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Bastide MF, Meissner WG, Picconi B, Fasano S, Fernagut PO, Feyder M, Francardo V, Alcacer C, Ding Y, Brambilla R, Fisone G, Jon Stoessl A, Bourdenx M, Engeln M, Navailles S, De Deurwaerdère P, Ko WKD, Simola N, Morelli M, Groc L, Rodriguez MC, Gurevich EV, Quik M, Morari M, Mellone M, Gardoni F, Tronci E, Guehl D, Tison F, Crossman AR, Kang UJ, Steece-Collier K, Fox S, Carta M, Angela Cenci M, Bézard E. Pathophysiology of L-dopa-induced motor and non-motor complications in Parkinson's disease. Prog Neurobiol 2015. [PMID: 26209473 DOI: 10.1016/j.pneurobio.2015.07.002] [Citation(s) in RCA: 347] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Involuntary movements, or dyskinesia, represent a debilitating complication of levodopa (L-dopa) therapy for Parkinson's disease (PD). L-dopa-induced dyskinesia (LID) are ultimately experienced by the vast majority of patients. In addition, psychiatric conditions often manifested as compulsive behaviours, are emerging as a serious problem in the management of L-dopa therapy. The present review attempts to provide an overview of our current understanding of dyskinesia and other L-dopa-induced dysfunctions, a field that dramatically evolved in the past twenty years. In view of the extensive literature on LID, there appeared a critical need to re-frame the concepts, to highlight the most suitable models, to review the central nervous system (CNS) circuitry that may be involved, and to propose a pathophysiological framework was timely and necessary. An updated review to clarify our understanding of LID and other L-dopa-related side effects was therefore timely and necessary. This review should help in the development of novel therapeutic strategies aimed at preventing the generation of dyskinetic symptoms.
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Affiliation(s)
- Matthieu F Bastide
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Wassilios G Meissner
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; Department of Neurology, University Hospital Bordeaux, France
| | - Barbara Picconi
- Laboratory of Neurophysiology, Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Stefania Fasano
- Division of Neuroscience, Institute of Experimental Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Pierre-Olivier Fernagut
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Michael Feyder
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Veronica Francardo
- Basal Ganglia Pathophysiology Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Cristina Alcacer
- Basal Ganglia Pathophysiology Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Yunmin Ding
- Department of Neurology, Columbia University, New York, USA
| | - Riccardo Brambilla
- Division of Neuroscience, Institute of Experimental Neurology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Gilberto Fisone
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - A Jon Stoessl
- Pacific Parkinson's Research Centre and National Parkinson Foundation Centre of Excellence, University of British Columbia, Vancouver, Canada
| | - Mathieu Bourdenx
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Michel Engeln
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Sylvia Navailles
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Philippe De Deurwaerdère
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Wai Kin D Ko
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - Nicola Simola
- Department of Biomedical Sciences, Section of Neuropsychopharmacology, Cagliari University, 09124 Cagliari, Italy
| | - Micaela Morelli
- Department of Biomedical Sciences, Section of Neuropsychopharmacology, Cagliari University, 09124 Cagliari, Italy
| | - Laurent Groc
- Univ. de Bordeaux, Institut Interdisciplinaire de neurosciences, UMR 5297, 33000 Bordeaux, France; CNRS, Institut Interdisciplinaire de neurosciences, UMR 5297, 33000 Bordeaux, France
| | - Maria-Cruz Rodriguez
- Department of Neurology, Hospital Universitario Donostia and Neuroscience Unit, Bio Donostia Research Institute, San Sebastian, Spain
| | - Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Maryka Quik
- Center for Health Sciences, SRI International, CA 94025, USA
| | - Michele Morari
- Department of Medical Sciences, Section of Pharmacology, University of Ferrara, Ferrara, Italy
| | - Manuela Mellone
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milano, Italy
| | - Fabrizio Gardoni
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, 20133 Milano, Italy
| | - Elisabetta Tronci
- Department of Biomedical Sciences, Physiology Section, Cagliari University, Cagliari, Italy
| | - Dominique Guehl
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France
| | - François Tison
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; Department of Neurology, University Hospital Bordeaux, France
| | | | - Un Jung Kang
- Basal Ganglia Pathophysiology Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Kathy Steece-Collier
- Michigan State University, College of Human Medicine, Department of Translational Science and Molecular Medicine & The Udall Center of Excellence in Parkinson's Disease Research, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Susan Fox
- Morton & Gloria Shulman Movement Disorders Center, Toronto Western Hospital, Toronto, Ontario M4T 2S8, Canada
| | - Manolo Carta
- Department of Biomedical Sciences, Physiology Section, Cagliari University, Cagliari, Italy
| | - M Angela Cenci
- Basal Ganglia Pathophysiology Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Erwan Bézard
- Univ. de Bordeaux, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; CNRS, Institut des Maladies Neurodégénératives, UMR 5293, 33000 Bordeaux, France; Motac Neuroscience Ltd, Manchester, UK.
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O’Neill MJ, Siemers ER. Pharmacological approaches to disease-modifying therapies in Parkinson’s disease. Expert Rev Neurother 2014; 2:819-34. [DOI: 10.1586/14737175.2.6.819] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Quik M, Mallela A, Chin M, McIntosh JM, Perez XA, Bordia T. Nicotine-mediated improvement in L-dopa-induced dyskinesias in MPTP-lesioned monkeys is dependent on dopamine nerve terminal function. Neurobiol Dis 2012; 50:30-41. [PMID: 23009753 DOI: 10.1016/j.nbd.2012.09.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 09/12/2012] [Accepted: 09/14/2012] [Indexed: 10/27/2022] Open
Abstract
L-dopa-induced dyskinesias (LIDs) are abnormal involuntary movements that develop with long term L-dopa therapy for Parkinson's disease. Studies show that nicotine administration reduced LIDs in several parkinsonian animal models. The present work was done to understand the factors that regulate the nicotine-mediated reduction in LIDs in MPTP-lesioned nonhuman primates. To approach this, we used two groups of monkeys, one with mild-moderate and the other with more severe parkinsonism rendered dyskinetic using L-dopa. In mild-moderately parkinsonian monkeys, nicotine pretreatment (300 μg/ml via drinking water) prevented the development of LIDs by ~75%. This improvement was maintained when the nicotine dose was lowered to 50 μg/ml but was lost with nicotine removal. Nicotine re-exposure again decreased LIDs. By contrast, nicotine treatment did not reduce LIDs in monkeys with more severe parkinsonism. We next determined how nicotine's ability to reduce LIDs correlated with lesion-induced changes in the striatal dopamine transporter and (3)H-dopamine release in these two groups of monkeys. The striatal dopamine transporter was reduced to 54% and 28% of control in mild-moderately and more severely parkinsonian monkeys, respectively. However, basal, K(+), α4β2* and α6β2* nAChR-evoked (3)H-dopamine release were near control levels in striatum of mild-moderately parkinsonian monkeys. By contrast, these same release measures were reduced to a significantly greater extent in striatum of more severely parkinsonian monkeys. Thus, nicotine best improves LIDs in lesioned monkeys in which striatal dopamine transmission is still relatively intact. These data suggest that nicotine treatment would most effectively reduce LIDs in patients with mild to moderate Parkinson's disease.
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Affiliation(s)
- Maryka Quik
- Center for Health Sciences, SRI International, Menlo Park, CA 94025, USA.
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Quik M, Wonnacott S. α6β2* and α4β2* nicotinic acetylcholine receptors as drug targets for Parkinson's disease. Pharmacol Rev 2012; 63:938-66. [PMID: 21969327 DOI: 10.1124/pr.110.003269] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Parkinson's disease is a debilitating movement disorder characterized by a generalized dysfunction of the nervous system, with a particularly prominent decline in the nigrostriatal dopaminergic pathway. Although there is currently no cure, drugs targeting the dopaminergic system provide major symptomatic relief. As well, agents directed to other neurotransmitter systems are of therapeutic benefit. Such drugs may act by directly improving functional deficits in these other systems, or they may restore aberrant motor activity that arises as a result of a dopaminergic imbalance. Recent research attention has focused on a role for drugs targeting the nicotinic cholinergic systems. The rationale for such work stems from basic research findings that there is an extensive overlap in the organization and function of the nicotinic cholinergic and dopaminergic systems in the basal ganglia. In addition, nicotinic acetylcholine receptor (nAChR) drugs could have clinical potential for Parkinson's disease. Evidence for this proposition stems from studies with experimental animal models showing that nicotine protects against neurotoxin-induced nigrostriatal damage and improves motor complications associated with l-DOPA, the "gold standard" for Parkinson's disease treatment. Nicotine interacts with multiple central nervous system receptors to generate therapeutic responses but also produces side effects. It is important therefore to identify the nAChR subtypes most beneficial for treating Parkinson's disease. Here we review nAChRs with particular emphasis on the subtypes that contribute to basal ganglia function. Accumulating evidence suggests that drugs targeting α6β2* and α4β2* nAChR may prove useful in the management of Parkinson's disease.
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Affiliation(s)
- Maryka Quik
- Center for Health Sciences, SRI International, Menlo Park, CA 94025, USA.
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Quik M, Campos C, Parameswaran N, Langston JW, McIntosh JM, Yeluashvili M. Chronic nicotine treatment increases nAChRs and microglial expression in monkey substantia nigra after nigrostriatal damage. J Mol Neurosci 2009; 40:105-13. [PMID: 19685015 DOI: 10.1007/s12031-009-9265-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 11/27/2022]
Abstract
Our previous work had shown that long-term nicotine administration improved dopaminergic markers and nicotinic receptors (nAChRs) in the striatum of monkeys with nigrostriatal damage. The present experiments were done to determine whether nicotine treatment also led to changes in the substantia nigra, the region containing dopaminergic cell bodies. Monkeys were chronically treated with nicotine in the drinking water for 6 months after which they were injected with low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydrophridine (MPTP) for a further 6-month period. Nicotine was administered until the monkeys were euthanized 2 months after the last MPTP injection. Nicotine treatment did not affect the dopamine transporter or the number of tyrosine hydroxylase positive cells in the substantia nigra of lesioned monkeys. However, nicotine administration did lead to a greater increase in alpha3/alpha6beta2* and alpha4beta2* nAChRs in lesioned monkeys compared to controls. Nicotine also significantly elevated microglia and reduced the number of extracellular neuromelanin deposits in the substantia nigra of MPTP-lesioned monkeys. These findings indicate that long-term nicotine treatment modulates expression of several molecular measures in monkey substantia nigra that may result in an improvement in nigral integrity and/or function. These observations may have therapeutic implications for Parkinson's disease.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, Sunnyvale, CA 94085, USA.
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Nicotine modulates GABAergic transmission to dopaminergic neurons in substantia nigra pars compacta. Acta Pharmacol Sin 2009; 30:851-8. [PMID: 19498424 DOI: 10.1038/aps.2009.65] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
AIM Dopaminergic neurons in the substantia nigra pars compacta (SNc) play important roles in motor control and drug addiction. As the major afferent, GABAergic innervation controls the activity of SNc dopaminergic neurons. Although it is clear that nicotine modulates SNc dopaminergic neurons by activating subtypes of somatodendritic nicotinic acetylcholine receptors (nAChRs), the detailed mechanisms of this activation remain to be addressed. METHODS In the current study, we recorded GABA(A) receptor-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) from dissociated SNc dopaminergic neurons that were obtained using an enzyme-free procedure. These neurons preserved some functional terminals after isolation, including those that release GABA. RESULTS We found that both extra- and intra-cellular calcium modulates sIPSCs in these neurons. Furthermore, both nicotine and endogenous acetylcholine enhance the frequency of sIPSCs. Moreover, endogenous acetylcholine tonically facilitates sIPSC frequency, primarily by activating the alpha4beta2* nAChRs on the GABAergic terminals. CONCLUSION Nicotine facilitates GABA release onto SNc dopaminergic neurons mainly via the activation of presynaptic alpha4beta2* nAChRs.
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Bencherif M. Neuronal nicotinic receptors as novel targets for inflammation and neuroprotection: mechanistic considerations and clinical relevance. Acta Pharmacol Sin 2009; 30:702-14. [PMID: 19498416 PMCID: PMC4002381 DOI: 10.1038/aps.2009.37] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 03/09/2009] [Indexed: 01/18/2023] Open
Abstract
A number of studies have confirmed the potential for neuronal nicotinic acetylcholine receptor (NNR)-mediated neuroprotection and, more recently, its anti-inflammatory effects. The mechanistic overlap between these pathways and the ubiquitous effects observed following diverse insults suggest that NNRs modulate fundamental pathways involved in cell survival. These results have wide-reaching implications for the design of experimental therapeutics that regulate inflammatory and anti-apoptotic responses through NNRs and represent an initial step toward understanding the benefits of novel therapeutic strategies for the management of central nervous system disorders that target neuronal survival and associated inflammatory processes.
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Exley R, Clements MA, Hartung H, McIntosh JM, Cragg SJ. Alpha6-containing nicotinic acetylcholine receptors dominate the nicotine control of dopamine neurotransmission in nucleus accumbens. Neuropsychopharmacology 2008; 33:2158-66. [PMID: 18033235 DOI: 10.1038/sj.npp.1301617] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Modulation of striatal dopamine (DA) neurotransmission plays a fundamental role in the reinforcing and ultimately addictive effects of nicotine. Nicotine, by desensitizing beta2 subunit-containing (beta2*) nicotinic acetylcholine receptors (nAChRs) on striatal DA axons, significantly enhances how DA is released by reward-related burst activity compared to nonreward-related tonic activity. This action provides a synaptic mechanism for nicotine to facilitate the DA-dependent reinforcement. The subfamily of beta2*-nAChRs responsible for these potent synaptic effects could offer a molecular target for therapeutic strategies in nicotine addiction. We explored the role of alpha6beta2*-nAChRs in the nucleus accumbens (NAc) and caudate-putamen (CPu) by observing action potential-dependent DA release from synapses in real-time using fast-scan cyclic voltammetry at carbon-fiber microelectrodes in mouse striatal slices. The alpha6-specific antagonist alpha-conotoxin-MII suppressed DA release evoked by single and low-frequency action potentials and concurrently enhanced release by high-frequency bursts in a manner similar to the beta2*-selective antagonist dihydro-beta-erythroidine (DHbetaE) in NAc, but less so in CPu. The greater role for alpha6*-nAChRs in NAc was not due to any confounding regional difference in ACh tone since elevated ACh levels (after the acetylcholinesterase inhibitor ambenonium) had similar outcomes in NAc and CPu. Rather, there appear to be underlying differences in nAChR subtype function in NAc and CPu. In summary, we reveal that alpha6beta2*-nAChRs dominate the effects of nicotine on DA release in NAc, whereas in CPu their role is minor alongside other beta2*-nAChRs (eg alpha4*), These data offer new insights to suggest striatal alpha6*-nAChRs as a molecular target for a therapeutic strategy for nicotine addiction.
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Affiliation(s)
- Richard Exley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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O'Leary KT, Parameswaran N, Johnston LC, McIntosh JM, Di Monte DA, Quik M. Paraquat exposure reduces nicotinic receptor-evoked dopamine release in monkey striatum. J Pharmacol Exp Ther 2008; 327:124-9. [PMID: 18606871 DOI: 10.1124/jpet.108.141861] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Paraquat, an herbicide widely used in the agricultural industry, has been associated with lung, liver, and kidney toxicity in humans. In addition, it is linked to an increased risk of Parkinson's disease. For this reason, we had previously investigated the effects of paraquat in mice and showed that it influenced striatal nicotinic receptor (nAChR) expression but not nAChR-mediated dopaminergic function. Because nonhuman primates are evolutionarily closer to humans and may better model the effects of pesticide exposure in man, we examined the effects of paraquat on striatal nAChR function and expression in monkeys. Monkeys were administered saline or paraquat once weekly for 6 weeks, after which nAChR levels and receptor-evoked [(3)H]dopamine ([(3)H]DA) release were measured in the striatum. The functional studies showed that paraquat exposure attenuated dopamine (DA) release evoked by alpha3/alpha6beta2(*) (nAChR that is composed of the alpha3 or alpha6 subunits, and beta2; the asterisk indicates the possible presence of additional subunits) nAChRs, a subtype present only on striatal dopaminergic terminals, with no decline in release mediated by alpha4beta2(*) (nAChR containing alpha4 and beta2 subunits, but not alpha3 or alpha6) nAChRs, present on both DA terminals and striatal neurons. Paraquat treatment decreased alpha4beta2(*) but not alpha3/alpha6beta2(*) nAChR expression. The differential effects of paraquat on nAChR expression and receptor-evoked [(3)H]DA release emphasize the importance of evaluating changes in functional measures. The finding that paraquat treatment has a negative impact on striatal nAChR-mediated dopaminergic activity in monkeys but not mice indicates the need for determining the effects of pesticides in higher species.
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Affiliation(s)
- Kathryn T O'Leary
- The Parkinson's Institute, 675 Almanor Ave., Sunnyvale, CA 94085-2934, USA
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Faghih R, Gopalakrishnan M, Briggs CA. Allosteric modulators of the alpha7 nicotinic acetylcholine receptor. J Med Chem 2008; 51:701-12. [PMID: 18198823 DOI: 10.1021/jm070256g] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ramin Faghih
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064, USA.
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Presynaptic nicotinic receptors: a dynamic and diverse cholinergic filter of striatal dopamine neurotransmission. Br J Pharmacol 2007; 153 Suppl 1:S283-97. [PMID: 18037926 DOI: 10.1038/sj.bjp.0707510] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The effects of nicotine on dopamine transmission from mesostriatal dopamine neurons are central to its reinforcing properties. Only recently however, has the influence of presynaptic nicotinic receptors (nAChRs) on dopaminergic axon terminals within striatum begun to be understood. Here, rather than simply enhancing (or inhibiting) dopamine release, nAChRs perform the role of a presynaptic filter, whose influence on dopamine release probability depends on presynaptic activity in dopaminergic as well as cholinergic neurons. Both mesostriatal dopaminergic neurons and striatal cholinergic interneurons play key roles in motivational and sensorimotor processing by the basal ganglia. Moreover, it appears that the striatal influence of dopamine and ACh cannot be fully appreciated without an understanding of their reciprocal interactions. We will review the powerful filtering by nAChRs of striatal dopamine release and discuss its dependence on activity in dopaminergic and cholinergic neurons. We will also review how nicotine, acting via nAChR desensitization, promotes the sensitivity of dopamine synapses to activity. This filtering action might provide a mechanism through which nicotine promotes how burst activity in dopamine neurons facilitates goal-directed behaviour and reinforcement processing. More generally, it indicates that we should not restrict our view of presynaptic nAChRs to simply enhancing neurotransmitter release. We will also summarize current understanding of the forms and functions of the diverse nAChRs purported to exist on dopaminergic axons. A greater understanding of nAChR form and function is imperative to guide the design of ligands with subtype-selective efficacy for improved therapeutic interventions in nicotine addiction as well as Parkinson's disease.
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Bordia T, Grady SR, McIntosh JM, Quik M. Nigrostriatal damage preferentially decreases a subpopulation of alpha6beta2* nAChRs in mouse, monkey, and Parkinson's disease striatum. Mol Pharmacol 2007; 72:52-61. [PMID: 17409284 DOI: 10.1124/mol.107.035998] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Parkinson's disease is a neurodegenerative movement disorder characterized by a loss of substantia nigra dopamine neurons, and corresponding declines in molecular components present on striatal dopaminergic nerve terminals. These include the alpha6beta2(*) nicotinic acetylcholine receptors (nAChRs), which are localized exclusively on dopamine terminals in striatum ((*)denotes the presence of possible additional subunits). In this study, we used a novel alpha-conotoxin MII (alpha-CtxMII) analog E11A to further investigate alpha6beta2(*) nAChR subtypes in mouse, monkey, and human striatum. Receptor competition studies with (125)I-alpha-CtxMII showed that E11A inhibition curves were biphasic, suggesting the presence of two distinct alpha6beta2(*) nAChR subtypes. These include a very high (femtomolar) and a high (picomolar) affinity site, with approximately 40% of the sites in the very high affinity form. It is noteworthy that only the high-affinity form was detected in alpha4 nAChR-null mutant mice. Because (125)I-alpha-CtxMII binds primarily to alpha6alpha4beta2beta3 and alpha6beta2beta3 nAChR subtypes in mouse striatum, these data suggest that the population lost in the alpha4 knockout mice was the alpha6alpha4beta2beta3 subtype. We next investigated the effect of nigrostriatal lesioning on these two striatal alpha6beta2(*) populations in two animal models and in Parkinson's disease. There was a preferential loss of the very high affinity subtype in striatum of mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), monkeys treated with MPTP, and patients with Parkinson's disease. These data suggest that dopaminergic terminals expressing the alpha6alpha4beta2beta3 population are selectively vulnerable to nigrostriatal damage. This latter nAChR subtype, identified with alpha-CtxMII E11A, may therefore provide a unique marker for dopaminergic terminals particularly sensitive to nigrostriatal degeneration in Parkinson's disease.
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Affiliation(s)
- Tanuja Bordia
- The Parkinson's Institute, 1170 Morse Ave, Sunnyvale, CA 94089-1605, USA
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Kulak JM, Carroll FI, Schneider JS. [125I]Iodomethyllycaconitine binds to α7 nicotinic acetylcholine receptors in monkey brain. Eur J Neurosci 2006; 23:2604-10. [PMID: 16817863 DOI: 10.1111/j.1460-9568.2006.04804.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We examined the binding of the novel nicotinic acetylcholine receptor (nAChR) ligand [125I]iodomethyllycaconitine (iodoMLA) in the brains of M. cynomologous (macaque) monkeys. [125I]iodoMLA bound throughout the brain with the greatest density in the thalamus and moderate intensity in the basal ganglia and cortical regions. The Kd and Bmax in whole brain tissue were similar whether 1 mM nicotine (Kd 33.25 +/- 15.17 nM, Bmax 5.80 +/- 1.06 fmol/mg) or 2 microM of the alpha7-selective antagonist alpha-bungarotoxin (Kd 46.12 +/- 18.45 nM, Bmax 6.30 +/- 1.06 fmol/mg) was used for nonspecific binding. The subtype-selectivity of this ligand was further studied with competition binding studies using nicotine, alpha-bungarotoxin and noniodinated MLA. Each ligand completely inhibited [125I]iodoMLA binding throughout the monkey brain, with Ki values of 2.23 +/- 0.85 microM for nicotine, 2.72 +/- 1.71 nM for alpha-bungarotoxin and 1.83 +/- 0.35 nM MLA in the caudate and 2.03 +/- 1.14 microM, 2.65 +/- 0.86 nM and 3.32 +/- 0.71 nM, respectively, in the putamen. The alpha3beta2/alpha6*-selective antagonist alpha-conotoxin MII failed to inhibit [125I]iodoMLA binding in any brain region. In monkeys with cognitive deficits resulting from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration, [125I]iodoMLA binding was significantly increased in the striatum, similar to results previously observed for [125I]alpha-bungarotoxin. These results suggest that, under the present experimental conditions, [125I]iodoMLA was selective for alpha7-containing nAChRs and did not bind to alpha6-containing nAChRs. This radioligand may be a useful tool for selectively imaging alpha7-containing nAChRs in vivo.
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Affiliation(s)
- Jennifer M Kulak
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust St., 521 JAH, Philadelphia, PA 19107, USA.
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McCallum SE, Parameswaran N, Perez XA, Bao S, McIntosh JM, Grady SR, Quik M. Compensation in pre-synaptic dopaminergic function following nigrostriatal damage in primates. J Neurochem 2006; 96:960-72. [PMID: 16412097 DOI: 10.1111/j.1471-4159.2005.03610.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Clinical symptoms of Parkinson's disease only become evident after 70-80% reductions in striatal dopamine. To investigate the importance of pre-synaptic dopaminergic mechanisms in this compensation, we determined the effect of nigrostriatal damage on dopaminergic markers and function in primates. MPTP treatment resulted in a graded dopamine loss with moderate to severe declines in ventromedial striatum (approximately 60-95%) and the greatest reductions (approximately 95-99%) in dorsolateral striatum. A somewhat less severe pattern of loss was observed for striatal nicotinic receptor, tyrosine hydroxylase and vesicular monoamine transporter expression. Declines in striatal dopamine uptake and transporter sites were also less severe than the reduction in dopamine levels, with enhanced dopamine turnover in the dorsolateral striatum after lesioning. The greatest degree of adaptation occurred for nicotine-evoked [(3)H]dopamine release from striatal synaptosomes, which was relatively intact in ventromedial striatum after lesioning, despite > 50% declines in dopamine. This maintenance of evoked release was not due to compensatory alterations in nicotinic receptor characteristics. Rather, there appeared to be a generalized preservation of release processes in ventromedial striatum, with K(+)-evoked release also near control levels after lesioning. These combined compensatory mechanisms help explain the finding that Parkinson's disease symptomatology develops only with major losses of striatal dopamine.
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Affiliation(s)
- S E McCallum
- The Parkinson's Institute, Sunnyvale, California 94089, USA
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15
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Janhunen S, Mielikäinen P, Paldánius P, Tuominen RK, Ahtee L, Kaakkola S. The effect of nicotine in combination with various dopaminergic drugs on nigrostriatal dopamine in rats. Naunyn Schmiedebergs Arch Pharmacol 2005; 371:480-91. [PMID: 16012872 DOI: 10.1007/s00210-005-1066-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Accepted: 04/20/2005] [Indexed: 10/25/2022]
Abstract
It is well established that nicotine activates brain dopaminergic systems and in addition has neuroprotective actions. Thus, nicotinic acetylcholine receptor (nAChR) agonists might be beneficial in the treatment of Parkinson's disease, and it is important to study the interactions of nicotine with drugs affecting the nigrostriatal dopaminergic pathway. We used brain microdialysis to study the effects of nicotine on extracellular levels of dopamine (DA) and its metabolites in the rat dorsal striatum in combination with drugs inhibiting either DA uptake (nomifensine), catechol-O-methyltransferase (COMT; tolcapone), monoamine oxidase B (MAO-B; selegiline) or DA receptors (haloperidol). Nicotine (0.5 mg/kg, s.c.) modestly increased DA output, and this effect was antagonised by mecamylamine but not by hexamethonium. Nomifensine (3 mg/kg, i.p.) substantially further enhanced the nicotine-induced increase in DA output and nomifensine+nicotine also evoked a strong mecamylamine-sensitive ipsilateral rotational behaviour in 6-hydroxydopamine lesioned rats. Tolcapone (10 mg/kg, i.p.) did not alter DA output, but markedly decreased homovanillic acid (HVA) and increased 3,4-dihydroxyphenylacetic acid (DOPAC). Selegiline pretreatment (5 x 1 mg/kg, i.p.) significantly increased extracellular DA and decreased DOPAC and HVA. Haloperidol (0.1 mg/kg, s.c.) slightly increased DA output and more clearly DOPAC and HVA. Tolcapone, selegiline or haloperidol did not enhance the nicotine-induced DA output. These results indicate that the activation of nigrostriatal nAChRs induces a significant DA release in the striatum, which is potentiated by DA uptake inhibition but not by COMT, MAO-B or presynaptic DA receptor inhibition. Our findings therefore agree with the notion that the termination of the effect of DA in the synapse mainly occurs via neuronal reuptake. Thus, selective nAChR agonists, possibly in combination with a DA uptake inhibitor, might improve dopaminergic transmission in Parkinson's disease.
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Affiliation(s)
- Sanna Janhunen
- Division of Pharmacology and Toxicology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014 Helsinki, Finland
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16
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McCallum SE, Parameswaran N, Bordia T, McIntosh JM, Grady SR, Quik M. Decrease in alpha3*/alpha6* nicotinic receptors but not nicotine-evoked dopamine release in monkey brain after nigrostriatal damage. Mol Pharmacol 2005; 68:737-46. [PMID: 15933214 DOI: 10.1124/mol.105.012773] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are decreased in the striata of patients with Parkinson's disease (PD) or in experimental models after nigrostriatal damage. Because presynaptic nAChRs on striatal dopamine terminals mediate dopamine release, receptor loss may contribute to behavioral deficits in PD. The present experiments were done to determine whether nAChR function is affected by nigrostriatal damage in nonhuman primates, because this model shares many features with PD. Initial characterization of nicotine-evoked [3H]dopamine release from monkey striatal synaptosomes revealed that release was calcium-dependent and inhibited by selective nAChR antagonists. It is noteworthy that a greater proportion (approximately 70%) of release was inhibited by the alpha3*/alpha6* antagonist alpha-conotoxinMII (alpha-CtxMII) compared with rodents. Monkeys were lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and [3H]dopamine release, dopamine transporter, and nAChRs were measured. As anticipated, lesioning decreased the transporter and alpha3*/alpha6* nAChRs in caudate and putamen. In contrast, alpha3*/alpha6* nAChR-evoked [3H]dopamine release was reduced in caudate but not putamen, demonstrating a dissociation between nAChR sites and function. A different pattern was observed in the mesolimbic dopamine system. Dopamine transporter levels in nucleus accumbens were not reduced after MPTP, as expected; however, there was a 50% decline in alpha3*/alpha6* nAChR sites with no decrease in alpha3*/alpha6* receptor-evoked dopamine release. No declines in alpha-CtxMII-resistant nAChR (alpha4*) binding or nicotine-evoked release were observed in any region. These results show a selective preservation of alpha3*/alpha6* nAChR-mediated function in the nigrostriatal and mesolimbic dopamine systems after nigrostriatal damage. Maintenance of function in putamen, a region with a selective loss of dopaminergic terminals, may be important in PD.
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Affiliation(s)
- Sarah E McCallum
- The Parkinson's Institute, 1170 Morse Ave, Sunnyvale, CA 94089-1605, USA
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17
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Nicke A, Wonnacott S, Lewis RJ. Alpha-conotoxins as tools for the elucidation of structure and function of neuronal nicotinic acetylcholine receptor subtypes. ACTA ACUST UNITED AC 2004; 271:2305-19. [PMID: 15182346 DOI: 10.1111/j.1432-1033.2004.04145.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cone snails comprise approximately 500 species of venomous molluscs, which have evolved the ability to generate multiple toxins with varied and often exquisite selectivity. One class, the alpha-conotoxins, is proving to be a powerful tool for the differentiation of nicotinic acetylcholine receptors (nAChRs). These comprise a large family of complex subtypes, whose significance in physiological functions and pathological conditions is increasingly becoming apparent. After a short introduction into the structure and diversity of nAChRs, this overview summarizes the identification and characterization of alpha-conotoxins with selectivity for neuronal nAChR subtypes and provides examples of their use in defining the compositions and function of neuronal nAChR subtypes in native vertebrate tissues.
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Affiliation(s)
- Annette Nicke
- Max Planck-Institute for Brain Research, Frankfurt, Germany.
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18
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Hernandez SC, Vicini S, Xiao Y, Dávila-García MI, Yasuda RP, Wolfe BB, Kellar KJ. The nicotinic receptor in the rat pineal gland is an alpha3beta4 subtype. Mol Pharmacol 2004; 66:978-87. [PMID: 15247319 DOI: 10.1124/mol.104.002345] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rat pineal gland contains a high density of neuronal nicotinic acetylcholine receptors (nAChRs). We characterized the pharmacology of the binding sites and function of these receptors, measured the nAChR subunit mRNA, and used subunit-specific antibodies to establish the receptor subtype as defined by subunit composition. In ligand binding studies, [3H]epibatidine ([3H]EB) binds with an affinity of approximately 100 pM to nAChRs in the pineal gland, and the density of these sites is approximately 5 times that in rat cerebral cortex. The affinities of nicotinic drugs for binding sites in the pineal gland are similar to those at alpha3beta4 nAChRs heterologously expressed in human embryonic kidney 293 cells. In functional studies, the potencies and efficacies of nicotinic drugs to activate or block whole-cell currents in dissociated pinealocytes match closely their potencies and efficacies to activate or block 86Rb+ efflux in the cells expressing heterologous alpha3beta4 nAChRs. Measurements of mRNA indicated the presence of transcripts for alpha3, beta2, and beta4 nAChR subunits but not those for alpha2, alpha4, alpha5, alpha6, alpha7, or beta3 subunits. Immunoprecipitation with subunit-specific antibodies showed that virtually all [3H]EB-labeled nAChRs contained alpha3 and beta4 subunits associated in one complex. The beta2 subunit was not associated with this complex. Taken together, these results indicate that virtually all of the nAChRs in the rat pineal gland are the alpha3beta4 nAChR subtype and that the pineal gland can therefore serve as an excellent and convenient model in which to study the pharmacology and function of these receptors in a native tissue.
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Affiliation(s)
- Susan C Hernandez
- Department of Pharmacology, Georgetown University School of Medicine, Washington, DC 20057, USA
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19
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Kulak JM, Schneider JS. Differences in alpha7 nicotinic acetylcholine receptor binding in motor symptomatic and asymptomatic MPTP-treated monkeys. Brain Res 2004; 999:193-202. [PMID: 14759498 DOI: 10.1016/j.brainres.2003.10.062] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/16/2003] [Indexed: 10/26/2022]
Abstract
We studied [(125)I]alpha-bungarotoxin (btx) binding to alpha7 nicotinic acetylcholine receptors in normal and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) exposed macaque monkeys. [(125)I]alpha-Btx binds throughout the normal monkey brain, with the greatest density in the thalamic nuclei and with moderate to low binding in the hippocampus, prefrontal cortex, caudate, putamen, and substantia nigra. Chronic administration of low doses of MPTP resulted in animals with stable cognitive deficits without overt parkinsonian motor symptoms. [(125)I]alpha-Btx binding in the brains of these animals was significantly increased in the outermost layers of the supplementary motor cortex (area 6M, approximately 50%), primary motor cortex (area 4, approximately 112%) and throughout the putamen (approximately 50-72%). In contrast, there was no change in [(125)I]alpha-btx binding in the brain regions thought to be involved in mediating the cognitive functions impaired in these monkeys (e.g., the hippocampus, areas 9/46D and 46D of the principal sulcus, and area 24c of the cingulate sulcus). Animals with cognitive dysfunction that received escalating doses of MPTP for >6 months developed motor signs of parkinsonism which were indistinguishable from those seen in animals rendered acutely parkinsonian with short term administration of large doses of MPTP. These two "motor symptomatic" groups had significantly increased [(125)I]alpha-btx binding only in the dorsolateral putamen. Immunohistochemical studies showed that the increased [(125)I]alpha-btx binding, when observed, was associated with enhanced immunohistochemical staining localized to neurons and was not a result of an astrocytic response to MPTP. These results suggest that the increase in alpha7 nicotinic acetylcholine receptor expression in the chronic low-dose MPTP treated, motor asymptomatic monkeys may be a part of compensatory processes contributing to the maintained motor functioning in these animals.
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Affiliation(s)
- Jennifer M Kulak
- Department of Pathology, Thomas Jefferson University, 1020 Locust Street, 521 JAH, Philadelphia, PA 19107, USA.
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20
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Quik M, Sum JD, Whiteaker P, McCallum SE, Marks MJ, Musachio J, McIntosh JM, Collins AC, Grady SR. Differential declines in striatal nicotinic receptor subtype function after nigrostriatal damage in mice. Mol Pharmacol 2003; 63:1169-79. [PMID: 12695545 DOI: 10.1124/mol.63.5.1169] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nigrostriatal damage leads to a reduction in striatal nicotinic acetylcholine receptors (nAChRs) in rodents, monkeys, and patients with Parkinson's disease. The present studies were undertaken to investigate whether these nAChR declines are associated with alterations in striatal nAChR function and, if so, to identify the receptor subtypes involved. To induce nigrostriatal damage, mice were injected with the selective dopaminergic toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We measured [(125)I]3 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid isopropyl ester (RTI-121, dopamine transporter), (125)I-alpha-conotoxin MII (putative alpha 6-containing sites in the central nervous system), (125)I-epibatidine (multiple sites), 5-[(125)I]iodo-3-[2(S)-azetidinylmethoxy]pyridine-2HCl ([(125)I]A85380; beta2-containing sites), and (125)I-alpha-bungarotoxin (alpha 7-containing sites) binding in brains from control and MPTP-treated mice, as well as nAChR function by [(3)H]dopamine release, [(3)H]GABA release, and [(86)Rb(+)] efflux. After MPTP treatment, declines were observed in striatal dopamine transporter levels, both binding and functional measures of striatal alpha-conotoxin MII-sensitive nAChRs, and selected measures of striatal alpha-conotoxin MII-resistant nAChRs. In contrast, (125)I-alpha-bungarotoxin binding sites were not altered after nigrostriatal damage. The changes in striatal nAChRs were selective, with no declines in cortex, thalamus, or septum. Those striatal binding and functional measures of nAChRs that decreased with MPTP treatment correlated with dopamine transporter declines, an observation suggesting that the binding and functional changes in nAChRs are limited to dopaminergic terminals. The present results are the first to demonstrate differential alterations in nAChR subtype function after nigrostriatal damage, with a close correspondence between changes in receptor binding sites and function. These data suggest that the declines in nAChR sites observed in Parkinson's disease brains may be of functional significance.
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Affiliation(s)
- Maryka Quik
- The Parkinson's Institute, Sunnyvale, California 94089-1605, USA.
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21
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Evans NM, Bose S, Benedetti G, Zwart R, Pearson KH, McPhie GI, Craig PJ, Benton JP, Volsen SG, Sher E, Broad LM. Expression and functional characterisation of a human chimeric nicotinic receptor with alpha6beta4 properties. Eur J Pharmacol 2003; 466:31-9. [PMID: 12679139 DOI: 10.1016/s0014-2999(03)01540-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite being cloned several years ago, the expression of functional nicotinic acetylcholine receptors containing the human alpha6 subunit in recombinant mammalian cell lines has yet to be demonstrated. The resulting lack of selective ligands has hindered the evaluation of the role of alpha6-containing nicotinic receptors. We report that functional channels were recorded following co-transfection of human embryonic kidney (HEK-293) cells with a chimeric alpha6/alpha4 subunit and the beta4 nicotinic receptor subunit. They displayed an agonist rank order potency of epibatidinez.>>1,1-dimethyl-4-phenylpiperazinium (DMPP)>/=cytisine>acetylcholine>nicotine measured in a fluorescent imaging plate reader assay. Nicotine, cytisine, DMPP and epibatidine displayed partial agonist properties whilst alpha-conotoxin MII and methyllycaconitine blocked the functional responses elicited by acetylcholine stimulation. Co-transfection of the alpha6/alpha4 chimera with the beta2 nicotinic receptor subunit did not result in functional receptors. The human alpha6/alpha4beta4 chimeric nicotinic receptor expressed in HEK-293 cells may provide a valuable tool for the generation of subtype specific ligands.
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Affiliation(s)
- Non M Evans
- Eli Lilly and Company Ltd., Lilly Research Centre, Erl Wood Manor, Windlesham, GU20 6PH, Surrey, UK.
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22
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Gahring LC, Persiyanov K, Rogers SW. Neuronal and astrocyte expression of nicotinic receptor subunit ?4 in the adult mouse brain. J Comp Neurol 2003; 468:322-33. [PMID: 14681928 DOI: 10.1002/cne.10942] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neuronal nicotinic acetylcholine receptor (nAChR) expression and function are customized in different brain regions through assembling receptors from closely related but genetically distinct subunits. Immunohistochemical analysis of one of these subunits, nAChRbeta4, in the mouse brain suggests an extensive and potentially diverse role for this subunit in both excitatory and inhibitory neurotransmission. Prominent immunostaining included: 1) the medial habenula, efferents composing the fasciculus retroflexus, and the interpeduncular nucleus; 2) nuclei and ascending tracts of the auditory system inclusive of the medial geniculate; 3) the sensory cortex barrel field and cell bodies of the ventral thalamic nucleus; 4) olfactory-associated structures and the piriform cortex; and 5) sensory and motor trigeminal nuclei. In the hippocampus, nAChRbeta4 staining was limited to dendrites and soma of a subset of glutamic acid dehydrogenase-positive neurons. In C57BL/6 mice, but to a lesser extent in C3H/J, CBA/J, or CF1 mice, a subpopulation of astrocytes in the hippocampal CA1 region prominently expressed nAChRbeta4 (and nAChRalpha4). Collectively, these results suggest that the unique functional and pharmacological properties exerted by nAChRbeta4 on nAChR function could modify and specialize the development of strain-specific sensory and hippocampal-related characteristics of nicotine sensitivity including the development of tolerance.
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Affiliation(s)
- Lorise C Gahring
- Salt Lake City Veterans Administration-Geriatrics Research, Education and Clinical Center, Salt Lake City, Utah 84132, USA.
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