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Tsuzuki A, Yamasaki M, Konno K, Miyazaki T, Takei N, Tomita S, Yuzaki M, Watanabe M. Abundant extrasynaptic expression of α3β4-containing nicotinic acetylcholine receptors in the medial habenula-interpeduncular nucleus pathway in mice. Sci Rep 2024; 14:14193. [PMID: 38902419 PMCID: PMC11189931 DOI: 10.1038/s41598-024-65076-3] [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: 03/15/2024] [Accepted: 06/17/2024] [Indexed: 06/22/2024] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) in the medial habenula (MHb)-interpeduncular nucleus (IPN) pathway play critical roles in nicotine-related behaviors. This pathway is particularly enriched in nAChR α3 and β4 subunits, both of which are genetically linked to nicotine dependence. However, the cellular and subcellular expression of endogenous α3β4-containing nAChRs remains largely unknown because specific antibodies and appropriate detection methods were unavailable. Here, we successfully uncovered the expression of endogenous nAChRs containing α3 and β4 subunits in the MHb-IPN pathway using novel specific antibodies and a fixative glyoxal that enables simultaneous detection of synaptic and extrasynaptic molecules. Immunofluorescence and immunoelectron microscopy revealed that both subunits were predominantly localized to the extrasynaptic cell surface of somatodendritic and axonal compartments of MHb neurons but not at their synaptic junctions. Immunolabeling for α3 and β4 subunits disappeared in α5β4-knockout brains, which we used as negative controls. The enriched and diffuse extrasynaptic expression along the MHb-IPN pathway suggests that α3β4-containing nAChRs may enhance the excitability of MHb neurons and neurotransmitter release from their presynaptic terminals in the IPN. The revealed distribution pattern provides a molecular and anatomical basis for understanding the functional role of α3β4-containing nAChRs in the crucial pathway of nicotine dependence.
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Grants
- 17KK0160 Ministry of Education, Culture, Sports, Science and Technology
- 21K06746 Ministry of Education, Culture, Sports, Science and Technology
- 22K06784 Ministry of Education, Culture, Sports, Science and Technology
- 20H05628 Ministry of Education, Culture, Sports, Science and Technology
- 20H05628 Ministry of Education, Culture, Sports, Science and Technology
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Affiliation(s)
- Asuka Tsuzuki
- Department of Anatomy, Graduate School of Medicine, Hokkaido University, Sapporo, 060-8638, Japan
| | - Miwako Yamasaki
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, 060-8638, Japan.
| | - Kohtarou Konno
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, 060-8638, Japan
| | - Taisuke Miyazaki
- Department of Functioning and Disability, Faculty of Health Sciences, Hokkaido University, Sapporo, 060-8638, Japan
| | - Norio Takei
- Institute for Animal Experimentation, Faculty of Medicine, Hokkaido University, Sapporo, 060-8638, Japan
| | - Susumu Tomita
- Department of Cellular and Molecular Physiology, Department of Neuroscience, and Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Michisuke Yuzaki
- Department of Physiology, School of Medicine, Keio University, Tokyo, 160-8582, Japan
| | - Masahiko Watanabe
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, 060-8638, Japan
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2
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Asogwa NC, Toji N, He Z, Shao C, Shibata Y, Tatsumoto S, Ishikawa H, Go Y, Wada K. Nicotinic acetylcholine receptors in a songbird brain. J Comp Neurol 2022; 530:1966-1991. [PMID: 35344610 DOI: 10.1002/cne.25314] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/07/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that mediate fast synaptic transmission and cell signaling, which contribute to learning, memory, and the execution of motor skills. Birdsong is a complex learned motor skill in songbirds. Although the existence of 15 nAChR subunits has been predicted in the avian genome, their expression patterns and potential contributions to song learning and production have not been comprehensively investigated. Here, we cloned all the 15 nAChR subunits (ChrnA1-10, B2-4, D, and G) from the zebra finch brain and investigated the mRNA expression patterns in the neural pathways responsible for the learning and production of birdsong during a critical period of song learning. Although there were no detectable hybridization signals for ChrnA1, A6, A9, and A10, the other 11 nAChR subunits were uniquely expressed in one or more major subdivisions in the song nuclei of the songbird brain. Of these 11 subunits, ChrnA3-5, A7, and B2 were differentially regulated in the song nuclei compared with the surrounding anatomically related regions. ChrnA5 was upregulated during the critical period of song learning in the lateral magnocellular nucleus of the anterior nidopallium. Furthermore, single-cell RNA sequencing revealed ChrnA7 and B2 to be the major subunits expressed in neurons of the vocal motor nuclei HVC and robust nucleus of the arcopallium, indicating the potential existence of ChrnA7-homomeric and ChrnB2-heteromeric nAChRs in limited cell populations. These results suggest that relatively limited types of nAChR subunits provide functional contributions to song learning and production in songbirds.
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Affiliation(s)
| | - Noriyuki Toji
- Faculty of Science, Hokkaido University, Sapporo, Japan
| | - Ziwei He
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Chengru Shao
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Yukino Shibata
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
| | - Shoji Tatsumoto
- Cognitive Genomics Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Japan
| | - Hiroe Ishikawa
- Cognitive Genomics Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Japan
| | - Yasuhiro Go
- Cognitive Genomics Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Japan
- School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan
- Department of Physiological Sciences, National Institute for Physiological Sciences, Okazaki, Japan
| | - Kazuhiro Wada
- Graduate School of Life Science, Hokkaido University, Sapporo, Japan
- Faculty of Science, Hokkaido University, Sapporo, Japan
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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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Cano M, Reynaga DD, Belluzzi JD, Loughlin SE, Leslie F. Chronic exposure to cigarette smoke extract upregulates nicotinic receptor binding in adult and adolescent rats. Neuropharmacology 2020; 181:108308. [PMID: 32950561 PMCID: PMC7655523 DOI: 10.1016/j.neuropharm.2020.108308] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 09/11/2020] [Accepted: 09/13/2020] [Indexed: 01/23/2023]
Abstract
Heavy smokers display increased radioligand binding of nicotinic acetylcholine receptors (nAChRs). This "upregulation" is thought to be a contributing factor to tobacco dependence. Although cigarette smoke contains thousands of constituents that can contribute to nicotine dependence, it is not well understood whether non-nicotine constituents contribute to nAChR upregulation. In this study, we used an aqueous cigarette smoke extract (CSE), which contains nicotine and soluble constituents of cigarette smoke, to induce nAChR upregulation in adult and adolescent rats. To do this, male rats were exposed to nicotine or CSE (1.5 mg/kg/day nicotine equivalent, intravenously) daily for ten days. This experimental procedure produces equivalent levels of brain and plasma nicotine in nicotine- and CSE-treated animals. We then assessed nAChR upregulation using quantitative autoradiography to measure changes in three nAChR types. Adolescents were found to have consistently greater α4β2 nAChR binding than adults in many brain regions. Chronic nicotine exposure did not significantly increase nAChR binding in any brain region at either age. Chronic CSE exposure selectively increased α4β2 nAChR binding in adolescent medial amygdala and α7 binding in adolescent central amygdala and lateral hypothalamus. CSE also increased α3β4 nAChR binding in the medial habenula and interpeduncular nucleus, and α7 binding in the medial amygdala, independent of age. Overall, this work provides evidence that cigarette smoke constituents influence nAChR upregulation in an age-, nAChR type- and region-dependent manner.
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Affiliation(s)
- Michelle Cano
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA.
| | - Daisy D Reynaga
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - James D Belluzzi
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - Sandra E Loughlin
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA
| | - Frances Leslie
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA
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Icick R, Forget B, Cloëz-Tayarani I, Pons S, Maskos U, Besson M. Genetic susceptibility to nicotine addiction: Advances and shortcomings in our understanding of the CHRNA5/A3/B4 gene cluster contribution. Neuropharmacology 2020; 177:108234. [PMID: 32738310 DOI: 10.1016/j.neuropharm.2020.108234] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 06/28/2020] [Accepted: 07/07/2020] [Indexed: 12/12/2022]
Abstract
Over the last decade, robust human genetic findings have been instrumental in elucidating the heritable basis of nicotine addiction (NA). They highlight coding and synonymous polymorphisms in a cluster on chromosome 15, encompassing the CHRNA5, CHRNA3 and CHRNB4 genes, coding for three subunits of the nicotinic acetylcholine receptor (nAChR). They have inspired an important number of preclinical studies, and will hopefully lead to the definition of novel drug targets for treating NA. Here, we review these candidate gene and genome-wide association studies (GWAS) and their direct implication in human brain function and NA-related phenotypes. We continue with a description of preclinical work in transgenic rodents that has led to a mechanistic understanding of several of the genetic hits. We also highlight important issues with regards to CHRNA3 and CHRNB4 where we are still lacking a dissection of their role in NA, including even in preclinical models. We further emphasize the use of human induced pluripotent stem cell-derived models for the analysis of synonymous and intronic variants on a human genomic background. Finally, we indicate potential avenues to further our understanding of the role of this human genetic variation. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.
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Affiliation(s)
- Romain Icick
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; Département de Psychiatrie et de Médecine Addictologique, Groupe Hospitalier Saint-Louis, Lariboisière, Fernand Widal, Assistance-Publique Hôpitaux de Paris, Paris, F-75010, France; INSERM UMR-S1144, Paris, F-75006, France; FHU "NOR-SUD", Assistance-Publique Hôpitaux de Paris, Paris, F-75001, France
| | - Benoît Forget
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; Génétique Humaine et Fonctions Cognitives, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France
| | - Isabelle Cloëz-Tayarani
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; FHU "NOR-SUD", Assistance-Publique Hôpitaux de Paris, Paris, F-75001, France
| | - Stéphanie Pons
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; FHU "NOR-SUD", Assistance-Publique Hôpitaux de Paris, Paris, F-75001, France
| | - Uwe Maskos
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; FHU "NOR-SUD", Assistance-Publique Hôpitaux de Paris, Paris, F-75001, France
| | - Morgane Besson
- Neurobiologie Intégrative des Systèmes Cholinergiques, CNRS UMR3571, Institut Pasteur, 25 Rue du Dr Roux, 75724, Paris Cedex 15, France; FHU "NOR-SUD", Assistance-Publique Hôpitaux de Paris, Paris, F-75001, France.
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6
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Abbasi F, Baradaran R, Khoshdel-Sarkarizi H, Kargozar S, Hami J, Mohammadipour A, Kheradmand H, Haghir H. Distribution pattern of nicotinic acetylcholine receptors in developing cerebellum of rat neonates born of diabetic mothers. J Chem Neuroanat 2020; 108:101819. [PMID: 32522497 DOI: 10.1016/j.jchemneu.2020.101819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 05/25/2020] [Accepted: 05/28/2020] [Indexed: 11/15/2022]
Affiliation(s)
- Faeze Abbasi
- Department of Anatomy and cell Biology, School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran
| | - Raheleh Baradaran
- Department of Anatomy and cell Biology, School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran
| | - Hoda Khoshdel-Sarkarizi
- Department of Anatomy and cell Biology, School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran
| | - Saeid Kargozar
- Tissue Engineering Research Group (TERG), Department of Anatomy and Cell Biology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Javad Hami
- Department of Anatomical Sciences, School of Medicine, BirjandUniversity of Medical Sciences, Birjand, Iran
| | - Abbas Mohammadipour
- Department of Anatomy and cell Biology, School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran
| | - Hamed Kheradmand
- Hazrat Rasoul Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Hossein Haghir
- Department of Anatomy and cell Biology, School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran; Medical Genetic Research Center (MGRC), School of Medicine, MashhadUniversity of Medical Sciences, Mashhad, Iran.
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7
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Broide RS, Winzer-Serhan UH, Chen Y, Leslie FM. Distribution of α7 Nicotinic Acetylcholine Receptor Subunit mRNA in the Developing Mouse. Front Neuroanat 2019; 13:76. [PMID: 31447654 PMCID: PMC6691102 DOI: 10.3389/fnana.2019.00076] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 07/12/2019] [Indexed: 01/10/2023] Open
Abstract
Homomeric α7 nicotinic acetylcholine receptors (nAChRs) are abundantly expressed in the central and peripheral nervous system (CNS and PNS, respectively), and spinal cord. In addition, expression and functional responses have been reported in non-neuronal tissue. In the nervous system, α7 nAChR subunit expression appears early during embryonic development and is often transiently upregulated, but little is known about their prenatal expression outside of the nervous system. For understanding potential short-term and long-term effects of gestational nicotine exposure, it is important to know the temporal and spatial expression of α7 nAChRs throughout the body. To that end, we studied the expression of α7 nAChR subunit mRNA using highly sensitive isotopic in situ hybridization in embryonic and neonatal whole-body mouse sections starting at gestational day 13. The results revealed expression of α7 mRNA as early as embryonic day 13 in the PNS, including dorsal root ganglia, parasympathetic and sympathetic ganglia, with the strongest expression in the superior cervical ganglion, and low to moderate levels were detected in brain and spinal cord, respectively, which rapidly increased in intensity with embryonic age. In addition, robust α7 mRNA expression was detected in the adrenal medulla, and low to moderate expression in selected peripheral tissues during embryonic development, potentially related to cells derived from the neural crest. Little or no mRNA expression was detected in thymus or spleen, sites of immune cell maturation. The results suggest that prenatal nicotine exposure could potentially affect the nervous system with limited effects in non-neural tissues.
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Affiliation(s)
- Ron S Broide
- Department of Pharmacology, University of California, Irvine, Irvine, CA, United States
| | - Ursula H Winzer-Serhan
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University College of Medicine, Bryan, TX, United States
| | - Yling Chen
- Department of Pharmacology, University of California, Irvine, Irvine, CA, United States
| | - Frances M Leslie
- Department of Pharmacology, University of California, Irvine, Irvine, CA, United States
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Morton G, Nasirova N, Sparks DW, Brodsky M, Sivakumaran S, Lambe EK, Turner EE. Chrna5-Expressing Neurons in the Interpeduncular Nucleus Mediate Aversion Primed by Prior Stimulation or Nicotine Exposure. J Neurosci 2018; 38:6900-6920. [PMID: 29954848 PMCID: PMC6070661 DOI: 10.1523/jneurosci.0023-18.2018] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 06/08/2018] [Accepted: 06/15/2018] [Indexed: 11/21/2022] Open
Abstract
Genetic studies have shown an association between smoking and variation at the CHRNA5/A3/B4 gene locus encoding the α5, α3, and β4 nicotinic receptor subunits. The α5 receptor has been specifically implicated because smoking-associated haplotypes contain a coding variant in the CHRNA5 gene. The Chrna5/a3/b4 locus is conserved in rodents and the restricted expression of these subunits suggests neural pathways through which the reinforcing and aversive properties of nicotine may be mediated. Here, we show that, in the interpeduncular nucleus (IP), the site of the highest Chrna5 mRNA expression in rodents, electrophysiological responses to nicotinic acetylcholine receptor stimulation are markedly reduced in α5-null mice. IP neurons differ markedly from their upstream ventral medial habenula cholinergic partners, which appear unaltered by loss of α5. To probe the functional role of α5-containing IP neurons, we used BAC recombineering to generate transgenic mice expressing Cre-recombinase from the Chrna5 locus. Reporter expression driven by Chrna5Cre demonstrates that transcription of Chrna5 is regulated independently from the Chrna3/b4 genes transcribed on the opposite strand. Chrna5-expressing IP neurons are GABAergic and project to distant targets in the mesopontine raphe and tegmentum rather than forming local circuits. Optogenetic stimulation of Chrna5-expressing IP neurons failed to elicit physical manifestations of withdrawal. However, after recent prior stimulation or exposure to nicotine, IP stimulation becomes aversive. These results using mice of both sexes support the idea that the risk allele of CHRNA5 may increase the drive to smoke via loss of IP-mediated nicotine aversion.SIGNIFICANCE STATEMENT Understanding the receptors and neural pathways underlying the reinforcing and aversive effects of nicotine may suggest new treatments for tobacco addiction. Part of the individual variability in smoking is associated with specific forms of the α5 nicotinic receptor subunit gene. Here, we show that deletion of the α5 subunit in mice markedly reduces the cellular response to nicotine and acetylcholine in the interpeduncular nucleus (IP). Stimulation of α5-expressing IP neurons using optogenetics is aversive, but this effect requires priming by recent prior stimulation or exposure to nicotine. These results support the idea that the smoking-associated variant of the α5 gene may increase the drive to smoke via loss of IP-mediated nicotine aversion.
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Affiliation(s)
- Glenn Morton
- Center for Integrative Brain Research, Seattle Children's Research Institute
| | - Nailyam Nasirova
- Center for Integrative Brain Research, Seattle Children's Research Institute
| | | | - Matthew Brodsky
- Center for Integrative Brain Research, Seattle Children's Research Institute
| | | | - Evelyn K Lambe
- Department of Physiology
- Department of Obstetrics and Gynecology, and
- Department of Psychiatry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Eric E Turner
- Center for Integrative Brain Research, Seattle Children's Research Institute,
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, Washington 98101
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9
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Vivekanandarajah A, Waters KA, Machaalani R. Cigarette smoke exposure effects on the brainstem expression of nicotinic acetylcholine receptors (nAChRs), and on cardiac, respiratory and sleep physiologies. Respir Physiol Neurobiol 2018; 259:1-15. [PMID: 30031221 DOI: 10.1016/j.resp.2018.07.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 07/16/2018] [Accepted: 07/17/2018] [Indexed: 12/15/2022]
Abstract
Cigarette smoking during pregnancy is the largest modifiable risk factor for adverse outcomes in the infant. Investigations have focused on the psychoactive component of cigarettes, nicotine. One proposed mechanism leading to adverse effects is the interaction between nicotine and its nicotinic acetylcholine receptors (nAChRs). Much data has been generated over the past three decades on the effects of cigarette smoke exposure (CSE) on the expression of the nAChRs in the brainstem and physiological parameters related to cardiac, respiration and sleep, in the offspring of smoking mothers and animal models of nicotine exposure. This review summarises this data and discusses the main findings, highlighting that findings in animal models closely correlate with those from human studies, and that the major brainstem sites where the expression level for the nAChRs are consistently affected include those that play vital roles in cardiorespiration (hypoglossal nucleus, dorsal motor nucleus of the vagus, nucleus of the solitary tract), chemosensation (nucleus of the solitary tract, arcuate nucleus) and arousal (rostral mesopontine sites such as the locus coeruleus and nucleus pontis oralis). These findings provide evidence for the adverse effects of CSE during and after pregnancy to the infant and the need to continue with the health campaign advising against CSE.
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Affiliation(s)
- Arunnjah Vivekanandarajah
- SIDS and Sleep Apnea Laboratory, Sydney Medical School, Medical Foundation Building K25, University of Sydney, NSW 2006, Australia.
| | - Karen A Waters
- SIDS and Sleep Apnea Laboratory, Sydney Medical School, Medical Foundation Building K25, University of Sydney, NSW 2006, Australia; Discipline of Paediatrics and Child Health, Children's Hospital Westmead, NSW, Australia
| | - Rita Machaalani
- SIDS and Sleep Apnea Laboratory, Sydney Medical School, Medical Foundation Building K25, University of Sydney, NSW 2006, Australia; Discipline of Paediatrics and Child Health, Children's Hospital Westmead, NSW, Australia
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10
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Halawa AA, Damborsky JC, Slaton GS, Winzer-Serhan UH. Activation of immediate early genes by nicotine after chronic neonatal nicotine exposure in brain areas involved in stress and anxiety responses. Brain Res 2018; 1687:32-40. [DOI: 10.1016/j.brainres.2018.02.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/16/2018] [Accepted: 02/18/2018] [Indexed: 12/29/2022]
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11
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Attenuation of nicotine taking and seeking in rats by the stoichiometry-selective alpha4beta2 nicotinic acetylcholine receptor positive allosteric modulator NS9283. Psychopharmacology (Berl) 2017; 234:475-484. [PMID: 27844094 DOI: 10.1007/s00213-016-4475-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Accepted: 11/02/2016] [Indexed: 12/16/2022]
Abstract
RATIONALE The rewarding and reinforcing effects of nicotine are produced, in large part, by activation of neuronal α4β2* nicotinic acetylcholine receptors (nAChRs), pentameric protein complexes comprised of different stoichiometries of α4 and β2 subunits. However, little is known about the functional role of distinct subtypes of α4β2* nAChRs in nicotine addiction. OBJECTIVES NS9283 represents a new class of stoichiometry-selective positive allosteric modulators (PAMs) that selectively bind to α4β2 nAChRs containing three α4 and two β2 subunits (3(α4)2(β2) nAChRs). The present experiments were designed to determine the effects of NS9283 on nicotine self-administration and the reinstatement of nicotine-seeking behavior, an animal model of smoking relapse. Parallel studies of sucrose self-administration and reinstatement were conducted in separate cohorts of rats to determine if the effects of NS9283 generalized to other reinforced behaviors. RESULTS Acute and repeated administration of NS9283 dose-dependently reduced nicotine self-administration and reinstatement in male Sprague Dawley rats. These effects were reinforcer specific as no effects of NS9283 on sucrose self-administration and reinstatement were noted. NS9283 also failed to substitute for nicotine in supporting self-administration behavior suggesting that, at the doses tested, NS9283 alone is not reinforcing. CONCLUSION Taken together, these results provide compelling evidence that stoichiometry-selective PAMs of 3(α4)2(β2) nAChRs attenuate nicotine taking and seeking in rats and suggest that targeting 3(α4)2(β2) nAChRs may represent a promising therapeutic strategy for preventing smoking relapse.
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Zoli M, Pistillo F, Gotti C. Diversity of native nicotinic receptor subtypes in mammalian brain. Neuropharmacology 2015; 96:302-11. [DOI: 10.1016/j.neuropharm.2014.11.003] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/11/2014] [Accepted: 11/08/2014] [Indexed: 01/01/2023]
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13
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Yuan M, Cross SJ, Loughlin SE, Leslie FM. Nicotine and the adolescent brain. J Physiol 2015; 593:3397-412. [PMID: 26018031 PMCID: PMC4560573 DOI: 10.1113/jp270492] [Citation(s) in RCA: 335] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 05/14/2015] [Indexed: 12/11/2022] Open
Abstract
Adolescence encompasses a sensitive developmental period of enhanced clinical vulnerability to nicotine, tobacco, and e-cigarettes. While there are sociocultural influences, data at preclinical and clinical levels indicate that this adolescent sensitivity has strong neurobiological underpinnings. Although definitions of adolescence vary, the hallmark of this period is a profound reorganization of brain regions necessary for mature cognitive and executive function, working memory, reward processing, emotional regulation, and motivated behavior. Regulating critical facets of brain maturation are nicotinic acetylcholine receptors (nAChRs). However, perturbations of cholinergic systems during this time with nicotine, via tobacco or e-cigarettes, have unique consequences on adolescent development. In this review, we highlight recent clinical and preclinical data examining the adolescent brain's distinct neurobiology and unique sensitivity to nicotine. First, we discuss what defines adolescence before reviewing normative structural and neurochemical alterations that persist until early adulthood, with an emphasis on dopaminergic systems. We review how acute exposure to nicotine impacts brain development and how drug responses differ from those seen in adults. Finally, we discuss the persistent alterations in neuronal signaling and cognitive function that result from chronic nicotine exposure, while highlighting a low dose, semi-chronic exposure paradigm that may better model adolescent tobacco use. We argue that nicotine exposure, increasingly occurring as a result of e-cigarette use, may induce epigenetic changes that sensitize the brain to other drugs and prime it for future substance abuse.
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Affiliation(s)
| | - Sarah J Cross
- Anatomy & Neurobiology, School of Medicine, University of California, Irvine, CA, USA
| | | | - Frances M Leslie
- Departments of Pharmacology
- Anatomy & Neurobiology, School of Medicine, University of California, Irvine, CA, USA
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Molas S, Gener T, Güell J, Martín M, Ballesteros-Yáñez I, Sanchez-Vives MV, Dierssen M. Hippocampal changes produced by overexpression of the human CHRNA5/A3/B4 gene cluster may underlie cognitive deficits rescued by nicotine in transgenic mice. Acta Neuropathol Commun 2014; 2:147. [PMID: 25384568 PMCID: PMC4236452 DOI: 10.1186/s40478-014-0147-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 10/02/2014] [Indexed: 11/10/2022] Open
Abstract
Addiction involves long-lasting maladaptive changes including development of disruptive drug-stimuli associations. Nicotine-induced neuroplasticity underlies the development of tobacco addiction but also, in regions such as the hippocampus, the ability of this drug to enhance cognitive capabilities. Here, we propose that the genetic locus of susceptibility to nicotine addiction, the CHRNA5/A3/B4 gene cluster, encoding the α5, α3 and β4 subunits of the nicotinic acetylcholine receptors (nAChRs), may influence nicotine-induced neuroadaptations. We have used transgenic mice overexpressing the human cluster (TgCHRNA5/A3/B4) to investigate hippocampal structure and function in genetically susceptible individuals. TgCHRNA5/A3/B4 mice presented a marked reduction in the dendrite complexity of CA1 hippocampal pyramidal neurons along with an increased dendritic spine density. In addition, TgCHRNA5/A3/B4 exhibited increased VGLUT1/VGAT ratio in the CA1 region, suggesting an excitatory/inhibitory imbalance. These hippocampal alterations were accompanied by a significant impairment in short-term novelty recognition memory. Interestingly, chronic infusion of nicotine (3.25 mg/kg/d for 7 d) was able to rescue the reduced dendritic complexity, the excitatory/inhibitory imbalance and the cognitive impairment in TgCHRNA5/A3/B4. Our results suggest that chronic nicotine treatment may represent a compensatory strategy in individuals with altered expression of the CHRNA5/A3/B4 region.
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Differential expression and function of nicotinic acetylcholine receptors in subdivisions of medial habenula. J Neurosci 2014; 34:9789-802. [PMID: 25031416 DOI: 10.1523/jneurosci.0476-14.2014] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuronal nAChRs in the medial habenula (MHb) to the interpeduncular nucleus (IPN) pathway are key mediators of nicotine's aversive properties. In this paper, we report new details regarding nAChR anatomical localization and function in MHb and IPN. A new group of knock-in mice were created that each expresses a single nAChR subunit fused to GFP, allowing high-resolution mapping. We find that α3 and β4 nAChR subunit levels are strong throughout the ventral MHb (MHbV). In contrast, α6, β2, β3, and α4 subunits are selectively found in some, but not all, areas of MHbV. All subunits were found in both ChAT-positive and ChAT-negative cells in MHbV. Next, we examined functional properties of neurons in the lateral and central part of MHbV (MHbVL and MHbVC) using brain slice patch-clamp recordings. MHbVL neurons were more excitable than MHbVC neurons, and they also responded more strongly to puffs of nicotine. In addition, we studied firing responses of MHbVL and MHbVC neurons in response to bath-applied nicotine. Cells in MHbVL, but not those in MHbVC, increased their firing substantially in response to 1 μm nicotine. Additionally, MHbVL neurons from mice that underwent withdrawal from chronic nicotine were less responsive to nicotine application compared with mice withdrawn from chronic saline. Last, we characterized rostral and dorsomedial IPN neurons that receive input from MHbVL axons. Together, our data provide new details regarding neurophysiology and nAChR localization and function in cells within the MHbV.
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Molas S, Dierssen M. The role of nicotinic receptors in shaping and functioning of the glutamatergic system: a window into cognitive pathology. Neurosci Biobehav Rev 2014; 46 Pt 2:315-25. [PMID: 24879992 DOI: 10.1016/j.neubiorev.2014.05.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 04/13/2014] [Accepted: 05/20/2014] [Indexed: 10/25/2022]
Abstract
The involvement of the cholinergic system in learning, memory and attention has long been recognized, although its neurobiological mechanisms are not fully understood. Recent evidence identifies the endogenous cholinergic signaling via nicotinic acetylcholine receptors (nAChRs) as key players in determining the morphological and functional maturation of the glutamatergic system. Here, we review the available experimental and clinical evidence of nAChRs contribution to the establishment of the glutamatergic system, and therefore to cognitive function. We provide some clues of the putative underlying molecular mechanisms and discuss recent human studies that associate genetic variability of the genes encoding nAChR subunits with cognitive disorders. Finally, we discuss the new avenues to therapeutically targeting nAChRs in persons with cognitive dysfunction for which the α7-nAChR subunit is an important etiological mechanism.
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Affiliation(s)
- Susanna Molas
- Systems Biology Program, Centre for Genomic Regulation (CRG), Barcelona E-08003, Spain; University Pompeu Fabra (UPF), Spain; CIBER de Enfermedades Raras (CIBERER), Barcelona E-08003, Spain
| | - Mara Dierssen
- Systems Biology Program, Centre for Genomic Regulation (CRG), Barcelona E-08003, Spain; University Pompeu Fabra (UPF), Spain; CIBER de Enfermedades Raras (CIBERER), Barcelona E-08003, Spain.
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Cholinergic left-right asymmetry in the habenulo-interpeduncular pathway. Proc Natl Acad Sci U S A 2013; 110:21171-6. [PMID: 24327734 DOI: 10.1073/pnas.1319566110] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The habenulo-interpeduncular pathway, a highly conserved cholinergic system, has emerged as a valuable model to study left-right asymmetry in the brain. In larval zebrafish, the bilaterally paired dorsal habenular nuclei (dHb) exhibit prominent left-right differences in their organization, gene expression, and connectivity, but their cholinergic nature was unclear. Through the discovery of a duplicated cholinergic gene locus, we now show that choline acetyltransferase and vesicular acetylcholine transporter homologs are preferentially expressed in the right dHb of larval zebrafish. Genes encoding the nicotinic acetylcholine receptor subunits α2 and β4 are transcribed in the target interpeduncular nucleus (IPN), suggesting that the asymmetrical cholinergic pathway is functional. To confirm this, we activated channelrhodopsin-2 specifically in the larval dHb and performed whole-cell patch-clamp recording of IPN neurons. The response to optogenetic or electrical stimulation of the right dHb consisted of an initial fast glutamatergic excitatory postsynaptic current followed by a slow-rising cholinergic current. In adult zebrafish, the dHb are divided into discrete cholinergic and peptidergic subnuclei that differ in size between the left and right sides of the brain. After exposing adults to nicotine, fos expression was activated in subregions of the IPN enriched for specific nicotinic acetylcholine receptor subunits. Our studies of the newly identified cholinergic gene locus resolve the neurotransmitter identity of the zebrafish habenular nuclei and reveal functional asymmetry in a major cholinergic neuromodulatory pathway of the vertebrate brain.
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Grupe M, Paolone G, Jensen AA, Sandager-Nielsen K, Sarter M, Grunnet M. Selective potentiation of (α4)3(β2)2 nicotinic acetylcholine receptors augments amplitudes of prefrontal acetylcholine- and nicotine-evoked glutamatergic transients in rats. Biochem Pharmacol 2013; 86:1487-96. [PMID: 24051136 DOI: 10.1016/j.bcp.2013.09.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 09/09/2013] [Accepted: 09/09/2013] [Indexed: 12/16/2022]
Abstract
Prefrontal glutamate release evoked through activation of α4β2* nicotinic acetylcholine receptors (nAChRs) situated on thalamic glutamatergic afferents mediates cue detection processes and thus contributes to attentional performance. However, little is known about the respective contributions of the high sensitivity and low sensitivity (LS) stoichiometries of the α4β2 nAChR, (α4)2(β2)3 and (α4)3(β2)2, to these processes. In the present study we employed glutamate-sensitive microelectrodes and the (α4)3(β2)2-selective positive allosteric modulator (PAM) NS9283 to investigate the importance of the LS α4β2 nAChR for glutamate release in the rat medial prefrontal cortex (mPFC). Firstly, the signaling evoked by physiologically relevant ACh concentrations through the (α4)3(β2)2 nAChR in HEK293 cells was potentiated by NS9283, consistent with the classification of NS9283 as a PAM. In urethane-anesthetized rats, intra-prefrontal pressure ejections of NS9283 evoked glutamatergic transients. Importantly, this glutamate release was attenuated by removal of cholinergic projections to the recording area. This finding indicates that the effects of NS9283 depend on endogenous ACh, again consistent with effects of a PAM. We then conducted microdialysis to demonstrate the presence of extracellular ACh in urethane-anesthetized control rats. While detectable, those levels were significantly lower than in awake rats. Finally, the amplitudes of glutamatergic transients evoked by local pressure ejections of a low concentration of nicotine were significantly augmented following systemic administration of NS9283 (3.0mg/kg). In conclusion, our results indicate that a LS α4β2 nAChR PAM such as NS9283 may enhance the cholinergic modulation of glutamatergic neurotransmission in the cortex, thereby perhaps alleviating the attentional impairments common to a range of brain disorders.
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Affiliation(s)
- Morten Grupe
- Department of Psychology and Neuroscience Program, University of Michigan, 530 Church Street, 4030 East Hall, Ann Arbor, MI 48109-1109, USA; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark; NeuroSearch A/S, Pederstrupvej 93, 2750 Ballerup, Denmark.
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Lee YA, Goto Y. Habenula and ADHD: Convergence on time. Neurosci Biobehav Rev 2013; 37:1801-9. [DOI: 10.1016/j.neubiorev.2013.07.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 06/27/2013] [Accepted: 07/11/2013] [Indexed: 12/11/2022]
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Gudehithlu KP, Duchemin AM, Tejwani GA, Neff NH, Hadjiconstantinou M. Nicotine-induced changes of brain β-endorphin. Neuropeptides 2012; 46:125-31. [PMID: 22483037 DOI: 10.1016/j.npep.2012.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 01/31/2012] [Accepted: 03/05/2012] [Indexed: 10/28/2022]
Abstract
A consensus has emerged that endogenous opioid peptides and their receptors play an important role in the psychoactive properties of nicotine. Although behavioral studies have shown that β-endorphin contributes to the rewarding and emotional effects of nicotine, whether the drug alters the function of brain endorphinergic neurons is not fully explored. These studies investigated the effect of acute, 1mg/kg, sc, and chronic, daily injection of 1mg/kg, sc, for 14 days, administration of free base nicotine on brain β-endorphin and its precursor proopiomelanocortin (POMC). Acute and chronic treatment with nicotine decreased β-endorphin content in hypothalamus, the principal site of β-endorphin producing neurons in the brain, and in the endorphinergic terminal fields in striatum and hippocampus. The acute effect of nicotine on β-endorphin was reversed by the nicotinic antagonist mecamylamine and the dopamine antagonist haloperidol, indicating pharmacological specificity and involvement of dopamine D2-like receptors. Similar observations were made in prefrontal cortex. POMC mRNA in hypothalamus and prefrontal cortex was unchanged following acute nicotine, but it decreased moderately with chronic treatment. The nicotine treatments had no effect on pituitary and plasma β-endorphin. Taken together, these results could be interpreted to indicate that nicotine alters the synthesis and release of β-endorphin in the limbic brain in vivo. Altered endorphinergic function may contribute to the behavioral effects of acute and chronic nicotine treatment and play a role in nicotine addiction.
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Affiliation(s)
- K P Gudehithlu
- Department of Pharmacology, College of Medicine, The Ohio State University, Columbus, OH 43210, USA.
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21
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Abbott LC, Winzer-Serhan UH. Smoking during pregnancy: lessons learned from epidemiological studies and experimental studies using animal models. Crit Rev Toxicol 2012; 42:279-303. [DOI: 10.3109/10408444.2012.658506] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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22
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García-Colunga J, Godoy-García U, Vázquez-Gómez E. Interaction of bupropion and zinc with neuronal nicotinic acetylcholine receptors. Neuropharmacology 2011; 61:1202-9. [DOI: 10.1016/j.neuropharm.2011.07.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Revised: 06/06/2011] [Accepted: 07/10/2011] [Indexed: 12/28/2022]
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Role of α7- and β4-containing nicotinic acetylcholine receptors in the affective and somatic aspects of nicotine withdrawal: studies in knockout mice. Behav Genet 2011; 42:423-36. [PMID: 22009521 DOI: 10.1007/s10519-011-9511-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 10/08/2011] [Indexed: 10/16/2022]
Abstract
To assess which nicotinic acetylcholine receptors (nAChRs) are involved in the aversive aspects of nicotine withdrawal, brain reward function and the somatic signs of nicotine withdrawal were assessed in mice that lack α7 and β4 nAChR subunits. Brain reward function was assessed with the intracranial self-stimulation (ICSS) procedure, in which elevations in ICSS thresholds reflect an anhedonic mood state. At 3-6 h of spontaneous nicotine/saline withdrawal, thresholds were elevated in nicotine-withdrawing α7(+/+) and β4(+/+), but not α7(-/-) or β4(-/-), mice compared with saline-withdrawing mice, indicating a delay in the onset of withdrawal in the knockout mice. From 8 to 100 h of withdrawal, thresholds in α7(+/+) and α7(-/-) mice were equally elevated, whereas thresholds in β4(+/+) and β4(-/-) mice returned to baseline levels. Somatic signs were attenuated in nicotine-withdrawing β4(-/-), but not α7(-/-), mice. Administration of a low dose of the nAChR antagonist mecamylamine induced threshold elevations in α7(-/-), but not α7(+/+), mice, whereas the highest dose tested only elevated thresholds in α7(+/+) mice. Mecamylamine-induced threshold elevations were similar in β4(-/-) and β4(+/+) mice. In conclusion, null mutation of the α7 and β4 nAChR subunits resulted in a delayed onset of the anhedonic aspects of the spontaneous nicotine withdrawal syndrome. Previous findings of attenuated somatic signs of nicotine withdrawal in β4(-/-), but not α7(-/-), mice were confirmed in the present study, indicating an important role for β4-containing nAChRs in the somatic signs of nicotine withdrawal. The mecamylamine-precipitated withdrawal data suggest that compensatory adaptations may occur in constitutive α7(-/-) mice or that mecamylamine may interact with other receptors besides nAChRs in these mice. In summary, the present results indicate an important role for α7 and β4-containing nAChRs in the anhedonic or somatic signs of nicotine withdrawal.
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Wu J, Lukas RJ. Naturally-expressed nicotinic acetylcholine receptor subtypes. Biochem Pharmacol 2011; 82:800-7. [PMID: 21787755 DOI: 10.1016/j.bcp.2011.07.067] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2011] [Revised: 07/01/2011] [Accepted: 07/05/2011] [Indexed: 12/31/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) warrant attention, as they play many critical roles in brain and body function and have been implicated in a number of neurological and psychiatric disorders, including nicotine dependence. nAChRs are composed as diverse subtypes containing specific combinations of genetically-distinct subunits and that have different functional properties, distributions, and pharmacological profiles. There had been confidence that the rules that define ranges of assembly partners for specific subunits were well-established, especially for the more prominent nAChR subtypes. However, we review here some newer findings indicating that nAChRs having largely the same, major subunits exist as isoforms with unexpectedly different properties. Moreover, we also summarize our own studies indicating that novel nAChR subtypes exist and/or have distributions not heretofore described. Importantly, the nAChRs that exist as new isoforms or subtypes or have interesting distributions require alteration in thinking about their roles in health and disease.
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Affiliation(s)
- Jie Wu
- Division of Neurology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013, United States.
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Dao JM, McQuown SC, Loughlin SE, Belluzzi JD, Leslie FM. Nicotine alters limbic function in adolescent rat by a 5-HT1A receptor mechanism. Neuropsychopharmacology 2011; 36:1319-31. [PMID: 21412223 PMCID: PMC3096821 DOI: 10.1038/npp.2011.8] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Epidemiological studies have shown that adolescent smoking is associated with health risk behaviors, including high-risk sexual activity and illicit drug use. Using rat as an animal model, we evaluated the behavioral and biochemical effects of a 4-day, low-dose nicotine pretreatment (60 μg/kg; intravenous) during adolescence and adulthood. Nicotine pretreatment significantly increased initial acquisition of cocaine self-administration, quinpirole-induced locomotor activity, and penile erection in adolescent rats, aged postnatal day (P)32. These effects were long lasting, remaining evident 10 days after the last nicotine treatment, and were observed when nicotine pretreatment was administered during early adolescence (P28-31), but not late adolescence (P38-41) or adulthood (P86-89). Neurochemical analyses of c-fos mRNA expression, and of monoamine transmitter and transporter levels, showed that forebrain limbic systems are continuing to develop during early adolescence, and that this maturation is critically altered by brief nicotine exposure. Nicotine selectively increased c-fos mRNA expression in the nucleus accumbens shell and basolateral amygdala in adolescent, but not adult animals, and altered serotonin markers in these regions as well as the prefrontal cortex. Nicotine enhancement of cocaine self-administration and quinpirole-induced locomotor activity was blocked by co-administration of WAY 100 635 (N-{2-[4-(2-methoxyphenyl)-1-piperazinyl] ethyl}-N-(2-pyridinyl)cyclohexanecarboxamide), a selective serotonin 1A (5-HT1A) receptor antagonist. Early adolescent pretreatment with the mixed autoreceptor/heteroceptor 5-HT1A receptor agonist, 8-OH-DPAT, but not the autoreceptor-selective agonist, S-15535, also enhanced quinpirole-induced locomotor activation. Nicotine enhancement of quinpirole-induced penile erection was not blocked by WAY 100 635 nor mimicked by 8-OH-DPAT. These findings indicate that early adolescent nicotine exposure uniquely alters limbic function by both 5-HT1A and non-5-HT1A receptor mechanisms.
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Affiliation(s)
- Jasmin M Dao
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, CA 92697-3800, USA.
| | - Susan C McQuown
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA, USA
| | - Sandra E Loughlin
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA, USA
| | - James D Belluzzi
- Department of Pharmacology, School of Medicine, University of California, Irvine, CA, USA
| | - Frances M Leslie
- Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, CA, USA,Department of Pharmacology, School of Medicine, University of California, Irvine, CA, USA
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Lee YA, Goto Y. Neurodevelopmental disruption of cortico-striatal function caused by degeneration of habenula neurons. PLoS One 2011; 6:e19450. [PMID: 21559387 PMCID: PMC3084869 DOI: 10.1371/journal.pone.0019450] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 04/06/2011] [Indexed: 01/01/2023] Open
Abstract
Background The habenula plays an important role on cognitive and affective functions by regulating monoamines transmission such as the dopamine and serotonin, such that its dysfunction is thought to underlie a number of psychiatric conditions. Given that the monoamine systems are highly vulnerable to neurodevelopmental insults, damages in the habenula during early neurodevelopment may cause devastating effects on the wide-spread brain areas targeted by monoamine innervations. Methodology/Principal Findings Using a battery of behavioral, anatomical, and biochemical assays, we examined the impacts of neonatal damage in the habenula on neurodevelopmental sequelae of the prefrontal cortex (PFC) and nucleus accumbens (NAcc) and associated behavioral deficits in rodents. Neonatal lesion of the medial and lateral habenula by ibotenic acid produced an assortment of behavioral manifestations consisting of hyper-locomotion, impulsivity, and attention deficit, with hyper-locomotion and impulsivity being observed only in the juvenile period, whereas attention deficit was sustained up until adulthood. Moreover, these behavioral alterations were also improved by amphetamine. Our study further revealed that impulsivity and attention deficit were associated with disruption of PFC volume and dopamine (DA) receptor expression, respectively. In contrast, hyper-locomotion was associated with decreased DA transporter expression in the NAcc. We also found that neonatal administration of nicotine into the habenula of neonatal brains produced selective lesion of the medial habenula. Behavioral deficits with neonatal nicotine administration were similar to those caused by ibotenic acid lesion of both medial and lateral habenula during the juvenile period, whereas they were different in adulthood. Conclusions/Significance Because of similarity between behavioral and brain alterations caused by neonatal insults in the habenula and the symptoms and suggested neuropathology in attention deficit/hyperactivity disorder (ADHD), these results suggest that neurodevelopmental deficits in the habenula and the consequent cortico-striatal dysfunctions may be involved in the pathogenesis and pathophysiology of ADHD.
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Affiliation(s)
- Young-A Lee
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada
| | - Yukiori Goto
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada
- * E-mail:
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Gorini C, Philbin K, Bateman R, Mendelowitz D. Endogenous inhibition of the trigeminally evoked neurotransmission to cardiac vagal neurons by muscarinic acetylcholine receptors. J Neurophysiol 2010; 104:1841-8. [PMID: 20719927 DOI: 10.1152/jn.00442.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Stimulation of the nasal mucosa by airborne irritants or water evokes a pronounced bradycardia accompanied by peripheral vasoconstriction and apnea. The dive response, which includes the trigeminocardiac reflex, is among the most powerful autonomic responses. These responses slow the heart rate and reduce myocardial oxygen consumption. Although normally cardioprotective, exaggeration of this reflex can be detrimental and has been implicated in cardiorespiratory diseases, including sudden infant death syndrome (SIDS). An essential component of the diving response and trigeminocardiac reflex is activation of the parasympathetic cardiac vagal neurons (CVNs) in the nucleus ambiguus that control heart rate. This study examined the involvement of cholinergic receptors in trigeminally evoked excitatory postsynaptic currents in CVNs in an in vitro preparation from rats. CVNs were identified using a retrograde tracer injected into the fat pads at the base of the heart. Application of the acetylcholinesterase inhibitor neostigmine significantly decreased the amplitude of glutamatergic neurotransmission to CVNs on stimulation of trigeminal fibers. Whereas nicotine did not have any effect on the glutamatergic responses, the muscarinic acetylcholine receptor (mAChR) agonist bethanechol significantly decreased the excitatory neurotransmission. Atropine, an mAChR antagonist, facilitated these responses indicating this trigeminally evoked brain stem pathway in vitro is endogenously inhibited by mAChRs. Tropicamide, an m4 mAChR antagonist, prevented the inhibitory action of the muscarinic agonist bethanechol. These results indicate that the glutamatergic synaptic neurotransmission in the trigeminally evoked pathway to CVNs is endogenously inhibited in vitro by m4 mAChRs.
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Affiliation(s)
- C Gorini
- George Washington University, Department of Pharmacology and Physiology, 2300 Eye St NW, Washington, DC 20037, USA
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A transcriptional regulatory element critical for CHRNB4 promoter activity in vivo. Neuroscience 2010; 170:1056-64. [PMID: 20696214 DOI: 10.1016/j.neuroscience.2010.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 08/01/2010] [Accepted: 08/03/2010] [Indexed: 11/23/2022]
Abstract
Genome-wide association studies have underscored the importance of the clustered neuronal nicotinic acetylcholine receptor (nAChR) subunit genes with respect to nicotine dependence as well as lung cancer susceptibility. CHRNB4, which encodes the nAChR β4 subunit, plays a major role in the molecular mechanisms that govern nicotine withdrawal. Thus, elucidating how expression of the β4 gene is regulated is critical for understanding the pathophysiology of nicotine addiction. We previously identified a CA box regulatory element, (5'-CCACCCCT-3') critical for β4 promoter activity in vitro. We further demonstrated that a 2.3-kb fragment of the β4 promoter region containing the 5'-CCACCCCT-3' regulatory element in the β4 gene promoter (CA box) is capable of directing cell-type specific expression of a reporter gene to a myriad of brain regions that endogenously express the β4 gene. To test the hypothesis that the CA box is critical for β4 promoter activity in vivo, transgenic animals expressing a mutant form of the β4 promoter were generated. Reporter gene expression was not detected in any tissue or cell type at embryonic day 18.5 (ED 18.5). Similarly, we observed drastically reduced reporter gene expression at postnatal day 30 (PD30) when compared to wild type (WT) transgenic animals. Finally, we demonstrated that CA box mutation results in decreased interaction of the transcription factor Sp1 with the mutant β4 promoter. Taken together these results demonstrate that the CA box is critical for β4 promoter activity in vivo.
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Improgo MRD, Scofield MD, Tapper AR, Gardner PD. The nicotinic acetylcholine receptor CHRNA5/A3/B4 gene cluster: dual role in nicotine addiction and lung cancer. Prog Neurobiol 2010; 92:212-26. [PMID: 20685379 DOI: 10.1016/j.pneurobio.2010.05.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 05/15/2010] [Accepted: 05/27/2010] [Indexed: 01/19/2023]
Abstract
More than 1 billion people around the world smoke, with 10 million cigarettes sold every minute. Cigarettes contain thousands of harmful chemicals including the psychoactive compound, nicotine. Nicotine addiction is initiated by the binding of nicotine to nicotinic acetylcholine receptors, ligand-gated cation channels activated by the endogenous neurotransmitter, acetylcholine. These receptors serve as prototypes for all ligand-gated ion channels and have been extensively studied in an attempt to elucidate their role in nicotine addiction. Many of these studies have focused on heteromeric nicotinic acetylcholine receptors containing α4 and β2 subunits and homomeric nicotinic acetylcholine receptors containing the α7 subunit, two of the most abundant subtypes expressed in the brain. Recently however, a series of linkage analyses, candidate-gene analyses and genome-wide association studies have brought attention to three other members of the nicotinic acetylcholine receptor family: the α5, α3 and β4 subunits. The genes encoding these subunits lie in a genomic cluster that contains variants associated with increased risk for several diseases including nicotine dependence and lung cancer. The underlying mechanisms for these associations have not yet been elucidated but decades of research on the nicotinic receptor gene family as well as emerging data provide insight on how these receptors may function in pathological states. Here, we review this body of work, focusing on the clustered nicotinic acetylcholine receptor genes and evaluating their role in nicotine addiction and lung cancer.
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Affiliation(s)
- Ma Reina D Improgo
- Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, University of Massachusetts Medical School, 303 Belmont Street, Worcester, MA 01604, United States
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Bruschweiler-Li L, Fuentes Medel YF, Scofield MD, Trang EBT, Binke SA, Gardner PD. Temporally- and spatially-regulated transcriptional activity of the nicotinic acetylcholine receptor beta4 subunit gene promoter. Neuroscience 2010; 166:864-77. [PMID: 20096338 DOI: 10.1016/j.neuroscience.2010.01.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 01/13/2010] [Accepted: 01/13/2010] [Indexed: 11/27/2022]
Abstract
Signaling through nicotinic acetylcholine (nACh) receptors underlies a diverse array of behaviors. In order for appropriate signaling to occur via nACh receptors, it is necessary for the genes encoding the receptor subunits to be expressed in a highly regulated temporal and spatial manner. Here we report a transgenic mouse approach to characterize the transcriptional regulation of the gene encoding the nACh receptor beta4 subunit. nACh receptors containing this subunit play critical roles in both the central and peripheral nervous systems. We demonstrate that a 2.3-kilobase pair fragment of the beta4 5'-flanking region is capable of directing reporter gene expression in transgenic animals. Importantly, the transcriptional activity of the promoter region is cell-type-specific and developmentally regulated and overlaps to a great extent with endogenous beta4 mRNA expression. These data indicate that the 2.3-kilobase pair fragment contains transcriptional regulatory elements critical for appropriate beta4 subunit gene expression.
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Affiliation(s)
- L Bruschweiler-Li
- Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, University of Massachusetts Medical School, Worcester, MA 01604, USA
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Smith AM, Dwoskin LP, Pauly JR. Early exposure to nicotine during critical periods of brain development: Mechanisms and consequences. JOURNAL OF PEDIATRIC BIOCHEMISTRY 2010; 1:125-141. [PMID: 24904708 PMCID: PMC4042244 DOI: 10.3233/jpb-2010-0012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Tobacco use during pregnancy continues to be a major problem with more than 16% of pregnant women in the United States continuing to smoke during pregnancy. Tobacco smoke is known to contain more than 4,000 different chemicals, and while many of these compounds have the potential to interfere with proper neurodevelopment, there is direct evidence that nicotine, the major psychoactive substance present in tobacco, acts as a neuroteratogen. Nicotine activates, and subsequently desensitizes, neuronal nicotinic acetylcholine receptor subtypes (AChRs), which are expressed in the developing central nervous system (CNS) prior to the in-growth of cholinergic neurons. Nicotinic AChRs are present by the first trimester of development in both humans and rodents, and activation of these receptors by acetylcholine is thought to play a critical role in CNS development. The purpose of the current review is to provide an overview of the role that nicotinic AChRs play in the developing CNS and to describe the effects of nicotine exposure during early development on neuronal cell biology, nicotinic AChR expression and neurotransmitter system (e.g., dopamine, norepinephrine, serotonin) function. In particular, differences that occur as a result of the timing and duration of nicotine exposure will be discussed. Emphasis will be placed on preclinical studies examining particular periods of time which correspond to periods of prenatal development in humans (i.e., first, second and third trimesters). Finally, the effects of early nicotine exposure on neurobehavioral development as it pertains to specific disorders, i.e., attention deficit hyperactivity disorder (ADHD), depression and addiction, will be discussed.
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Affiliation(s)
- Andrew M. Smith
- College of Pharmacy, Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40536-0082, USA
| | - Linda P. Dwoskin
- College of Pharmacy, Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40536-0082, USA
| | - James R. Pauly
- College of Pharmacy, Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40536-0082, USA
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Dwoskin LP, Smith AM, Wooters TE, Zhang Z, Crooks PA, Bardo MT. Nicotinic receptor-based therapeutics and candidates for smoking cessation. Biochem Pharmacol 2009; 78:732-43. [PMID: 19523455 PMCID: PMC4110684 DOI: 10.1016/j.bcp.2009.06.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 05/29/2009] [Accepted: 06/01/2009] [Indexed: 12/29/2022]
Abstract
Tobacco dependence is the most preventable cause of death and is a chronic, relapsing disorder in which compulsive tobacco use persists despite known negative health consequences. All currently available cessation agents (nicotine, varenicline and bupropion) have limited efficacy and are associated with high relapse rates, revealing a need for more efficacious, alternative pharmacotherapies. The major alkaloid in tobacco, nicotine, activates nicotinic receptors (nAChRs) which increase brain extracellular dopamine producing nicotine reward leading to addiction. nAChRs are located primarily presynaptically and modulate synaptic activity by regulating neurotransmitter release. Subtype-selective nAChR antagonists that block reward-relevant mesocorticolimbic and nigrostriatal dopamine release induced by nicotine may offer advantages over current therapies. An innovative approach is to provide pharmacotherapies which are antagonists at nAChR subtypes mediating nicotine evoked dopamine release. In addition, providing multiple medications with a wider array of targets and mechanisms should provide more treatment options for individuals who are not responsive to the currently available pharmacotherapies. This review summarizes the currently available smoking cessation therapies and discusses emerging potential therapeutic approaches employing pharmacological agents which act as antagonists at nicotinic receptors.
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Affiliation(s)
- Linda P Dwoskin
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY 40536, USA.
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Son JH, Winzer-Serhan UH. Chronic neonatal nicotine exposure increases mRNA expression of neurotrophic factors in the postnatal rat hippocampus. Brain Res 2009; 1278:1-14. [DOI: 10.1016/j.brainres.2009.04.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/21/2009] [Accepted: 04/27/2009] [Indexed: 01/19/2023]
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Dwyer JB, McQuown SC, Leslie FM. The dynamic effects of nicotine on the developing brain. Pharmacol Ther 2009; 122:125-39. [PMID: 19268688 DOI: 10.1016/j.pharmthera.2009.02.003] [Citation(s) in RCA: 420] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Accepted: 02/05/2009] [Indexed: 12/25/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) regulate critical aspects of brain maturation during the prenatal, early postnatal, and adolescent periods. During these developmental windows, nAChRs are often transiently upregulated or change subunit composition in those neural structures that are undergoing major phases of differentiation and synaptogenesis, and are sensitive to environmental stimuli. Nicotine exposure, most often via tobacco smoke, but increasingly via nicotine replacement therapy, has been shown to have unique effects on the developing human brain. Consistent with a dynamic developmental role for acetylcholine, exogenous nicotine produces effects that are unique to the period of exposure and that impact the developing structures regulated by acetylcholine at that time. Here we present a review of the evidence, available from both the clinical literature and preclinical animal models, which suggests that the diverse effects of nicotine exposure are best evaluated in the context of regional and temporal expression patterns of nAChRs during sensitive maturational periods, and disruption of the normal developmental influences of acetylcholine. We present evidence that nicotine interferes with catecholamine and brainstem autonomic nuclei development during the prenatal period of the rodent (equivalent to first and second trimester of the human), alters the neocortex, hippocampus, and cerebellum during the early postnatal period (third trimester of the human), and influences limbic system and late monoamine maturation during adolescence.
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Affiliation(s)
- Jennifer B Dwyer
- Department of Pharmacology, Med Surge II, School of Medicine, University of California, Irvine, CA 92697, USA.
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35
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Son JH, Winzer-Serhan UH. Signal intensities of radiolabeled cRNA probes used alone or in combination with non-isotopic in situ hybridization histochemistry. J Neurosci Methods 2009; 179:159-65. [PMID: 19428522 DOI: 10.1016/j.jneumeth.2009.01.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Revised: 01/19/2009] [Accepted: 01/21/2009] [Indexed: 11/25/2022]
Abstract
This study addressed the question of whether radioactive hybridization signal intensities are reduced in combined isotopic and non-isotopic double in situ hybridization (DISH) compared with those in single in situ hybridization (ISH). Non-isotopic digoxigenin (Dig)-labeled hybrids were detected using an alkaline phosphatase (AP) enzymatic reaction which results in nitroblue tetrazolium chloride (NBT)/5-bromo-4-chloro-3-indolyl phosphate (BCIP)-salt precipitation that could shield S35-radiation from penetrating to the surface. Sections were plastic coated of with 2% parlodion to prevent a chemical reaction between AP and developer during processing of the photosensitive emulsion, which could further reduce radioactive hybridization signal detection by autoradiography. We used DISH with a hybridization cocktail of radioactive S35- and Dig-labeled GAD67 cRNA probes. In order to avoid competition for the same complementary sequence, the probes were directed towards different sequences of the glutamic acid decarboxylase (GAD67) mRNA, resulting in co-detection of isotopic and non-isotopic hybrids in close to 100% of GAD67 positive cells. Quantitation of autoradiograms showed that there was no reduction of autoradiographic signal intensity from S35-labeled hybrids in the presence of Dig-labeled hybrids. Plastic coating of single or dual hybridized sections did not reduce the radioactive signal intensity. When mRNAs for nicotinic acetylcholine receptor (nAChR) subunits were detected with subunit specific S35-labeled cRNA probes in GAD67 hippocampal interneurons the total numbers of nAChR subunit expressing cells remained the same in single or double hybridized sections even for low abundant mRNAs. Together, these results indicate that combined radioactive and non-radioactive DISH does not interfere with the detection of the radiation signal from the S35-labeled hybrids, and neither specificity nor sensitivity is compromised.
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Affiliation(s)
- Jong-Hyun Son
- Department of Neuroscience & Experimental Therapeutics, College of Medicine, 262 Reynolds Medical Building, Texas A&M University System, Health Sciences Center, College Station, TX 77843-1114, USA
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36
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Cellular events in nicotine addiction. Semin Cell Dev Biol 2009; 20:418-31. [PMID: 19560047 DOI: 10.1016/j.semcdb.2009.01.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 12/19/2008] [Accepted: 01/09/2009] [Indexed: 11/23/2022]
Abstract
In the 25 years since the observation that chronic exposure to nicotine could regulate the number and function of high affinity nicotine binding sites in the brain there has been a major effort to link alterations in nicotinic acetylcholine receptors (nAChRs) to nicotine-induced behaviors that drive the addiction to tobacco products. Here we review the proposed roles of various nAChR subtypes in the addiction process, with emphasis on how they are regulated by nicotine and the implications for understanding the cellular neurobiology of addiction to this drug.
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37
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Son JH, Winzer-Serhan UH. Expression of neuronal nicotinic acetylcholine receptor subunit mRNAs in rat hippocampal GABAergic interneurons. J Comp Neurol 2008; 511:286-99. [PMID: 18792073 DOI: 10.1002/cne.21828] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Hippocampal inhibitory interneurons are a diverse population of cells widely scattered in the hippocampus, where they regulate hippocampal circuit activity. The hippocampus receives cholinergic projections from the basal forebrain, and functional studies have suggested the presence of different subtypes of nicotinic acetylcholine receptors (AChRs) on gamma-aminobutyric acid (GABA)ergic interneurons. Single-cell polymerase chain reaction analysis had confirmed that several nAChR subunit mRNAs are co-expressed with glutamate decarboxylase 67 (GAD67), the marker for GABAergic interneurons. In this anatomical study, we systematically investigated the co-expression of GAD67 with different nAChR subunits by using double in situ hybridization with a digoxigenin-labeled GAD67 probe and (35)S-labeled probes for nAChR subunits (alpha2, alpha3, alpha4, alpha5, alpha6, alpha7, beta2, beta3, and beta4). The results revealed that most GAD67-positive interneurons expressed beta2, and 67 % also expressed alpha7 mRNA. In contrast, mRNA expression of other subunits was limited; only 13 % of GAD67-positive neurons co-expressed alpha4, and less than 10% expressed transcripts for alpha2, alpha3, alpha5, or beta4. Most GAD67/alpha2 co-expression was located in CA1/CA3 stratum oriens, and GAD67/alpha5 co-expression was predominantly detected in CA1/CA3 stratum radiatum/lacunosum moleculare and the dentate gyrus. Expression of alpha6 and beta3 mRNAs was rarely detected in the hippocampus, and mRNAs were not co-expressed with GAD67. These findings suggest that the majority of nicotinic responses in GABAergic interneurons should be mediated by a homomeric alpha7 or heteromeric alpha7*-containing nAChRs. Other possible combinations such as alpha2beta2*, alpha4beta2*, or alpha5beta2* heteromeric nAChRs could contribute to functional nicotinic response in subsets of GABAergic interneurons but overall would have a minor role.
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Affiliation(s)
- Jong-Hyun Son
- Department of Neuroscience and Experimental Therapeutics, Texas A&M University System, Health Science Center, College Station, Texas 77843-1114, USA
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38
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O'Leary KT, Loughlin SE, Chen Y, Leslie FM. Nicotinic acetylcholine receptor subunit mRNA expression in adult and developing rat medullary catecholamine neurons. J Comp Neurol 2008; 510:655-72. [PMID: 18698592 DOI: 10.1002/cne.21833] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate numerous visceral functions via medullary catecholamine (CA) neurons found in the nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMV), and ventrolateral medulla (VLM). However, the nAChR subtypes involved are not known. We have therefore characterized expression of nine nAChR subunit mRNAs in adult and developing rat medullary CA nuclei using combined isotopic/nonisotopic in situ hybridization. Tyrosine hydroxylase (TH) mRNA, the CA-synthesizing enzyme, was used as a marker for CA neurons, because these nuclei consist of heterogeneous populations of cells. Subunit mRNA expression varied within and between nuclei, along the rostrocaudal axis, between cell types, and across development. All CA neurons expressed beta2 mRNA, whereas alpha2 mRNA was completely absent. alpha6 And beta3 mRNA expression were restricted mainly to the VLM. alpha4, alpha5, And alpha7 mRNA expression was significantly greater in the rostral than in the caudal VLM. alpha3 And beta4 mRNAs were highly expressed in the dorsal region of the NTS, whereas dense alpha7 mRNA expression was restricted to the DMV and ventral NTS. The remaining subunit mRNAs were detected to some degree in both DMV and NTS. Except for alpha4 mRNA, which peaked prenatally, expression levels of subunit transcripts in the NTS and DMV were lower during development compared with adults. In the VLM, alpha3, alpha4, and alpha5 mRNAs expression peaked perinatally, whereas alpha6 and beta3 levels increased with age. These variations in nAChR subunit mRNA expression suggest that different receptor subtypes may produce function-specific regulation of medullary CA systems.
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Affiliation(s)
- Kathryn T O'Leary
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, California 92697, USA
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40
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Schmitt HF, Huang LZ, Son JH, Pinzon-Guzman C, Slaton GS, Winzer-Serhan UH. Acute nicotine activates c-fos and activity-regulated cytoskeletal associated protein mRNA expression in limbic brain areas involved in the central stress-response in rat pups during a period of hypo-responsiveness to stress. Neuroscience 2008; 157:349-59. [PMID: 18848603 DOI: 10.1016/j.neuroscience.2008.09.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Revised: 07/14/2008] [Accepted: 09/10/2008] [Indexed: 10/21/2022]
Abstract
In adult rats, acute nicotine, the major psychoactive ingredient in tobacco smoke, stimulates the hypothalamic-pituitary-adrenal axis (HPA), resulting in activation of brain areas involved in stress and anxiety-linked behavior. However, in rat pups the first two postnatal weeks are characterized by hypo-responsiveness to stress, also called the 'stress non-responsive period' (SNRP). Therefore, we wanted to address the question if acute nicotine stimulates areas involved in the stress response during SNRP. To determine neuronal activation, the expression of the immediate-early genes c-fos and activity-regulated cytoskeletal associated protein (Arc) was studied in the central nucleus of the amygdala (CeA), bed nucleus stria terminalis (BST) and paraventricular hypothalamic nucleus (PVN), which are areas involved in the neuroendocrine and central stress response. Rat pups received nicotine tartrate (2 mg/kg) or saline by i.p. injection at postnatal days (P) 5, 7 and 10 and their brains were removed after 30 min. We used semi-quantitative radioactive in situ hybridization with gene specific antisense cRNA probes in coronal sections. In control pups, c-fos expression was low in most brain regions, but robust Arc hybridization was found in several areas including cingulate cortex, hippocampus and caudate. Acute nicotine resulted in significant induction of c-fos expression in the PVN and CeA at P5, P7 and P10, and in the BST at P7 and P10. Acute nicotine significantly induced expression of Arc in CeA at P5, P7 and P10, and in the BST at P10. In conclusion, acute nicotine age dependently activated different brain areas of the HPA axis during the SNRP. After P7, the response was more pronounced and included the BST, suggesting differential maturation of the HPA axis in response to nicotine.
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Affiliation(s)
- H F Schmitt
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, TX A&M University System, 203 Reynolds Medical Building, College Station, TX 77843-1114, USA
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Yeh JJ, Yasuda RP, Dávila-García MI, Xiao Y, Ebert S, Gupta T, Kellar KJ, Wolfe BB. Neuronal nicotinic acetylcholine receptor α3 subunit protein in rat brain and sympathetic ganglion measured using a subunit-specific antibody: regional and ontogenic expression. J Neurochem 2008. [DOI: 10.1046/j.1471-4159.2001.00259.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Abstract
Preclinical studies, using primarily rodent models, have shown acetylcholine to have a critical role in brain maturation via activation of nicotinic acetylcholine receptors (nAChRs), a structurally diverse family of ligand-gated ion channels. nAChRs are widely expressed in fetal central nervous system, with transient upregulation in numerous brain regions during critical developmental periods. Activation of nAChRs can have varied developmental influences that are dependent on the pharmacologic properties and localization of the receptor. These include regulation of transmitter release, gene expression, neurite outgrowth, cell survival, and synapse formation and maturation. Aberrant exposure of fetal and neonatal brain to nicotine, through maternal smoking or nicotine replacement therapy (NRT), has been shown to have detrimental effects on cholinergic modulation of brain development. These include alterations in sexual differentiation of the brain, and in cell survival and synaptogenesis. Long-term alterations in the functional status and pharmacologic properties of nAChRs may also occur, which result in modifications of specific neural circuitry such as the brainstem cardiorespiratory network and sensory thalamocortical gating. Such alterations in brain structure and function may contribute to clinically characterized deficits that result from maternal smoking, such as sudden infant death syndrome and auditory-cognitive dysfunction. Although not the only constituent of tobacco smoke, there is now abundant evidence that nicotine is a neural teratogen. Thus, alternatives to NRT should be sought as tobacco cessation treatments in pregnant women.
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Affiliation(s)
- Jennifer B Dwyer
- Department of Pharmacology, University of California, Irvine, California 92697, USA.
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43
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Characterization of the hypothalamic proopiomelanocortin gene and β-endorphin expression in the hypothalamic arcuate nucleus of mice elicited by inflammatory pain. Neuroscience 2008; 152:1054-66. [DOI: 10.1016/j.neuroscience.2007.06.047] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 06/25/2007] [Accepted: 06/27/2007] [Indexed: 01/05/2023]
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Alpha4* nicotinic receptors in preBotzinger complex mediate cholinergic/nicotinic modulation of respiratory rhythm. J Neurosci 2008; 28:519-28. [PMID: 18184794 DOI: 10.1523/jneurosci.3666-07.2008] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Acetylcholine and nicotine can modulate respiratory patterns by acting on nicotinic acetylcholine receptors (nAChRs) in the preBötzinger complex (preBötC). To further explore the molecular composition of these nAChRs, we studied a knock-in mouse strain with a leucine-to-alanine mutation in the M2 pore-lining region (L9'A) of the nAChR alpha4 subunit; this mutation renders alpha4-containing receptors hypersensitive to agonists. We recorded respiratory-related rhythmic motor activity from hypoglossal nerve (XIIn) and patch-clamped preBötC inspiratory neurons in an in vitro medullary slice preparation from neonatal mice. Nicotine affected respiratory rhythm at concentrations approximately 100-fold lower in the homozygous L9'A knock-in mice compared with wild-type mice. Bath application of 5 nm nicotine increased the excitability of preBötC inspiratory neurons, increased respiratory frequency, and induced tonic/seizure-like activities in XIIn in L9'A mice, effects similar to those induced by 1 microM nicotine in wild-type mice. In L9'A mice, microinjection of low nanomolar concentrations of nicotine into the preBötC increased respiratory frequency, whereas injection into the ipsilateral hypoglossal (XII) nucleus induced tonic/seizure-like activity. The alpha4*-selective nAChR antagonist dihydro-beta-erythroidine produced opposite effects and blocked the nicotinic responses. These data, showing that nAChRs in the preBötC and XII nucleus in L9'A mice are hypersensitive to nicotine and endogenous ACh, suggest that functional alpha4* nAChRs are present in the preBötC. They mediate cholinergic/nicotinic modulation of the excitability of preBötC inspiratory neurons and of respiratory rhythm. Furthermore, functional alpha4* nAChRs are present in XII nucleus and mediate cholinergic/nicotinic modulation of tonic activity in XIIn.
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Quik M, Bordia T, O'Leary K. Nicotinic receptors as CNS targets for Parkinson's disease. Biochem Pharmacol 2007; 74:1224-34. [PMID: 17631864 PMCID: PMC2046219 DOI: 10.1016/j.bcp.2007.06.015] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 06/09/2007] [Accepted: 06/12/2007] [Indexed: 10/23/2022]
Abstract
Parkinson's disease is a debilitating neurodegenerative movement disorder characterized by damage to the nigrostriatal dopaminergic system. Current therapies are symptomatic only and may be accompanied by serious side effects. There is therefore a continual search for novel compounds for the treatment of Parkinson's disease symptoms, as well as to reduce or halt disease progression. Nicotine administration has been reported to improve motor deficits that arise with nigrostriatal damage in parkinsonian animals and in Parkinson's disease. In addition, nicotine protects against nigrostriatal damage in experimental models, findings that have led to the suggestion that the reduced incidence of Parkinson's disease in smokers may be due to the nicotine in tobacco. Altogether, these observations suggest that nicotine treatment may be beneficial in Parkinson's disease. Nicotine interacts with multiple nicotinic receptor (nAChR) subtypes in the peripheral and central nervous system, as well as in skeletal muscle. Work to identify the subtypes affected in Parkinson's disease is therefore critical for the development of targeted therapies. Results show that striatal alpha6beta2-containing nAChRs are particularly susceptible to nigrostriatal damage, with a decline in receptor levels that closely parallels losses in striatal dopamine. In contrast, alpha4beta2-containing nAChRs are decreased to a much smaller extent under the same conditions. These observations suggest that development of nAChR agonists or antagonists targeted to alpha6beta2-containing nAChRs may represent a particularly relevant target for Parkinson's disease therapeutics.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, Sunnyvale, CA 94089, USA.
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46
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Huang LZ, Abbott LC, Winzer-Serhan UH. Effects of chronic neonatal nicotine exposure on nicotinic acetylcholine receptor binding, cell death and morphology in hippocampus and cerebellum. Neuroscience 2007; 146:1854-68. [PMID: 17434679 PMCID: PMC2001269 DOI: 10.1016/j.neuroscience.2007.03.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 02/27/2007] [Accepted: 03/01/2007] [Indexed: 10/23/2022]
Abstract
Nicotine, the major psychoactive ingredient in tobacco interacting with nicotinic acetylcholine receptors (nAChR), is believed to have neuroprotective and neurotoxic effects on the developing brain. Neurotoxicity has been attributed to activation of homomeric alpha7 nAChRs, neuroprotection to heteromeric alpha4beta2 nAChRs. Thus, developmental nicotine could have opposite effects in different brain regions, depending on nAChR subtype expression. Here, we determined if chronic neonatal nicotine exposure (CNN), during a period of brain growth corresponding to the third human trimester, differentially regulates nAChR expression, cell death, and morphological properties in hippocampus and cerebellum, two structures maturing postnatally. Rat pups were orally treated with 6 mg/kg/day nicotine from postnatal day (P)1 to P7. On P8, expression for alpha4, alpha7 and beta2 mRNA was determined by in situ hybridization; nAChR binding sites by receptor autoradiography, dying neurons by TUNEL and Fluoro-Jade staining and morphological properties by analysis of Cresyl Violet-stained sections. In control cerebellum, strong expression of alpha4, beta2 mRNA and heteromeric nAChRs labeled with [125I]-epibatidine was found in granule cells, and alpha7 mRNA and homomeric nAChRs labeled with [125I]-alpha-bungarotoxin were in the external germinal layer. In control hippocampus, low expression of alpha4 mRNA and heteromeric nAChRs and high expression of alpha7 mRNA and homomeric nAChRs were detected. CNN increased heteromeric nAChR binding in hippocampus but not cerebellum and significantly decreased neuronal soma size and increased packing density in hippocampal principal cells but not in cerebellum. CNN did not increase the number of dying cells in any area, but significantly fewer TUNEL-labeled cells were found in CA3 strata oriens and radiatum and cerebellar granule layer. Thus, the hippocampus seems to be more sensitive than the cerebellum to CNN which could result from different nAChR subtype expression and might explain long-lasting altered cognitive functions correlated with gestational nicotine exposure due to changes in hippocampal cell morphology.
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Affiliation(s)
- L Z Huang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University System, 369 Reynolds Medical Building, College Station, TX 77843-1114, USA
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47
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Abstract
Transient currents occur at rest in cortical neurones that reflect the quantal release of transmitters such as glutamate and γ-aminobutyric acid (GABA). We found a bimodal amplitude distribution for spontaneously occurring inward currents recorded from mouse pyramidal neurones in situ, in acutely isolated brain slices superfused with picrotoxin. Larger events were blocked by glutamate receptor (AMPA, kainate) antagonists; smaller events were partially inhibited by P2X receptor antagonists suramin and PPADS. The decay of the larger events was selectively prolonged by cyclothiazide. Stimulation of single intracortical axons elicited quantal glutamate-mediated currents and also quantal currents with amplitudes corresponding to the smaller spontaneous inward currents. It is likely that the lower amplitude spontaneous events reflect packaged ATP release. This occurs with a lower probability than that of glutamate, and evokes unitary currents about half the amplitude of those mediated through AMPA receptors. Furthermore, the packets of ATP appear to be released from vesicle in a subset of glutamate-containing terminals.
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Affiliation(s)
- Yuriy Pankratov
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK
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Medel YFF, Gardner PD. Transcriptional Repression by a Conserved Intronic Sequence in the Nicotinic Receptor α3 Subunit Gene. J Biol Chem 2007; 282:19062-70. [PMID: 17504758 DOI: 10.1074/jbc.m702354200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The genes encoding the nicotinic acetylcholine receptor alpha3, alpha5, and beta4 subunits are genomically clustered. These genes are co-expressed in a variety of cells in the peripheral and central nervous systems. Their gene products assemble in a number of stoichiometries to generate several nicotinic receptor subtypes that have distinct pharmacological and physiological properties. Signaling through these receptors is critical for a variety of fundamental biological processes. Despite their importance, the transcriptional mechanisms underlying their coordinated expression remain to be completely elucidated. By using a bioinformatics approach, we identified a highly conserved intronic sequence within the fifth intron of the alpha3 subunit gene. Reporter gene analysis demonstrated that this sequence, termed "alpha3 intron 5," inhibits the transcriptional activities of the alpha3 and beta4 subunit gene promoters. This repressive activity is position- and orientation-independent. Importantly, repression occurs in a cell type-specific manner, being present in cells that do not express the receptor genes or expresses them at very low levels. Electrophoretic mobility shift assays demonstrate that nuclear proteins specifically interact with alpha3 intron 5 at two distinct sites. We propose that this intronic repressor element is important for the restricted expression patterns of the nicotinic receptor alpha3 and beta4 subunit genes.
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Affiliation(s)
- Yuly F Fuentes Medel
- Brudnick Neuropsychiatric Research Institute, Department of Psychiatry, University of Massachusetts Medical School, Worcester, Massachusetts 01604, USA
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Yu WF, Guan ZZ, Nordberg A. Postnatal upregulation of alpha4 and alpha3 nicotinic receptor subunits in the brain of alpha7 nicotinic receptor-deficient mice. Neuroscience 2007; 146:1618-28. [PMID: 17434683 DOI: 10.1016/j.neuroscience.2007.03.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2006] [Revised: 02/28/2007] [Accepted: 03/01/2007] [Indexed: 11/15/2022]
Abstract
The nicotinic receptor subtypes are important for several physiological functions in brain and may therefore play a critical role in brain development. The alpha7 nicotinic receptors which have high Ca2+ permeability are important for cognitive, neuroprotective and trophic functions. In this study, the brain development and the expression of alpha4, alpha3, alpha7, alpha5 and beta2 nicotinic receptors were investigated in the brains of alpha7 deficient (alpha7 -/-), alpha7 heterozygous null (alpha7 +/-) and alpha7 wild-type (alpha7 +/+) mice from postnatal days (P) 7-84. The specific binding of [3H] cytisine and [3H] epibatidine, as well as the expressions of alpha4 and alpha3 nicotinic receptor subunits at mRNA and protein levels, were significantly increased in the cortex and hippocampus of alpha7 -/- and alpha7 +/- mice compared with alpha7 +/+ mice. Furthermore, the alpha4 and alpha3 nicotinic acetylcholine receptor (nAChR) subunits appeared to co-assemble with the alpha5 nAChR subunit in these above brain regions of these mice. No significant change in synaptophysin level was observed. These data suggest that increased levels of alpha4, alpha3-containing nAChRs, co-assembled with the alpha5 nAChR subunit, may contribute to the normal brain development of alpha7 -/- and alpha7 +/- mice.
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Affiliation(s)
- W-F Yu
- Karolinska Institutet, Department of Neurobiology, Care Sciences and Society, Division of Molecular Neuropharmacology, Karolinska University Hospital Huddinge, S-141 86 Stockholm, Sweden
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Patz S, Wahle P. Developmental changes of neurotrophin mRNA expression in the layers of rat visual cortex. Eur J Neurosci 2007; 24:2453-60. [PMID: 17100834 DOI: 10.1111/j.1460-9568.2006.05126.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Neurotrophins are essential factors for the structural, neurochemical and functional maturation of the brain including developmental and adult plasticity. Northern blots and polymerase chain reaction revealed the expression of neurotrophin 4 (NT4), neurotrophin 3 (NT3), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the cortex. The cellular producers of NT3 and BDNF have been characterized by anatomical methods as being mostly pyramidal, and the tyrosine kinase B (TrkB) receptor is expressed by many cortical neurons. However, these methods have so far failed to identify the cells producing NT4 and NGF mRNA. These factors are much lower in expression than, e.g. BDNF, and apparently remain below detection levels of in situ hybridization. Given their specific actions on cell types and afferent systems, knowledge about the producing cell types is highly desirable. To narrow down on the producing cell types, we quantified by reverse transcriptase-polymerase chain reaction (RT-PCR) the developmental changes of BDNF, NT3, NT4, NGF and TrkB mRNA expression in total visual cortex lysates, and in the cortical layers dissected by tangential cryostat sectioning. We found dramatic changes in laminar expression of NT3 and NGF, mild changes of NT4, and no changes of BDNF and TrkB mRNA. For instance, NT3 is important early on for thalamocortical axons, and we found transient peaks of NT3 mRNA expression first in layer VI, then in layer IV. NT4 mRNA was in layers IV and VI, suggesting NT4 protein production in thalamorecipient layers, but peak expression gradually shifted to upper layers as did NGF expression. The layer-specific developmental expression shifts of neurotrophin mRNAs correlate with morphogenetic processes.
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Affiliation(s)
- Silke Patz
- AG Entwicklungsneurobiologie, Fakultät für Biologie, ND 6/72, Ruhr-Universität, 44780 Bochum, Germany.
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