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Pulido LN, Pochapski JA, Sugi A, Esaki JY, Stresser JL, Sanchez WN, Baltazar G, Levcik D, Fuentes R, Da Cunha C. Pre-clinical evidence that methylphenidate increases motivation and/or reward preference to search for high value rewards. Behav Brain Res 2023; 437:114065. [PMID: 36037842 DOI: 10.1016/j.bbr.2022.114065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/04/2022] [Accepted: 08/16/2022] [Indexed: 11/25/2022]
Abstract
Methylphenidate is a stimulant used to treat attention deficit and hyperactivity disorder (ADHD). In the last decade, illicit use of methylphenidate has increased among healthy young adults, who consume the drug under the assumption that it will improve cognitive performance. However, the studies that aimed to assess the methylphenidate effects on memory are not consistent. Here, we tested whether the effect of methylphenidate on a spatial memory task can be explained as a motivational and/or a reward effect. We tested the effects of acute and chronic i.p. administration of 0.3, 1 or 3 mg/kg of methylphenidate on motivation, learning and memory by using the 8-arm radial maze task. Adult male Wistar rats learned that 3 of the 8 arms of the maze were consistently baited with 1, 3, or 6 sucrose pellets, and the number of entries and reentries into reinforced and non-reinforced arms of the maze were scored. Neither acute nor chronic (20 days) methylphenidate treatment affected the number of entries in the non-baited arms. However, chronic, but not acute, 1-3 mg/kg methylphenidate increased the number of reentries in the higher reward arms, which suggests a motivational/rewarding effect rather than a working memory deficit. In agreement with this hypothesis, the methylphenidate treatment also decreased the approach latency to the higher reward arms, increased the approach latency to the low reward arm, and increased the time spent in the high, but not low, reward arm. These findings suggest that methylphenidate may act more as a motivational enhancer rather than a cognitive enhancer in healthy people.
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Affiliation(s)
- Laura N Pulido
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil
| | - Jose A Pochapski
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil; Department of Biochemistry, Universidade Federal do Parana, Curitiba, Brazil
| | - Adam Sugi
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil; Department of Biochemistry, Universidade Federal do Parana, Curitiba, Brazil
| | - Julie Y Esaki
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil
| | - Joao L Stresser
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil
| | - William N Sanchez
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil; Department of Biochemistry, Universidade Federal do Parana, Curitiba, Brazil; Integrative Neurobiology Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
| | - Gabriel Baltazar
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil; Department of Biochemistry, Universidade Federal do Parana, Curitiba, Brazil
| | - David Levcik
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Romulo Fuentes
- Departamento de Neurociencias, Facultad de Medicina, Universidad de Chile, Santiago de Chile, Chile
| | - Claudio Da Cunha
- Laboratorio de Fisiologia e Farmacologia do Sistema Nervoso Central, Department of Pharmacology, Universidade Federal do Parana, Curitiba, Brazil; Department of Biochemistry, Universidade Federal do Parana, Curitiba, Brazil.
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2
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Sheynikhovich D, Otani S, Bai J, Arleo A. Long-term memory, synaptic plasticity and dopamine in rodent medial prefrontal cortex: Role in executive functions. Front Behav Neurosci 2023; 16:1068271. [PMID: 36710953 PMCID: PMC9875091 DOI: 10.3389/fnbeh.2022.1068271] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 12/26/2022] [Indexed: 01/12/2023] Open
Abstract
Mnemonic functions, supporting rodent behavior in complex tasks, include both long-term and (short-term) working memory components. While working memory is thought to rely on persistent activity states in an active neural network, long-term memory and synaptic plasticity contribute to the formation of the underlying synaptic structure, determining the range of possible states. Whereas, the implication of working memory in executive functions, mediated by the prefrontal cortex (PFC) in primates and rodents, has been extensively studied, the contribution of long-term memory component to these tasks received little attention. This review summarizes available experimental data and theoretical work concerning cellular mechanisms of synaptic plasticity in the medial region of rodent PFC and the link between plasticity, memory and behavior in PFC-dependent tasks. A special attention is devoted to unique properties of dopaminergic modulation of prefrontal synaptic plasticity and its contribution to executive functions.
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Affiliation(s)
- Denis Sheynikhovich
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France,*Correspondence: Denis Sheynikhovich ✉
| | - Satoru Otani
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
| | - Jing Bai
- Institute of Psychiatry and Neuroscience of Paris, INSERM U1266, Paris, France
| | - Angelo Arleo
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, Paris, France
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3
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Caragea VM, Manahan-Vaughan D. Bidirectional Regulation of Hippocampal Synaptic Plasticity and Modulation of Cumulative Spatial Memory by Dopamine D2-Like Receptors. Front Behav Neurosci 2022; 15:803574. [PMID: 35095441 PMCID: PMC8789653 DOI: 10.3389/fnbeh.2021.803574] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/20/2021] [Indexed: 01/11/2023] Open
Abstract
Dopamine is a key factor in the enablement of cognition and hippocampal information processing. Its action in the hippocampus is mediated by D1/D5 and D2-like (D2, D3, D4) receptors. While D1/D5-receptors are well recognized as strong modulators of hippocampal synaptic plasticity and information storage, much less is known about the role of D2-like receptors (D2R) in these processes. Here, we explored to what extent D2R contribute to synaptic plasticity and cumulative spatial memory derived from semantic and episodic-like information storage. In freely behaving adult rats, we also assessed to what extent short and long-term forms of synaptic plasticity are influenced by pharmacological activation or blockade of D2R. Antagonism of D2R by means of intracerebral treatment with remoxipride, completely prevented the expression of both short-term (<1 h) and long-term potentiation (>4 h), as well as the expression of short-term depression (STD, <1 h) in the hippocampal CA1 region. Scrutiny of involvement of D2R in spatial learning revealed that D2R-antagonism prevented retention of a semantic spatial memory task, and also significantly impaired retention of recent spatiotemporal aspects of an episodic-like memory task. Taken together, these findings indicate that D2R are required for bidirectional synaptic plasticity in the hippocampal CA1 region. Furthermore, they are critically involved in enabling cumulative and episodic-like forms of spatial learning.
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Affiliation(s)
- Violeta-Maria Caragea
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
- International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
| | - Denise Manahan-Vaughan
- Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany
- International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany
- *Correspondence: Denise Manahan-Vaughan
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4
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Espadas I, Ortiz O, García-Sanz P, Sanz-Magro A, Alberquilla S, Solis O, Delgado-García JM, Gruart A, Moratalla R. Dopamine D2R is Required for Hippocampal-dependent Memory and Plasticity at the CA3-CA1 Synapse. Cereb Cortex 2021; 31:2187-2204. [PMID: 33264389 PMCID: PMC7945019 DOI: 10.1093/cercor/bhaa354] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/04/2020] [Accepted: 10/23/2020] [Indexed: 12/24/2022] Open
Abstract
Dopamine receptors play an important role in motivational, emotional, and motor responses. In addition, growing evidence suggests a key role of hippocampal dopamine receptors in learning and memory. It is well known that associative learning and synaptic plasticity of CA3-CA1 requires the dopamine D1 receptor (D1R). However, the specific role of the dopamine D2 receptor (D2R) on memory-related neuroplasticity processes is still undefined. Here, by using two models of D2R loss, D2R knockout mice (Drd2-/-) and mice with intrahippocampal injections of Drd2-small interfering RNA (Drd2-siRNA), we aimed to investigate how D2R is involved in learning and memory as well as in long-term potentiation of the hippocampus. Our studies revealed that the genetic inactivation of D2R impaired the spatial memory, associative learning, and the classical conditioning of eyelid responses. Similarly, deletion of D2R reduced the activity-dependent synaptic plasticity in the hippocampal CA1-CA3 synapse. Our results demonstrate the first direct evidence that D2R is essential in behaving mice for trace eye blink conditioning and associated changes in hippocampal synaptic strength. Taken together, these results indicate a key role of D2R in regulating hippocampal plasticity changes and, in consequence, acquisition and consolidation of spatial and associative forms of memory.
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Affiliation(s)
- Isabel Espadas
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | - Oscar Ortiz
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | - Patricia García-Sanz
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | - Adrián Sanz-Magro
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | - Samuel Alberquilla
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | - Oscar Solis
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
| | | | - Agnès Gruart
- División de Neurociencias, Univ. Pablo de Olavide, Sevilla 41013, Spain
| | - Rosario Moratalla
- Neurobiologia Funcional y de Sistemas, Instituto Cajal, CSIC, Madrid 28002, Spain
- CIBERNED, ISCIII, Madrid 28002, Spain
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Nasehi M, Hasanvand S, Khakpai F, Zarrindast MR. The effect of CA1 dopaminergic system on amnesia induced by harmane in mice. Acta Neurol Belg 2019; 119:369-377. [PMID: 29767374 DOI: 10.1007/s13760-018-0926-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/16/2018] [Indexed: 12/28/2022]
Abstract
In the present study, the effects of bilateral injections of dopaminergic drugs into the hippocampal CA1 regions (intra-CA1) on harmane-induced amnesia were examined in mice. We used a single-trial step-down inhibitory avoidance task for the assessment of memory acquisition in adult male mice. Our data indicated that pre-training intra-peritoneal (i.p.) administration of harmane (12 mg/kg) impaired memory acquisition. Moreover, intra-CA1 administration of dopamine D1 receptor agonist, SKF38393 (0.25 µg/mouse), dopamine D1 receptor antagonist, SCH23390 (0.25 µg/mouse), dopamine D2 receptor agonist, quinpirole (0.125 and 0.25 µg/mouse) and dopamine D2 receptor antagonist, sulpiride (0.2 and 0.4 µg/mouse) decreased the learning of a single-trial inhibitory avoidance task. Furthermore, pre-training intra-CA1 injection of sub-threshold doses of SKF38393 (0.0625 µg/mouse) or sulpiride (0.1 µg/mouse) increased pre-training harmane (4 and 8 mg/kg, i.p.)-induced amnesia. On the other hand, pre-training intra-CA1 injection of a sub-threshold dose of SCH23390 (0.0625 µg/mouse) reversed amnesia induced by an effective dose of harmane (12 mg/kg; i.p.). In addition, Pre-training intra-CA1 injection of quinpirole (0.0625 µg/mouse) had no effect on memory impairment induced by harmane. These findings indicate the involvement of CA1 dopaminergic system on harmane-induced impairment of memory acquisition.
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6
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Lima BFC, Ramos DC, Barbiero JK, Pulido L, Redgrave P, Robinson DL, Gómez-A A, Da Cunha C. Partial lesion of dopamine neurons of rat substantia nigra impairs conditioned place aversion but spares conditioned place preference. Neuroscience 2017; 349:264-277. [PMID: 28279753 DOI: 10.1016/j.neuroscience.2017.02.052] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 02/24/2017] [Accepted: 02/26/2017] [Indexed: 12/27/2022]
Abstract
Midbrain dopamine neurons play critical roles in reward- and aversion-driven associative learning. However, it is not clear whether they do this by a common mechanism or by separate mechanisms that can be dissociated. In the present study we addressed this question by testing whether a partial lesion of the dopamine neurons of the rat SNc has comparable effects on conditioned place preference (CPP) learning and conditioned place aversion (CPA) learning. Partial lesions of dopamine neurons in the rat substantia nigra pars compacta (SNc) induced by bilateral intranigral infusion of 6-hydroxydopamine (6-OHDA, 3μg/side) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 200μg/side) impaired learning of conditioned place aversion (CPA) without affecting conditioned place preference (CPP) learning. Control experiments demonstrated that these lesions did not impair motor performance and did not alter the hedonic value of the sucrose and quinine. The number of dopamine neurons in the caudal part of the SNc positively correlated with the CPP scores of the 6-OHDA rats and negatively correlated with CPA scores of the SHAM rats. In addition, the CPA scores of the 6-OHDA rats positively correlated with the tissue content of striatal dopamine. Insomuch as reward-driven learning depends on an increase in dopamine release by nigral neurons, these findings show that this mechanism is functional even in rats with a partial lesion of the SNc. On the other hand, if aversion-driven learning depends on a reduction of extracellular dopamine in the striatum, the present study suggests that this mechanism is no longer functional after the partial SNc lesion.
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Affiliation(s)
- Bernardo F C Lima
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil
| | - Daniele C Ramos
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil
| | - Janaína K Barbiero
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil
| | - Laura Pulido
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil
| | | | - Donita L Robinson
- Department of Psychiatry and Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC 27599-7178, USA
| | - Alexander Gómez-A
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil
| | - Claudio Da Cunha
- Departamento de Farmacologia, Universidade Federal do Paraná, Curitiba 81.530-980, PR, Brazil.
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7
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André MAE, Manahan-Vaughan D. Involvement of Dopamine D1/D5 and D2 Receptors in Context-Dependent Extinction Learning and Memory Reinstatement. Front Behav Neurosci 2016; 9:372. [PMID: 26834599 PMCID: PMC4720788 DOI: 10.3389/fnbeh.2015.00372] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 12/24/2015] [Indexed: 01/01/2023] Open
Abstract
Dopamine contributes to the regulation of higher order information processing and executive control. It is important for memory consolidation processes, and for the adaptation of learned responses based on experience. In line with this, under aversive learning conditions, application of dopamine receptor antagonists prior to extinction result in enhanced memory reinstatement. Here, we investigated the contribution of the dopaminergic system to extinction and memory reinstatement (renewal) of an appetitive spatial learning task in rodents. Rats were trained for 3 days in a T-maze (context "A") to associate a goal arm with a food reward, despite low reward probability (acquisition phase). On day 4, extinction learning (unrewarded) occurred, that was reinforced by a context change ("B"). On day 5, re-exposure to the (unrewarded) "A" context took place (renewal of context "A", followed by extinction of context "A"). In control animals, significant extinction occurred on day 4, that was followed by an initial memory reinstatement (renewal) on day 5, that was, in turn, succeeded by extinction of renewal. Intracerebral treatment with a D1/D5-receptor antagonist prior to the extinction trials, elicited a potent enhancement of extinction in context "B". By contrast, a D1/D5-agonist impaired renewal in context "A". Extinction in the "A" context on day 5 was unaffected by the D1/D5-ligands. Treatment with a D2-receptor antagonist prior to extinction had no overall effect on extinction in context "B" or renewal in context "A", although extinction of the renewal effect was impaired on day 5, compared to controls. Taken together, these data suggest that dopamine acting on the D1/D5-receptor modulates both acquisition and consolidation of context-dependent extinction. By contrast, the D2-receptor may contribute to context-independent aspects of this kind of extinction learning.
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Affiliation(s)
- Marion Agnès Emma André
- Medical Faculty, Department of Neurophysiology, Ruhr University BochumBochum, Germany; International Graduate School for Neuroscience, Ruhr University BochumBochum, Germany
| | - Denise Manahan-Vaughan
- Medical Faculty, Department of Neurophysiology, Ruhr University BochumBochum, Germany; International Graduate School for Neuroscience, Ruhr University BochumBochum, Germany
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Narayanan SN, Kumar RS, Karun KM, Nayak SB, Bhat PG. Possible cause for altered spatial cognition of prepubescent rats exposed to chronic radiofrequency electromagnetic radiation. Metab Brain Dis 2015; 30:1193-206. [PMID: 26033310 DOI: 10.1007/s11011-015-9689-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/22/2015] [Indexed: 12/11/2022]
Abstract
The effects of chronic and repeated radiofrequency electromagnetic radiation (RFEMR) exposure on spatial cognition and hippocampal architecture were investigated in prepubescent rats. Four weeks old male Wistar rats were exposed to RF-EMR (900 MHz; SAR-1.15 W/kg with peak power density of 146.60 μW/cm(2)) for 1 h/day, for 28 days. Followed by this, spatial cognition was evaluated by Morris water maze test. To evaluate the hippocampal morphology; H&E staining, cresyl violet staining, and Golgi-Cox staining were performed on hippocampal sections. CA3 pyramidal neuron morphology and surviving neuron count (in CA3 region) were studied using H&E and cresyl violet stained sections. Dendritic arborization pattern of CA3 pyramidal neuron was investigated by concentric circle method. Progressive learning abilities were found to be decreased in RF-EMR exposed rats. Memory retention test performed 24 h after the last training revealed minor spatial memory deficit in RF-EMR exposed group. However, RF-EMR exposed rats exhibited poor spatial memory retention when tested 48 h after the final trial. Hirano bodies and Granulovacuolar bodies were absent in the CA3 pyramidal neurons of different groups studied. Nevertheless, RF-EMR exposure affected the viable cell count in dorsal hippocampal CA3 region. RF-EMR exposure influenced dendritic arborization pattern of both apical and basal dendritic trees in RF-EMR exposed rats. Structural changes found in the hippocampus of RF-EMR exposed rats could be one of the possible reasons for altered cognition.
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Affiliation(s)
- Sareesh Naduvil Narayanan
- Department of Physiology, Melaka Manipal Medical College (Manipal Campus), Manipal University, Manipal, 576104, India,
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Ciruela F, Jacobson KA, Fernández-Dueñas V. Portraying G protein-coupled receptors with fluorescent ligands. ACS Chem Biol 2014; 9:1918-28. [PMID: 25010291 PMCID: PMC4168789 DOI: 10.1021/cb5004042] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
![]()
The
thermodynamics of ligand–receptor interactions at the
surface of living cells represents a fundamental aspect of G protein-coupled
receptor (GPCR) biology; thus, its detailed elucidation constitutes
a challenge for modern pharmacology. Interestingly, fluorescent ligands
have been developed for a variety of GPCRs in order to monitor ligand–receptor
binding in living cells. Accordingly, new methodological strategies
derived from noninvasive fluorescence-based approaches, especially
fluorescence resonance energy transfer (FRET), have been successfully
developed to characterize ligand–receptor interactions. Importantly,
these technologies are supplanting more hazardous and expensive radioactive
binding assays. In addition, FRET-based tools have also become extremely
powerful approaches for visualizing receptor–receptor interactions
(i.e., GPCR oligomerization) in living cells. Thus, by means of the
synthesis of compatible fluorescent ligands these novel techniques
can be implemented to demonstrate the existence of GPCR oligomerization
not only in heterologous systems but also in native tissues. Finally,
there is no doubt that these methodologies would also be relevant
in drug discovery in order to develop new high-throughput screening
approaches or to identify new therapeutic targets. Overall, herein,
we provide a thorough assessment of all technical and biological aspects,
including strengths and weaknesses, of these fluorescence-based methodologies
when applied to the study of GPCR biology at the plasma membrane of
living cells.
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Affiliation(s)
- Francisco Ciruela
- Unitat
de Farmacologia, Departament Patologia i Terapèutica Experimental,
Facultat de Medicina, IDIBELL, Universitat de Barcelona, L’Hospitalet
de Llobregat, 08907 Barcelona, Spain
| | - Kenneth A. Jacobson
- Molecular
Recognition Section, Laboratory of Bioorganic Chemistry, National
Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Víctor Fernández-Dueñas
- Unitat
de Farmacologia, Departament Patologia i Terapèutica Experimental,
Facultat de Medicina, IDIBELL, Universitat de Barcelona, L’Hospitalet
de Llobregat, 08907 Barcelona, Spain
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Dopaminergic control of long-term depression/long-term potentiation threshold in prefrontal cortex. J Neurosci 2013; 33:13914-26. [PMID: 23966711 DOI: 10.1523/jneurosci.0466-13.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Long-term memory in the prefrontal cortex is a necessary component of adaptive executive control and is strongly modulated by dopamine. However, the functional significance of this dopaminergic modulation remains elusive. In vitro experimental results on dopamine-dependent shaping of prefrontal long-term plasticity often appear inconsistent and, altogether, draw a complicated picture. It is also generally difficult to relate these findings to in vivo observations given strong differences between the two experimental conditions. This study presents a unified view of the functional role of dopamine in the prefrontal cortex by framing it within the Bienenstock-Cooper-Munro theory of cortical plasticity. We investigate dopaminergic modulation of long-term plasticity through a multicompartment Hodgkin-Huxley model of a prefrontal pyramidal neuron. Long-term synaptic plasticity in the model is governed by a calcium- and dopamine-dependent learning rule, in which dopamine exerts its action via D1 and D2 dopamine receptors in a concentration-dependent manner. Our results support a novel function of dopamine in the prefrontal cortex, namely that it controls the synaptic modification threshold between long-term depression and potentiation in pyramidal neurons. The proposed theoretical framework explains a wide range of experimental results and provides a link between in vitro and in vivo studies of dopaminergic plasticity modulation. It also suggests that dopamine may constitute a new player in metaplastic and homeostatic processes in the prefrontal cortex.
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11
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Glucocorticoid-induced enhancement of contextual fear memory consolidation in rats: Involvement of D1 receptor activity of hippocampal area CA1. Brain Res 2013; 1524:26-33. [DOI: 10.1016/j.brainres.2013.05.030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 05/01/2013] [Accepted: 05/19/2013] [Indexed: 01/01/2023]
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12
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Evidence that conditioned avoidance responses are reinforced by positive prediction errors signaled by tonic striatal dopamine. Behav Brain Res 2013; 241:112-9. [DOI: 10.1016/j.bbr.2012.06.031] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/23/2012] [Accepted: 06/27/2012] [Indexed: 11/18/2022]
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13
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Chronic haloperidol-induced spatial memory deficits accompany the upregulation of D(1) and D(2) receptors in the caudate putamen of C57BL/6 mouse. Life Sci 2012; 91:322-8. [PMID: 22884478 DOI: 10.1016/j.lfs.2012.07.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 07/03/2012] [Accepted: 07/13/2012] [Indexed: 11/23/2022]
Abstract
AIMS Haloperidol (HAL) is an antipsychotic drug that has high affinities to the dopamine D(2), but low affinities to D(1) receptors in the brain. Of brain regions, caudate putamen (CP) has the highest levels of the D(1) and D(2) receptors. In this study we evaluated the spatial memory of C57BL/6 mice following chronic administration of HAL and measured levels of D(1) and D(2) receptors in specific brain regions, with the hypothesis that the D(1) and D(2) receptors in CP are important players in spatial memory function of the brain. MAIN METHODS C57BL/6 mice received daily intraperitoneal injections of saline or HAL at 1.0 or 2.0mg/kg/day for 3 or 6 weeks. Two days after the last injection, spontaneous alternation of mice in a Y-maze was evaluated to measure their exploratory behavior and spatial working memory. The Morris water maze test was performed to measure their spatial learning and memory. D(1) and D(2) receptors in specific brain regions were measured by Western-blot analysis. KEY FINDINGS HAL treatment for 6 weeks decreased the spontaneous alternation of mice in Y-maze, altered the acquisition process and impaired spatial memory in Morris water maze. The same treatment increased levels of D(1) and D(2) receptors in CP and up-regulated D(2) receptors in the hippocampus, but did not change the receptors in the prefrontal cortex. SIGNIFICANCE These results suggest that the D(1) and D(2) receptors in CP are among the main targets of HAL and the receptors in CP play an important role in spatial learning and memory.
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da Silva WCN, Köhler CC, Radiske A, Cammarota M. D1/D5 dopamine receptors modulate spatial memory formation. Neurobiol Learn Mem 2012; 97:271-5. [PMID: 22266268 DOI: 10.1016/j.nlm.2012.01.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/19/2011] [Accepted: 01/04/2012] [Indexed: 10/14/2022]
Abstract
We investigated the effect of the intra-CA1 administration of the D1/D5 receptor antagonist SCH23390 and the D1/D5 receptor agonist SKF38393 on spatial memory in the water maze. When given immediately, but not 3h after training, SCH23390 hindered long-term spatial memory formation without affecting non-spatial memory or the normal functionality of the hippocampus. On the contrary, post-training infusion of SKF38393 enhanced retention and facilitated the spontaneous recovery of the original spatial preference after reversal learning. Our findings demonstrate that hippocampal D1/D5 receptors play an essential role in spatial memory processing.
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Affiliation(s)
- Weber C N da Silva
- Laboratório de Neuroquímica & Neurofisiologia da Memória, Centro de Memória, Instituto do Cérebro, Pontifícia Universidade Católica de Rio Grande do Sul, Av. Ipiranga, 6690-2nd floor, 90610-000 Porto Alegre, RS, Brazil
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15
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Boschen SL, Wietzikoski EC, Winn P, Cunha CD. The role of nucleus accumbens and dorsolateral striatal D2 receptors in active avoidance conditioning. Neurobiol Learn Mem 2011; 96:254-62. [DOI: 10.1016/j.nlm.2011.05.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 03/30/2011] [Accepted: 05/04/2011] [Indexed: 10/18/2022]
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16
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Mioranzza S, Costa MS, Botton PHS, Ardais AP, Matte VL, Espinosa J, Souza DO, Porciúncula LO. Blockade of adenosine A(1) receptors prevents methylphenidate-induced impairment of object recognition task in adult mice. Prog Neuropsychopharmacol Biol Psychiatry 2011; 35:169-76. [PMID: 21044657 DOI: 10.1016/j.pnpbp.2010.10.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Revised: 10/25/2010] [Accepted: 10/25/2010] [Indexed: 11/18/2022]
Abstract
Methylphenidate (MPH) is the preferred treatment used for attention-deficit/hyperactivity disorder (ADHD). Recently, misuse for MPH due to its apparent cognitive enhancer properties has been reported. Adenosine is a neuromodulator known to exert influence on the dopaminergic neurotransmission, which is the main pharmacological target of MPH. We have reported that an overdosage of MPH up-regulates adenosine A(1) receptors in the frontal cortex, but this receptor was not involved in its anxiolytic effects. In this study, the role of adenosine A(1) receptor was investigated on MPH-induced effects on aversive and recognition memory in adult mice. Adult mice received acute and chronic (15 days) administration of methylphenidate (5mg/kg, i.p.), or an acute overdosage (50mg/kg, i.p) in order to model misuse. Memory was assessed in the inhibitory avoidance and object recognition task. Acute administration 5mg/kg improved whereas 50mg/kg disrupted recognition memory and decreased performance in the inhibitory avoidance task. Chronic administration did not cause any effect on memory, but decreased adenosine A(1) receptors immunocontent in the frontal cortex. The selective adenosine A(1) receptor antagonist, (DPCPX 1mg/kg, i.p.), prevented methylphenidate-triggered recognition memory impairment. Our findings showed that recognition memory rather than aversive memory was differently affected by acute administration at both doses. Memory recognition was fully impaired by the overdosage, suggesting that misuse can be harmful for cognitive functions. The adenosinergic system via A(1) receptors may play a role in the methylphenidate actions probably by interfering with dopamine-enhancing properties of this drug.
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Affiliation(s)
- Sabrina Mioranzza
- Department of Biochemistry, Laboratory of Studies on the Purinergic System, Federal University of Rio Grande do Sul, Health and Basic Sciences Institute, Porto Alegre/RS, Brazil
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17
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Cognitive enhancers: focus on modulatory signaling influencing memory consolidation. Pharmacol Biochem Behav 2011; 99:155-63. [PMID: 21236291 DOI: 10.1016/j.pbb.2010.12.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 12/20/2010] [Accepted: 12/22/2010] [Indexed: 12/24/2022]
Abstract
Biological research has unraveled many of the molecular and cellular mechanisms involved in the formation of long-lasting memory, providing new opportunities for the development of cognitive-enhancing drugs. Studies of drug enhancement of cognition have benefited from the use of pharmacological treatments given after learning, allowing the investigation of mechanisms regulating the consolidation phase of memory. Modulatory systems influencing consolidation processes include stress hormones and several neurotransmitter and neuropeptide systems. Here, we review some of the findings on memory enhancement by drug administration in animal models, and discuss their implications for the development of cognitive enhancers.
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Effect of neuroleptic haloperidol, L-DOPA precursor dopamine, and neurotoxic dopamine analog 6-OHDA on acquisition of conditioned defensive reflex in edible snail. Bull Exp Biol Med 2010; 148:750-3. [PMID: 20396784 DOI: 10.1007/s10517-010-0808-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The effect of neuroleptic haloperidol, a dopamine precursor L-DOPA, and dopamine analog 6-OHDA on the development of conditioned defensive reflex was studied in edible snails. Injection of L-DOPA to intact snails and to snails pretreated with 6-OHDA 2 h before learning session decelerated acquisition of the conditioned reflex and exerted a toxic action. In contrast, injection of 6-OHDA or haloperidol did not affect acquisition of the conditioned reflex.
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19
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NCS-1 in the dentate gyrus promotes exploration, synaptic plasticity, and rapid acquisition of spatial memory. Neuron 2009; 63:643-56. [PMID: 19755107 DOI: 10.1016/j.neuron.2009.08.014] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Revised: 08/21/2009] [Accepted: 08/21/2009] [Indexed: 11/24/2022]
Abstract
The molecular underpinnings of exploration and its link to learning and memory remain poorly understood. Here we show that inducible, modest overexpression of neuronal calcium sensor 1 (Ncs1) selectively in the adult murine dentate gyrus (DG) promotes a specific form of exploratory behavior. The mice also display a selective facilitation of long-term potentiation (LTP) in the medial perforant path and a selective enhancement in rapid-acquisition spatial memory, phenotypes that are reversed by direct application of a cell-permeant peptide (DNIP) designed to interfere with NCS-1 binding to the dopamine type-2 receptor (D2R). Moreover, the DNIP and the D2R-selective antagonist L-741,626 attenuated exploratory behavior, DG LTP, and spatial memory in control mice. These data demonstrate a role for NCS-1 and D2R in DG plasticity and provide insight for understanding how the DG contributes to the origin of exploration and spatial memory acquisition.
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Deguil J, Chavant F, Lafay-Chebassier C, Pérault-Pochat MC, Fauconneau B, Pain S. Neuroprotective effect of PACAP on translational control alteration and cognitive decline in MPTP parkinsonian mice. Neurotox Res 2009; 17:142-55. [PMID: 19626386 DOI: 10.1007/s12640-009-9091-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2008] [Revised: 05/29/2009] [Accepted: 07/08/2009] [Indexed: 02/01/2023]
Abstract
Parkinson's disease (PD) is characterized by a triade of motor symptoms due to the degeneration of nigrostriatal pathway. In addition to these motor impairments, cognitive disturbances have been reported to occur in PD patients in the early stage of the disease. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin widely used to produce experimental models of PD. In a previous work, we showed that MPTP altered the expression of proteins involved in mTOR antiapoptotic and PKR apoptotic pathways of translational control (TC) in neuroblastoma cells. In the present study, the results indicated that a subchronic MPTP intoxication in mice decreased the dopaminergic neuron number, produced an activation of PKR way and an inhibition of mTOR way of TC especially in striatum and frontal cortex associated with a great activation of PKR in hippocampus. Moreover, in parallel to biochemical analysis, the mnesic disturbances induced by MPTP were characterized in C57Bl/6 mice, by testing their performance in three versions of the Morris Water Maze task. Behavioral results showed that the MPTP lesion altered mice learning of a spatial working memory, of a cued version and of a spatial reference memory task in the water maze. Furthermore, we previously demonstrated that the neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) could counteract the MPTP toxicity on TC factors in neuroblastoma cells. Thus, the second objective of our study was to assess the PACAP effect on MPTP-induced TC impairment and cognitive deficit in mice. The pretreatment with PACAP27 by intravenous injections partially protected TH-positive neuron loss induced by MPTP, prevented the MPTP-induced protein synthesis control dysregulation and mnesic impairment of mice. Therefore, our results could indicate that PACAP may be a promising therapeutic agent in Parkinson's disease.
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Affiliation(s)
- Julie Deguil
- Research Group on Brain Aging, GReViC, EA 3808, Pôle de Biologie Santé, University of Poitiers, Poitiers cedex, France
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Halpern CH, Rick JH, Danish SF, Grossman M, Baltuch GH. Cognition following bilateral deep brain stimulation surgery of the subthalamic nucleus for Parkinson's disease. Int J Geriatr Psychiatry 2009; 24:443-51. [PMID: 19016252 DOI: 10.1002/gps.2149] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Parkinson's disease (PD) is a neurodegenerative disorder characterized by significant motor dysfunction and various non-motor disturbances, including cognitive alterations. Deep brain stimulation (DBS) is an increasingly utilized therapeutic option for patients with PD that yields remarkable success in alleviating disabling motor symptoms. DBS has additionally been associated with changes in cognition, yet the evidence is not consistent across studies. The following review sought to provide a clearer understanding of the various cognitive sequelae of bilateral subthalamic nucleus (STN) DBS while taking into account corresponding neuroanatomy and potential confounding variables. DESIGN A literature search was performed using the following inclusion criteria: (1) at least five subjects followed for a mean of at least 3 months after surgery; (2) pre- and postoperative cognitive data using at least one standardized measure; (3) adequate report of study results using means and standard deviations. RESULTS Two recent meta-analyses found mild post-operative impairments in verbal learning and executive function in patients who underwent DBS surgery. However, studies have revealed improved working memory and psychomotor speed in the 'on' vs 'off' stimulation state. A deficit in language may be a consequence of the surgical procedure. CONCLUSIONS While cognitive decline has been observed in some domains, our review of the data suggests that STN DBS is a worthwhile and safe method to treat PD.
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Affiliation(s)
- Casey H Halpern
- Department of Neurosurgery, Neurology and Psychiatry, University of Pennsylvania, Philadelphia, PA, USA
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Tremblay PL, Bedard MA, Levesque M, Chebli M, Parent M, Courtemanche R, Blanchet PJ. Motor sequence learning in primate: role of the D2 receptor in movement chunking during consolidation. Behav Brain Res 2008; 198:231-9. [PMID: 19041898 DOI: 10.1016/j.bbr.2008.11.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 10/29/2008] [Accepted: 11/02/2008] [Indexed: 10/21/2022]
Abstract
Motor learning disturbances have been shown in diseases involving dopamine insufficiency such as Parkinson's disease and schizophrenic patients under antipsychotic drug treatment. In non-human primates, motor learning deficits have also been observed following systemic administration of raclopride, a selective D2-receptor antagonist. These deficits were characterized by persistent fluctuations of performance from trial to trial, and were described as difficulties in consolidating movements following a learning period. Moreover, it has been suggested that these raclopride-induced fluctuations can result from impediments in grouping separate movements into one fluent sequence. In the present study, we explore the hypothesis that such fluctuations during movement consolidation can be prevented through the use of sumanirole - a highly selective D2 agonist - if administered before raclopride. Two monkeys were trained to execute a well known sequence of movements, which was later recalled under three pharmacological conditions: (1) no drug, (2) raclopride, and (3) sumanirole+raclopride. The same three pharmacological conditions were repeated with the two monkeys, trained this time to learn new sequences of movements. Results show that raclopride has no deleterious effect on the well known sequence, nor the sumanirole+raclopride co-administration. However, results on the new sequence to be learned revealed continuous fluctuations of performances in the raclopride condition, but not in the sumanirole+raclopride condition. These fluctuations occurred concurrently with a difficulty in merging separate movement components, known as a "chunking deficit". D2 receptors seem therefore to be involved in the consolidation of new motor skills, and this might involve the chunking of separate movements into integrated motor sequences.
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Fields HL, Hjelmstad GO, Margolis EB, Nicola SM. Ventral tegmental area neurons in learned appetitive behavior and positive reinforcement. Annu Rev Neurosci 2007; 30:289-316. [PMID: 17376009 DOI: 10.1146/annurev.neuro.30.051606.094341] [Citation(s) in RCA: 414] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ventral tegmental area (VTA) neuron firing precedes behaviors elicited by reward-predictive sensory cues and scales with the magnitude and unpredictability of received rewards. These patterns are consistent with roles in the performance of learned appetitive behaviors and in positive reinforcement, respectively. The VTA includes subpopulations of neurons with different afferent connections, neurotransmitter content, and projection targets. Because the VTA and substantia nigra pars compacta are the sole sources of striatal and limbic forebrain dopamine, measurements of dopamine release and manipulations of dopamine function have provided critical evidence supporting a VTA contribution to these functions. However, the VTA also sends GABAergic and glutamatergic projections to the nucleus accumbens and prefrontal cortex. Furthermore, VTA-mediated but dopamine-independent positive reinforcement has been demonstrated. Consequently, identifying the neurotransmitter content and projection target of VTA neurons recorded in vivo will be critical for determining their contribution to learned appetitive behaviors.
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Affiliation(s)
- Howard L Fields
- Ernest Gallo Clinic and Research Center and Wheeler Center for the Neurobiology of Addiction, University of California, San Francisco, Emeryville, California 94608, USA.
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Achat-Mendes C, Anderson KL, Itzhak Y. Impairment in consolidation of learned place preference following dopaminergic neurotoxicity in mice is ameliorated by N-acetylcysteine but not D1 and D2 dopamine receptor agonists. Neuropsychopharmacology 2007; 32:531-41. [PMID: 16760923 DOI: 10.1038/sj.npp.1301119] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Some of the major concerns related to methamphetamine (METH) abuse are the neuronal damage inflicted at dopamine (DA) nerve terminals and the cognitive deficits observed in human METH abusers. We have shown that a high dose of METH selectively depleted dopaminergic markers in striatum, frontal cortex and amygdala of Swiss Webster mice, and impaired learned place preference. In this study, we investigated whether deficits in consolidation of place learning, as a consequence of METH neurotoxicity, underlie the underperformance of cocaine conditioned place preference (CPP). Administration of METH (5 mg/kg x 3) to Swiss Webster mice decreased striatal tyrosine hydroxylase (TH) immunoreactive neurons and significantly increased glial fibrillary acidic protein (GFAP) expression, confirming the neurotoxic potential of METH in mice. This treatment significantly attenuated the establishment of cocaine (15 mg/kg) CPP compared to control. To investigate whether manipulation of the consolidation phase improves learned place preference, mice were trained by cocaine and received daily post-training injections of DA receptor agonists or N-acetylcysteine (NAC). As memory consolidation occurs shortly after training, drugs were administered either immediately or 2 h post-training. Immediate post-training administration of the D1 DA receptor agonist SKF38393 (5, 10, and 20 mg/kg) or the D2 DA receptor agonist quinpirole (0.25, 0.5, and 1.0 mg/kg) did not improve the establishment of CPP following METH neurotoxicity. However, immediate but not delayed NAC administration (50 and 100 mg/kg) enhanced cocaine CPP following METH neurotoxicity and had no effect on control CPP. The levels of the reduced form of glutathione (GSH) in striatum, amygdala, hippocampus and frontal cortex were significantly lower in METH-treated mice compared to control during the period of CPP training. Acute and repeated administration of NAC to METH-treated mice restored the decreased brain GSH but had no effect on controls. Results suggest that METH-induced dopaminergic neurotoxicity is associated with impairment of consolidation of learned place preference, and that this impairment is improved by immediate post-training administration of the glutathione precursor NAC and not by D1 or D2 DA receptor agonists. Restoration of brain glutathione levels immediately post-training may facilitate the consolidation process.
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Affiliation(s)
- Cindy Achat-Mendes
- Department of Psychiatry and Behavioral Sciences, University of Miami School of Medicine, Miami, FL 33136, USA
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25
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Pakdel R, Rashidy-Pour A. Microinjections of the dopamine D2 receptor antagonist sulpiride into the medial prefrontal cortex attenuate glucocorticoid-induced impairment of long-term memory retrieval in rats. Neurobiol Learn Mem 2007; 87:385-90. [PMID: 17118678 DOI: 10.1016/j.nlm.2006.10.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2006] [Revised: 09/30/2006] [Accepted: 10/07/2006] [Indexed: 10/23/2022]
Abstract
We recently reported that blockade of dopamine (DA) D2 receptors attenuated deficits in long-term memory retrieval induced by a systemic injection of corticosterone, but the anatomical sites of such interaction were not known. In this study, we investigated whether the DA D2 receptors located in the medial prefrontal cortex (mPFC) may play a role in the impairing effects of glucocorticoids on the memory retrieval process. Young adult male rats were trained in a one trial inhibitory avoidance task (0.5 mA, 3s footshock). On the retention test given 48 h after training, the latency to re-enter the dark compartment and the time spent in light compartment of the apparatus were recorded. Systemically administered corticosterone (1mg/kg) given to rats 30 min before retention testing impaired their memory retrieval. Bilateral microinjections of the DA D2 receptor antagonist sulpiride (10 or 100 ng/0.5 microl per side) into the mPFC 30 min before corticosterone administration attenuated the glucocorticoid-induced impairment of memory retrieval. Furthermore, applied doses of sulpiride alone were ineffective in modulating memory retrieval. These findings indicate that D2 receptors located in the mPFC play an important role in mediating the impairing effects of glucocorticoids on memory retrieval.
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Affiliation(s)
- Roghayeh Pakdel
- Laboratory of Learning and Memory, Physiological Research Center, Semnan University of Medical Sciences, Semnan, Iran
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Anguiano-Rodríguez PB, Gaytán-Tocavén L, Olvera-Cortés ME. Striatal serotonin depletion facilitates rat egocentric learning via dopamine modulation. Eur J Pharmacol 2007; 556:91-8. [PMID: 17126827 DOI: 10.1016/j.ejphar.2006.10.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 10/16/2006] [Accepted: 10/19/2006] [Indexed: 11/28/2022]
Abstract
Egocentric spatial learning has been defined as the ability to navigate in an environment using only proprioceptive information, thereby performing a motor response based on one's own movement. This form of learning has been associated with the neural memory system, including the striatum body. Cerebral serotonin depletion induces better performance, both in tasks with strong egocentric components and in egocentric navigation in the Morris' maze. Based on this, we propose that the striatal serotonergic depletion must facilitate egocentric learning. Fifteen female Sprague Dawley rats weighing 250-350 g and maintained under standard conditions were chronically implanted with infusion cannulas for bilateral application of drugs into the striatum. The animals were evaluated for egocentric navigation using the Morris' maze, under different conditions: saline solution infusion, serotonin depletion by infusion of 5,7-Dihydroxytryptamine (25 microg of free base solved in 2.5 microl of ascorbic acid 1% in saline solution), infusion of mixed dopamine D(1) and D(2) receptor antagonists (0.5 microl/min during 5 min of mixed spiperone 20 microM and SCH23390 10 microM), or serotonin depletion and dopamine blockade simultaneously. Striatal serotonin depletion facilitated egocentric learning, which was demonstrated as shorter escape latencies and the display of a defined sequence of movements for reaching the platform. The facilitation was not observed under condition of simultaneous dopamine blockade. Striatal serotonin depletion produced a dopamine-dependent facilitation of egocentric learning. A role for serotonin in the inhibition of striatal-mediated learning strategies is proposed.
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Affiliation(s)
- Patricia B Anguiano-Rodríguez
- Laboratorio de Neurofisiología Experimental, Centro de Investigación Biomédica de Michoacán, Instituto Mexicano del Seguro Social, A.P. 7-70, C.P. 58261, Morelia, Mich., México
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27
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El-Ghundi M, O'Dowd BF, George SR. Insights into the Role of Dopamine Receptor Systems in Learning and Memory. Rev Neurosci 2007; 18:37-66. [PMID: 17405450 DOI: 10.1515/revneuro.2007.18.1.37] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
It is well established that learning and memory are complex processes involving and recruiting different brain modulatory neurotransmitter systems. Considerable evidence points to the involvement of dopamine in various aspects of cognition, and interest has been focused on investigating the clinical relevance of dopamine systems to age-related cognitive decline and manifestations of cognitive impairment in schizophrenia, Alzheimer's disease, Parkinson's disease and other neurodegenerative diseases. In the past decade or so, in spite of the molecular cloning of the five dopamine receptor subtypes, their specific roles in brain function remained inconclusive due to the lack of completely selective ligands that could distinguish between the members of the D1-like and D2-like dopamine receptor families. One of the most important advances in the field of dopamine research has been the generation of mutant mouse models permitting evaluation of the dopaminergic system using gene targeting technologies. These mouse models represent an important approach to explore the functional roles of closely related receptor subtypes. In this review, we present and discuss evidence on the role of dopamine receptors in different aspects of learning and memory at the cellular, molecular and behavioral levels. We compare evidence using conventional pharmacological, lesion or electrophysiological studies with results from mice with targeted deletions of different subtypes of dopamine receptor genes. We particularly focus on dopamine D1 and D2 receptors in an effort to delineate their specific roles in various aspects of cognitive function. We provide strong evidence, from our own recent work as well as others, that dopamine is part of the network that plays a very important role in cognitive function, and that although multiple dopamine receptor subtypes contribute to different aspects of learning and memory, the D1 receptor seems to play a more prominent role in mediating plasticity and specific aspects of cognitive function, including spatial learning and memory processes, reversal learning, extinction learning, and incentive learning.
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Affiliation(s)
- Mufida El-Ghundi
- Department of Pharmacology, University of Toronto, Ontario, Canada
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28
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Rezayof A, Motevasseli T, Rassouli Y, Zarrindast MR. Dorsal hippocampal dopamine receptors are involved in mediating ethanol state-dependent memory. Life Sci 2007; 80:285-92. [PMID: 17046026 DOI: 10.1016/j.lfs.2006.09.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2006] [Revised: 09/11/2006] [Accepted: 09/13/2006] [Indexed: 10/24/2022]
Abstract
In the present study, the effects of bilateral injections of dopaminergic agents into the hippocampal CA1 regions (intra-CA1) on ethanol (EtOH) state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice. Pre-training intra-peritoneal (i.p.) administration of EtOH (0.25, 0.5 and 1 g/kg) dose dependently induced impairment of memory retention. Pre-test administration of EtOH (0.5 g/kg)-induced state-dependent retrieval of the memory acquired under pre-training EtOH (0.5 g/kg) influence. Intra-CA1 administration of the dopamine D(1) receptor agonist, SKF 38393 (0.5, 1 and 2 g/mouse) or the dopamine D(2) receptor agonist, quinpirole (0.25, 0.5 and 1 microg/mouse) alone cannot affect memory retention. While, pre-test intra-CA1 injection of SKF 38393 (2 microg/mouse, intra-CA1) or quinpirole (0.25, 0.5 and 1 microg/mouse, intra-CA1) improved pre-training EtOH (0.5 g/kg)-induced retrieval impairment. Moreover, pre-test administration of SKF 38393 (0.5, 1 and 2 microg/mouse, intra-CA1) or quinpirole (0.5 and 1 microg/mouse, intra-CA1) with an ineffective dose of EtOH (0.25 g/kg) significantly restored the retrieval and induced EtOH state-dependent memory. Furthermore, pre-training injection of the dopamine D(1) receptor antagonist, SCH 23390 (4 microg/mouse), but not the dopamine D(2) receptor antagonist, sulpiride, into the CA1 regions suppressed the learning of a single-trial passive avoidance task. Pre-test intra-CA1 injection of SCH 23390 (2 and 4 microg/mouse, intra-CA1) or sulpiride (2.5 and 5 microg/mouse, intra-CA1) 5 min before the administration of EtOH (0.5 g/kg, i.p.) dose dependently inhibited EtOH state-dependent memory. These findings implicate the involvement of a dorsal hippocampal dopaminergic mechanism in EtOH state-dependent memory and also it can be concluded that there may be a cross-state dependency between EtOH and dopamine.
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MESH Headings
- 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine/pharmacology
- Animals
- Avoidance Learning/drug effects
- Central Nervous System Depressants/pharmacology
- Dose-Response Relationship, Drug
- Drug Synergism
- Ethanol/pharmacology
- Hippocampus/drug effects
- Hippocampus/metabolism
- Injections, Intraperitoneal
- Injections, Intraventricular
- Male
- Memory/drug effects
- Mice
- Mice, Inbred Strains
- Quinpirole/pharmacology
- Receptors, Dopamine D1/agonists
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D2/agonists
- Receptors, Dopamine D2/metabolism
- Sulpiride/pharmacology
- Time Factors
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Affiliation(s)
- Ameneh Rezayof
- School of Biology, University College of Science, University of Tehran, Tehran, Iran
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29
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Torrente M, Colomina MT, Domingo JL. Behavioral effects of adult rats concurrently exposed to high doses of oral manganese and restraint stress. Toxicology 2005; 211:59-69. [PMID: 15863248 DOI: 10.1016/j.tox.2005.02.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 02/22/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022]
Abstract
The behavioral effects of concurrent exposure of high doses of manganese (Mn) and restraint stress were assessed in adult rats. Male Sprague-Dawley rats (250-300 g) received 0, 275 and 550 mg/kg/day of Mn in the drinking water for 19 weeks. Each group was divided into two subgroups. Animals in one subgroup were restrained for 2h/day. During the treatment period, food and water intake, and body weight were weekly recorded. At the end of the treatment period, activity levels were monitored in an open-field. Learning was evaluated by a water-maze task during five consecutive days. A trial probe was also conducted to assess the time spent in the platform quadrant. Body weight and food consumption were significantly reduced in the group receiving 550 mg/kg/day of Mn. A two-way analysis of variance (ANOVA) revealed an overall effect of Mn on the total distance traveled. Differences on spatial learning were observed in the acquisition period, in which rats given 550 mg/kg/day of Mn (alone or restrained) were impaired in comparison with the control and the restrained only groups. In the probe trial, there was an impaired retention in the group treated with Mn at 550 mg/kg/day. The results of this investigation in the open-field and water maze suggest that it would be plausible that restraint stress and a high exposure to Mn interact at common neurotransmitter levels but inducing opposite effects.
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Affiliation(s)
- Margarita Torrente
- Laboratory of Toxicology and Environmental Health, School of Medicine, Rovira i Virgili University, 43201 Reus, Spain
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Liu Z, Richmond BJ, Murray EA, Saunders RC, Steenrod S, Stubblefield BK, Montague DM, Ginns EI. DNA targeting of rhinal cortex D2 receptor protein reversibly blocks learning of cues that predict reward. Proc Natl Acad Sci U S A 2004; 101:12336-41. [PMID: 15302926 PMCID: PMC514406 DOI: 10.1073/pnas.0403639101] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2003] [Indexed: 11/18/2022] Open
Abstract
When schedules of several operant trials must be successfully completed to obtain a reward, monkeys quickly learn to adjust their behavioral performance by using visual cues that signal how many trials have been completed and how many remain in the current schedule. Bilateral rhinal (perirhinal and entorhinal) cortex ablations irreversibly prevent this learning. Here, we apply a recombinant DNA technique to investigate the role of dopamine D2 receptor in rhinal cortex for this type of learning. Rhinal cortex was injected with a DNA construct that significantly decreased D2 receptor ligand binding and temporarily produced the same profound learning deficit seen after ablation. However, unlike after ablation, the D2 receptor-targeted, DNA-treated monkeys recovered cue-related learning after 11-19 weeks. Injecting a DNA construct that decreased N-methyl-d-aspartate but not D2 receptor ligand binding did not interfere with learning associations between the cues and the schedules. A second D2 receptor-targeted DNA treatment administered after either recovery from a first D2 receptor-targeted DNA treatment (one monkey), after N-methyl-d-aspartate receptor-targeted DNA treatment (two monkeys), or after a vector control treatment (one monkey) also induced a learning deficit of similar duration. These results suggest that the D2 receptor in primate rhinal cortex is essential for learning to relate the visual cues to the schedules. The specificity of the receptor manipulation reported here suggests that this approach could be generalized in this or other brain pathways to relate molecular mechanisms to cognitive functions.
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Affiliation(s)
- Zheng Liu
- Laboratory of Neuropsychology, Clinical Neuroscience Branch, and Behavioral Endocrinology Branch, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA
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Hälbig TD, Gruber D, Kopp UA, Scherer P, Schneider GH, Trottenberg T, Arnold G, Kupsch A. Subthalamic stimulation differentially modulates declarative and nondeclarative memory. Neuroreport 2004; 15:539-43. [PMID: 15094519 DOI: 10.1097/00001756-200403010-00031] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Declarative memory has been reported to rely on the medial temporal lobe system, whereas non-declarative memory depends on basal ganglia structures. We investigated the functional role of the subthalamic nucleus (STN), a structure closely connected with the basal ganglia for both types of memory. Via deep brain high frequency stimulation (DBS) we manipulated neural activity of the STN in humans. We found that DBS-STN differentially modulated memory performance: declarative memory was impaired, whereas non-declarative memory was improved in the presence of STN-DBS indicating a specific role of the STN in the activation of memory systems.
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Affiliation(s)
- Thomas D Hälbig
- Department of Neurology, Charité-University Medicine Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, D-13353 Berlin, Germany.
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During MJ, Cao L, Zuzga DS, Francis JS, Fitzsimons HL, Jiao X, Bland RJ, Klugmann M, Banks WA, Drucker DJ, Haile CN. Glucagon-like peptide-1 receptor is involved in learning and neuroprotection. Nat Med 2003; 9:1173-9. [PMID: 12925848 DOI: 10.1038/nm919] [Citation(s) in RCA: 626] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2003] [Accepted: 07/29/2003] [Indexed: 11/09/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) is a gut peptide that, together with its receptor, GLP-1R, is expressed in the brain. Here we show that intracerebroventricular (i.c.v.) GLP-1 and [Ser(2)]exendin(1-9) (HSEGTFTSD; homologous to a conserved domain in the glucagon/GLP-1 family) enhance associative and spatial learning through GLP-1R. [Ser(2)]exendin(1-9), but not GLP-1, is also active when administered peripherally. GLP-1R-deficient mice have a phenotype characterized by a learning deficit that is restored after hippocampal Glp1r gene transfer. In addition, rats overexpressing GLP-1R in the hippocampus show improved learning and memory. GLP-1R-deficient mice also have enhanced seizure severity and neuronal injury after kainate administration, with an intermediate phenotype in heterozygotes and phenotypic correction after Glp1r gene transfer in hippocampal somatic cells. Systemic administration of [Ser(2)]exendin(1-9) in wild-type animals prevents kainate-induced apoptosis of hippocampal neurons. Brain GLP-1R represents a promising new target for both cognitive-enhancing and neuroprotective agents.
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Affiliation(s)
- Matthew J During
- Department of Molecular Medicine and Pathology, University of Auckland, Private Bag 92019, Auckland 86716, New Zealand.
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Evidence for the substantia nigra pars compacta as an essential component of a memory system independent of the hippocampal memory system. Neurobiol Learn Mem 2003; 79:236-42. [PMID: 12676522 DOI: 10.1016/s1074-7427(03)00008-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of the present study was to test if the nigrostriatal pathway is an essential component for a water maze cued task learning and if it works independently of the hippocampal memory system. This hypothesis was tested using an animal model of Parkinson's disease in which male Wistar rats were lesioned in the substantia nigra pars compacta (SNc) by the intranigral infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), thus causing a partial depletion of striatal dopamine. SNc-lesioned and sham-operated animals were implanted bilaterally with guide cannulae above the dorsal hippocampus in order to be tested after the administration of 0.4 microl 2% lidocaine or saline into this structure. The animals were tested in a spatial or in a cued version of the water maze, memory tasks previously reported to model hippocampal-dependent spatial/relational and striatal-dependent S-R learning, respectively. Hippocampal inactivation, but not SNc lesion, impaired learning and memory in the spatial version of the water maze. An opposite situation was observed with the cued version. No significant interaction was observed between the SNc lesion and hippocampal inactivation conditions affecting scores in the spatial or in the cued version of the water maze. These results suggest that the nigrostriatal pathway is an essential part of the memory system that processes S-R learning and that it works independently of the hippocampal memory system that processes spatial/relational memories.
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Abstract
It is only recently that a number of studies on synaptic plasticity in the hippocampus and other brain areas have considered that a heterosynaptic modulatory input could be recruited as well as the coincident firing of pre- and post-synaptic neurons. So far, the strongest evidence for such a regulation has been attributed to dopaminergic (DA) systems but other modulatory pathways have also been considered to influence synaptic plasticity. This review will focus on dopamine contribution to synaptic plasticity in different brain areas (hippocampus, striatum and prefrontal cortex) with, for each region, a few lines on the distribution of DA projections and receptors. New insights into the possible mechanisms underlying these plastic changes will be considered. The contribution of various DA systems in certain forms of learning and memory will be reviewed with recent advances supporting the hypothesis of similar cellular mechanisms underlying DA regulation of synaptic plasticity and memory processes in which the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway has a potential role. To summarize, endogenous DA, which depends on the activity patterns of DA midbrain neurons in freely moving animals, appears as a key regulator in specific synaptic changes observed at certain stages of learning and memory and of synaptic plasticity.
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Affiliation(s)
- Thérèse M Jay
- Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, CNRS UMR 8620, Université Paris Sud, Bât. 446, 91405 Orsay, France.
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Rosengarten H, Quartermain D. The effect of chronic treatment with typical and atypical antipsychotics on working memory and jaw movements in three- and eighteen-month-old rats. Prog Neuropsychopharmacol Biol Psychiatry 2002; 26:1047-54. [PMID: 12452525 DOI: 10.1016/s0278-5846(02)00221-x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The effects of chronic treatment with typical and atypical antipsychotics on acquisition, working memory, motor activity, and rat tardive dyskinesia (TD) were studied in 3- and 18-month-old Sprague-Dawley rats. Acquisition and working memory were studied in eight-arm radial mazes. TD liability of antipsychotic drugs (APD) was evaluated in rat model of TD in which spontaneous repetitive jaw movements (RJM) occur during withdrawal from neuroleptic treatment. Motor behavior was assessed using the traverse beam test. D1 and D2 receptor occupancy was determined in the rat brain during treatment with typical and atypical antipsychotics. Chronic administration of clozapine, haloperidol, and risperidone impaired acquisition of the eight-arm radial maze in both young and aging rats while olanzapine had no effect. Retention tests showed that aging rats made more errors than the adults and that the antipsychotics haloperidol and risperidone significantly impaired retention in both age groups. Evaluation of motor behavior revealed that typical and atypical antipsychotics used in comparable doses in young rats had no effect on motor behavior, whereas in aging rats performance was impaired by clozapine, haloperidol, and risperidone but not by olanzapine. RJM responses were increased during washout from haloperidol treatment in young and aging rats whereas olanzapine, clozapine, and risperidone had no effect. D2 receptor occupancy in haloperidol- and risperidone-treated rats was above 70% while olanzapine and clozapine receptor occupancy was below 70%, which is the threshold for the appearance of extrapyramidal syndrome (EPS) and TD.
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Affiliation(s)
- Helen Rosengarten
- Department of Psychiatry, Millhauser Laboratories, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
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Miyoshi E, Wietzikoski S, Camplessei M, Silveira R, Takahashi RN, Da Cunha C. Impaired learning in a spatial working memory version and in a cued version of the water maze in rats with MPTP-induced mesencephalic dopaminergic lesions. Brain Res Bull 2002; 58:41-7. [PMID: 12121811 DOI: 10.1016/s0361-9230(02)00754-2] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A lesion in the substantia nigra pars compacta (SNc) of rats induced by intra-nigral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused specific loss of dopamine and its nonconjugated metabolites in the dorsal striatum and in the prefrontal cortex (PFC), but not in the hippocampus or the ventral striatum (nucleus accumbens). This lesion did not alter the motor performance of the rats or learning of a spatial reference memory task in the water maze but impaired learning of a spatial working memory task and also of a cued version of the water maze. The results are discussed by relating the selective memory deficits observed in these water maze tasks to the PFC, dorsal striatum, and hippocampus. Some parallels between the memory deficits in these SNc-lesioned rats and Parkinson's disease patients are also discussed.
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Affiliation(s)
- Edmar Miyoshi
- Laboratório de Fisiologia e Farmacologia do Sistema Nervoso Central, Departamento de Farmacologia, Universidade Federal do Paraná, C.P.:19.031, 81.531-990 Curitiba PR, Brazil
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Bertrand F, Lehmann O, Galani R, Lazarus C, Jeltsch H, Cassel JC. Effects of MDL 73005 on water-maze performances and locomotor activity in scopolamine-treated rats. Pharmacol Biochem Behav 2001; 68:647-60. [PMID: 11526961 DOI: 10.1016/s0091-3057(01)00448-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The stimulation of 5-HT1A receptors in the raphe or their blockade in the hippocampus can reduce cognitive deficits induced by blockade of muscarinic receptors in the hippocampus. We investigated the effects of MDL 73005 (8-[2-(2,3-dihydro-1,4-benzodioxin-2-ylmethylamino) ethyl]-8-azaspiro[4,5] decane-7,9-dione methyl sulphonate), an agonist at 5-HT1A somatodendritic autoreceptors and an antagonist at postsynaptic 5-HT1A receptors in rats treated systemically with scopolamine. Spatial memory was assessed in a water maze using protocols testing reference and working memory. Home cage locomotor activity was also determined. Working memory and locomotor activity were evaluated before and after para-chlorophenylalanine (pCPA) treatment. Scopolamine produced a weak impairment of reference memory at 0.5 mg/kg, and a more pronounced impairment of working memory at 0.25 and 0.5 mg/kg. MDL 73005 alone (2 mg/kg, i.p.) had no effect, but prevented the memory impairments induced by 0.25 mg/kg of scopolamine. Scopolamine induced hyperlocomotion. MDL 73005 alone did not affect locomotor activity, but exacerbated the hyperlocomotion induced by 0.5 mg/kg of scopolamine. pCPA did not abolish the effects of MDL 73005, suggesting that these effects were not due to an action at presynaptic receptors, or even that they involved receptors other than serotonergic ones (e.g., D2). In conclusion, MDL 73005 is able to antagonise moderate spatial memory dysfunctions induced by systemic muscarinic blockade.
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Affiliation(s)
- F Bertrand
- Laboratoire de Neurosciences Comportementales et Cognitives, Université Louis Pasteur/Centre National de la Recherche Scientifique, Strasbourg, France
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