeed, for several decades FSCV studies have provided substantial insights into our understanding of the role of abnormal dopaminergic transmission in pathogenetic mechanisms of drug and alcohol addiction, Parkinson’s disease, schizophrenia, etc. Here we review the applications of FSCV to research neuropsychiatric disorders with particular attention to recent technological advances.
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Affiliation(s)
- Vladimir P. Grinevich
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
| | - Amir N. Zakirov
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
| | - Uliana V. Berseneva
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
| | - Elena V. Gerasimova
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
| | - Raul R. Gainetdinov
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
- Institute of Translational Biomedicine and St. Petersburg State University Hospital, St. Petersburg State University, Universitetskaya Emb. 7-9, St. Petersburg 199034, Russia
| | - Evgeny A. Budygin
- Department of Neurobiology, Sirius University, 1 Olympic Ave., Sirius, Sochi 353340, Russia; (V.P.G.); (A.N.Z.); (U.V.B.); (E.V.G.); (R.R.G.)
- Correspondence:
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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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9
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Nall RW, Beloate LN, Meyerink ME, Penaloza T, Doolittle J, Froeliger B, Kalivas PW, Garcia-Keller C. Assessing combined effects of varenicline and N-acetylcysteine on reducing nicotine seeking in rats. Addict Biol 2022; 27:e13151. [PMID: 35229943 PMCID: PMC10777539 DOI: 10.1111/adb.13151] [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: 05/12/2021] [Revised: 12/22/2021] [Accepted: 01/14/2022] [Indexed: 11/27/2022]
Abstract
Nicotine addiction is a chronic relapsing brain disorder, and cigarette smoking is the leading cause of preventable death in the United States. Currently, the most effective pharmacotherapy for smoking cessation is Varenicline (VRN), which reduces both positive and negative reinforcement by nicotine. Clinically, VRN attenuates withdrawal symptoms and promotes abstinence, but >50% of smokers relapse within 3 months following a quit attempt. This may indicate that VRN fails to ameliorate components of nicotine-induced neuroplasticity that promote relapse vulnerability. Animal models reveal that glutamate dysregulation in the nucleus accumbens is associated with nicotine relapse. N-acetylcysteine (NAC) normalizes glutamate transmission and prolongs cocaine abstinence. Thus, combining VRN and NAC may promote and maintain, respectively, nicotine abstinence. In rats, we found that VRN effectively reduced nicotine self-administration and seeking in early abstinence, but not seeking later in abstinence. In contrast, NAC reduced seeking only later in abstinence. Because VRN and NAC are sometimes associated with mild adverse effects, we also evaluated a sequential approach combining subthreshold doses of VRN during self-administration and early abstinence with subthreshold doses of NAC during late abstinence. As expected, subthreshold VRN did not reduce nicotine intake. However, subthreshold VRN and NAC reduced seeking in late abstinence, suggesting a combined effect. Overall, our results suggest that combining subthreshold VRN and NAC is a viable and drug-specific approach to promote abstinence and reduce relapse while minimizing adverse effects. Our data also suggest that different components and time points in addiction engage the different neurocircuits targeted by VRN and NAC.
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Affiliation(s)
- Rusty W. Nall
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
- Department of Psychology, Jacksonville State University, 700 Pelham Rd. N., Jacksonville, AL, 36265
| | - Lauren N. Beloate
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
- Department of Biomedical Engineering, The Pennsylvania State University, 122 Chemical and Biomedical Engineering Building, University Park, PA 16802
| | - Michael E. Meyerink
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
| | - Tiffany Penaloza
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
| | - Jade Doolittle
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
| | - Brett Froeliger
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
- Department of Psychiatry, Department of Psychological Sciences, University of Missouri-Columbia, 1 Hospital Dr, Columbia, MO 65201
| | - Peter W. Kalivas
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
| | - Constanza Garcia-Keller
- Department of Neuroscience, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425
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10
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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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11
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Partial and full deletion of nicotinic acetylcholine receptor α4 and β2 subunits reduces sensitivity to acute nicotine administration and development of tolerance following chronic nicotine administration. Behav Pharmacol 2021; 31:688-701. [PMID: 32568759 DOI: 10.1097/fbp.0000000000000575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The diversity of nicotinic cholinergic receptor (nAChR) subunits underlies the complex responses to nicotine. Mice differing in the expression of α4 and β2 subunits, which are most widely expressed in brain, were evaluated for the responses to acute nicotine administration on Y-maze crossings and rears, open-field locomotion and body temperature following chronic treatment with nicotine (0, 0.25, 1.0 and 4.0 mg/kg/h). Deletion or partial deletion of the α4, β2 or both nAChR subunits reduced the sensitivity of mice to acute nicotine administration. This reduced sensitivity was gene dose-dependent. Modification of α4 subunit expression elicited a greater reduction in sensitivity than the modification of β2 subunit expression. No measurable tolerance was observed for mice of any genotype following chronic treatment with 0.25 mg/kg/h nicotine. Modest tolerance was noted following treatment with 1.0 mg/kg/h. Greater tolerance was observed following treatment with 4.0 mg/kg/h. The extent of tolerance differed among the mice depending on genotype: wild-type (α4 and β2) developed measurable tolerance for all four tests. Heterozygotes (α4, β2 and α4/β2) developed tolerance for only Y-maze crossings and body temperature. Null mutants (α4 and β2) did not become tolerant. However, following chronic treatment with 4.0 mg/kg/h nicotine, wild type, α4 and α4 mice displayed increased Y-maze crossings following acute administration of 0.5 mg/kg nicotine that may reflect the activity of α6β2*-nAChR. These results confirm the importance of the α4 and β2 nAChR subunits in mediating acute and chronic effects of nicotine on locomotion and body temperature in the mouse.
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12
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Wills L, Kenny PJ. Addiction-related neuroadaptations following chronic nicotine exposure. J Neurochem 2021; 157:1652-1673. [PMID: 33742685 DOI: 10.1111/jnc.15356] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/14/2021] [Accepted: 03/15/2021] [Indexed: 12/16/2022]
Abstract
The addiction-relevant molecular, cellular, and behavioral actions of nicotine are derived from its stimulatory effects on neuronal nicotinic acetylcholine receptors (nAChRs) in the central nervous system. nAChRs expressed by dopamine-containing neurons in the ventral midbrain, most notably in the ventral tegmental area (VTA), contribute to the reward-enhancing properties of nicotine that motivate the use of tobacco products. nAChRs are also expressed by neurons in brain circuits that regulate aversion. In particular, nAChRs expressed by neurons in the medial habenula (mHb) and the interpeduncular nucleus (IPn) to which the mHb almost exclusively projects regulate the "set-point" for nicotine aversion and control nicotine intake. Different nAChR subtypes are expressed in brain reward and aversion circuits and nicotine intake is titrated to maximally engage reward-enhancing nAChRs while minimizing the recruitment of aversion-promoting nAChRs. With repeated exposure to nicotine, reward- and aversion-related nAChRs and the brain circuits in which they are expressed undergo adaptations that influence whether tobacco use will transition from occasional to habitual. Genetic variation that influences the sensitivity of addiction-relevant brain circuits to the actions of nicotine also influence the propensity to develop habitual tobacco use. Here, we review some of the key advances in our understanding of the mechanisms by which nicotine acts on brain reward and aversion circuits and the adaptations that occur in these circuits that may drive addiction to nicotine-containing tobacco products.
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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, NY, USA
| | - Paul J Kenny
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, USA
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13
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Cytisine and cytisine derivatives. More than smoking cessation aids. Pharmacol Res 2021; 170:105700. [PMID: 34087351 DOI: 10.1016/j.phrs.2021.105700] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Revised: 05/29/2021] [Accepted: 05/29/2021] [Indexed: 12/12/2022]
Abstract
Cytisine, a natural bioactive compound that is mainly isolated from plants of the Leguminosae family (especially the seeds of Laburnum anagyroides), has been marketed in central and eastern Europe as an aid in the clinical management of smoking cessation for more than 50 years. Its main targets are neuronal nicotinic acetylcholine receptors (nAChRs), and pre-clinical studies have shown that its interactions with various nAChR subtypes located in different areas of the central and peripheral nervous systems are neuroprotective, have a wide range of biological effects on nicotine and alcohol addiction, regulate mood, food intake and motor activity, and influence the autonomic and cardiovascular systems. Its relatively rigid conformation makes it an attractive template for research of new derivatives. Recent studies of structurally modified cytisine have led to the development of new compounds and for some of them the biological activities are mediated by still unidentified targets other than nAChRs, whose mechanisms of action are still being investigated. The aim of this review is to describe and discuss: 1) the most recent pre-clinical results obtained with cytisine in the fields of neurological and non-neurological diseases; 2) the effects and possible mechanisms of action of the most recent cytisine derivatives; and 3) the main areas warranting further research.
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14
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Brynildsen JK, Blendy JA. Linking the CHRNA5 SNP to drug abuse liability: From circuitry to cellular mechanisms. Neuropharmacology 2021; 186:108480. [PMID: 33539855 PMCID: PMC7958463 DOI: 10.1016/j.neuropharm.2021.108480] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 12/10/2020] [Accepted: 01/28/2021] [Indexed: 10/22/2022]
Abstract
Genetics are known to be a significant risk factor for drug abuse. In human populations, the single nucleotide polymorphism (SNP) D398N in the gene CHRNA5 has been associated with addiction to nicotine, opioids, cocaine, and alcohol. In this paper, we review findings from studies in humans, rodent models, and cell lines and provide evidence that collectively suggests that the Chrna5 SNP broadly influences the response to drugs of abuse in a manner that is not substance-specific. This finding has important implications for our understanding of the role of the cholinergic system in reward and addiction vulnerability. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'
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Affiliation(s)
- Julia K Brynildsen
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Julie A Blendy
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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15
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Kwiatkowski MA, Roberts BZ, van Enkhuizen J, Ji B, Zhou X, Young JW. Chronic nicotine, but not suramin or resveratrol, partially remediates the mania-like profile of dopamine transporter knockdown mice. Eur Neuropsychopharmacol 2021; 42:75-86. [PMID: 33191077 PMCID: PMC8853461 DOI: 10.1016/j.euroneuro.2020.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 10/19/2020] [Accepted: 11/02/2020] [Indexed: 01/17/2023]
Abstract
Bipolar disorder (BD) is a severe mental illness affecting 2% of the global population. Current pharmacotherapies provide incomplete symptom remediation, highlighting the need for novel therapeutics. BD is characterized by fluctuations between mania and depression, likely driven by shifts between hyperdopaminergia and hypercholinergia, respectively. Hyperdopaminergia may result from insufficient activity of the dopamine transporter (DAT), the primary mediator of synaptic dopamine clearance. The DAT knockdown (DAT KD) mouse recreates this mechanism and exhibits a highly reproducible hyperexploratory profile in the cross-species translatable Behavioral Pattern Monitor (BPM) that is: (a) consistent with that observed in BD mania patients; and (b) partially normalized by chronic lithium and valproate treatment. The DAT KD/BPM model of mania therefore exhibits high levels of face-, construct-, and predictive-validity for the pre-clinical assessment of putative anti-mania drugs. Three different drug regimens - chronic nicotine (nicotinic acetylcholine receptor (nAChR) agonist; 40 mg/kg/d, 26 d), subchronic suramin (anti-purinergic; 20 mg/kg, 1 × /wk, 4 wks), and subchronic resveratrol (striatal DAT upregulator; 20 mg/kg/d, 4 d) - were administered to separate cohorts of male and female DAT KD- and wildtype (WT) littermate mice, and exploration was assessed in the BPM. Throughout, DAT KD mice exhibited robust hyperexploratory profiles relative to WTs. Nicotine partially normalized this behavior. Resveratrol modestly upregulated DAT expression but did not normalize DAT KD behavior. These results support the mania-like profile of DAT KD mice, which may be partially remediated by nAChR agonists via restoration of disrupted catecholaminergic/cholinergic equilibrium. Delineating the precise mechanism of action of nicotine could identify more selective therapeutic targets.
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Affiliation(s)
- Molly A Kwiatkowski
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States
| | - Benjamin Z Roberts
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States
| | - Jordy van Enkhuizen
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States
| | - Baohu Ji
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States
| | - Xianjin Zhou
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States
| | - Jared W Young
- Department of Psychiatry, UC San Diego School of Medicine, University of California, San Diego, CA 92093-0804, United States; Research Service, VA San Diego Healthcare System, United States.
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16
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Scholze P, Huck S. The α5 Nicotinic Acetylcholine Receptor Subunit Differentially Modulates α4β2 * and α3β4 * Receptors. Front Synaptic Neurosci 2020; 12:607959. [PMID: 33343327 PMCID: PMC7744819 DOI: 10.3389/fnsyn.2020.607959] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 11/11/2020] [Indexed: 11/30/2022] Open
Abstract
Nicotine, the principal reinforcing compound in tobacco, acts in the brain by activating neuronal nicotinic acetylcholine receptors (nAChRs). This review summarizes our current knowledge regarding how the α5 accessory nAChR subunit, encoded by the CHRNA5 gene, differentially modulates α4β2* and α3β4* receptors at the cellular level. Genome-wide association studies have linked a gene cluster in chromosomal region 15q25 to increased susceptibility to nicotine addiction, lung cancer, chronic obstructive pulmonary disease, and peripheral arterial disease. Interestingly, this gene cluster contains a non-synonymous single-nucleotide polymorphism (SNP) in the human CHRNA5 gene, causing an aspartic acid (D) to asparagine (N) substitution at amino acid position 398 in the α5 nAChR subunit. Although other SNPs have been associated with tobacco smoking behavior, efforts have focused predominantly on the D398 and N398 variants in the α5 subunit. In recent years, significant progress has been made toward understanding the role that the α5 nAChR subunit—and the role of the D398 and N398 variants—plays on nAChR function at the cellular level. These insights stem primarily from a wide range of experimental models, including receptors expressed heterologously in Xenopus oocytes, various cell lines, and neurons derived from human induced pluripotent stem cells (iPSCs), as well as endogenous receptors in genetically engineered mice and—more recently—rats. Despite providing a wealth of available data, however, these studies have yielded conflicting results, and our understanding of the modulatory role that the α5 subunit plays remains incomplete. Here, we review these reports and the various techniques used for expression and analysis in order to examine how the α5 subunit modulates key functions in α4β2* and α3β4* receptors, including receptor trafficking, sensitivity, efficacy, and desensitization. In addition, we highlight the strikingly different role that the α5 subunit plays in Ca2+ signaling between α4β2* and α3β4* receptors, and we discuss whether the N398 α5 subunit variant can partially replace the D398 variant.
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Affiliation(s)
- Petra Scholze
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Sigismund Huck
- Department of Pathobiology of the Nervous System, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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17
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Yavas E, Young AM. Repeated phencyclidine disrupts nicotinic acetylcholine regulation of dopamine release in nucleus accumbens: Implications for models of schizophrenia. Neurochem Int 2020; 140:104836. [DOI: 10.1016/j.neuint.2020.104836] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/11/2020] [Accepted: 08/13/2020] [Indexed: 01/02/2023]
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18
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Abstract
Addiction is commonly identified with habitual nonmedical self-administration of drugs. It is usually defined by characteristics of intoxication or by characteristics of withdrawal symptoms. Such addictions can also be defined in terms of the brain mechanisms they activate; most addictive drugs cause elevations in extracellular levels of the neurotransmitter dopamine. Animals unable to synthesize or use dopamine lack the conditioned reflexes discussed by Pavlov or the appetitive behavior discussed by Craig; they have only unconditioned consummatory reflexes. Burst discharges (phasic firing) of dopamine-containing neurons are necessary to establish long-term memories associating predictive stimuli with rewards and punishers. Independent discharges of dopamine neurons (tonic or pacemaker firing) determine the motivation to respond to such cues. As a result of habitual intake of addictive drugs, dopamine receptors expressed in the brain are decreased, thereby reducing interest in activities not already stamped in by habitual rewards.
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Affiliation(s)
- Roy A Wise
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA; .,Behavioral Genetics Laboratory, McLean Hospital, Belmont, Massachusetts 02478, USA;
| | - Mykel A Robble
- Behavioral Genetics Laboratory, McLean Hospital, Belmont, Massachusetts 02478, USA;
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19
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Cooper SY, Henderson BJ. The Impact of Electronic Nicotine Delivery System (ENDS) Flavors on Nicotinic Acetylcholine Receptors and Nicotine Addiction-Related Behaviors. Molecules 2020; 25:E4223. [PMID: 32942576 PMCID: PMC7571084 DOI: 10.3390/molecules25184223] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/11/2020] [Accepted: 09/13/2020] [Indexed: 12/18/2022] Open
Abstract
Over the past two decades, combustible cigarette smoking has slowly declined by nearly 11% in America; however, the use of electronic cigarettes has increased tremendously, including among adolescents. While nicotine is the main addictive component of tobacco products and a primary concern in electronic cigarettes, this is not the only constituent of concern. There is a growing market of flavored products and a growing use of zero-nicotine e-liquids among electronic cigarette users. Accordingly, there are few studies that examine the impact of flavors on health and behavior. Menthol has been studied most extensively due to its lone exception in combustible cigarettes. Thus, there is a broad understanding of the neurobiological effects that menthol plus nicotine has on the brain including enhancing nicotine reward, altering nicotinic acetylcholine receptor number and function, and altering midbrain neuron excitability. Although flavors other than menthol were banned from combustible cigarettes, over 15,000 flavorants are available for use in electronic cigarettes. This review seeks to summarize the current knowledge on nicotine addiction and the various brain regions and nicotinic acetylcholine receptor subtypes involved, as well as describe the most recent findings regarding menthol and green apple flavorants, and their roles in nicotine addiction and vaping-related behaviors.
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Affiliation(s)
| | - Brandon J. Henderson
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25703, USA;
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20
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Mahmood HM, Aldhalaan HM, Alshammari TK, Alqasem MA, Alshammari MA, Albekairi NA, AlSharari SD. The Role of Nicotinic Receptors in the Attenuation of Autism-Related Behaviors in a Murine BTBR T + tf/J Autistic Model. Autism Res 2020; 13:1311-1334. [PMID: 32691528 DOI: 10.1002/aur.2342] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 04/28/2020] [Accepted: 05/31/2020] [Indexed: 12/15/2022]
Abstract
Nicotinic receptors are distributed throughout the central and peripheral nervous system. Postmortem studies have reported that some nicotinic receptor subtypes are altered in the brains of autistic people. Recent studies have demonstrated the importance of nicotinic acetylcholine receptors (nAChRs) in the autistic behavior of BTBR T + tf/J mouse model of autism. This study was undertaken to examine the behavioral effects of targeted nAChRs using pharmacological ligands, including nicotine and mecamylamine in BTBR T + tf/J and C57BL/6J mice in a panel of behavioral tests relating to autism. These behavioral tests included the three-chamber social interaction, self-grooming, marble burying, locomotor activity, and rotarod test. We examined the effect of various oral doses of nicotine (50, 100, and 400 mcg/mL; po) over a period of 2 weeks in BTBR T + tf/J mouse model. The results indicated that the chronic administration of nicotine modulated sociability and repetitive behavior in BTBR T + tf/J mice while no effects observed in C57BL/6J mice. Furthermore, the nonselective nAChR antagonist, mecamylamine, reversed nicotine effects on sociability and increased repetitive behaviors in BTBR T + tf/J mice. Overall, the findings indicate that the pharmacological modulation of nicotinic receptors is involved in modulating core behavioral phenotypes in the BTBR T + tf/J mouse model. LAY SUMMARY: The involvement of brain nicotinic neurotransmission system plays a crucial role in regulating autism-related behavioral features. In addition, the brain of the autistic-like mouse model has a low acetylcholine level. Here, we report that nicotine, at certain doses, improved sociability and reduced repetitive behaviors in a mouse model of autism, implicating the potential therapeutic values of a pharmacological intervention targeting nicotinic receptors for autism therapy. Autism Res 2020, 13: 1311-1334. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.
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Affiliation(s)
- Hafiz M Mahmood
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Hesham M Aldhalaan
- Department of Neuroscience, Center for Autism Research, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Tahani K Alshammari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Mashael A Alqasem
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Musaad A Alshammari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Norah A Albekairi
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Shakir D AlSharari
- Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.,Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia, USA
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21
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Nolan SO, Zachry JE, Johnson AR, Brady LJ, Siciliano CA, Calipari ES. Direct dopamine terminal regulation by local striatal microcircuitry. J Neurochem 2020; 155:475-493. [PMID: 32356315 DOI: 10.1111/jnc.15034] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 04/20/2020] [Accepted: 04/22/2020] [Indexed: 02/06/2023]
Abstract
Regulation of axonal dopamine release by local microcircuitry is at the hub of several biological processes that govern the timing and magnitude of signaling events in reward-related brain regions. An important characteristic of dopamine release from axon terminals in the striatum is that it is rapidly modulated by local regulatory mechanisms. These processes can occur via homosynaptic mechanisms-such as presynaptic dopamine autoreceptors and dopamine transporters - as well heterosynaptic mechanisms such as retrograde signaling from postsynaptic cholinergic and dynorphin systems, among others. Additionally, modulation of dopamine release via diffusible messengers, such as nitric oxide and hydrogen peroxide, allows for various metabolic factors to quickly and efficiently regulate dopamine release and subsequent signaling. Here we review how these mechanisms work in concert to influence the timing and magnitude of striatal dopamine signaling, independent of action potential activity at the level of dopaminergic cell bodies in the midbrain, thereby providing a parallel pathway by which dopamine can be modulated. Understanding the complexities of local regulation of dopamine signaling is required for building comprehensive frameworks of how activity throughout the dopamine system is integrated to drive signaling and control behavior.
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Affiliation(s)
- Suzanne O Nolan
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Jennifer E Zachry
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Amy R Johnson
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Lillian J Brady
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Cody A Siciliano
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Center for Addiction Research, Vanderbilt University, Nashville, TN TN, USA
| | - Erin S Calipari
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.,Vanderbilt Center for Addiction Research, Vanderbilt University, Nashville, TN TN, USA.,Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, USA.,Department of Psychiatry and Behavioral Sciences, Vanderbilt University, Nashville, TN, USA
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22
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Faiq MA, Wollstein G, Schuman JS, Chan KC. Cholinergic nervous system and glaucoma: From basic science to clinical applications. Prog Retin Eye Res 2019; 72:100767. [PMID: 31242454 PMCID: PMC6739176 DOI: 10.1016/j.preteyeres.2019.06.003] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 06/19/2019] [Accepted: 06/21/2019] [Indexed: 02/08/2023]
Abstract
The cholinergic system has a crucial role to play in visual function. Although cholinergic drugs have been a focus of attention as glaucoma medications for reducing eye pressure, little is known about the potential modality for neuronal survival and/or enhancement in visual impairments. Citicoline, a naturally occurring compound and FDA approved dietary supplement, is a nootropic agent that is recently demonstrated to be effective in ameliorating ischemic stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, cerebrovascular diseases, memory disorders and attention-deficit/hyperactivity disorder in both humans and animal models. The mechanisms of its action appear to be multifarious including (i) preservation of cardiolipin, sphingomyelin, and arachidonic acid contents of phosphatidylcholine and phosphatidylethanolamine, (ii) restoration of phosphatidylcholine, (iii) stimulation of glutathione synthesis, (iv) lowering glutamate concentrations and preventing glutamate excitotoxicity, (v) rescuing mitochondrial function thereby preventing oxidative damage and onset of neuronal apoptosis, (vi) synthesis of myelin leading to improvement in neuronal membrane integrity, (vii) improving acetylcholine synthesis and thereby reducing the effects of mental stress and (viii) preventing endothelial dysfunction. Such effects have vouched for citicoline as a neuroprotective, neurorestorative and neuroregenerative agent. Retinal ganglion cells are neurons with long myelinated axons which provide a strong rationale for citicoline use in visual pathway disorders. Since glaucoma is a form of neurodegeneration involving retinal ganglion cells, citicoline may help ameliorate glaucomatous damages in multiple facets. Additionally, trans-synaptic degeneration has been identified in humans and experimental models of glaucoma suggesting the cholinergic system as a new brain target for glaucoma management and therapy.
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Affiliation(s)
- Muneeb A Faiq
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, United States
| | - Gadi Wollstein
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, United States
| | - Joel S Schuman
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, United States
| | - Kevin C Chan
- Department of Ophthalmology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, United States; Department of Radiology, New York University (NYU) School of Medicine, NYU Langone Health, New York, NY, United States; Center for Neural Science, Faculty of Arts and Science, New York University, New York, NY, United States.
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23
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Correa VL, Flores RJ, Carcoba LM, Arreguin MC, O'Dell LE. Sex differences in cholinergic systems in the interpeduncular nucleus following nicotine exposure and withdrawal. Neuropharmacology 2019; 158:107714. [PMID: 31325431 DOI: 10.1016/j.neuropharm.2019.107714] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 07/01/2019] [Accepted: 07/15/2019] [Indexed: 12/27/2022]
Abstract
The medial habenula-interpeduncular nucleus (MHb-IPN) pathway modulates negative affective states produced by nicotine withdrawal. Sex differences in the contribution of acetylcholine (ACh) systems in this pathway have not been explored. Thus, this study assessed ACh levels and gene expression of α- and β-containing nicotinic acetylcholine receptor (nAChR) subunits in the IPN of female and male rats following nicotine treatment and withdrawal. Rats were prepared with a pump that delivered nicotine for 14 days, and naïve controls received a sham surgery. In Study 1, rats were prepared with a probe in the IPN, and ACh levels were measured following saline and then mecamylamine administration. In Study 2, separate groups of naïve control or nicotine-treated rats received saline or mecamylamine and physical signs and anxiety-like behavior were assessed using elevated plus maze (EPM) procedures. The IPN was then dissected and mRNA levels were assessed using RT-qPCR methods. Nicotine treatment increased ACh levels to a larger extent in females than males. Nicotine withdrawal produced a similar increase in physical signs; however, females displayed greater anxiety-like behavior than males. In females, gene expression of α5 increased following nicotine treatment and withdrawal. In males, α7 increased following nicotine treatment and α2 and α3 increased during nicotine withdrawal. Both females and males displayed an increase in β3 and β4 during nicotine withdrawal. In females, anxiety-like behavior was correlated with α4, α5, and β2 gene expression in the IPN. These results suggest that sex differences in withdrawal are modulated via cholinergic systems in the IPN.
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Affiliation(s)
- Victor L Correa
- Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX, USA
| | - Rodolfo J Flores
- Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX, USA
| | - Luis M Carcoba
- Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX, USA
| | - Montserrat C Arreguin
- Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX, USA
| | - Laura E O'Dell
- Department of Psychology, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX, USA.
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24
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Gao F, Chen D, Ma X, Sudweeks S, Yorgason JT, Gao M, Turner D, Eaton JB, McIntosh JM, Lukas RJ, Whiteaker P, Chang Y, Steffensen SC, Wu J. Alpha6-containing nicotinic acetylcholine receptor is a highly sensitive target of alcohol. Neuropharmacology 2019; 149:45-54. [PMID: 30710570 PMCID: PMC7323585 DOI: 10.1016/j.neuropharm.2019.01.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 01/01/2019] [Accepted: 01/17/2019] [Indexed: 02/05/2023]
Abstract
Alcohol use disorder (AUD) is a serious public health problem that results in tremendous social, legal and medical costs to society. Unlike other addictive drugs, there is no specific molecular target for ethanol (EtOH). Here, we report a novel molecular target that mediates EtOH effects at concentrations below those that cause legally-defined inebriation. Using patch-clamp recording of human α6*-nicotinic acetylcholine receptor (α6*-nAChR) function when heterologously expressed in SH-EP1 human epithelial cells, we found that 0.1-5 mM EtOH significantly enhances α6*-nAChR-mediated currents with effects that are dependent on both EtOH and nicotine concentrations. EtOH exposure increased both whole-cell current rising slope and decay constants. This EtOH modulation was selective for α6*-nAChRs since it did not affect α3β4-, α4β2-, or α7-nAChRs. In addition, 5 mM EtOH also increased the frequency and amplitude of dopaminergic neuron transients in mouse brain nucleus accumbens slices, that were blocked by the α6*-nAChR antagonist, α-conotoxin MII, suggesting a role for native α6*-nAChRs in low-dose EtOH effects. Collectively, our data suggest that α6*-nAChRs are sensitive targets mediating low-dose EtOH effects through a positive allosteric mechanism, which provides new insight into mechanisms involved in pharmacologically-relevant alcohol effects contributing to AUD.
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Affiliation(s)
- Fenfei Gao
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong, 51504, China; Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Dejie Chen
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA; Department of Neurology, Yunfu People's Hospital, Yunfu, Guangdong, 527300, China
| | - Xiaokuang Ma
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong, 51504, China; Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Sterling Sudweeks
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT, 84602, USA
| | - Jordan T Yorgason
- Department of Psychology and Neuroscience, Brigham Young University, Provo, UT, 84602, USA
| | - Ming Gao
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Dharshaun Turner
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Jason Brek Eaton
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - J Michael McIntosh
- George E. Wahlen Veterans Affairs Medical Center, Salt Lake City, UT, USA 84108, USA
| | - Ronald J Lukas
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Paul Whiteaker
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Yongchang Chang
- Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA
| | - Scott C Steffensen
- Department of Psychology and Neuroscience, Brigham Young University, Provo, UT, 84602, USA
| | - Jie Wu
- Department of Pharmacology, Shantou University Medical College, Shantou, Guangdong, 51504, China; Division of Neurobiology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, 85013, USA; Department of Neurology, Yunfu People's Hospital, Yunfu, Guangdong, 527300, China.
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25
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Buck JM, Sanders KN, Wageman CR, Knopik VS, Stitzel JA, O'Neill HC. Developmental nicotine exposure precipitates multigenerational maternal transmission of nicotine preference and ADHD-like behavioral, rhythmometric, neuropharmacological, and epigenetic anomalies in adolescent mice. Neuropharmacology 2019; 149:66-82. [PMID: 30742847 DOI: 10.1016/j.neuropharm.2019.02.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 01/11/2019] [Accepted: 02/04/2019] [Indexed: 12/20/2022]
Abstract
Maternal smoking during pregnancy, a form of developmental nicotine exposure (DNE), is associated with increased nicotine use and neurodevelopmental disorders such as ADHD in children. Here, we characterize the behavioral, rhythmometric, neuropharmacological, and epigenetic consequences of DNE in the F1 (first) and F2 (second) generation adolescent offspring of mice exposed to nicotine prior to and throughout breeding. We assessed the effects of passive oral methylphenidate (MPH) administration and voluntary nicotine consumption on home cage activity rhythms and activity and risk-taking behaviors in the open field. Results imply a multigenerational predisposition to nicotine consumption in DNE mice and demonstrate ADHD-like diurnal and nocturnal hyperactivity and anomalies in the rhythmicity of home cage activity that are reversibly rescued by MPH and modulated by voluntary nicotine consumption. DNE mice are hyperactive in the open field and display increased risk-taking behaviors that are normalized by MPH. Pharmacological characterization of nicotinic and dopaminergic systems in striatum and frontal cortex reveals altered expression and dysfunction of nicotinic acetylcholine receptors (nAChRs), hypersensitivity to nicotine-induced nAChR-mediated dopamine release, and impaired dopamine transporter (DAT) function in DNE mice. Global DNA methylation assays indicate DNA methylome deficits in striatum and frontal cortex of DNE mice. Collectively, our data demonstrate that DNE enhances nicotine preference, elicits hyperactivity and risk-taking behaviors, perturbs the rhythmicity of activity, alters nAChR expression and function, impairs DAT function, and causes DNA hypomethylation in striatum and frontal cortex of both first and second-generation adolescent offspring. These findings recapitulate multiple domains of ADHD symptomatology.
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Affiliation(s)
- Jordan M Buck
- Institute for Behavioral Genetics, University of Colorado, Boulder, United States; Department of Integrative Physiology, University of Colorado, Boulder, United States.
| | - Kelsey N Sanders
- Institute for Behavioral Genetics, University of Colorado, Boulder, United States
| | - Charles R Wageman
- Institute for Behavioral Genetics, University of Colorado, Boulder, United States
| | - Valerie S Knopik
- Department of Human Development and Family Studies, Purdue University, United States
| | - Jerry A Stitzel
- Institute for Behavioral Genetics, University of Colorado, Boulder, United States; Department of Integrative Physiology, University of Colorado, Boulder, United States
| | - Heidi C O'Neill
- Institute for Behavioral Genetics, University of Colorado, Boulder, United States
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Gu S, Matta JA, Davini WB, Dawe GB, Lord B, Bredt DS. α6-Containing Nicotinic Acetylcholine Receptor Reconstitution Involves Mechanistically Distinct Accessory Components. Cell Rep 2019; 26:866-874.e3. [PMID: 30673609 DOI: 10.1016/j.celrep.2018.12.103] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 09/26/2018] [Accepted: 12/21/2018] [Indexed: 01/29/2023] Open
Abstract
Acetylcholine gates a large family of nicotinic receptor cation channels that control neuronal excitation and neurotransmitter release. These receptors are key targets for neuropsychiatric disorders; however, difficulties in expressing nicotinic acetylcholine (nACh) receptors hamper elaboration of their pharmacology and obscure elucidation of their biological functions. Particularly intriguing are α6-containing nACh receptors, which mediate nicotine-induced dopamine release in striatum-nucleus accumbens. Using genome-wide cDNA screening, we identify three accessory proteins, β-anchoring and -regulatory protein (BARP), lysosomal-associated membrane protein 5 (LAMP5), and SULT2B1, that complement the nACh receptor chaperone NACHO to reconstitute α6β2β3 channel function. Whereas NACHO mediates α6β2β3 assembly, BARP primarily enhances channel gating and LAMP5 and SULT2B1 promote receptor surface trafficking. BARP knockout mice show perturbations in presynaptic striatal nACh receptors that are consistent with BARP modulation of receptor desensitization. These studies unravel the molecular complexity of α6β2β3 biogenesis and enable physiological studies of this crucial neuropharmacological target.
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Affiliation(s)
- Shenyan Gu
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA
| | - Jose A Matta
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA
| | - Weston B Davini
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA
| | - G Brent Dawe
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA
| | - Brian Lord
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA
| | - David S Bredt
- Neuroscience Discovery, Janssen Pharmaceutical Companies of Johnson & Johnson, 3210 Merryfield Row, San Diego, CA 92121, USA.
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Fowler CD, Turner JR, Imad Damaj M. Molecular Mechanisms Associated with Nicotine Pharmacology and Dependence. Handb Exp Pharmacol 2019; 258:373-393. [PMID: 31267166 DOI: 10.1007/164_2019_252] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Tobacco dependence is a leading cause of preventable disease and death worldwide. Nicotine, the main psychoactive component in tobacco cigarettes, has also been garnering increased popularity in its vaporized form, as derived from e-cigarette devices. Thus, an understanding of the molecular mechanisms underlying nicotine pharmacology and dependence is required to ascertain novel approaches to treat drug dependence. In this chapter, we review the field's current understanding of nicotine's actions in the brain, the neurocircuitry underlying drug dependence, factors that modulate the function of nicotinic acetylcholine receptors, and the role of specific genes in mitigating the vulnerability to develop nicotine dependence. In addition to nicotine's direct actions in the brain, other constituents in nicotine and tobacco products have also been found to alter drug use, and thus, evidence is provided to highlight this issue. Finally, currently available pharmacotherapeutic strategies are discussed, along with an outlook for future therapeutic directions to achieve to the goal of long-term nicotine cessation.
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Affiliation(s)
- Christie D Fowler
- Department of Neurobiology and Behavior, University of California Irvine, Irvine, CA, USA
| | - Jill R Turner
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY, USA
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA. .,Translational Research Initiative for Pain and Neuropathy at VCU, Richmond, VA, USA.
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28
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Abudukeyoumu N, Hernandez-Flores T, Garcia-Munoz M, Arbuthnott GW. Cholinergic modulation of striatal microcircuits. Eur J Neurosci 2018; 49:604-622. [PMID: 29797362 PMCID: PMC6587740 DOI: 10.1111/ejn.13949] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 03/30/2018] [Accepted: 04/04/2018] [Indexed: 12/15/2022]
Abstract
The purpose of this review is to bridge the gap between earlier literature on striatal cholinergic interneurons and mechanisms of microcircuit interaction demonstrated with the use of newly available tools. It is well known that the main source of the high level of acetylcholine in the striatum, compared to other brain regions, is the cholinergic interneurons. These interneurons provide an extensive local innervation that suggests they may be a key modulator of striatal microcircuits. Supporting this idea requires the consideration of functional properties of these interneurons, their influence on medium spiny neurons, other interneurons, and interactions with other synaptic regulators. Here, we underline the effects of intrastriatal and extrastriatal afferents onto cholinergic interneurons and discuss the activation of pre‐ and postsynaptic muscarinic and nicotinic receptors that participate in the modulation of intrastriatal neuronal interactions. We further address recent findings about corelease of other transmitters in cholinergic interneurons and actions of these interneurons in striosome and matrix compartments. In addition, we summarize recent evidence on acetylcholine‐mediated striatal synaptic plasticity and propose roles for cholinergic interneurons in normal striatal physiology. A short examination of their role in neurological disorders such as Parkinson's, Huntington's, and Tourette's pathologies and dystonia is also included.
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Affiliation(s)
| | | | | | - Gordon W Arbuthnott
- Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
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29
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Hone AJ, Talley TT, Bobango J, Huidobro Melo C, Hararah F, Gajewiak J, Christensen S, Harvey PJ, Craik DJ, McIntosh JM. Molecular determinants of α-conotoxin potency for inhibition of human and rat α6β4 nicotinic acetylcholine receptors. J Biol Chem 2018; 293:17838-17852. [PMID: 30249616 DOI: 10.1074/jbc.ra118.005649] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 09/20/2018] [Indexed: 12/15/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) containing α6 and β4 subunits are expressed by dorsal root ganglion neurons and have been implicated in neuropathic pain. Rodent models are often used to evaluate the efficacy of analgesic compounds, but species differences may affect the activity of some nAChR ligands. A previous candidate α-conotoxin-based therapeutic yielded promising results in rodent models, but failed in human clinical trials, emphasizing the importance of understanding species differences in ligand activity. Here, we show that human and rat α6/α3β4 nAChRs expressed in Xenopus laevis oocytes exhibit differential sensitivity to α-conotoxins. Sequence homology comparisons of human and rat α6β4 nAChR subunits indicated that α6 residues forming the ligand-binding pocket are highly conserved between the two species, but several residues of β4 differed, including a Leu-Gln difference at position 119. X-ray crystallography of α-conotoxin PeIA complexed with the Aplysia californica acetylcholine-binding protein (AChBP) revealed that binding of PeIA orients Pro13 in close proximity to residue 119 of the AChBP complementary subunit. Site-directed mutagenesis studies revealed that Leu119 of human β4 contributes to higher sensitivity of human α6/α3β4 nAChRs to α-conotoxins, and structure-activity studies indicated that PeIA Pro13 is critical for high potency. Human and rat α6/α3β4 nAChRs displayed differential sensitivities to perturbations of the interaction between PeIA Pro13 and residue 119 of the β4 subunit. These results highlight the potential significance of species differences in α6β4 nAChR pharmacology that should be taken into consideration when evaluating the activity of candidate human therapeutics in rodent models.
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Affiliation(s)
| | | | - Janet Bobango
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana 59812
| | | | | | | | | | - Peta J Harvey
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - David J Craik
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
| | - J Michael McIntosh
- From the Departments of Biology; Psychiatry, University of Utah, Salt Lake City, Utah 84112; George E. Whalen Veterans Affairs Medical Center, Salt Lake City, Utah 84148.
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30
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Rollema H, Hurst RS. The contribution of agonist and antagonist activities of α4β2* nAChR ligands to smoking cessation efficacy: a quantitative analysis of literature data. Psychopharmacology (Berl) 2018; 235:2479-2505. [PMID: 29980822 DOI: 10.1007/s00213-018-4921-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Accepted: 04/29/2018] [Indexed: 12/14/2022]
Abstract
RATIONALE AND OBJECTIVE Two mechanisms underlie smoking cessation efficacies of α4β2* nicotinic acetylcholine receptor (nAChR) agonists: a "nicotine-like" agonist activity reduces craving by substituting for nicotine during a quit attempt, and a "nicotine-blocking" antagonist activity attenuates reinforcement by competing with inhaled nicotine during a relapse. To evaluate the contribution of each mechanism to clinical efficacy, we estimated the degree of agonist and antagonist activities of nicotine replacement therapy (NRT), varenicline, cytisine, and the discontinued nAChR agonists dianicline, ABT-418, ABT-089, CP-601927, and CP-601932, relative to the functional effects of nicotine from smoking. METHODS Functional activities that occur in vivo with clinical doses were predicted from literature data on binding and functional potencies at the target α4β2 nAChR, as well as at α6β2* nAChRs, and from estimates of free drug exposures in human brain. Agonist activity is comprised of nAChR activation and desensitization, which were expressed as percentages of desensitization and activation by nicotine from smoking. Antagonist activity was expressed as the reduction in nAChR occupancy by nicotine during smoking in the presence of an agonist. RESULTS Comparisons with odds ratios at end of treatment suggest that extensive α4β2 and α6β2* nAChR desensitization combined with α6β2* nAChR activation at similar levels as nicotine from smoking is associated with clinical efficacy (NRT, varenicline, cytisine, ABT-418). Effective competition with inhaled nicotine for α4β2 and α6β2* nAChRs further improves clinical efficacy (varenicline). Other discontinued nAChR agonists have lower agonist and antagonist activities at α4β2 nAChRs and are inactive or less efficacious than NRT (dianicline, ABT-089, CP-601927, CP-601932). CONCLUSION Three pharmacological effects appear to be key factors underlying smoking cessation efficacy: the degree of activation of α6β2* nAChRs, desensitization of α4β2 and α6β2* nAChRs (agonist activity), and the reduction of nicotine occupancy at α4β2 and α6β2* nAChRs (antagonist activity). No single activity is dominant, and the level of smoking cessation efficacy depends on the profile of these activities achieved at clinical doses. While adequate agonist activity alone seems sufficient for a clinical effect (e.g., NRT, cytisine), clinical efficacy is improved with substantial competitive antagonism of α4β2 nAChRs, i.e., if the drug has a dual agonist-antagonist mechanism of action (e.g., varenicline).
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Affiliation(s)
- Hans Rollema
- Rollema Biomedical Consulting, 20 Holdridge Court, Mystic, CT, 06355, USA.
| | - Raymond S Hurst
- Hurst Neuropharmacology Consulting, 30 Brook Trail Road, Wayland, MA, 01778, USA
- Concert Pharmaceuticals, Inc., 99 Hayden Avenue, Suite 500, Lexington, MA, 02421, USA
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31
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Peng C, Yan Y, Kim VJ, Engle SE, Berry JN, McIntosh JM, Neve RL, Drenan RM. Gene editing vectors for studying nicotinic acetylcholine receptors in cholinergic transmission. Eur J Neurosci 2018; 50:2224-2238. [PMID: 29779223 DOI: 10.1111/ejn.13957] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/19/2018] [Accepted: 04/16/2018] [Indexed: 01/28/2023]
Abstract
Nicotinic acetylcholine receptors (nAChRs), prototype members of the cys-loop ligand-gated ion channel family, are key mediators of cholinergic transmission in the central nervous system. Despite their importance, technical gaps exist in our ability to dissect the function of individual subunits in the brain. To overcome these barriers, we designed CRISPR/Cas9 small guide RNA sequences (sgRNAs) for the production of loss-of-function alleles in mouse nAChR genes. These sgRNAs were validated in vitro via deep sequencing. We subsequently targeted candidate nAChR genes in vivo by creating herpes simplex virus (HSV) vectors delivering sgRNAs and Cas9 expression to mouse brain. The production of loss-of-function insertions or deletions (indels) by these 'all-in-one' HSV vectors was confirmed using brain slice patch clamp electrophysiology coupled with pharmacological analysis. Next, we developed a scheme for cell type-specific gene editing in mouse brain. Knockin mice expressing Cas9 in a Cre-dependent manner were validated using viral microinjections and genetic crosses to common Cre-driver mouse lines. We subsequently confirmed functional Cas9 activity by targeting the ubiquitous neuronal protein, NeuN, using adeno-associated virus (AAV) delivery of sgRNAs. Finally, the mouse β2 nAChR gene was successfully targeted in dopamine transporter (DAT)-positive neurons via CRISPR/Cas9. The sgRNA sequences and viral vectors, including our scheme for Cre-dependent gene editing, should be generally useful to the scientific research community. These tools could lead to new discoveries related to the function of nAChRs in neurotransmission and behavioral processes.
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Affiliation(s)
- Can Peng
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Searle 5-450, Chicago, IL, 60611, USA
| | - Yijin Yan
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Searle 5-450, Chicago, IL, 60611, USA
| | - Veronica J Kim
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Searle 5-450, Chicago, IL, 60611, USA
| | - Staci E Engle
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
| | - Jennifer N Berry
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, 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
| | - Rachael L Neve
- Gene Delivery Technology Core, Massachusetts General Hospital, Cambridge, MA, USA
| | - Ryan M Drenan
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, 320 East Superior Street, Searle 5-450, Chicago, IL, 60611, USA
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32
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Attenuated dopaminergic neurodegeneration and motor dysfunction in hemiparkinsonian mice lacking the α5 nicotinic acetylcholine receptor subunit. Neuropharmacology 2018; 138:371-380. [PMID: 29940207 DOI: 10.1016/j.neuropharm.2018.06.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 06/04/2018] [Accepted: 06/21/2018] [Indexed: 11/23/2022]
Abstract
Preclinical studies suggest the involvement of various subtypes of nicotinic acetylcholine receptors in the pathophysiology of Parkinson's disease, a neurodegenerative disorder characterized by the death of dopaminergic neurons in the substantia nigra pars compacta (SNC). We studied for the first time the effects of α5 nicotinic receptor subunit gene deletion on motor behavior and neurodegeneration in mouse models of Parkinson's disease and levodopa-induced dyskinesia. Unilateral dopaminergic lesions were induced in wild-type and α5-KO mice by 6-hydroxydopamine injections into the striatum or the medial forebrain bundle. Subsequently, rotational behavior induced by dopaminergic drugs was measured. A subset of animals received chronic treatments with levodopa and nicotine to assess levodopa-induced dyskinesia and antidyskinetic effects by nicotine. SNC lesion extent was assessed with tyrosine hydroxylase immunohistochemistry and stereological cell counting. Effects of α5 gene deletion on the dopaminergic system were investigated by measuring ex vivo striatal dopamine transporter function and protein expression, dopamine and metabolite tissue concentrations and dopamine receptor mRNA expression. Hemiparkinsonian α5-KO mice exhibited attenuated rotational behavior after amphetamine injection and attenuated levodopa-induced dyskinesia. In the intrastriatal lesion model, dopaminergic cell loss in the medial cluster of the SNC was less severe in α5-KO mice. Decreased striatal dopamine uptake in α5-KO animals suggested reduced dopamine transporter function as a mechanism of attenuated neurotoxicity. Nicotine reduced dyskinesia severity in wild-type but not α5-KO mice. The attenuated dopaminergic neurodegeneration and motor dysfunction observed in hemiparkinsonian α5-KO mice suggests potential for α5 subunit-containing nicotinic receptors as a novel target in the treatment of Parkinson's disease.
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Moretti M, Fasoli F, Gotti C, Marks MJ. Reduced α4 subunit expression in α4 +- and α4 +- /β2 +- nicotinic acetylcholine receptors alters α4β2 subtype up-regulation following chronic nicotine treatment. Br J Pharmacol 2018; 175:1944-1956. [PMID: 28585241 PMCID: PMC5980142 DOI: 10.1111/bph.13896] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 05/22/2017] [Accepted: 05/23/2017] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND AND PURPOSE Genomic analysis has shown many variants in both CHRNA4 and CHRNB2, genes which encode the α4 and β2 subunits of nicotinic ACh receptors (nAChR) respectively. Some variants influence receptor expression, raising the possibility that CHRNA4 variants may affect response to tobacco use in humans. Chronic exposure to nicotine increases expression of nAChRs, particularly α4β2-nAChRs, in humans and laboratory animals. Here, we have evaluated whether the initial level of receptor expression affects the increase in expression. EXPERIMENTAL APPROACH Mice differing in expression of α4 and/or β2 nAChR subunits were chronically treated with saline, 0.25, 1.0 or 4.0 mg·kg-1 ·h-1 nicotine. Brain preparations were analysed autoradiographically by [125 I]-epibatidine binding, immunoprecipitation and Western blotting. KEY RESULTS Immunochemical studies confirmed that most of the [3 H]-epibatidine binding corresponds to α4β2*-nAChR and that increases in binding correspond to increases in α4 and β2 proteins. Consistent with previous reports, the dose-dependent increase in nAChR in wild-type mice following chronic nicotine treatment, measured with any of the methods, reached a maximum. Although receptor expression was reduced by approximately 50% in β2+- mice, the pattern of response to chronic treatment resembled that of wild-type mice. In contrast, both α4+- and α4+- /β2+- exhibited relatively greater up-regulation. Consistent with previous reports, α4β2α5-nAChR did not increase in response to nicotine. CONCLUSIONS AND IMPLICATIONS These results indicate that mice with reduced expression of the α4 nAChR subunit have a more robust response to chronic nicotine than mice with normal expression of this subunit. LINKED ARTICLES This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.
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Affiliation(s)
- Milena Moretti
- CNR, Institute of Neuroscience Milan, Milan, Italy
- Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy
| | | | - Cecilia Gotti
- CNR, Institute of Neuroscience Milan, Milan, Italy
- Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy
| | - Michael J Marks
- Instute for Behavioral Genetics and Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, CO, USA
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Bagdas D, Alkhlaif Y, Jackson A, Carroll FI, Ditre JW, Damaj MI. New insights on the effects of varenicline on nicotine reward, withdrawal and hyperalgesia in mice. Neuropharmacology 2018; 138:72-79. [PMID: 29860196 DOI: 10.1016/j.neuropharm.2018.05.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 05/16/2018] [Accepted: 05/19/2018] [Indexed: 12/16/2022]
Abstract
Varenicline, a partial agonist for α4β2* nicotinic acetylcholine receptors (nAChRs) and a full agonist for α3β4 and α7 nAChRs, is approved for smoking cessation treatment. Although, partial agonism at α4β2* nAChRs is believed to be the mechanism underlying the effects of varenicline on nicotine reward, the contribution of other nicotinic subtypes to varenicline's effects on nicotine reward is currently unknown. Therefore, we examined the role of α5 and α7 nAChR subunits in the effects of varenicline on nicotine reward using the conditioned place preference (CPP) test in mice. Moreover, the effects of varenicline on nicotine withdrawal-induced hyperalgesia and aversion are unknown. We also examined the reversal of nicotine withdrawal in mouse models of dependence by varenicline. Varenicline dose-dependently blocked the development and expression of nicotine reward in the CPP test. The blockade of nicotine reward by varenicline (0.1 mg/kg) was preserved in α7 knockout mice but reduced in α5 knockout mice. Administration of varenicline at high dose of 2.5 mg/kg resulted in a place aversion that was dependent on α5 nAChRs but not β2 nAChRs. Furthermore, varenicline (0.1 and 0.5 mg/kg) reversed nicotine withdrawal signs such as hyperalgesia and somatic signs and withdrawal-induced aversion in a dose-related manner. Our results indicate that the α5 nAChR subunit plays a role in the effects of varenicline on nicotine reward in mice. Moreover, the mediation of α5 nAChRs, but not β2 nAChRs are probably needed for aversive properties of varenicline at high dose. Varenicline was also shown to reduce several nicotine withdrawal signs.
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Affiliation(s)
- Deniz Bagdas
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States; The Center for the Study for Tobacco Products, Virginia Commonwealth University, Richmond, VA, United States.
| | - Yasmin Alkhlaif
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - Asti Jackson
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - F Ivy Carroll
- Center for Organic and Medicinal Chemistry, Research Triangle Institute, Research Triangle Park, NC, United States
| | - Joseph W Ditre
- Department of Psychology, Syracuse University, Syracuse, NY, United States
| | - M Imad Damaj
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States; The Center for the Study for Tobacco Products, Virginia Commonwealth University, Richmond, VA, United States
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35
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Conti MM, Chambers N, Bishop C. A new outlook on cholinergic interneurons in Parkinson's disease and L-DOPA-induced dyskinesia. Neurosci Biobehav Rev 2018; 92:67-82. [PMID: 29782883 DOI: 10.1016/j.neubiorev.2018.05.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 01/05/2018] [Accepted: 05/16/2018] [Indexed: 02/07/2023]
Abstract
Traditionally, dopamine (DA) and acetylcholine (ACh) striatal systems were considered antagonistic and imbalances or aberrant signaling between these neurotransmitter systems could be detrimental to basal ganglia activity and pursuant motor function, such as in Parkinson's disease (PD) and L-DOPA-induced dyskinesia (LID). Herein, we discuss the involvement of cholinergic interneurons (ChIs) in striatally-mediated movement in a healthy, parkinsonian, and dyskinetic state. ChIs integrate numerous neurotransmitter signals using intrinsic glutamate, serotonin, and DA receptors and convey the appropriate transmission onto nearby muscarinic and nicotinic ACh receptors to produce movement. In PD, severe DA depletion causes abnormal rises in ChI activity which promote striatal signaling to attenuate normal movement. When treating PD with L-DOPA, hyperkinetic side effects, or LID, develop due to increased striatal DA; however, the role of ChIs and ACh transmission, until recently has been unclear. Fortunately, new technology and pharmacological agents have facilitated understanding of ChI function and ACh signaling in the context of LID, thus offering new opportunities to modify existing and discover future therapeutic strategies in movement disorders.
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Affiliation(s)
- Melissa M Conti
- Behavioral Neuroscience Program, Department of Psychology, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY 13902-6000, USA.
| | - Nicole Chambers
- Behavioral Neuroscience Program, Department of Psychology, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY 13902-6000, USA.
| | - Christopher Bishop
- Behavioral Neuroscience Program, Department of Psychology, Binghamton University, 4400 Vestal Parkway East, Binghamton, NY 13902-6000, USA.
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36
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O'Neill HC, Wageman CR, Sherman SE, Grady SR, Marks MJ, Stitzel JA. The interaction of the Chrna5 D398N variant with developmental nicotine exposure. GENES BRAIN AND BEHAVIOR 2018; 17:e12474. [PMID: 29573323 DOI: 10.1111/gbb.12474] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/26/2018] [Accepted: 03/14/2018] [Indexed: 12/14/2022]
Abstract
A single nucleotide polymorphism (SNP) in CHRNA5 (rs16969968, change from an aspartic acid [D] to asparagine [N] at position 398 of the human α5 nicotinic acetylcholine receptor subunit) has been associated with increased risk for nicotine dependence. Consequently, carriers of the risk variant may be at elevated risk for in utero nicotine exposure. To assess whether this gene-environment interaction might impact nicotine intake in developmental nicotine-exposed offspring, we utilized a mouse expressing this human SNP. D and N dams drank nicotine (100 μg/mL) in 0.2% saccharin water or 0.2% saccharin water alone (vehicle) as their sole source of fluid from 30 days prior to breeding until weaning of offspring. The nicotine (D Nic, N Nic) or vehicle (D Veh, N Veh) exposed offspring underwent a 2-bottle choice test between postnatal ages of 30 to 46 days. N Nic offspring consumed the most nicotine at the highest concentration (400 μg/mL) compared with all other groups. In contrast, D Nic offspring drank the least amount of nicotine at all concentrations tested. Nicotine-stimulated dopamine (DA) release measured from striatal synaptosomes was increased in D Nic offspring, while decreased in N Nic offspring relative to their genotype-matched controls. These data suggest that the α5 variant influences the effect of developmental nicotine exposure on nicotine intake of exposed offspring. This gene-environment interaction on striatal DA release may provide motivation for increased nicotine seeking in N Nic offspring and reduced consumption in D Nic offspring.
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Affiliation(s)
- H C O'Neill
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
| | - C R Wageman
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
| | - S E Sherman
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
| | - S R Grady
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado
| | - M J Marks
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado.,Department of Psychology and Neuroscience, University of Colorado, Boulder, Colorado
| | - J A Stitzel
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado.,Department of Integrative Physiology, University of Colorado, Boulder, Colorado
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37
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The striatal cholinergic system in L-dopa-induced dyskinesias. J Neural Transm (Vienna) 2018; 125:1251-1262. [PMID: 29492663 DOI: 10.1007/s00702-018-1845-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 01/23/2018] [Indexed: 12/18/2022]
Abstract
Cholinergic signaling plays a key role in regulating striatal function. The principal source of acetylcholine in the striatum is the cholinergic interneurons which, although low in number, densely arborize to modulate striatal neurotransmission. This modulation occurs via strategically positioned nicotinic and muscarinic acetylcholine receptors that influence striatal dopamine, GABA and other neurotransmitter release. Cholinergic interneurons integrate multiple striatal synaptic inputs and outputs to regulate motor activity under normal physiological conditions. Consequently, an imbalance between these systems is associated with basal ganglia disorders. Here, we provide an overview of how striatal cholinergic interneurons modulate striatal activity under normal and pathological conditions. Numerous studies show that nigrostriatal damage such as that occurs with Parkinson's disease affects cholinergic receptor-mediated striatal activity. This altered cholinergic signaling is an important contributor to Parkinson's disease as well as to the dyskinesias that develop with L-dopa therapy, the gold standard for treatment. Indeed, multiple preclinical studies show that cholinergic receptor drugs may be beneficial for the treatment of L-dopa-induced dyskinesias. In this review, we discuss the evidence indicating that therapeutic modulation of the cholinergic system, particularly targeting of nicotinic cholinergic receptors, may offer a novel approach to manage this debilitating side effect of dopamine replacement therapy for Parkinson's disease.
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38
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Effects of antidyskinetic nicotine treatment on dopamine release in dorsal and ventral striatum. Neurosci Lett 2018; 672:40-45. [PMID: 29474871 DOI: 10.1016/j.neulet.2018.02.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 01/08/2018] [Accepted: 02/19/2018] [Indexed: 11/23/2022]
Abstract
The treatment of Parkinson's disease is often complicated by levodopa-induced dyskinesia (LID), and antidyskinetic treatment options are currently sparse. Nicotinic acetylcholine receptors have been suggested as potential targets for treatment of LID, as nicotinic agonists have been reported to alleviate LID in animal models. We aimed at the first independent replication of an antidyskinetic effect by nicotine using a mouse model of LID, and at investigation of its mechanisms by studying the release of [3H]dopamine from synaptosomes prepared from the dorsal and ventral striatum. Chronic nicotine treatment in drinking water inhibited the development of LID in mice lesioned unilaterally with 6-hydroxydopamine and treated chronically with levodopa and benserazide. The antidyskinetic nicotine treatment had no effect on [3H]dopamine release mediated by α4β2* nicotinic receptors, but decreased α6β2*-mediated [3H]dopamine release in the lesioned dorsal striatum and the ventral striatum. In addition, nicotine treatment restored [3H]dopamine release in the lesioned ventral striatum to intact levels. The results support a role for nicotinic receptors as drug targets for treatment of LID, and suggest that striatal presynaptic α6β2* receptors are important mediators of nicotine's antidyskinetic effect.
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39
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Designing selective modulators for the nicotinic receptor subtypes: challenges and opportunities. Future Med Chem 2018; 10:433-459. [PMID: 29451400 DOI: 10.4155/fmc-2017-0169] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Nicotinic receptors are membrane proteins involved in several physiological processes. They are considered suitable drug targets for various CNS disorders or conditions, as shown by the large number of compounds which have entered clinical trials. In recent years, nonconventional agonists have been discovered: positive allosteric modulators, allosteric agonists, site-specific agonists and silent desensitizers are compounds able to modulate the receptor interacting at sites different from the orthodox one, or to desensitize the receptor without prior opening. While these new findings can further complicate the pharmacology of these proteins and the design and optimization of ligands, they undoubtedly offer new opportunities to find drugs for the many therapeutic indications involving nicotinic receptors.
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40
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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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Wall TR, Henderson BJ, Voren G, Wageman CR, Deshpande P, Cohen BN, Grady SR, Marks MJ, Yohannes D, Kenny PJ, Bencherif M, Lester HA. TC299423, a Novel Agonist for Nicotinic Acetylcholine Receptors. Front Pharmacol 2017; 8:641. [PMID: 29033834 PMCID: PMC5626944 DOI: 10.3389/fphar.2017.00641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 08/29/2017] [Indexed: 01/11/2023] Open
Abstract
(E)-5-(Pyrimidin-5-yl)-1,2,3,4,7,8-hexahydroazocine (TC299423) is a novel agonist for nicotinic acetylcholine receptors (nAChRs). We examined its efficacy, affinity, and potency for α6β2∗ (α6β2-containing), α4β2∗, and α3β4∗ nAChRs, using [125I]-epibatidine binding, whole-cell patch-clamp recordings, synaptosomal 86Rb+ efflux, [3H]-dopamine release, and [3H]-acetylcholine release. TC299423 displayed an EC50 of 30–60 nM for α6β2∗ nAChRs in patch-clamp recordings and [3H]-dopamine release assays. Its potency for α6β2∗ in these assays was 2.5-fold greater than that for α4β2∗, and much greater than that for α3β4∗-mediated [3H]-acetylcholine release. We observed no major off-target binding on 70 diverse molecular targets. TC299423 was bioavailable after intraperitoneal or oral administration. Locomotor assays, measured with gain-of-function, mutant α6 (α6L9′S) nAChR mice, show that TC299423 elicits α6β2∗ nAChR-mediated responses at low doses. Conditioned place preference assays show that low-dose TC299423 also produces significant reward in α6L9′S mice, and modest reward in WT mice, through a mechanism that probably involves α6(non-α4)β2∗ nAChRs. However, TC299423 did not suppress nicotine self-administration in rats, indicating that it did not block nicotine reinforcement in the dosage range that was tested. In a hot-plate test, TC299423 evoked antinociceptive responses in mice similar to those of nicotine. TC299423 and nicotine similarly inhibited mouse marble burying as a measure of anxiolytic effects. Taken together, our data suggest that TC299423 will be a useful small-molecule agonist for future in vitro and in vivo studies of nAChR function and physiology.
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Affiliation(s)
- Teagan R Wall
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Brandon J Henderson
- Department of Biomedical Sciences, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV, United States
| | - George Voren
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | - Charles R Wageman
- Institute of Behavioral Genetics, University of Colorado, Boulder, Boulder, CO, United States
| | - Purnima Deshpande
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Bruce N Cohen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
| | - Sharon R Grady
- Institute of Behavioral Genetics, University of Colorado, Boulder, Boulder, CO, United States
| | - Michael J Marks
- Institute of Behavioral Genetics, University of Colorado, Boulder, Boulder, CO, United States.,Department of Psychology and Neuroscience, University of Colorado, Boulder, Boulder, CO, United States
| | | | - Paul J Kenny
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Henry A Lester
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, United States
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Kamens HM, Silva C, McCarthy R, Cox RJ, Ehringer MA. No evidence of a role of the β4 subunit of the nicotinic acetylcholine receptor in alcohol-related behaviors. BMC Res Notes 2017; 10:151. [PMID: 28381286 PMCID: PMC5382442 DOI: 10.1186/s13104-017-2470-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 03/27/2017] [Indexed: 11/10/2022] Open
Abstract
Background Nicotinic acetylcholine receptors have gained attention in the last several years as mediators of alcohol-related behaviors. The genes that code for the α5, α3, and β4 subunits (Chrna5, Chrna3, and Chrnb4, respectively) map adjacent to each other on human chromosome 15/mouse chromosome 9. Genetic variants in this region have been associated with alcohol phenotypes and mice that overexpress these three subunits have reduced ethanol intake. In the present experiments, we examined the role of the Chrnb4 gene in three ethanol behaviors: consumption, ataxia, and sedation. Wildtype, heterozygous, and knockout mice were tested for ethanol consumption with a 2-bottle choice procedure and the drinking-in-the-dark paradigm. Ethanol-induced ataxia was measured with the balance beam and dowel test. Finally, the sedative effects of ethanol were measured with the loss of righting reflex paradigm. Results We observed no significant genotypic effects on any of the ethanol behaviors examined, suggesting that the β4 subunit is not involved in mediating these responses. Conclusions While we found no evidence for the involvement of the β4 subunit in ethanol responses, it is possible that this subunit modulates other behaviors not tested and further work should address this before completely ruling out its involvement. Electronic supplementary material The online version of this article (doi:10.1186/s13104-017-2470-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Helen M Kamens
- Department of Biobehavioral Health, Penn State University, University Park, PA, USA. .,Center for Brain, Behavior, and Cognition, Penn State University, University Park, PA, USA.
| | - Constanza Silva
- Department of Biobehavioral Health, Penn State University, University Park, PA, USA
| | - Riley McCarthy
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
| | - Ryan J Cox
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
| | - Marissa A Ehringer
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA.,Institute for Behavioral Genetics, University of Colorado, Boulder, CO, USA
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43
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Zuo L, Tan Y, Li CSR, Wang Z, Wang K, Zhang X, Lin X, Chen X, Zhong C, Wang X, Guo X, Wang J, Lu L, Luo X. Associations of rare nicotinic cholinergic receptor gene variants to nicotine and alcohol dependence. Am J Med Genet B Neuropsychiatr Genet 2016; 171:1057-1071. [PMID: 27473937 PMCID: PMC5587505 DOI: 10.1002/ajmg.b.32476] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 07/06/2016] [Indexed: 12/23/2022]
Abstract
Nicotine's rewarding effects are mediated through distinct subunits of nAChRs, encoded by different nicotinic cholinergic receptor (CHRN) genes and expressed in discrete regions in the brain. In the present study, we aimed to test the associations between rare variants at CHRN genes and nicotine dependence (ND), and alcohol dependence (AD). A total of 26,498 subjects with nine different neuropsychiatric disorders in 15 independent cohorts, which were genotyped on Illumina, Affymetrix, or PERLEGEN microarray platforms, were analyzed. Associations between rare variants (minor allele frequency (MAF) <0.05) at CHRN genes and nicotine dependence, and alcohol dependence were tested. The mRNA expression of all Chrn genes in whole mouse brain and 10 specific brain areas was investigated. All CHRN genes except the muscle-type CHRNB1, including eight genomic regions containing 11 neuronal CHRN genes and three genomic regions containing four muscle-type CHRN genes, were significantly associated with ND, and/or AD. All of these genes were expressed in the mouse brain. We conclude that CHRNs are associated with ND (mainly) and AD, supporting the hypothesis that the full catalog of ND/AD risk genes may contain most neuronal nAChRs-encoding genes. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Lingjun Zuo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Yunlong Tan
- Biological Psychiatry Research Center, Beijing Huilongguan Hospital, Beijing, China
| | - Chiang-Shan R. Li
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
| | - Zhiren Wang
- Biological Psychiatry Research Center, Beijing Huilongguan Hospital, Beijing, China
| | - Kesheng Wang
- Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City, TN, USA
| | - Xiangyang Zhang
- Department of Psychiatry and Behavioral Sciences, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Xiandong Lin
- Provincial Key Laboratory of Translational Cancer Medicine, Fujian Provincial Cancer Hospital, Fuzhou, Fujian, China
| | - Xiangning Chen
- Nevada Institute of Personalized Medicine and Department of Psychology, University of Nevada, Las Vegas, NV, USA
| | - Chunlong Zhong
- Department of Neurosurgery, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaoping Wang
- Department of Neurology, Shanghai First People’s Hospital, Shanghai Jiao-Tong University, Shanghai, China
| | - Xiaoyun Guo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Department of EEG & Neuroimaging, Shanghai Mental Health Center, Shanghai, China
| | - Jijun Wang
- Department of EEG & Neuroimaging, Shanghai Mental Health Center, Shanghai, China
| | - Lu Lu
- Provincial Key Laboratory for Inflammation and Molecular Drug Target, Medical College of Nantong University, China
- Departments of Genetics, Genomics, Informatics, Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Xingguang Luo
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA
- Biological Psychiatry Research Center, Beijing Huilongguan Hospital, Beijing, China
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44
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Replicated Risk Nicotinic Cholinergic Receptor Genes for Nicotine Dependence. Genes (Basel) 2016; 7:genes7110095. [PMID: 27827986 PMCID: PMC5126781 DOI: 10.3390/genes7110095] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 10/20/2016] [Accepted: 11/02/2016] [Indexed: 01/31/2023] Open
Abstract
It has been hypothesized that the nicotinic acetylcholine receptors (nAChRs) play important roles in nicotine dependence (ND) and influence the number of cigarettes smoked per day (CPD) in smokers. We compiled the associations between nicotinic cholinergic receptor genes (CHRNs) and ND/CPD that were replicated across different studies, reviewed the expression of these risk genes in human/mouse brains, and verified their expression using independent samples of both human and mouse brains. The potential functions of the replicated risk variants were examined using cis-eQTL analysis or predicted using a series of bioinformatics analyses. We found replicated and significant associations for ND/CPD at 19 SNPs in six genes in three genomic regions (CHRNB3-A6, CHRNA5-A3-B4 and CHRNA4). These six risk genes are expressed in at least 18 distinct areas of the human/mouse brain, with verification in our independent human and mouse brain samples. The risk variants might influence the transcription, expression and splicing of the risk genes, alter RNA secondary or protein structure. We conclude that the replicated associations between CHRNB3-A6, CHRNA5-A3-B4,CHRNA4 and ND/CPD are very robust. More research is needed to examine how these genetic variants contribute to the risk for ND/CPD.
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45
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Charntikov S, Falco AM, Fink K, Dwoskin LP, Bevins RA. The effect of sazetidine-A and other nicotinic ligands on nicotine controlled goal-tracking in female and male rats. Neuropharmacology 2016; 113:354-366. [PMID: 27765626 DOI: 10.1016/j.neuropharm.2016.10.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 10/05/2016] [Accepted: 10/12/2016] [Indexed: 10/20/2022]
Abstract
Nicotine is the primary addictive component of tobacco products and its complex stimulus effects are readily discriminated by human and non-human animals. Previous research with rodents directly investigating the nature of the nicotine stimulus has been limited to males. The current study began to address this significant gap in the literature by training female and male rats to discriminate 0.4 mg/kg nicotine from saline in the discriminated goal-tracking task. In this task, access to sucrose was intermittently available on nicotine session. On interspersed saline session, sucrose was not available. Both sexes acquired the discrimination as evidenced by increased head entries into sucrose receptacle (goal-tracking) evoked by nicotine; the nicotine generalization curves were also similar between females and males. The pharmacological profile of the nicotine stimulus was assessed using substitution and targeted combination tests with the following ligands: sazetidine-A, PHA-543613, PNU-120596, bupropion, nornicotine, and cytisine. For females and males, nornicotine fully substituted for the nicotine stimulus, whereas sazetidine-A, bupropion, and cytisine all evoked partial substitution. Female and male rats responded in a similar manner to interaction tests where a combination of 1 mg/kg of sazetidine-A plus nicotine or nornicotine shifted the nicotine dose-effect curve to the left. The combination of sazetidine-A plus bupropion or cytisine failed to do so. These findings begin to fill a significant gap the in scientific literature by studying the nature of the nicotine stimulus and response to therapeutically interesting combinations using a model that includes both sexes.
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Affiliation(s)
- S Charntikov
- Department of Psychology, University of New Hampshire, 15 Academic Way, Durham, NH 03824, USA
| | - A M Falco
- Department of Psychology, University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE 68588-0308, USA
| | - K Fink
- Department of Psychology, University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE 68588-0308, USA
| | - L P Dwoskin
- Department of Pharmaceutical Sciences, University of Kentucky, 465 College of Pharmacy, 789 S. Limestone Street, Lexington, KY 40536-0596, USA
| | - R A Bevins
- Department of Psychology, University of Nebraska-Lincoln, 238 Burnett Hall, Lincoln, NE 68588-0308, USA.
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46
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Fox-Loe AM, Dwoskin LP, Richards CI. Nicotinic Acetylcholine Receptors as Targets for Tobacco Cessation Therapeutics: Cutting-Edge Methodologies to Understand Receptor Assembly and Trafficking. NEUROMETHODS 2016; 117:119-132. [PMID: 28025590 DOI: 10.1007/978-1-4939-3768-4_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Tobacco dependence is a chronic relapsing disorder and nicotine, the primary alkaloid in tobacco, acts at nicotinic receptors to stimulate dopamine release in brain, which is responsible for the reinforcing properties of nicotine, leading to addiction. Although the majority of tobacco users express the desire to quit, only a small percentage of those attempting to quit are successful using the currently available pharmacotherapies. Nicotine upregulates the number of specific nicotinic receptors on the neuronal cell surface. An increase in receptor trafficking or preferential stoichiometric assembly of receptor subunits involves changes in assembly, endoplasmic reticulum export, vesicle transport, decreased degradation, desensitization, enhanced maturation of functional pentamers, and pharmacological chaperoning. Understanding these changes on a mechanistic level is important to the development of nicotinic receptors as drug targets. For this reason, cutting-edge methodologies are being developed and employed to pinpoint distinct changes in localization, assembly, export, vesicle trafficking, and stoichiometry in order to further understand the physiology of these receptors and to evaluate the action of novel therapeutics for smoking cessation.
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47
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Ondachi PW, Castro AH, Luetje CW, Wageman CR, Marks MJ, Damaj MI, Mascarella SW, Navarro HA, Carroll FI. Synthesis, Nicotinic Acetylcholine Binding, and in Vitro and in Vivo Pharmacological Properties of 2'-Fluoro-(carbamoylpyridinyl)deschloroepibatidine Analogues. ACS Chem Neurosci 2016; 7:1004-12. [PMID: 27166021 DOI: 10.1021/acschemneuro.6b00107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In this study, we report the synthesis, nAChR in vitro and in vivo pharmacological properties of 2'-fluoro-(carbamoylpyridinyl)deschloroepibatidine analogues (5, 6a,b, and 7a,b), which are analogues of our lead structure epibatidine. All of the analogues had subnanomolar binding affinity for α4β2*-nAChRs, and all were potent antagonists of α4β2-nAChRs in an in vitro functional assay. Analogues 6a,b were also highly selective for α4β2- relative to α3β4- and α7-nAChRs. Surprisingly, all of the analogues were exceptionally potent antagonists of nicotine-induced antinociception in the mouse tail-flick test, relative to standard nAChR antagonists such as DHβE. 2'-Fluoro-(4-carbamoyl-3-pyridinyl)deschloroepitabidine (6a) displayed an attractive combination of properties, including subnanomolar binding affinity (Ki = 0.07 nM), submicromolar inhibition of α4β2-nAChRs in the functional assay (IC50 = 0.46 μM) with a high degree of selectivity for α4β2- relative to the α3β4/α7-nAChRs (54-/348-fold, respectively), potent inhibition of [(3)H]dopamine release mediated by α4β2*- and α6β2*-nAChRs in a synaptosomal preparation (IC50 = 21 and 32 nM, respectively), and an AD50 of 0.007 μg/kg as an antagonist of nicotine induced antinociception in the mouse tail-flick test which is 64 250 times more potent than DHβE. These data suggest that compound 6a will be highly useful as a pharmacological tool for studying nAChRs and merits further development.
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Affiliation(s)
- Pauline W. Ondachi
- Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, United States
| | - Ana H. Castro
- Department
of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, Florida 33101, United States
| | - Charles W. Luetje
- Department
of Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, Florida 33101, United States
| | | | | | - M. Imad Damaj
- Department
of Pharmacology, Virginia Commonwealth University Medical Campus, P.O. Box 980615, Richmond, Virginia 23298-0613, United States
| | - S. Wayne Mascarella
- Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, United States
| | - Hernán A. Navarro
- Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, United States
| | - F. Ivy Carroll
- Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709, United States
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48
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Grasing K. A threshold model for opposing actions of acetylcholine on reward behavior: Molecular mechanisms and implications for treatment of substance abuse disorders. Behav Brain Res 2016; 312:148-62. [PMID: 27316344 DOI: 10.1016/j.bbr.2016.06.022] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 06/11/2016] [Accepted: 06/13/2016] [Indexed: 12/26/2022]
Abstract
The cholinergic system plays important roles in both learning and addiction. Medications that modify cholinergic tone can have pronounced effects on behaviors reinforced by natural and drug reinforcers. Importantly, enhancing the action of acetylcholine (ACh) in the nucleus accumbens and ventral tegmental area (VTA) dopamine system can either augment or diminish these behaviors. A threshold model is presented that can explain these seemingly contradictory results. Relatively low levels of ACh rise above a lower threshold, facilitating behaviors supported by drugs or natural reinforcers. Further increases in cholinergic tone that rise above a second upper threshold oppose the same behaviors. Accordingly, cholinesterase inhibitors, or agonists for nicotinic or muscarinic receptors, each have the potential to produce biphasic effects on reward behaviors. Pretreatment with either nicotinic or muscarinic antagonists can block drug- or food- reinforced behavior by maintaining cholinergic tone below its lower threshold. Potential threshold mediators include desensitization of nicotinic receptors and biphasic effects of ACh on the firing of medium spiny neurons. Nicotinic receptors with high- and low- affinity appear to play greater roles in reward enhancement and inhibition, respectively. Cholinergic inhibition of natural and drug rewards may serve as mediators of previously described opponent processes. Future studies should evaluate cholinergic agents across a broader range of doses, and include a variety of reinforced behaviors.
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Affiliation(s)
- Kenneth Grasing
- From the Substance Abuse Research Laboratory, 151, Kansas City Veterans Affairs Medical Center, 4801 Linwood Boulevard, Kansas City, MO 64128, United States; From the Division of Clinical Pharmacology, Department of Medicine, University of Kansas School of Medicine, Kansas City, KS 66160, United States.
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How can we Improve on Modeling Nicotine Addiction to Develop Better Smoking Cessation Treatments? INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 126:121-56. [PMID: 27055613 DOI: 10.1016/bs.irn.2016.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Clinically effective smoking cessation treatments are few in number, mainly varenicline, bupropion, and nicotine replacement therapy being prescribed by health organizations. Of the many compounds tested for smoking cessation, a good proportion fail in human trials despite positive findings in rodents. This chapter aims to cover the uses and some pit falls of current methodologies employed to discover clinical treatments in the laboratory. Complicating factors include the complex nature of genetics in tobacco smoking and the comorbidity associated with other psychiatric disorders, which has not been addressed fully in the rodent laboratory. This chapter reviews the evidence from intravenous nicotine self-administration studies and proposes modifications on how we can improve the validity of the animal models by incorporating clinically relevant factors considered to be critical in tobacco smoking. For example, choice procedures that incorporate alternative reinforcers, use of reinstatement models, and second-order schedules of reinforcement are proposed to have better scientific validity that may lead to better clinical outcomes. Furthermore, improved experimental methods will also improve our chances of discovering effective treatments that ultimately may mitigate the effects of tobacco smoking with regard to health worldwide.
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Melroy-Greif WE, Stitzel JA, Ehringer MA. Nicotinic acetylcholine receptors: upregulation, age-related effects and associations with drug use. GENES, BRAIN, AND BEHAVIOR 2016; 15:89-107. [PMID: 26351737 PMCID: PMC4780670 DOI: 10.1111/gbb.12251] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/01/2015] [Accepted: 09/02/2015] [Indexed: 12/16/2022]
Abstract
Nicotinic acetylcholine receptors are ligand-gated ion channels that exogenously bind nicotine. Nicotine produces rewarding effects by interacting with these receptors in the brain's reward system. Unlike other receptors, chronic stimulation by an agonist induces an upregulation of receptor number that is not due to increased gene expression in adults; while upregulation also occurs during development and adolescence there have been some opposing findings regarding a change in corresponding gene expression. These receptors have also been well studied with regard to human genetic associations and, based on evidence suggesting shared genetic liabilities between substance use disorders, numerous studies have pointed to a role for this system in comorbid drug use. This review will focus on upregulation of these receptors in adulthood, adolescence and development, as well as the findings from human genetic association studies which point to different roles for these receptors in risk for initiation and continuation of drug use.
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Affiliation(s)
- Whitney E. Melroy-Greif
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla, CA, USA
| | - Jerry A. Stitzel
- Institute for Behavioral Genetics, University of Colorado Boulder, CO, USA
- Department of Integrative Physiology, University of Colorado Boulder, CO, USA
| | - Marissa A. Ehringer
- Institute for Behavioral Genetics, University of Colorado Boulder, CO, USA
- Department of Integrative Physiology, University of Colorado Boulder, CO, USA
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