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Ferré S, Belcher AM, Bonaventura J, Quiroz C, Sánchez-Soto M, Casadó-Anguera V, Cai NS, Moreno E, Boateng CA, Keck TM, Florán B, Earley CJ, Ciruela F, Casadó V, Rubinstein M, Volkow ND. Functional and pharmacological role of the dopamine D 4 receptor and its polymorphic variants. Front Endocrinol (Lausanne) 2022; 13:1014678. [PMID: 36267569 PMCID: PMC9578002 DOI: 10.3389/fendo.2022.1014678] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/14/2022] [Indexed: 11/13/2022] Open
Abstract
The functional and pharmacological significance of the dopamine D4 receptor (D4R) has remained the least well understood of all the dopamine receptor subtypes. Even more enigmatic has been the role of the very prevalent human DRD4 gene polymorphisms in the region that encodes the third intracellular loop of the receptor. The most common polymorphisms encode a D4R with 4 or 7 repeats of a proline-rich sequence of 16 amino acids (D4.4R and D4.7R). DRD4 polymorphisms have been associated with individual differences linked to impulse control-related neuropsychiatric disorders, with the most consistent associations established between the gene encoding D4.7R and attention-deficit hyperactivity disorder (ADHD) and substance use disorders. The function of D4R and its polymorphic variants is being revealed by addressing the role of receptor heteromerization and the relatively avidity of norepinephrine for D4R. We review the evidence conveying a significant and differential role of D4.4R and D4.7R in the dopaminergic and noradrenergic modulation of the frontal cortico-striatal pyramidal neuron, with implications for the moderation of constructs of impulsivity as personality traits. This differential role depends on their ability to confer different properties to adrenergic α2A receptor (α2AR)-D4R heteromers and dopamine D2 receptor (D2R)-D4R heteromers, preferentially localized in the perisomatic region of the frontal cortical pyramidal neuron and its striatal terminals, respectively. We also review the evidence to support the D4R as a therapeutic target for ADHD and other impulse-control disorders, as well as for restless legs syndrome.
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Affiliation(s)
- Sergi Ferré
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
- *Correspondence: Sergi Ferré,
| | - Annabelle M. Belcher
- Division of Addiction Research and Treatment, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Jordi Bonaventura
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, L'Hospitalet de Llobregat, Spain
- Neuropharmacology & Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Spain
| | - César Quiroz
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Marta Sánchez-Soto
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Verònica Casadó-Anguera
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Ning-Sheng Cai
- Integrative Neurobiology Section, National Institute on Drug Abuse, Intramural Research Program, National Institutes on Drug Abuse, Baltimore, MD, United States
| | - Estefanía Moreno
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Comfort A. Boateng
- Department of Basic Pharmaceutical Sciences, Fred Wilson School of Pharmacy, High Point, NC, United States
| | - Thomas M. Keck
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ, United States
| | - Benjamín Florán
- Departament of Physiology, Biophysics and Neurosciences, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Mexico City, Mexico
| | - Christopher J. Earley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, L'Hospitalet de Llobregat, Spain
- Neuropharmacology & Pain Group, Neuroscience Program, Bellvitge Institute for Biomedical Research, L'Hospitalet de Llobregat, Spain
| | - Vicent Casadó
- Department of Biochemistry and Molecular Biomedicine, Faculty of Biology, Institute of Biomedicine of the University of Barcelona (IBUB), University of Barcelona, Barcelona, Spain
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas and, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Nora D. Volkow
- National Institute on Drug Abuse, National Institutes of Health, Rockville, MD, United States
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Klein M, Onnink M, van Donkelaar M, Wolfers T, Harich B, Shi Y, Dammers J, Arias-Vásquez A, Hoogman M, Franke B. Brain imaging genetics in ADHD and beyond - Mapping pathways from gene to disorder at different levels of complexity. Neurosci Biobehav Rev 2017; 80:115-155. [PMID: 28159610 PMCID: PMC6947924 DOI: 10.1016/j.neubiorev.2017.01.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 12/08/2016] [Accepted: 01/09/2017] [Indexed: 01/03/2023]
Abstract
Attention-deficit/hyperactivity disorder (ADHD) is a common and often persistent neurodevelopmental disorder. Beyond gene-finding, neurobiological parameters, such as brain structure, connectivity, and function, have been used to link genetic variation to ADHD symptomatology. We performed a systematic review of brain imaging genetics studies involving 62 ADHD candidate genes in childhood and adult ADHD cohorts. Fifty-one eligible research articles described studies of 13 ADHD candidate genes. Almost exclusively, single genetic variants were studied, mostly focussing on dopamine-related genes. While promising results have been reported, imaging genetics studies are thus far hampered by methodological differences in study design and analysis methodology, as well as limited sample sizes. Beyond reviewing imaging genetics studies, we also discuss the need for complementary approaches at multiple levels of biological complexity and emphasize the importance of combining and integrating findings across levels for a better understanding of biological pathways from gene to disease. These may include multi-modal imaging genetics studies, bioinformatic analyses, and functional analyses of cell and animal models.
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Affiliation(s)
- Marieke Klein
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Marten Onnink
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Marjolein van Donkelaar
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Thomas Wolfers
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Benjamin Harich
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Yan Shi
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Janneke Dammers
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; Department of Psychiatry, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Alejandro Arias-Vásquez
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; Department of Psychiatry, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; Department of Cognitive Neuroscience, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Martine Hoogman
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Barbara Franke
- Department of Human Genetics, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands; Department of Psychiatry, Radboud university medical center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
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3
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Mariath LM, Silva AMD, Kowalski TW, Gattino GS, Araujo GAD, Figueiredo FG, Tagliani-Ribeiro A, Roman T, Vianna FSL, Schuler-Faccini L, Schuch JB. Music genetics research: Association with musicality of a polymorphism in the AVPR1A gene. Genet Mol Biol 2017; 40:421-429. [PMID: 28534928 PMCID: PMC5488451 DOI: 10.1590/1678-4685-gmb-2016-0021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 12/15/2016] [Indexed: 01/01/2023] Open
Abstract
Musicality is defined as a natural tendency, sensibility, knowledge, or talent to
create, perceive, and play music. Musical abilities involve a great range of social
and cognitive behaviors, which are influenced by both environmental and genetic
factors. Although a number of studies have yielded insights into music genetics
research, genes and biological pathways related to these traits are not fully
understood. Our hypothesis in the current study is that genes associated with
different behaviors could also influence the musical phenotype. Our aim was to
investigate whether polymorphisms in six genes (AVPR1A, SLC6A4, ITGB3, COMT, DRD2 and
DRD4) related to social and cognitive traits are associated with musicality in a
sample of children. Musicality was assessed through an individualized music therapy
assessment profile (IMTAP) which has been validated in Brazil to measure musical
ability. We show here that the RS1 microsatellite of the AVPR1A gene is nominally
associated with musicality, corroborating previous results linking AVPR1A with
musical activity. This study is one of the first to investigate musicality in a
comprehensive way, and it contributes to better understand the genetic basis
underlying musical ability.
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Affiliation(s)
- Luiza Monteavaro Mariath
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Alexandre Mauat da Silva
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Thayne Woycinck Kowalski
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Gustavo Schulz Gattino
- Programa de Pos-Graduação em Saúde da Criança e Adolescente, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Gustavo Andrade de Araujo
- Programa de Pos-Graduação em Saúde da Criança e Adolescente, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Felipe Grahl Figueiredo
- Programa de Pos-Graduação em Saúde da Criança e Adolescente, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Alice Tagliani-Ribeiro
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Tatiana Roman
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Fernanda Sales Luiz Vianna
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Lavínia Schuler-Faccini
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Jaqueline Bohrer Schuch
- Programa de Pós-Graduação em Genética e Biologia Molecular, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
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4
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Halley AC, Boretsky M, Puts DA, Shriver M. Self-Reported Sexual Behavioral Interests and Polymorphisms in the Dopamine Receptor D4 (DRD4) Exon III VNTR in Heterosexual Young Adults. ARCHIVES OF SEXUAL BEHAVIOR 2016; 45:2091-2100. [PMID: 26581567 DOI: 10.1007/s10508-015-0646-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 10/06/2015] [Accepted: 10/10/2015] [Indexed: 06/05/2023]
Abstract
Polymorphisms in the dopamine D4 receptor (DRD4) have previously been shown to associate with a variety of human behavioral phenotypes, including ADHD pathology, alcohol and tobacco craving, financial risk-taking in males, and broader personality traits such as novelty seeking. Recent research has linked the presence of a 7-repeat (7R) allele in a 48-bp variable number of tandem repeats (VNTR) along exon III of DRD4 to age at first sexual intercourse, sexual desire, arousal and function, and infidelity and promiscuity. We hypothesized that carriers of longer DRD4 alleles may report interest in a wider variety of sexual behaviors and experiences than noncarriers. Participants completed a 37-item questionnaire measuring sexual interests as well as Cloninger's Temperament and Character Inventory, and were genotyped for the 48-bp VNTR on exon III of DRD4. Based on our final genotyped sample of female (n = 139) and male (n = 115) participants, we found that 7R carriers reported interest in a wider variety of sexual behaviors (r = 0.16) within a young adult heterosexual sample of European descent. To our knowledge, this is the first reported association between DRD4 exon III VNTR genotype and interest in a variety of sexual behaviors. We discuss these findings within the context of DRD4 research and broader trends in human evolutionary history.
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Affiliation(s)
- Andrew C Halley
- Department of Anthropology, University of California Berkeley, Berkeley, CA, USA
| | - Melanie Boretsky
- College of Veterinary Medicine, Ohio State University, Columbus, OH, USA
| | - David A Puts
- Department of Anthropology, Pennsylvania State University, 218 Carpenter Building, University Park, PA, 16802, USA.
| | - Mark Shriver
- Department of Anthropology, Pennsylvania State University, 218 Carpenter Building, University Park, PA, 16802, USA
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5
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Pérez-Fernández J, Megías M, Pombal MA. Expression of a Novel D4 Dopamine Receptor in the Lamprey Brain. Evolutionary Considerations about Dopamine Receptors. Front Neuroanat 2016; 9:165. [PMID: 26778974 PMCID: PMC4701969 DOI: 10.3389/fnana.2015.00165] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 12/08/2015] [Indexed: 12/28/2022] Open
Abstract
Numerous data reported in lampreys, which belong to the phylogenetically oldest branch of vertebrates, show that the dopaminergic system was already well developed at the dawn of vertebrate evolution. The expression of dopamine in the lamprey brain is well conserved when compared to other vertebrates, and this is also true for the D2 receptor. Additionally, the key role of dopamine in the striatum, modulating the excitability in the direct and indirect pathways through the D1 and D2 receptors, has also been recently reported in these animals. The moment of divergence regarding the two whole genome duplications occurred in vertebrates suggests that additional receptors, apart from the D1 and D2 previously reported, could be present in lampreys. We used in situ hybridization to characterize the expression of a novel dopamine receptor, which we have identified as a D4 receptor according to the phylogenetic analysis. The D4 receptor shows in the sea lamprey a more restricted expression pattern than the D2 subtype, as reported in mammals. Its main expression areas are the striatum, lateral and ventral pallial sectors, several hypothalamic regions, habenula, and mesencephalic and rhombencephalic motoneurons. Some expression areas are well conserved through vertebrate evolution, as is the case of the striatum or the habenula, but the controversies regarding the D4 receptor expression in other vertebrates hampers for a complete comparison, especially in rhombencephalic regions. Our results further support that the dopaminergic system in vertebrates is well conserved and suggest that at least some functions of the D4 receptor were already present before the divergence of lampreys.
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Affiliation(s)
- Juan Pérez-Fernández
- Neurolam Group, Department of Functional Biology and Health Sciences, Faculty of Biology - Centro de Investigaciones Biomédicas - Instituto de Investigación Biomédica de Vigo, Uiversity of Vigo Vigo, Spain
| | - Manuel Megías
- Neurolam Group, Department of Functional Biology and Health Sciences, Faculty of Biology - Centro de Investigaciones Biomédicas - Instituto de Investigación Biomédica de Vigo, Uiversity of Vigo Vigo, Spain
| | - Manuel A Pombal
- Neurolam Group, Department of Functional Biology and Health Sciences, Faculty of Biology - Centro de Investigaciones Biomédicas - Instituto de Investigación Biomédica de Vigo, Uiversity of Vigo Vigo, Spain
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6
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Leopoldo M, Selivanova SV, Müller A, Lacivita E, Schetz JA, Ametamey SM. In vitro and in vivo evaluation of N-{2-[4-(3-Cyanopyridin-2-yl)piperazin-1-yl]ethyl}-3-[(11) C]methoxybenz-amide, a positron emission tomography (PET) radioligand for dopamine D4 receptors, in rodents. Chem Biodivers 2014; 11:1298-308. [PMID: 25238073 DOI: 10.1002/cbdv.201400178] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Indexed: 12/24/2022]
Abstract
The D4 dopamine receptor belongs to the D2 -like family of dopamine receptors, and its exact regional distribution in the central nervous system is still a matter of considerable debate. The availability of a selective radioligand for the D4 receptor with suitable properties for positron emission tomography (PET) would help resolve issues of D4 receptor localization in the brain, and the presumed diurnal change of expressed protein in the eye and pineal gland. We report here on in vitro and in vivo characteristics of the high-affinity D4 receptor-selective ligand N-{2-[4-(3-cyanopyridin-2-yl)piperazin-1-yl]ethyl}-3-[(11) C]methoxybenzamide ([(11) C]2) in rat. The results provide new insights on the in vitro properties that a brain PET dopamine D4 radioligand should possess in order to have improved in vivo utility in rodents.
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Affiliation(s)
- Marcello Leopoldo
- Dipartimento di Farmacia - Scienze del Farmaco, Università degli Studi di Bari 'A. Moro', via Orabona, 4, IT-70125 Bari
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7
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Genro JP, Kieling C, Rohde LA, Hutz MH. Attention-deficit/hyperactivity disorder and the dopaminergic hypotheses. Expert Rev Neurother 2014; 10:587-601. [DOI: 10.1586/ern.10.17] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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8
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Lacivita E, De Giorgio P, Lee IT, Rodeheaver SI, Weiss BA, Fracasso C, Caccia S, Berardi F, Perrone R, Zhang MR, Maeda J, Higuchi M, Suhara T, Schetz JA, Leopoldo M. Design, synthesis, radiolabeling, and in vivo evaluation of carbon-11 labeled N-[2-[4-(3-cyanopyridin-2-yl)piperazin-1-yl]ethyl]-3-methoxybenzamide, a potential positron emission tomography tracer for the dopamine D(4) receptors. J Med Chem 2010; 53:7344-55. [PMID: 20873719 DOI: 10.1021/jm100925m] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here we describe the design, synthesis, and evaluation of physicochemical and pharmacological properties of D(4) dopamine receptor ligands related to N-[2-[4-(4-chlorophenyl)piperazin-1-yl]ethyl]-3-methoxybenzamide (2). Structural features were incorporated to increase affinity for the target receptor, to improve selectivity over D(2) and σ(1) receptors, to enable labeling with carbon-11 or fluorine-18, and to adjust lipophilicity within the range considered optimal for brain penetration and low nonspecific binding. Compounds 7 and 13 showed the overall best characteristics: nanomolar affinity for the D(4) receptor, >100-fold selectivity over D(2) and D(3) dopamine receptors, 5-HT(1A), 5-HT(2A), and 5-HT(2C) serotonin receptors and σ(1) receptors, and log P = 2.37-2.55. Following intraperitoneal administration in mice, both compounds rapidly entered the central nervous system. The methoxy of N-[2-[4-(3-cyanopyridin-2-yl)piperazin-1-yl]ethyl]-3-methoxybenzamide (7) was radiolabeled with carbon-11 and subjected to PET analysis in non-human primate. [(11)C]7 time-dependently accumulated to saturation in the posterior eye in the region of the retina, a tissue containing a high density of D(4) receptors.
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Affiliation(s)
- Enza Lacivita
- Dipartimento Farmaco-Chimico, Università degli Studi di Bari A Moro, Via Orabona 4, 70125 Bari, Italy
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9
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Simpson J, Vetuz G, Wilson M, Brookes KJ, Kent L. The DRD4 receptor Exon 3 VNTR and 5' SNP variants and mRNA expression in human post-mortem brain tissue. Am J Med Genet B Neuropsychiatr Genet 2010; 153B:1228-33. [PMID: 20468066 DOI: 10.1002/ajmg.b.31084] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Genetic variation within the dopamine D4 receptor (DRD4) gene has been implicated in many neuropsychiatric disorders and behavioral traits. This variation includes the extensively studied exon 3 variably numbered tandem repeat (VNTR), and several 5' polymorphisms including a120-bp duplication and two single-nucleotide polymorphisms at -521 C/T (rs1800955) and -616 C/G (rs747302). Several reports have provided evidence for a functional role for some of these variants using in vitro techniques. This study investigated the functionality of these polymorphisms in 28 human post-mortem brain tissue samples by quantifying DRD4 mRNA expression in relation to genotype. No statistically significant relationship between genotype and mRNA expression levels was found for these four polymorphisms although a weak trend toward the 7-repeat of the exon 3 VNTR reducing DRD4 mRNA expression was found. Employing post-mortem brain tissue, rather than using in vitro techniques may provide a more relevant paradigm to study functional effects of reported risk alleles.
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Affiliation(s)
- Jennifer Simpson
- Bute Medical School, University of St. Andrews, St. Andrews, Scotland, UK
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10
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de Almeida J, Mengod G. D2 and D4 dopamine receptor mRNA distribution in pyramidal neurons and GABAergic subpopulations in monkey prefrontal cortex: implications for schizophrenia treatment. Neuroscience 2010; 170:1133-9. [PMID: 20727949 DOI: 10.1016/j.neuroscience.2010.08.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 08/09/2010] [Accepted: 08/11/2010] [Indexed: 11/25/2022]
Abstract
D2 and D4 dopamine receptors play an important role in cognitive functions in the prefrontal cortex and they are involved in the pathophysiology of neuropsychiatric disorders such as schizophrenia. The eventual effect of dopamine upon pyramidal neurons in the prefrontal cortex depends on which receptors are expressed in the different neuronal populations. Parvalbumin and calbindin mark two subpopulations of cortical GABAergic interneurons that differently innervate pyramidal cells. Recent hypotheses about schizophrenia hold that the root of the illness is a dysfunction of parvalbumin chandelier cells that produces disinhibition of pyramidal cells. In the present work we report double in situ hybridization histochemistry experiments to determine the prevalence of D2 receptor mRNA and D4 receptor mRNA in glutamatergic neurons, GABAergic interneurons and both parvalbumin and calbindin GABAergic subpopulations in monkey prefrontal cortex layer V. We found that around 54% of glutamatergic neurons express D2 mRNA and 75% express D4 mRNA, while GAD-positive interneurons express around 34% and 47% respectively. Parvalbumin cells mainly expressed D4 mRNA (65%) and less D2 mRNA (15-20%). Finally, calbindin cells expressed both receptors in similar proportions (37%). We hypothesized that D4 receptor could be a complementary target in designing new antipsychotics, mainly because of its predominance in parvalbumin interneurons.
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Affiliation(s)
- J de Almeida
- Departament de Neuroquimica i Neurofarmacologia, Institut d’Investigacions Biomèdiques de Barcelona, CSIC, IDIBAPS, CIBERNED, 08036 Barcelona, Spain
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11
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Eisenberg DTA, Apicella CL, Campbell BC, Dreber A, Garcia JR, Lum JK. Assortative human pair-bonding for partner ancestry and allelic variation of the dopamine receptor D4 (DRD4) gene. Soc Cogn Affect Neurosci 2010; 5:194-202. [PMID: 19713452 PMCID: PMC2894670 DOI: 10.1093/scan/nsp026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Accepted: 05/24/2009] [Indexed: 11/13/2022] Open
Abstract
The 7 repeat (7R) allele of the dopamine receptor D4 gene has been associated with attention deficit hyperactivity disorder and risk taking. On the cross-population scale, 7R allele frequencies have been shown to be higher in populations with more of a history of long-term migrations. It has also been shown that the 7R allele is associated with individuals having multiple ancestries. Here, we conduct a replication of this latter finding with two independent samples. Measures of subjects' ancestry are used to examine past reproductive bonds. The individuals' history of interracial/ancestral dating and their feelings about this are also assessed. Tentative support for an association between multiple ancestries and the 7R allele was found. These results are dependent upon the method of questioning subjects about their ancestries, with only finer-scale measures of ancestry being associated with 7R. Interracial dating and feelings about interracial pairing were not related to the presence of the 7R allele. This study provides continued support for a role for the 7R allele in migration and/or mate choice patterns. However, replications and extensions of this study are needed and the way ancestry/race is assessed must be carefully considered.
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Affiliation(s)
- Dan T A Eisenberg
- Department of Anthropology, Northwestern University, Evanston, IL 60208, USA.
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12
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Rondou P, Haegeman G, Van Craenenbroeck K. The dopamine D4 receptor: biochemical and signalling properties. Cell Mol Life Sci 2010; 67:1971-86. [PMID: 20165900 PMCID: PMC11115718 DOI: 10.1007/s00018-010-0293-y] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 01/19/2010] [Accepted: 01/26/2010] [Indexed: 01/20/2023]
Abstract
Dopamine is an important neurotransmitter that regulates several key functions in the brain, such as motor output, motivation and reward, learning and memory, and endocrine regulation. Dopamine does not mediate fast synaptic transmission, but rather modulates it by triggering slow-acting effects through the activation of dopamine receptors, which belong to the G-protein-coupled receptor superfamily. Besides activating different effectors through G-protein coupling, dopamine receptors also signal through interaction with a variety of proteins, collectively termed dopamine receptor-interacting proteins. We focus on the dopamine D4 receptor, which contains an important polymorphism in its third intracellular loop. This polymorphism has been the subject of numerous studies investigating links with several brain disorders, such as attention-deficit hyperactivity disorder and schizophrenia. We provide an overview of the structure, signalling properties and regulation of dopamine D4 receptors, and briefly discuss their physiological and pathophysiological role in the brain.
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Affiliation(s)
- Pieter Rondou
- Laboratory of Eukaryotic Gene Expression and Signal Transduction (LEGEST), Ghent University (UGent), K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
- Present Address: Center for Medical Genetics Ghent (CMGG), Ghent University Hospital, Medical Research Building, De Pintelaan 185, 9000 Ghent, Belgium
| | - Guy Haegeman
- Laboratory of Eukaryotic Gene Expression and Signal Transduction (LEGEST), Ghent University (UGent), K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Kathleen Van Craenenbroeck
- Laboratory of Eukaryotic Gene Expression and Signal Transduction (LEGEST), Ghent University (UGent), K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
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Turic D, Swanson J, Sonuga-Barke E. DRD4 and DAT1 in ADHD: Functional neurobiology to pharmacogenetics. PHARMACOGENOMICS & PERSONALIZED MEDICINE 2010; 3:61-78. [PMID: 23226043 PMCID: PMC3513209 DOI: 10.2147/pgpm.s6800] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Indexed: 12/26/2022]
Abstract
Attention deficit/hyperactivity disorder (ADHD) is a common and potentially very impairing neuropsychiatric disorder of childhood. Statistical genetic studies of twins have shown ADHD to be highly heritable, with the combination of genes and gene by environment interactions accounting for around 80% of phenotypic variance. The initial molecular genetic studies where candidates were selected because of the efficacy of dopaminergic compounds in the treatment of ADHD were remarkably successful and provided strong evidence for the role of DRD4 and DAT1 variants in the pathogenesis of ADHD. However, the recent application of non-candidate gene strategies (eg, genome-wide association scans) has failed to identify additional genes with substantial genetic main effects, and the effects for DRD4 and DAT1 have not been replicated. This is the usual pattern observed for most other physical and mental disorders evaluated with current state-of-the-art methods. In this paper we discuss future strategies for genetic studies in ADHD, highlighting both the pitfalls and possible solutions relating to candidate gene studies, genome-wide studies, defining the phenotype, and statistical approaches.
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Affiliation(s)
- Darko Turic
- Institute for Disorders of Impulse and Attention, School of Psychology, University of Southampton, UK
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14
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Testosterone exposure, dopaminergic reward, and sensation-seeking in young men. Physiol Behav 2010; 99:451-6. [DOI: 10.1016/j.physbeh.2009.12.011] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2009] [Revised: 12/04/2009] [Accepted: 12/14/2009] [Indexed: 11/19/2022]
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15
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Marazziti D, Baroni S, Masala I, Giannaccini G, Betti L, Palego L, Dell’Osso MC, Consoli G, Castagna M, Lucacchini A. [3H]-YM-09151-2 binding sites in human brain postmortem. Neurochem Int 2009; 55:643-7. [DOI: 10.1016/j.neuint.2009.06.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 06/09/2009] [Accepted: 06/10/2009] [Indexed: 11/16/2022]
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Monuteaux MC, Seidman LJ, Faraone SV, Makris N, Spencer T, Valera E, Brown A, Bush G, Doyle AE, Hughes S, Helliesen M, Mick E, Biederman J. A preliminary study of dopamine D4 receptor genotype and structural brain alterations in adults with ADHD. Am J Med Genet B Neuropsychiatr Genet 2008; 147B:1436-41. [PMID: 18951431 DOI: 10.1002/ajmg.b.30870] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
An emerging literature has demonstrated an association between the dopamine D4 receptor (DRD4) gene and volumetric brain abnormalities in children with ADHD. However, these results have not been extended to adults and have not addressed the impact of comorbidity. Our objective was to examine the DRD4 7R gene and volumetric brain abnormalities in adults with ADHD while accounting for comorbidity with bipolar disorder (BPD). Subjects were male and female adult outpatient referrals stratified into two diagnostic groups: 24 with ADHD, 19 with ADHD and BPD, as well as 20 male and female adult community controls without ADHD or BPD. We measured volumes (cm(3)) of a priori selected brain regions (superior frontal, middle frontal, anterior cingulate, and cerebellum cortices) by structural magnetic resonance imaging. Among adults with ADHD, subjects with the 7-repeat allele of the DRD4 gene had a significantly smaller mean volume in the superior frontal cortex and cerebellum cortex compared to subjects without this allele. In contrast, no such effects were detected in the adults with ADHD + BPD or controls. Our findings suggest that volumetric abnormalities in the dorsolateral prefrontal cortex and cerebellum may represent an intermediate neuroanatomical phenotype between DRD4 genotype and the clinical expression of ADHD in adults, but only in ADHD subjects without comorbid BPD. These result support the heterogeneity of ADHD and provides insights as to its underlying pathophysiology.
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Affiliation(s)
- Michael C Monuteaux
- Clinical and Research Program in Pediatric Psychopharmacology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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17
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Imaging genetics in ADHD: a focus on cognitive control. Neurosci Biobehav Rev 2008; 33:674-89. [PMID: 18789356 DOI: 10.1016/j.neubiorev.2008.08.009] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 07/18/2008] [Accepted: 08/17/2008] [Indexed: 01/17/2023]
Abstract
This paper evaluates neuroimaging of cognitive control as an endophenotype for investigating the role of dopamine genes in ADHD. First, this paper reviews both data-driven and theory-driven approaches from genetics and neuroimaging. Several viable candidate genes have been implicated in ADHD, including the dopamine DRD4 and DAT1 genes. Neuroimaging studies have resulted in a good understanding of the neurobiological basis of deficits in cognitive control in this disorder. Second, this paper discusses imaging genetics in ADHD. Papers to date have taken one of two approaches: whereas early papers investigated the effects of one or two candidate genes on many brain areas, later papers constrained regions of interest by gene expression patterns. These papers have largely focused on cognitive control and the dopamine circuits involved in this ability. The results show that neuroimaging of cognitive control is useful as an endophenotype in investigating dopamine gene effects in ADHD. Other avenues of investigation are suggested by a combination of data- and theory-driven approaches in both genetics and neuroimaging.
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18
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Cellular localization and distribution of dopamine D4 receptors in the rat cerebral cortex and their relationship with the cortical dopaminergic and noradrenergic nerve terminal networks. Neuroscience 2008; 155:997-1010. [DOI: 10.1016/j.neuroscience.2008.05.060] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 05/21/2008] [Accepted: 05/26/2008] [Indexed: 01/10/2023]
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Abstract
Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disease that affects children, adolescents, and adults. Genetic research has confirmed that there is a large hereditary component to this condition and has helped identify some of the genes associated with it. Among these are several genes associated with the catecholaminergic system including the dopamine receptor genes (DRD4 and DRD5), the dopamine transporter gene, and the gene for dopamine beta-hydroxylase, which catalyzes conversion of dopamine to norepinephrine. Attention-deficit/hyperactivity disorder is believed to be a result of abnormalities in the frontal regions of the brain, particularly the prefrontal cortex and associated subcortical structures and circuits. Underpinning these abnormalities are disturbances of catecholamine neurotransmission. Studies have demonstrated that patients with ADHD have depleted levels of dopamine and norepinephrine thought to be largely the result of dysfunction of their respective transporter systems. The efficacy of stimulant agents confirms that the neurotransmitter abnormalities seen in ADHD are primarily catecholaminergic in origin. This article focuses on the catecholaminergic networks of higher cognitive functions such as attention and focus and of motor functions that may be associated with such networks, reviewing both the physiology of such functions and the pathophysiology of ADHD. Researchers are currently investigating whether other neurotransmitter systems may be partially involved and are investigating whether agents that affect these other systems will prove complementary to currently used treatments.
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Hertel P, Didriksen M, Pouzet B, Brennum LT, Søby KK, Larsen AK, Christoffersen CT, Ramirez T, Marcus MM, Svensson TH, Di Matteo V, Esposito E, Bang-Andersen B, Arnt J. Lu 35-138 ((+)-(S)-3-{1-[2-(1-acetyl-2,3-dihydro-1H-indol-3-yl)ethyl]-3,6-dihydro-2H-pyridin-4-yl}-6-chloro-1H-indole), a dopamine D4 receptor antagonist and serotonin reuptake inhibitor: Characterisation of its in vitro profile and pre-clinical antipsychotic potential. Eur J Pharmacol 2007; 573:148-60. [PMID: 17689529 DOI: 10.1016/j.ejphar.2007.06.052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 06/12/2007] [Accepted: 06/18/2007] [Indexed: 11/22/2022]
Abstract
The present study describes the pharmacological profile of the putative antipsychotic drug Lu 35-138 ((+)-(S)-3-{1-[2-(1-acetyl-2,3-dihydro-1H-indol-3-yl)ethyl]-3,6-dihydro-2H-pyridin-4-yl}-6-chloro-1H-indole). The in vitro receptor profile of Lu 35-138 revealed high affinity (K(i)=5 nM) and competitive antagonism (K(b)=8 nM) at dopamine D(4) receptors combined with potent 5-HT uptake inhibition (IC(50)=3.2 nM) and moderate alpha(1)-adrenoceptor affinity (K(i)=45 nM). In vivo, Lu 35-138 selectively counteracted hyperlocomotion induced by d-amphetamine (0.5 mg/kg; ED(50)=4.0 mg/kg, s.c.) in rats and phencyclidine (PCP; 2.5 mg/kg; ED(50)=13 mg/kg, s.c.) in mice. Lu 35-138 was unable to affect hyperlocomotion induced by a high dose of d-amphetamine (2.0 mg/kg), which indicates a preferential action on limbic versus striatal structures. A similar limbic selectivity of Lu 35-138 was indicated in voltammetric measure of dopamine output in the core and shell subdivisions of the nucleus accumbens in rats. Furthermore, a relatively large dose of Lu 35-138 (18 mg/kg, s.c.) counteracted d-amphetamine-induced disruption of pre-pulse inhibition in rats and repeated administration of Lu 35-138 (0.31 or 1.25 mg/kg, p.o. once daily for 3 weeks) reduced the number of spontaneously active dopamine neurones in the ventral tegmental area, underlining its antipsychotic-like profile. Lu 35-138 failed to induce catalepsy in rats or dystonia in Cebus apella monkeys and did not deteriorate spatial memory in rats as assessed by water maze performance. Collectively, these results suggest that Lu 35-138 possesses antipsychotic activity combined with a low extrapyramidal and cognitive side effect liability.
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Affiliation(s)
- Peter Hertel
- Research and Development, H. Lundbeck A/S, Copenhagen-Valby, Denmark.
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Kuznetsova AY, Deth RC. A model for modulation of neuronal synchronization by D4 dopamine receptor-mediated phospholipid methylation. J Comput Neurosci 2007; 24:314-29. [PMID: 17929154 DOI: 10.1007/s10827-007-0057-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2006] [Revised: 08/29/2007] [Accepted: 09/24/2007] [Indexed: 12/16/2022]
Abstract
We describe a new molecular mechanism of dopamine-induced membrane protein modulation that can tune neuronal oscillation frequency to attention-related gamma rhythm. This mechanism is based on the unique ability of D4 dopamine receptors (D4R) to carry out phospholipid methylation (PLM) that may affect the kinetics of ion channels. We show that by deceasing the inertia of the delayed rectifier potassium channel, a transition to 40 Hz oscillations can be achieved. Decreased potassium channel inertia shortens spike duration and decreases the interspike interval via its influence on the calcium-dependent potassium current. This mechanism leads to a transition to attention-related gamma oscillations in a pyramidal cell-interneuron network. The higher frequency and better synchronization is observed with PLM affecting pyramidal neurons only, and recurrent excitation between pyramidal neurons is important for synchronization. Thus dopamine-stimulated methylation of membrane phospholipids may be an important mechanism for modulating firing activity, while impaired methylation can contribute to disorders of attention.
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Affiliation(s)
- Anna Y Kuznetsova
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, 2020 Gravier St., Suite D, New Orleans, LA 70112, USA
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22
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Stefański R, Ziółkowska B, Kuśmider M, Mierzejewski P, Wyszogrodzka E, Kołomańska P, Dziedzicka-Wasylewska M, Przewłocki R, Kostowski W. Active versus passive cocaine administration: differences in the neuroadaptive changes in the brain dopaminergic system. Brain Res 2007; 1157:1-10. [PMID: 17544385 DOI: 10.1016/j.brainres.2007.04.074] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/11/2007] [Accepted: 04/20/2007] [Indexed: 10/23/2022]
Abstract
There is considerable evidence that chronic exposure to cocaine is associated with low striatal dopamine D2 receptor availability. In the present study we wished to determine whether neuroadaptive changes in densities of D2 receptors were due to direct pharmacological actions of cocaine or they reflected motivational states that were present when cocaine injection depended on active drug-seeking behavior and whether these changes were related to the actual expression of D2 mRNA. To achieve this goal we utilized a "yoked" procedure in which rats were tested simultaneously in groups of three, with only one rat actively self-administering cocaine while the other two received yoked injections of either cocaine or saline. Only passively administered cocaine produced a decrease in dopamine D2 receptor levels in the anterior and central regions of caudate/putamen, and both the shell and core of the nucleus accumbens, as measured by in vitro quantitative autoradiography. In contrast, examination of D2 receptor gene expression using in situ hybridization analysis revealed that there was an increase in D2 receptor mRNA levels in the ventral tegmental area of rats actively self-administered cocaine. We conclude that the reductions in striatal D2 receptor densities may be related to the chronic administration of cocaine per se and not to the motivated process of reinforced responding. Our results also suggest that increases in D2 receptor mRNA levels in limbic regions do not necessarily result in increased receptor densities and these changes likely reflect motivational states that were present when cocaine injection dependent on active drug self-administration.
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Affiliation(s)
- Roman Stefański
- Department of Pharmacology and Physiology of the Nervous System, Institute of Psychiatry and Neurology, Sobieskiego 9, 02-957 Warsaw, Poland
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Eisenberg DTA, MacKillop J, Modi M, Beauchemin J, Dang D, Lisman SA, Lum JK, Wilson DS. Examining impulsivity as an endophenotype using a behavioral approach: a DRD2 TaqI A and DRD4 48-bp VNTR association study. Behav Brain Funct 2007; 3:2. [PMID: 17214892 PMCID: PMC1781951 DOI: 10.1186/1744-9081-3-2] [Citation(s) in RCA: 196] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 01/10/2007] [Indexed: 01/26/2023] Open
Abstract
Background Research on the genetic basis for impulsivity has revealed an array of ambiguous findings. This may be a result of limitations to self-report assessments of impulsivity. Behavioral measures that assess more narrowly defined aspects of impulsivity may clarify genetic influences. This study examined the relationship between possession of the DRD2 TaqI A and DRD4 48 bp VNTR genetic polymorphisms and performance on a behavioral measure of impulsivity, the delay discounting task (DDT), and three traditional self-report measures. Methods 195 individuals (42% male) were recruited from a university campus and were assessed in small group sessions using personal computers. Genotyping was conducted using previously established protocols. For the DRD2 TaqI A locus, individuals were designated as possessing at least one copy of the A1 allele (A1+) or not (A1-), and for the DRD4 48-bp VNTR locus, individuals were designated as having at least one long allele (7 repeats or longer, L+) or not (L-). Principal analyses used multiple univariate factorial 2 (A1+/A1-) × 2 (L+/L-) analyses of variance. Results A significant main effect of A1+ status on DDT performance was evident (p = .006) as well as a significant interaction effect (p = .006) between both genes. No other significant effects were evident on the self-report measures, with the exception of a trend toward an interaction effect on the Sensation Seeking Scale. Exploratory analyses suggested that the significant effects were not a function of population stratification or gender. Discussion These data suggest that the DRD2 TaqI A and DRD4 VNTR polymorphisms influence impulsivity as measured with a delay discounting task. Specifically, these findings suggest that an interaction between the functional effects of the two unlinked genotypes results in significant difference in the balance of mesolimbic dopaminergic activation relative to frontal-parietal activation. However, these findings are also the first in this area and must be replicated. Conclusion These findings suggest a meaningful interaction between the DRD2 TaqI A and DRD4 VNTR polymorphisms in the expression of impulsivity and provide initial support for the utility of using behavioral measures for clarifying genetic influences on impulsivity.
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Affiliation(s)
- Dan TA Eisenberg
- State University of New York at Binghamton, Biology Department, Binghamton, NY, USA
- State University of New York at Binghamton, Anthropology Department, Binghamton, NY, USA
- State University of New York at Binghamton, Laboratory of Evolutionary Anthropology and Health, Binghamton, NY, USA
| | - James MacKillop
- State University of New York at Binghamton, Psychology Department, Binghamton, NY, USA
- Center for Alcohol and Addiction Studies, Brown University, Providence, RI, USA
| | - Meera Modi
- State University of New York at Binghamton, Biology Department, Binghamton, NY, USA
| | - Joshua Beauchemin
- State University of New York at Binghamton, Laboratory of Evolutionary Anthropology and Health, Binghamton, NY, USA
| | - David Dang
- State University of New York at Binghamton, Laboratory of Evolutionary Anthropology and Health, Binghamton, NY, USA
| | - Stephen A Lisman
- State University of New York at Binghamton, Psychology Department, Binghamton, NY, USA
| | - J Koji Lum
- State University of New York at Binghamton, Biology Department, Binghamton, NY, USA
- State University of New York at Binghamton, Anthropology Department, Binghamton, NY, USA
- State University of New York at Binghamton, Laboratory of Evolutionary Anthropology and Health, Binghamton, NY, USA
| | - David S Wilson
- State University of New York at Binghamton, Biology Department, Binghamton, NY, USA
- State University of New York at Binghamton, Anthropology Department, Binghamton, NY, USA
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DeYoung CG, Peterson JB, Séguin JR, Mejia JM, Pihl RO, Beitchman JH, Jain U, Tremblay RE, Kennedy JL, Palmour RM. The dopamine D4 receptor gene and moderation of the association between externalizing behavior and IQ. ACTA ACUST UNITED AC 2007; 63:1410-6. [PMID: 17146015 PMCID: PMC3283582 DOI: 10.1001/archpsyc.63.12.1410] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Dopaminergic neurotransmission is implicated in externalizing behavior problems, such as aggression and hyperactivity. Externalizing behavior is known to be negatively associated with cognitive ability. Activation of dopamine D4 receptors appears to inhibit the functioning of the prefrontal cortex, a brain region implicated in cognitive ability. The 7-repeat allele of the dopamine D4 receptor gene produces less efficient receptors, relative to other alleles, and this may alter the effects of dopamine on cognitive function. OBJECTIVE To examine the influence of a polymorphism in the third exon of the dopamine D4 receptor gene on the association between externalizing behavior and IQ. DESIGN In 1 community sample and 2 clinical samples, the presence or absence of the 7-repeat allele was examined as a moderator of the association between externalizing behavior and IQ; the strength of this effect across samples was estimated meta-analytically. PATIENTS Eighty-seven boys from a longitudinal community study, 48 boys referred clinically for aggression, and 42 adult males diagnosed with attention-deficit/hyperactivity disorder. MAIN OUTCOME MEASURES IQ scores and observer ratings of externalizing behavior were taken from existing data sets. RESULTS Among individuals lacking the 7-repeat allele, externalizing behavior was negatively correlated with IQ (mean r = -0.43; P<.001). Among individuals having at least 1 copy of the 7-repeat allele, externalizing behavior and IQ were uncorrelated (mean r = 0.02; P = .45). The difference between these correlations was significant (z = -2.99; P<.01). CONCLUSIONS Allelic variation of the dopamine D4 receptor gene appears to be a genetic factor moderating the association between externalizing behavior and cognitive ability. This finding may help to elucidate the adaptive value of the 7-repeat allele.
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Affiliation(s)
- Colin G DeYoung
- Department of Psychology, and Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada.
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Buhusi CV, Meck WH. Effect of clozapine on interval timing and working memory for time in the peak-interval procedure with gaps. Behav Processes 2006; 74:159-67. [PMID: 17141425 PMCID: PMC1849977 DOI: 10.1016/j.beproc.2006.10.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 10/09/2006] [Accepted: 10/09/2006] [Indexed: 01/26/2023]
Abstract
Previous research indicates that dopamine controls both the speed of an internal clock [Maricq, A.V., Church, R.M., 1983. The differential effects of haloperidol and methamphetamine on time estimation in the rat. Psychopharmacology 79, 10-15] and sharing of resources between the timer and other cognitive processes [Buhusi, C.V., 2003. Dopaminergic mechanisms of interval timing and attention. In: Meck, W.H. (Ed.), Functional and Neural Mechanisms of Interval Timing. CRC Press, Boca Raton, FL, pp. 317-338]. For example, dopamine agonist methamphetamine increases the speed of an internal clock and resets timing after a gap, while dopamine antagonist haloperidol decreases the speed of an internal clock and stops timing during a gap [Buhusi, C.V., Meck, W.H., 2002. Differential effects of methamphetamine and haloperidol on the control of an internal clock. Behav. Neurosci. 116, 291-297]. Using a 20-s peak-interval procedure with gaps we examined the acute effects of clozapine (2.0mg/kg i.p.), which exerts differential effects on dopamine and serotonin in the cortex and striatum, two brain areas involved in interval timing and working memory. Relative to saline, clozapine injections shifted the response functions leftward both in trials with and without gaps, suggesting that clozapine increased the speed of an internal clock and facilitated the maintenance of the pre-gap interval in working memory. These results suggest that clozapine exerts effects in different brain areas in a manner that allows for the pharmacological separation of clock speed and working memory as a function of peak trials without and with gaps.
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Affiliation(s)
- Catalin V Buhusi
- Duke University, Department of Psychology and Neuroscience, Durham, NC 27708, United States.
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Diamond A. Attention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): a neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity). Dev Psychopathol 2006; 17:807-25. [PMID: 16262993 PMCID: PMC1474811 DOI: 10.1017/s0954579405050388] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the combined type and emphasized a core problem in response inhibition. It is proposed here that the core problem in the truly inattentive type of ADHD (not simply the subthreshold combined type) is in working memory. It is further proposed that laboratory measures, such as complex-span and dual-task dichotic listening tasks, can detect this. Children with the truly inattentive type of ADHD, rather than being distractible, may instead be easily bored, their problem being more in motivation (underarousal) than in inhibitory control. Much converging evidence points to a primary disturbance in the striatum (a frontal-striatal loop) in the combined type of ADHD. It is proposed here that the primary disturbance in truly inattentive-type ADHD (ADD) is in the cortex (a frontal-parietal loop). Finally, it is posited that these are not two different types of ADHD, but two different disorders with different cognitive and behavioral profiles, different patterns of comorbidities, different responses to medication, and different underlying neurobiologies.
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Affiliation(s)
- Adele Diamond
- Department of Psychiatry, University of British Columbia, Vancouver, Canada.
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Abstract
Biogenic amine neurotransmitters are released from nerve terminals and activate pre- and postsynaptic receptors. Released neurotransmitters are sequestered by transporters into presynaptic neurons, a major mode of their inactivation in the brain. Genetic studies of human biogenic amine transporter genes, including the dopamine transporter (hDAT; SLC6A3), the serotonin transporter (hSERT; SLC6A4), and the norepinephrine transporter (hNET; SLC6A2) have provided insight into how genomic variations in these transporter genes influence pharmacology and brain physiology. Genetic variants can influence transporter function by various mechanisms, including substrate affinities, transport velocity, transporter expression levels (density), extracellular membrane expression, trafficking and turnover, and neurotransmitter release. It is increasingly apparent that genetic variants of monoamine transporters also contribute to individual differences in behavior and neuropsychiatric disorders. This chapter summarizes current knowledge of transporters with a focus on genomic variations, expression variations, pharmacology of protein variants, and known association with human diseases.
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Affiliation(s)
- Z Lin
- Department of Psychiatry, Harvard Medical School, Division of Neurochemistry, New England Primate Research Center, 1 Pine Hill Drive, Southborough, MA 01772-9102, USA
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Attention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): a neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity). Dev Psychopathol 2005. [PMID: 16262993 DOI: 10.1017/s0954579405050388"] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [3.0.co;2-7')">Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Most studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the combined type and emphasized a core problem in response inhibition. It is proposed here that the core problem in the truly inattentive type of ADHD (not simply the subthreshold combined type) is in working memory. It is further proposed that laboratory measures, such as complex-span and dual-task dichotic listening tasks, can detect this. Children with the truly inattentive type of ADHD, rather than being distractible, may instead be easily bored, their problem being more in motivation (underarousal) than in inhibitory control. Much converging evidence points to a primary disturbance in the striatum (a frontal-striatal loop) in the combined type of ADHD. It is proposed here that the primary disturbance in truly inattentive-type ADHD (ADD) is in the cortex (a frontal-parietal loop). Finally, it is posited that these are not two different types of ADHD, but two different disorders with different cognitive and behavioral profiles, different patterns of comorbidities, different responses to medication, and different underlying neurobiologies.
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Durston S, Fossella JA, Casey BJ, Hulshoff Pol HE, Galvan A, Schnack HG, Steenhuis MP, Minderaa RB, Buitelaar JK, Kahn RS, van Engeland H. Differential effects of DRD4 and DAT1 genotype on fronto-striatal gray matter volumes in a sample of subjects with attention deficit hyperactivity disorder, their unaffected siblings, and controls. Mol Psychiatry 2005; 10:678-85. [PMID: 15724142 DOI: 10.1038/sj.mp.4001649] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetic influences on behavior are complex and, as such, the effect of any single gene is likely to be modest. Neuroimaging measures may serve as a biological intermediate phenotype to investigate the effect of genes on human behavior. In particular, it is possible to constrain investigations by prior knowledge of gene characteristics and by including samples of subjects where the distribution of phenotypic variance is both wide and under heritable influences. Here, we use this approach to show a dissociation between the effects of two dopamine genes that are differentially expressed in the brain. We show that the DAT1 gene, a gene expressed predominantly in the basal ganglia, preferentially influences caudate volume, whereas the DRD4 gene, a gene expressed predominantly in the prefrontal cortex, preferentially influences prefrontal gray matter volume in a sample of subjects including subjects with ADHD, their unaffected siblings, and healthy controls. This demonstrates that, by constraining our investigations by prior knowledge of gene expression, including samples in which the distribution of phenotypic variance is wide and under heritable influences, and by using intermediate phenotypes, such as neuroimaging, we may begin to map out the pathways by which genes influence behavior.
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Affiliation(s)
- S Durston
- Department of Child and Adolescent Psychiatry, Rudolf Magnus Institute for Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.
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31
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Madras BK, Miller GM, Fischman AJ. The dopamine transporter and attention-deficit/hyperactivity disorder. Biol Psychiatry 2005; 57:1397-409. [PMID: 15950014 DOI: 10.1016/j.biopsych.2004.10.011] [Citation(s) in RCA: 285] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2004] [Revised: 09/29/2004] [Accepted: 10/25/2004] [Indexed: 11/23/2022]
Abstract
The high incidence of attention-deficit/hyperactivity disorder (ADHD) and escalating use of ADHD medications present a compelling case for clarifying the pathophysiology of, and developing laboratory or radiologic tests for, ADHD. Currently, the majority of specific genes implicated in ADHD encode components of catecholamine signaling systems. Of these, the dopamine transporter (DAT) is a principal target of the most widely used antihyperactivity medications (amphetamine and methylphenidate); the DAT gene is associated with ADHD, and some studies have detected abnormal levels of the DAT in brain striatum of ADHD subjects. Medications for ADHD interfere with dopamine transport by brain-region- and drug-specific mechanisms, indirectly activating dopamine- and possibly norepinephrine-receptor subtypes that are implicated in enhancing attention and experiential salience. The most commonly used DAT-selective ADHD medications raise extracellular dopamine levels in DAT-rich brain regions. In brain regions expressing both the DAT and the norepinephrine transporter (NET), the relative contributions of dopamine and norepinephrine to ADHD pathophysiology and therapeutic response are obfuscated by the capacity of the NET to clear dopamine as well as norepinephrine. Thus, ADHD medications targeting DAT or NET might disperse dopamine widely and consign dopamine storage and release to regulation by noradrenergic, as well as dopaminergic neurons.
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Affiliation(s)
- Bertha K Madras
- Department of Psychiatry, Harvard Medical School, New England Primate Research Center, Southborough, MA 01772-9102, USA.
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Boeckler F, Russig H, Zhang W, Löber S, Schetz J, Hübner H, Ferger B, Gmeiner P, Feldon J. FAUC 213, a highly selective dopamine D4 receptor full antagonist, exhibits atypical antipsychotic properties in behavioural and neurochemical models of schizophrenia. Psychopharmacology (Berl) 2004; 175:7-17. [PMID: 15007532 DOI: 10.1007/s00213-004-1782-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2003] [Accepted: 11/10/2003] [Indexed: 11/25/2022]
Abstract
RATIONALE 2-[4-(4-Chlorophenyl)piperazin-1-ylmethyl]pyrazolo[1,5-a]pyridine (FAUC 213) is a highly selective antagonist at the dopamine D(4) receptor subtype. It was designed as a derivative of two partial antagonists and has been proven to be a complete antagonist in mitogenesis assay. OBJECTIVES In the present study, FAUC 213 was examined for antipsychotic properties in animal models of behavioural neurobiology and neurochemistry. METHODS Different concentrations of FAUC 213 were screened for effects on spontaneous, as well as amphetamine-induced, locomotor activity and apomorphine-induced prepulse disruption. The liability of causing extrapyramidal side effects was investigated in models of catalepsy and by high-performance liquid chromatography (HPLC) detection of dopamine turnover in several brain regions. The application schedule was validated, and the bioavailability of the compound determined, by means of a HPLC-pharmacokinetic study. RESULTS A significant effect in both the reduction of amphetamine-induced locomotor hyperactivity and the restoration of apomorphine-disrupted prepulse inhibition was found at 30 mg/kg. This dose proved not to be high enough to induce catalepsy or to increase dopamine turnover in the dorsal striatum, nucleus accumbens and medial prefrontal cortex. The selective D(4) antagonist FAUC 213, therefore, is not believed to mediate the above-mentioned effects via D(2) receptor antagonism, but a partial involvement of 5-HT(2)- and alpha(1)-receptors cannot be ruled out at present. CONCLUSIONS We have gathered evidence that FAUC 213 exhibits atypical antipsychotic characteristics.
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Affiliation(s)
- Frank Boeckler
- Laboratory of Behavioural Neurobiology, Swiss Federal Institute of Technology Zürich, Schorenstrasse 16, 8603 Schwerzenbach, Switzerland
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Stefanski R, Justinova Z, Hayashi T, Takebayashi M, Goldberg SR, Su TP. Sigma1 receptor upregulation after chronic methamphetamine self-administration in rats: a study with yoked controls. Psychopharmacology (Berl) 2004; 175:68-75. [PMID: 15029471 DOI: 10.1007/s00213-004-1779-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2003] [Accepted: 12/23/2003] [Indexed: 10/26/2022]
Abstract
RATIONALE Sigma(1) receptors (Sig-1R) are implicated in behavioral sensitization, conditioned place preference, and cellular restructuring induced by psychostimulants. We previously reported that rats which actively self-administered methamphetamine for 5 weeks and were then withdrawn from methamphetamine for 24 h showed downregulation of dopamine D(2) autoreceptors (approximately 30%) in the midbrain and this was not seen in rats that passively received injections of methamphetamine or saline at the same time (yoked controls). Involvement of Sig-1R in the self-administration of psychostimulants, however, has never been reported. OBJECTIVES This study examined neuroadaptive changes in Sig-1R in the brains of rats self-administering methamphetamine. METHODS Three groups of rats were tested simultaneously 5 days per week, for 5 weeks (25 daily sessions). Two groups served as yoked controls and passively received an injection of either 0.1 mg/kg methamphetamine or saline (not contingent on responding) each time a response-contingent injection of 0.1 mg/kg methamphetamine was actively self-administered by the first group of rats. Protein and mRNA levels of Sig-1R were then measured by Western and Northern blottings, respectively. RESULTS There was a marked upregulation of Sig-1R proteins (50%) in the midbrain and altered levels of Sig-1R mRNA in the frontal cortex and hippocampus of rats that learned to actively self-administer methamphetamine, but not in yoked methamphetamine- or saline-control rats. CONCLUSIONS Neuroadaptive increases in Sig-1R seen in this study may contribute to the reinforcing effects of methamphetamine. This upregulation of Sig-1R may be mediated by increased protein kinase A activity due to downregulation of dopamine D(2) autoreceptors.
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Affiliation(s)
- Roman Stefanski
- Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, NIDA-IRP, NIH, DHHS, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA
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Rivera A, Trías S, Peñafiel A, Angel Narváez J, Díaz-Cabiale Z, Moratalla R, de la Calle A. Expression of D4 dopamine receptors in striatonigral and striatopallidal neurons in the rat striatum. Brain Res 2003; 989:35-41. [PMID: 14519509 DOI: 10.1016/s0006-8993(03)03328-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recent studies have reported the regional distribution of D(4) dopamine receptors in the rat striatum at the cellular and subcellular levels. However, the precise identity of the striatal neurons that express these receptors remains unknown. We have studied the expression of D(4) receptors in the striatal interneurons as well as in the output regions of the striatum using immunohistochemistry. Furthermore, we have evaluated the contribution of the striatum to D(4) receptor immunoreactivity in these areas by means of ibotenic acid lesion of the striatum. D(4) receptors were observed in the substantia nigra pars reticulata (SNr), the entopeduncular nucleus (EP) and the globus pallidus (GP), and they were found, using electron microscopy, to be located presynaptically. D(4) immunoreactivity in the striatal output nuclei was observed to dramatically decrease following lesion of the striatum with ibotenic acid. Striatal interneurons were not found to express D(4) receptors. These results demonstrate that D(4) receptors are located almost exclusively in striatal projection neurons, in both striatonigral and striatopallidal neurons.
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Affiliation(s)
- Alicia Rivera
- Department of Cell Biology, Campus de Teatinos s/n, University of Málaga, 29071 Málaga, Spain.
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Huang X, Lawler CP, Lewis MM, Nichols DE, Mailman RB. D1 dopamine receptors. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2002; 48:65-139. [PMID: 11526741 DOI: 10.1016/s0074-7742(01)48014-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- X Huang
- Department of Neurology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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Huang Y, Kegeles LS, Bae S, Hwang D, Roth BL, Savage JE, Laruelle M. Synthesis of potent and selective dopamine D4 antagonists as candidate radioligands. Bioorg Med Chem Lett 2001; 11:1375-7. [PMID: 11378358 DOI: 10.1016/s0960-894x(01)00241-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A series of dopamine D(4) antagonists was synthesized and evaluated as potential candidates for development as positron emission tomography (PET) radioligands. All new compounds display high affinity and selectivity for the D(4) receptors and compounds 5b, 5d, and 5e were identified as candidates for radioligand development.
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Affiliation(s)
- Y Huang
- Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
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37
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Swanson J, Posner M, Fusella J, Wasdell M, Sommer T, Fan J. Genes and attention deficit hyperactivity disorder. Curr Psychiatry Rep 2001; 3:92-100. [PMID: 11276403 DOI: 10.1007/s11920-001-0005-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The initial molecular genetic studies of attention deficit hyperactivity disorder (ADHD) evaluated two candidate genes (DAT and DRD4) suggested by dopamine theories of this common disorder and its treatment with stimulant medication. The initial reports of weak associations with ADHD have been replicated by many (but not all) investigators, as is expected for genes with small effects. This literature is reviewed, along with emerging literature generated by active research groups investigating additional genes that might contribute to the genetic basis of this complex disorder.
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Affiliation(s)
- J Swanson
- Child Development Center, University of California at Irvine, 19722 MacArthur Boulevard, Irvine, CA 92612, USA. jmswanso@uci,edu
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38
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Staley JK, Tamagnan G, Baldwin RM, Fujita M, Al Tikriti MS, Eshima L, Thornback J, Roe D, Lu L, Seibyl JP, Innis RB. SPECT imaging with the D(4) receptor antagonist L-750,667 in nonhuman primate brain. Nucl Med Biol 2000; 27:547-56. [PMID: 11056368 DOI: 10.1016/s0969-8051(00)00129-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The suitability of an (123)I-labeled form of the putative D(4) receptor ligand L750,667 as a radiotracer for single photon emission computed tomography imaging was assessed in nonhuman primates. [(123)I]L750,667, labeled by iododestannylation, was administered to baboons in bolus and bolus plus constant infusion paradigms and imaged for 6 h. Total [(123)I]L750,667 brain uptake peaked (2.3% injected dose) at 15 min postinjection. [(123)I]L750,667 uptake was observed in all brain regions measured including diencephalon, brainstem, basal ganglia, cingulate cortex, and cerebellum, and slightly lower levels were noted in the frontal, parietal, temporoinsular, and occipital cortices. Administration of the D(4) receptor antagonist NGD 94-1 (2 mg/kg) did not displace radioactivity from any of the brain regions examined. Thus, while L750,667 is selective for the D(4) receptor in vitro, because brain [(123)I]L750,667 uptake was not displaced by NGD 94-1 at receptor saturating doses, [(123)I]L750,667 does not appear to be a suitable radiotracer for in vivo imaging of the D(4) receptor.
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Affiliation(s)
- J K Staley
- Department of Psychiatry, Yale University School of Medicine & VA Connecticut Healthcare System, West Haven, Connecticut, USA.
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