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Lv S, Yao K, Zhang Y, Zhu S. NMDA receptors as therapeutic targets for depression treatment: Evidence from clinical to basic research. Neuropharmacology 2023; 225:109378. [PMID: 36539011 DOI: 10.1016/j.neuropharm.2022.109378] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/08/2022] [Accepted: 12/11/2022] [Indexed: 12/23/2022]
Abstract
Ketamine, functioning as a channel blocker of the excitatory glutamate-gated N-methyl-d-aspartate (NMDA) receptors, displays compelling fast-acting and sustained antidepressant effects for treatment-resistant depression. Over the past decades, clinical and preclinical studies have implied that the pathology of depression is associated with dysfunction of glutamatergic transmission. In particular, the discovery of antidepressant agents modulating NMDA receptor function has prompted breakthroughs for depression treatment compared with conventional antidepressants targeting the monoaminergic system. In this review, we first summarized the signalling pathway of the ketamine-mediated antidepressant effects, based on the glutamate hypothesis of depression. Second, we reviewed the hypotheses of the synaptic mechanism and network of ketamine antidepressant effects within different brain areas and distinct subcellular localizations, including NMDA receptor antagonism on GABAergic interneurons, extrasynaptic and synaptic NMDA receptor-mediated antagonism, and ketamine blocking bursting activities in the lateral habenula. Third, we reviewed the different roles of NMDA receptor subunits in ketamine-mediated cognitive and psychiatric behaviours in genetically-manipulated rodent models. Finally, we summarized the structural basis of NMDA receptor channel blockers and discussed NMDA receptor modulators that have been reported to exert potential antidepressant effects in animal models or in clinical trials. Integrating the cutting-edge technologies of cryo-EM and artificial intelligence-based drug design (AIDD), we expect that the next generation of first-in-class rapid antidepressants targeting NMDA receptors would be an emerging direction for depression therapeutics. This article is part of the Special Issue on 'Ketamine and its Metabolites'.
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Affiliation(s)
- Shiyun Lv
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China; University of Chinese Academy of Sciences, Beijing, China
| | - Kejie Yao
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China; University of Chinese Academy of Sciences, Beijing, China
| | - Youyi Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China; University of Chinese Academy of Sciences, Beijing, China
| | - Shujia Zhu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China; University of Chinese Academy of Sciences, Beijing, China.
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Parras GG, Leal-Campanario R, López-Ramos JC, Gruart A, Delgado-García JM. Functional properties of eyelid conditioned responses and involved brain centers. Front Behav Neurosci 2022; 16:1057251. [PMID: 36570703 PMCID: PMC9780278 DOI: 10.3389/fnbeh.2022.1057251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 11/14/2022] [Indexed: 12/14/2022] Open
Abstract
For almost a century the classical conditioning of nictitating membrane/eyelid responses has been used as an excellent and feasible experimental model to study how the brain organizes the acquisition, storage, and retrieval of new motor abilities in alert behaving mammals, including humans. Lesional, pharmacological, and electrophysiological approaches, and more recently, genetically manipulated animals have shown the involvement of numerous brain areas in this apparently simple example of associative learning. In this regard, the cerebellum (both cortex and nuclei) has received particular attention as a putative site for the acquisition and storage of eyelid conditioned responses, a proposal not fully accepted by all researchers. Indeed, the acquisition of this type of learning implies the activation of many neural processes dealing with the sensorimotor integration and the kinematics of the acquired ability, as well as with the attentional and cognitive aspects also involved in this process. Here, we address specifically the functional roles of three brain structures (red nucleus, cerebellar interpositus nucleus, and motor cortex) mainly involved in the acquisition and performance of eyelid conditioned responses and three other brain structures (hippocampus, medial prefrontal cortex, and claustrum) related to non-motor aspects of the acquisition process. The main conclusion is that the acquisition of this motor ability results from the contribution of many cortical and subcortical brain structures each one involved in specific (motor and cognitive) aspects of the learning process.
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Repeated Galvanic Vestibular Stimulation Modified the Neuronal Potential in the Vestibular Nucleus. Neural Plast 2020; 2020:5743972. [PMID: 32565777 PMCID: PMC7273393 DOI: 10.1155/2020/5743972] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 05/02/2020] [Indexed: 01/24/2023] Open
Abstract
Vestibular nucleus (VN) and cerebellar flocculus are known as the core candidates for the neuroplasticity of vestibular system. However, it has been still elusive how to induce the artificial neuroplasticity, especially caused by an electrical stimulation, and assess the neuronal information related with the plasticity. To understand the electrically induced neuroplasticity, the neuronal potentials in VN responding to the repeated electrical stimuli were examined. Galvanic vestibular stimulation (GVS) was applied to excite the neurons in VN, and their activities were measured by an extracellular neural recording technique. Thirty-eight neuronal responses (17 for the regular and 21 for irregular neurons) were recorded and examined the potentials before and after stimulation. Two-third of the population (63.2%, 24/38) modified the potentials under the GVS repetition before stimulation (p = 0.037), and more than half of the population (21/38, 55.3%) changed the potentials after stimulation (p = 0.209). On the other hand, the plasticity-related neuronal modulation was hardly observed in the temporal responses of the neurons. The modification of the active glutamate receptors was also investigated to see if the repeated stimulation changed the number of both types of glutamate receptors, and the results showed that AMPA and NMDA receptors decreased after the repeated stimuli by 28.32 and 16.09%, respectively, implying the modification in the neuronal amplitudes.
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A method for combining multiple-units readout of optogenetic control with natural stimulation-evoked eyeblink conditioning in freely-moving mice. Sci Rep 2019; 9:1857. [PMID: 30755637 PMCID: PMC6372581 DOI: 10.1038/s41598-018-37885-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 12/12/2018] [Indexed: 01/20/2023] Open
Abstract
A growing pool of transgenic mice expressing Cre-recombinases, together with Cre-dependent opsin viruses, provide good tools to manipulate specific neural circuits related to eyeblink conditioning (EBC). However, currently available methods do not enable to get fast and precise readout of optogenetic control when the freely-moving mice are receiving EBC training. In the current study, we describe a laser diode (LD)-optical fiber (OF)-Tetrode assembly that allows for simultaneous multiple units recording and optical stimulation. Since the numbers of various cables that require to be connected are minimized, the LD-OF-Tetrode assembly can be combined with CS-US delivery apparatus for revealing the effects of optical stimulation on EBC in freely- moving mice. Moreover, this combination of techniques can be utilized to optogenetically intervene in hippocampal neuronal activities during the post-conditioning sleep in a closed-loop manner. This novel device thus enhances our ability to explore how specific neuronal assembly contributes to associative motor memory in vivo.
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5
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van Lier B, Hierlemann A, Knoflach F. Parvalbumin expression and gamma oscillation occurrence increase over time in a neurodevelopmental model of NMDA receptor dysfunction. PeerJ 2018; 6:e5543. [PMID: 30258707 PMCID: PMC6151115 DOI: 10.7717/peerj.5543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 08/07/2018] [Indexed: 11/20/2022] Open
Abstract
Dysfunction of the N-methyl-d-aspartate receptor (NMDAR) is thought to play a role in the pathophysiology of neurodevelopmental diseases like schizophrenia. To study the effects of NMDAR dysfunction on synaptic transmission and network oscillations, we used hippocampal tissue of NMDAR subunit GluN2A knockout (KO) mice. Field excitatory postsynaptic potentials were recorded in acute hippocampal slices of adult animals. Synaptic transmission was impaired in GluN2A KO slices compared to wild-type (WT) slices. Further, to investigate whether NMDAR dysfunction would alter neurodevelopment in vitro, we used organotypic hippocampal slice cultures of WT and GluN2A KO mice. Immunostaining performed with cultures kept two, seven, 14, 25 days in vitro (DIV) revealed an increasing expression of parvalbumin (PV) over time. As a functional readout, oscillatory activity induced by the cholinergic agonist carbachol was recorded in cultures kept seven, 13, and 26 DIV using microelectrode arrays. Initial analysis focused on the occurrence of delta, theta, beta and gamma oscillations over genotype, DIV and hippocampal area (CA1, CA3, dentate gyrus (DG)). In a follow-up analysis, we studied the peak frequency and the peak power of each of the four oscillation bands per condition. The occurrence of gamma oscillations displayed an increase by DIV similar to the PV immunostaining. Unlike gamma occurrence, delta, theta, and beta occurrence did not change over time in culture. The peak frequency and peak power in the different bands of the oscillations were not different in slices of WT and GluN2A KO mice. However, the level of PV expression was lower in GluN2A KO compared to WT mice. Given the role of PV-containing fast-spiking basket cells in generation of oscillations and the decreased PV expression in subjects with schizophrenia, the study of gamma oscillations in organotypic hippocampal slices represents a potentially valuable tool for the characterization of novel therapeutic drugs.
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Affiliation(s)
- Ben van Lier
- Neuroscience Discovery, Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland.,Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Andreas Hierlemann
- Department of Biosystems Science and Engineering, ETH Zürich, Basel, Switzerland
| | - Frédéric Knoflach
- Neuroscience Discovery, Pharma Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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Pilkiw M, Takehara-Nishiuchi K. Neural representations of time-linked memory. Neurobiol Learn Mem 2018; 153:57-70. [PMID: 29614377 DOI: 10.1016/j.nlm.2018.03.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 03/29/2018] [Accepted: 03/30/2018] [Indexed: 10/17/2022]
Abstract
Many cognitive processes, such as episodic memory and decision making, rely on the ability to form associations between two events that occur separately in time. The formation of such temporal associations depends on neural representations of three types of information: what has been presented (trace holding), what will follow (temporal expectation), and when the following event will occur (explicit timing). The present review seeks to link these representations with firing patterns of single neurons recorded while rodents and non-human primates associate stimuli, outcomes, and motor responses over time intervals. Across these studies, two distinct firing patterns were observed in the hippocampus, neocortex, and striatum: some neurons change firing rates during or shortly after the stimulus presentation and sustain the firing rate stably or sidlingly during the subsequent intervals (tonic firings). Other neurons transiently change firing rates during a specific moment within the time intervals (phasic firings), and as a group, they form a sequential firing pattern that covers the entire interval. Clever task designs used in some of these studies collectively provide evidence that both tonic and phasic firing responses represent trace holding, temporal expectation, and explicit timing. Subsequently, we applied machine-learning based classification approaches to the two firing patterns within the same dataset collected from rat medial prefrontal cortex during trace eyeblink conditioning. This quantitative analysis revealed that phasic-firing patterns showed greater selectivity for stimulus identity and temporal position than tonic-firing patterns. Our summary illuminates distributed neural representations of temporal association in the forebrain and generates several ideas for future investigations.
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Affiliation(s)
- Maryna Pilkiw
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G3, Canada
| | - Kaori Takehara-Nishiuchi
- Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G3, Canada; Department of Psychology, University of Toronto, Toronto M5S 3G3, Canada; Neuroscience Program, University of Toronto, Toronto M5S 3G3, Canada.
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7
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Delgado-García JM, Gruart A. Learning as a Functional State of the Brain: Studies in Wild-Type and Transgenic Animals. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1015:75-93. [PMID: 29080022 DOI: 10.1007/978-3-319-62817-2_5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Contemporary neuroscientists are paying increasing attention to subcellular, molecular, and electrophysiological mechanisms underlying learning and memory processes. Recent studies have examined the development of transgenic mice affected at different stages of the learning process, or have emulated in animals various human pathological conditions involving cognition and motor learning. However, a parallel effort is needed to develop stimulating and recording techniques suitable for use in behaving mice in order to understand activity-dependent synaptic changes taking place during the very moment of the learning process. The in vivo models should incorporate information collected from different molecular and in vitro approaches. Long-term potentiation (LTP) has been proposed as the neural mechanism underlying synaptic plasticity, and NMDA receptors have been proposed as the molecular substrate of LTP. It now seems necessary to study the relationship of both LTP and NMDA receptors to functional changes in synaptic efficiency taking place during actual learning in selected cerebral cortical structures. Here, we review data collected in our laboratory during the past 10 years on the involvement of different hippocampal synapses in the acquisition of the classically conditioned eyelid responses in behaving mice. Overall the results indicate a specific contribution of each cortical synapse to the acquisition and storage of new motor and cognitive abilities. Available data show that LTP, evoked by high-frequency stimulation of Schaffer collaterals, disturbs both the acquisition of conditioned eyelid responses and the physiological changes that occur at hippocampal synapses during learning. Moreover, the administration of NMDA-receptor antagonists is able not only to prevent LTP induction in vivo, but also to hinder both the formation of conditioned eyelid responses and functional changes in the strength of the CA3-CA1 synapse. Nevertheless, many other neurotransmitter receptors, intracellular mediators, and transcription factors are also involved in learning and memory processes. In summary, it can be proposed that learning and memory in behaving mammals are the result of the activation of complex and distributed functional states involving many different cerebral cortical synapses, with the participation also of various neurotransmitter systems.
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Affiliation(s)
- José M Delgado-García
- Division of Neurosciences, Pablo de Olavide University, Ctra. de Utrera, Km. 1, Seville, 41013, Spain.
| | - Agnès Gruart
- Division of Neurosciences, Pablo de Olavide University, Ctra. de Utrera, Km. 1, Seville, 41013, Spain
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Karthick C, Periyasamy S, Jayachandran KS, Anusuyadevi M. Intrahippocampal Administration of Ibotenic Acid Induced Cholinergic Dysfunction via NR2A/NR2B Expression: Implications of Resveratrol against Alzheimer Disease Pathophysiology. Front Mol Neurosci 2016; 9:28. [PMID: 27199654 PMCID: PMC4844917 DOI: 10.3389/fnmol.2016.00028] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 04/01/2016] [Indexed: 01/27/2023] Open
Abstract
Although several drugs revealed moderate amelioration of symptoms, none of them have sufficient potency to prevent or reverse the progression toward Alzheimer's disease (AD) pathology. Resveratrol (RSV), a polyphenolic compound has shown an outstanding therapeutic effect on a broad spectrum of diseases like age-associated neurodegeneration, inflammation etc. The present study was thus conducted to assess the therapeutic efficacy of RSV in ameliorating the deleterious effects of Ibotenic acid (IBO) in male Wistar rats. Stereotactic intrahippocampal administration of IBO (5 μg/μl) lesioned rats impairs cholinergic transmission, learning and memory performance that is rather related to AD and thus chosen as a suitable model to understand the drug efficacy in preventing AD pathophysiology. Since IBO is an agonist of glutamate, it is expected to exhibit an excitotoxic effect by altering glutamatergic receptors like NMDA receptor. The current study displayed significant alterations in the mRNA expression of NR2A and NR2B subunits of NMDA receptors, and further it is surprising to note that cholinergic receptors decreased in expression particularly α7-nAChR with increased m1AChR. RSV administration (20 mg/kg body weight, i.p.) significantly reduced these changes in IBO induced rats. Glutamatergic and cholinergic receptor alterations were associated with significant changes in the behavioral parameters of rats induced by IBO. While RSV improved spatial learning performance, attenuated immobility, and improvised open field activity in IBO induced rats. NR2B activation in the present study might mediate cell death through oxidative stress that form the basis of abnormal behavioral pattern in IBO induced rats. Interestingly, RSV that could efficiently encounter oxidative stress have significantly decreased stress markers viz., nitrite, PCO, and MDA levels by enhancing antioxidant status. Histopathological analysis displayed significant reduction in the hippocampal pyramidal layer thickness and live neurons in IBO induced rats, with slight pathological changes in the entorhinal cortex (EC) of rat brain, which was prevented on RSV administration. Our study thus concludes that RSV administration significantly ameliorated the deleterious effects in the IBO lesioned rat model for AD by alleviating cholinergic pathways, reducing oxidative stress and thereby improving spatial memory.
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Affiliation(s)
- Chennakesavan Karthick
- Molecular Gerontology Laboratory, Department of Biochemistry (DST-FIST Sponsored), Bharathidasan University Tiruchirappalli, India
| | - Sabapathy Periyasamy
- Molecular Gerontology Laboratory, Department of Biochemistry (DST-FIST Sponsored), Bharathidasan University Tiruchirappalli, India
| | - Kesavan S Jayachandran
- Molecular Cardiology and Drug Discovery Laboratory, Department of Bioinformatics, Bharathidasan University Tiruchirappalli, India
| | - Muthuswamy Anusuyadevi
- Molecular Gerontology Laboratory, Department of Biochemistry (DST-FIST Sponsored), Bharathidasan University Tiruchirappalli, India
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9
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Kishimoto Y, Cagniard B, Yamazaki M, Nakayama J, Sakimura K, Kirino Y, Kano M. Task-specific enhancement of hippocampus-dependent learning in mice deficient in monoacylglycerol lipase, the major hydrolyzing enzyme of the endocannabinoid 2-arachidonoylglycerol. Front Behav Neurosci 2015; 9:134. [PMID: 26082696 PMCID: PMC4451424 DOI: 10.3389/fnbeh.2015.00134] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/11/2015] [Indexed: 12/03/2022] Open
Abstract
Growing evidence indicates that the endocannabinoid system is important for the acquisition and/or extinction of learning and memory. However, it is unclear which endocannabinoid(s) play(s) a crucial role in these cognitive functions, especially memory extinction. To elucidate the physiological role of 2-arachidonoylglycerol (2-AG), a major endocannabinoid, in behavioral and cognitive functions, we conducted a comprehensive behavioral test battery in knockout (KO) mice deficient in monoacylglycerol lipase (MGL), the major hydrolyzing enzyme of 2-AG. We found age-dependent increases in spontaneous physical activity (SPA) in MGL KO mice. Next, we tested the MGL KO mice using 5 hippocampus-dependent learning paradigms (i.e., Morris water maze (MWM), contextual fear conditioning, novel object recognition test, trace eyeblink conditioning, and water-finding test). In the MWM, MGL KO mice showed normal acquisition of reference memory, but exhibited significantly faster extinction of the learned behavior. Moreover, they showed faster memory acquisition on the reversal-learning task of the MWM. In contrast, in the contextual fear conditioning, MGL KO mice tended to show slower memory extinction. In the novel object recognition and water-finding tests, MGL KO mice exhibited enhanced memory acquisition. Trace eyeblink conditioning was not altered in MGL KO mice throughout the acquisition and extinction phases. These results indicate that 2-AG signaling is important for hippocampus-dependent learning and memory, but its contribution is highly task-dependent.
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Affiliation(s)
- Yasushi Kishimoto
- Laboratory of Neurobiophysics, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University Sanuki, Kagawa, Japan
| | - Barbara Cagniard
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo Bunkyo-ku, Tokyo, Japan
| | - Maya Yamazaki
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University Niigata, Japan
| | - Junko Nakayama
- Laboratory of Neurobiophysics, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University Sanuki, Kagawa, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University Niigata, Japan
| | - Yutaka Kirino
- Laboratory of Neurobiophysics, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University Sanuki, Kagawa, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo Bunkyo-ku, Tokyo, Japan
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10
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Gruart A, Leal-Campanario R, López-Ramos JC, Delgado-García JM. Functional basis of associative learning and its relationships with long-term potentiation evoked in the involved neural circuits: Lessons from studies in behaving mammals. Neurobiol Learn Mem 2015; 124:3-18. [PMID: 25916668 DOI: 10.1016/j.nlm.2015.04.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 04/14/2015] [Accepted: 04/15/2015] [Indexed: 12/27/2022]
Abstract
While contemporary neuroscience is paying increasing attention to subcellular and molecular events and other intracellular phenomena underlying the acquisition, storage, and retrieval of newly acquired motor and cognitive abilities, parallel attention should be paid to the study of the electrophysiological phenomena taking place at selected cortical and subcortical neuronal and synaptic sites during the precise moment of learning acquisition, extinction, and recall. These in vivo approaches to the study of learning and memory processes will allow the proper integration of the important information collected from in vitro and delayed molecular studies. Here, we summarize studies in behaving mammals carried out in our laboratory during the past ten years on the relationships between experimentally evoked long-term potentiation (LTP) and activity-dependent changes in synaptic strength taking place in hippocampal, prefrontal and related cortical and subcortical circuits during the acquisition of classical eyeblink conditioning or operant learning tasks. These studies suggest that different hippocampal synapses are selectively modified in strength during the acquisition of classical, but not instrumental, learning tasks. In contrast, selected prefrontal and striatum synapses are more directly modified by operant conditioning. These studies also show that besides N-methyl-D-aspartate (NMDA) receptors, many other neurotransmitter, intracellular mediating, and transcription factors participate in these two types of associative learning. Although experimentally evoked LTP seems to prevent the acquisition of classical eyeblink conditioning when induced at selected hippocampal synapses, it proved to be ineffective in preventing the acquisition of operant conditioned tasks when induced at numerous hippocampal, prefrontal, and striatal sites. The differential roles of these cortical structures during these two types of associative learning are discussed, and a diagrammatic representation of their respective functions is presented.
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Affiliation(s)
- Agnès Gruart
- Division of Neurosciences, Pablo de Olavide University, Seville 41013, Spain.
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11
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Tanninen SE, Yu X, Giritharan T, Tran L, Bakir R, Volle J, Morrissey MD, Takehara-Nishiuchi K. Cholinergic, but not NMDA, receptors in the lateral entorhinal cortex mediate acquisition in trace eyeblink conditioning. Hippocampus 2015; 25:1456-64. [PMID: 25865030 DOI: 10.1002/hipo.22466] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/06/2015] [Indexed: 01/16/2023]
Abstract
Anatomical and electrophysiological studies collectively suggest that the entorhinal cortex consists of several subregions, each of which is involved in the processing of different types of information. Consistent with this idea, we previously reported that the dorsolateral portion of the entorhinal cortex (DLE), but not the caudomedial portion, is necessary for the expression of a memory association between temporally discontiguous stimuli in trace eyeblink conditioning (Morrissey et al. (2012) J Neurosci 32:5356-5361). The present study examined whether memory acquisition depends on the DLE and what types of local neurotransmitter mechanisms are involved in memory acquisition and expression. Male Long-Evans rats experienced trace eyeblink conditioning, in which an auditory conditioned stimulus (CS) was paired with a mildly aversive electric shock to the eyelid (US) with a stimulus-free interval of 500 ms. Immediately before the conditioning, the rats received a microinfusion of neuroreactive substances into the DLE. We found that reversible inactivation of the DLE with GABAA receptor agonist, muscimol impaired memory acquisition. Furthermore, blockade of local muscarinic acetylcholine receptors (mACh) with scopolamine retarded memory acquisition while blockade of local NMDA receptors with APV had no effect. Memory expression was not impaired by either type of receptor blocker. These results suggest that the DLE is necessary for memory acquisition, and that acquisition depends on the integrity of local mACh receptor-dependent firing modulation, but not NMDA receptor-dependent synaptic plasticity.
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Affiliation(s)
| | | | | | - Lina Tran
- Department of Psychology, Toronto, Canada
| | - Rami Bakir
- Department of Psychology, Toronto, Canada
| | | | - Mark D Morrissey
- Department of Psychology, Toronto, Canada.,Neuroscience Program, University of Toronto, Toronto, Canada
| | - Kaori Takehara-Nishiuchi
- Department of Psychology, Toronto, Canada.,Neuroscience Program, University of Toronto, Toronto, Canada.,Department of Cell and Systems Biology, Toronto, Canada
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12
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Role of motor cortex NMDA receptors in learning-dependent synaptic plasticity of behaving mice. Nat Commun 2014; 4:2258. [PMID: 23978820 PMCID: PMC3759079 DOI: 10.1038/ncomms3258] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 07/05/2013] [Indexed: 01/22/2023] Open
Abstract
The primary motor cortex has an important role in the precise execution of learned motor responses. During motor learning, synaptic efficacy between sensory and primary motor cortical neurons is enhanced, possibly involving long-term potentiation and N-methyl-D-aspartate (NMDA)-specific glutamate receptor function. To investigate whether NMDA receptor in the primary motor cortex can act as a coincidence detector for activity-dependent changes in synaptic strength and associative learning, here we generate mice with deletion of the Grin1 gene, encoding the essential NMDA receptor subunit 1 (GluN1), specifically in the primary motor cortex. The loss of NMDA receptor function impairs primary motor cortex long-term potentiation in vivo. Importantly, it impairs the synaptic efficacy between the primary somatosensory and primary motor cortices and significantly reduces classically conditioned eyeblink responses. Furthermore, compared with wild-type littermates, mice lacking primary motor cortex show slower learning in Skinner-box tasks. Thus, primary motor cortex NMDA receptors are necessary for activity-dependent synaptic strengthening and associative learning. Motor cortex NMDA receptors have a key role in the acquisition of associative memories. Hasan et al. generate mice lacking NMDA receptor activity in the motor cortex and find that this impairs LTP, strengthening of synapses between somatosensory and motor cortices, and associative learning.
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13
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Thomas BT, Levy WB. Neuronal dynamics during the learning of trace conditioning in a CA3 model of hippocampal function. Cogn Neurodyn 2014; 8:127-41. [PMID: 24624232 DOI: 10.1007/s11571-013-9271-z] [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: 05/17/2013] [Revised: 09/09/2013] [Accepted: 09/25/2013] [Indexed: 11/26/2022] Open
Abstract
The present article develops quantitative behavioral and neurophysiological predictions for rabbits trained on an air-puff version of the trace-interval classical conditioning paradigm. Using a minimal hippocampal model, consisting of 8,000 primary cells sparsely and randomly interconnected as a model of hippocampal region CA-3, the simulations identify conditions which produce a clear split in the number of trials individual animals should need to learn a criterion response. A trace interval that is difficult to learn, but still learnable by half the experimental population, produces a bimodal population of learners: an early learner group and a late learner group. The model predicts that late learners are characterized by two kinds of CA-3 neuronal activity fluctuations that are not seen in the early learners. As is typical in our minimal hippocampal models, the off-rate constant of the N-methyl-d-aspartate receptor receptor gives a timescale to the model that leads to a temporally quantifiable behavior, the learnable trace interval.
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Affiliation(s)
- Blake T Thomas
- Informed Simplifications, LLC 520 Panorama Road, Earlysville, VA 22936 USA
| | - William B Levy
- Department of Neurosurgery and Psychology, University of Virginia, Charlottesville, VA 22908 USA
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14
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Kishimoto Y, Hirono M, Atarashi R, Sakaguchi S, Yoshioka T, Katamine S, Kirino Y. Age-dependent impairment of eyeblink conditioning in prion protein-deficient mice. PLoS One 2013; 8:e60627. [PMID: 23593266 PMCID: PMC3622692 DOI: 10.1371/journal.pone.0060627] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 02/28/2013] [Indexed: 02/02/2023] Open
Abstract
Mice lacking the prion protein (PrP(C)) gene (Prnp), Ngsk Prnp (0/0) mice, show late-onset cerebellar Purkinje cell (PC) degeneration because of ectopic overexpression of PrP(C)-like protein (PrPLP/Dpl). Because PrP(C) is highly expressed in cerebellar neurons (including PCs and granule cells), it may be involved in cerebellar synaptic function and cerebellar cognitive function. However, no studies have been conducted to investigate the possible involvement of PrP(C) and/or PrPLP/Dpl in cerebellum-dependent discrete motor learning. Therefore, the present cross-sectional study was designed to examine cerebellum-dependent delay eyeblink conditioning in Ngsk Prnp (0/0) mice in adulthood (16, 40, and 60 weeks of age). The aims of the present study were two-fold: (1) to examine the role of PrP(C) and/or PrPLP/Dpl in cerebellum-dependent motor learning and (2) to confirm the age-related deterioration of eyeblink conditioning in Ngsk Prnp (0/0) mice as an animal model of progressive cerebellar degeneration. Ngsk Prnp (0/0) mice aged 16 weeks exhibited intact acquisition of conditioned eyeblink responses (CRs), although the CR timing was altered. The same result was observed in another line of PrP(c)-deficient mice, ZrchI PrnP (0/0) mice. However, at 40 weeks of age, CR incidence impairment was observed in Ngsk Prnp (0/0) mice. Furthermore, Ngsk Prnp (0/0) mice aged 60 weeks showed more significantly impaired CR acquisition than Ngsk Prnp (0/0) mice aged 40 weeks, indicating the temporal correlation between cerebellar PC degeneration and motor learning deficits. Our findings indicate the importance of the cerebellar cortex in delay eyeblink conditioning and suggest an important physiological role of prion protein in cerebellar motor learning.
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Affiliation(s)
- Yasushi Kishimoto
- Laboratory of Neurobiophysics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
| | - Moritoshi Hirono
- Laboratory for Motor Learning Control, RIKEN Brain Science Institute, Wako, Japan
| | - Ryuichiro Atarashi
- Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
| | - Suehiro Sakaguchi
- Division of Molecular Neurobiology, The Institute for Enzyme Research, The University of Tokushima, Tokushima, Japan
| | - Tohru Yoshioka
- Center of Excellence for Environmental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Shigeru Katamine
- Department of Molecular Microbiology and Immunology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan
- Center for International Collaborative Research, Nagasaki University, Nagasaki, Japan
| | - Yutaka Kirino
- Laboratory of Neurobiophysics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan
- * E-mail:
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15
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Engle JR, Barnes CA. Characterizing cognitive aging of associative memory in animal models. Front Aging Neurosci 2012; 4:10. [PMID: 22988435 PMCID: PMC3439635 DOI: 10.3389/fnagi.2012.00010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 05/14/2012] [Indexed: 12/18/2022] Open
Abstract
An overview is provided of the simple single-cue delay and trace eyeblink conditioning paradigms as techniques to assess associative learning and memory in the aged. We highlight and focus this review on the optimization of the parameter space of eyeblink conditioning designs in the aged to avoid and control for potential confounds that may arise when studying aged mammals. The need to examine the contribution of non-associative factors that can contribute to performance outcomes is emphasized, and how age-related changes in the central nervous system as well as peripheral sensory factors can potentially bias the interpretation of the data in the aged is discussed. The way in which slight alterations of the parameter space in the delay and trace eyeblink conditioning paradigms can lead to delayed but intact conditioning, rather than impaired performance in aged animals is also discussed. Overall, the eyeblink conditioning paradigm, when optimized for the age of the animal in the study, is an elegantly simple technique for assessment of associative learning and memory. When design caveats described above are taken into account, this important type of memory, with its well-defined neural substrates, should definitely be included in cognitive assessment batteries for the aged.
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Affiliation(s)
- James R Engle
- Evelyn F. McKnight Brain Institute and ARL Division of Neural Systems, Memory and Aging, University of Arizona Tucson, AZ, USA ; California National Primate Research Center Davis, CA, USA
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16
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A train of electrical pulses applied to the primary auditory cortex evokes a conditioned response in guinea pigs. Neurosci Res 2011; 71:103-6. [DOI: 10.1016/j.neures.2011.05.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 05/19/2011] [Accepted: 05/30/2011] [Indexed: 11/18/2022]
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17
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Fontinha BM, Delgado-García JM, Madroñal N, Ribeiro JA, Sebastião AM, Gruart A. Adenosine A(2A) receptor modulation of hippocampal CA3-CA1 synapse plasticity during associative learning in behaving mice. Neuropsychopharmacology 2009; 34:1865-74. [PMID: 19212319 DOI: 10.1038/npp.2009.8] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Previous in vitro studies have characterized the electrophysiological and molecular signaling pathways of adenosine tonic modulation on long-lasting synaptic plasticity events, particularly for hippocampal long-term potentiation (LTP). However, it remains to be elucidated whether the long-term changes produced by endogenous adenosine in the efficiency of synapses are related to those required for learning and memory formation. Our goal was to understand how endogenous activation of adenosine excitatory A(2A) receptors modulates the associative learning evolution in conscious behaving mice. We have studied here the effects of the application of a highly selective A(2A) receptor antagonist, SCH58261, upon a well-known associative learning paradigm-classical eyeblink conditioning. We used a trace paradigm, with a tone as the conditioned stimulus (CS) and an electric shock presented to the supraorbital nerve as the unconditioned stimulus (US). A single electrical pulse was presented to the Schaffer collateral-commissural pathway to evoke field EPSPs (fEPSPs) in the pyramidal CA1 area during the CS-US interval. In vehicle-injected animals, there was a progressive increase in the percentage of conditioning responses (CRs) and in the slope of fEPSPs through conditioning sessions, an effect that was completely prevented (and lost) in SCH58261 (0.5 mg/kg, i.p.) -injected animals. Moreover, experimentally evoked LTP was impaired in SCH58261-injected mice. In conclusion, the endogenous activation of adenosine A(2A) receptors plays a pivotal effect on the associative learning process and its relevant hippocampal circuits, including activity-dependent changes at the CA3-CA1 synapse.
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Affiliation(s)
- Bruno M Fontinha
- Institute of Pharmacology and Neurosciences, Faculty of Medicine, Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal
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18
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Chaillan FA, Truchet B, Roman FS. Extracellular recordings of rodents in vivo: their contribution to integrative neuroscience. J Integr Neurosci 2008; 7:287-313. [PMID: 18763725 DOI: 10.1142/s0219635208001794] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 04/02/2008] [Indexed: 11/18/2022] Open
Abstract
The prevalent theory in learning and memory processes is that they are underlain by short and long-term changes in synaptic weight, which continuously modulates neural networks during acquisition and recall. This synaptic plasticity has been revealed by recording extracellular field potentials. The enhancement of synaptic transmission was primarily noted in the hippocampus and was named long-term potentiation (LTP). The opposite mechanism, long-term depression (LTD), a reduction of synaptic transmission, was first discovered in the cerebellum. Since then, the LTP-model has been studied mainly using in vitro and acute anesthetized in vivo preparations. This approach has led to remarkable progress in the comprehension of intracellular molecular processes during LTP and LTD. In this review, we focus mainly on what we can learn about molecular events using extracellular field potential recordings with a more ecological model, i.e., studies using the freely behaving animal, with animals that are genetically modified or not, in several behavioral paradigms aimed at gaining insight into some of the conflicting results obtained with in vitro and in vivo preparations.
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Affiliation(s)
- F A Chaillan
- Université Aix-Marseille, Laboratoire de Neurobiologie des Processus Mnésiques, 13331 Marseille cedex 03, France.
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19
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GABAA receptors in deep cerebellar nuclei play important roles in mouse eyeblink conditioning. Brain Res 2008; 1230:125-37. [DOI: 10.1016/j.brainres.2008.06.079] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 04/08/2008] [Accepted: 06/15/2008] [Indexed: 11/19/2022]
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20
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Kina SI, Tezuka T, Kusakawa S, Kishimoto Y, Kakizawa S, Hashimoto K, Ohsugi M, Kiyama Y, Horai R, Sudo K, Kakuta S, Iwakura Y, Iino M, Kano M, Manabe T, Yamamoto T. Involvement of protein-tyrosine phosphatase PTPMEG in motor learning and cerebellar long-term depression. Eur J Neurosci 2008; 26:2269-78. [PMID: 17953619 DOI: 10.1111/j.1460-9568.2007.05829.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Although protein-tyrosine phosphorylation is important for hippocampus-dependent learning, its role in cerebellum-dependent learning remains unclear. We previously found that PTPMEG, a cytoplasmic protein-tyrosine phosphatase expressed in Purkinje cells (PCs), bound to the carboxyl-terminus of the glutamate receptor delta2 via the postsynaptic density-95/discs-large/ZO-1 domain of PTPMEG. In the present study, we generated PTPMEG-knockout (KO) mice, and addressed whether PTPMEG is involved in cerebellar plasticity and cerebellum-dependent learning. The structure of the cerebellum in PTPMEG-KO mice appeared grossly normal. However, we found that PTPMEG-KO mice showed severe impairment in the accelerated rotarod test. These mice also exhibited impairment in rapid acquisition of the cerebellum-dependent delay eyeblink conditioning, in which conditioned stimulus (450-ms tone) and unconditioned stimulus (100-ms periorbital electrical shock) were co-terminated. Moreover, long-term depression at parallel fiber-PC synapses was significantly attenuated in these mice. Developmental elimination of surplus climbing fibers and the physiological properties of excitatory synaptic inputs to PCs appeared normal in PTPMEG-KO mice. These results suggest that tyrosine dephosphorylation events regulated by PTPMEG are important for both motor learning and cerebellar synaptic plasticity.
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Affiliation(s)
- Shin-ichiro Kina
- Division of Oncology, Department of Cancer Biology, Institute of Medical Science, University of Tokyo, Tokyo, 108-8639, Japan
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21
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Gruart A, Delgado-García JM. Activity-dependent changes of the hippocampal CA3-CA1 synapse during the acquisition of associative learning in conscious mice. GENES BRAIN AND BEHAVIOR 2007; 6 Suppl 1:24-31. [PMID: 17543036 DOI: 10.1111/j.1601-183x.2007.00319.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Contemporary neuroscientists are paying increasing attention to subcellular, molecular and electrophysiological mechanisms underlying learning and memory processes. Recent efforts have addressed the development of transgenic mice affected at different stages of the learning process, or emulating pathological conditions involving cognition and motor-learning capabilities. However, a parallel effort is needed to develop stimulating and recording techniques suitable for use in behaving mice, in order to grasp activity-dependent neural changes taking place during the very moment of the process. These in vivo models should integrate the fragmentary information collected by different molecular and in vitro approaches. In this regard, long-term potentiation (LTP) has been proposed as the neural mechanism underlying synaptic plasticity. Moreover, N-methyl-d-aspartate (NMDA) receptors are accepted as the molecular substrate of LTP. It now seems necessary to study the relationship of both LTP and NMDA receptors with the plastic changes taking place, in selected neural structures, during actual learning. Here, we review data on the involvement of the hippocampal CA3-CA1 synapse in the acquisition of classically conditioned eyelid conditioned responses (CRs) in behaving mice. Available data show that LTP, evoked by high-frequency stimulation of Schaffer collaterals, disturbs both the acquisition of CRs and the physiological changes that occur at the CA3-CA1 synapse during learning. Moreover, the administration of NMDA-receptor antagonists is able not only to prevent LTP induction in vivo, but also to hinder the formation of both CRs and functional changes in strength of the CA3-CA1 synapse. Thus, there is experimental evidence relating activity-dependent synaptic changes taking place during actual learning with LTP mechanisms and with the role of NMDA receptors in both processes.
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Affiliation(s)
- A Gruart
- División de Neurociencias, Universidad Pablo de Olavide, Sevilla, Spain.
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22
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Boyce-Rustay JM, Holmes A. Genetic inactivation of the NMDA receptor NR2A subunit has anxiolytic- and antidepressant-like effects in mice. Neuropsychopharmacology 2006; 31:2405-14. [PMID: 16482087 DOI: 10.1038/sj.npp.1301039] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
There is growing evidence implicating the glutamate system in the pathophysiology and treatment of mood and anxiety disorders. Glutamatergic neurotransmission is mediated by several receptor subfamilies including multiple NMDA receptor subunits (NR2A-D). However, little is currently understood about the specific roles of NMDA subunits in the mediation of emotional behavior due to a lack of subunit-specific ligands. In the present study, we employed a mouse gene-targeting approach to examine the role of the NR2A subunit in the mediation of anxiety- and depressive-related behaviors. Results showed that NR2A knockout (KO) mice exhibit decreased anxiety-like behavior relative to wild-type littermates (WT) across multiple tests (elevated plus maze, light-dark exploration test, novel open field). NR2A KO mice showed antidepressant-like profiles in the forced swim test and tail suspension test, as compared to WT controls. Locomotor activity in the nonaversive environments of the home cage or a familiar open field were normal in the NR2A KO mice, as were gross neurological and sensory functions, including prepulse inhibition of startle. Taken together, these data demonstrate a selective and robust reduction in anxiety- and depression-related behavior in NMDA receptor NR2A subunit KO mice. Present results support a role for the NR2A subunit in the modulation of emotional behaviors in rodents and provide insight into the role of glutamate in the pathophysiology and treatment of mood and anxiety disorders.
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Affiliation(s)
- Janel M Boyce-Rustay
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, MD 20892, USA.
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23
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Boyce-Rustay JM, Holmes A. Ethanol-related behaviors in mice lacking the NMDA receptor NR2A subunit. Psychopharmacology (Berl) 2006; 187:455-66. [PMID: 16835771 DOI: 10.1007/s00213-006-0448-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2006] [Accepted: 05/23/2006] [Indexed: 11/24/2022]
Abstract
RATIONALE The ionotropic NMDA glutamate receptor is composed of NR1 and NR2 (NR2A-D) subunits. While there is compelling evidence that NMDA receptors modulate behavioral effects of ethanol, there is little understanding of how the subunit composition of the NMDA receptor mediates these effects. OBJECTIVES In the current study, we assessed the relative roles of NMDA subunits via phenotypic assessment of ethanol-related behaviors in NR2A knockout (KO) mice. RESULTS Results demonstrated that NR2A KO and heterozygous mice failed to show evidence of ethanol-induced conditioned place preference. As compared to wild-type (WT) controls, KO mice showed impaired motor coordination at baseline and, in some instances, following ethanol treatment on the accelerating rotarod, balance beam, and wire-hang tests. By contrast, open field locomotor-stimulant, sedative/hypnotic, and hypothermic responses to ethanol were not different between genotypes, nor was voluntary ethanol consumption and preference in a two-bottle choice paradigm. Blood ethanol concentrations were lower in KO than WT mice following intraperitoneal ethanol injection. CONCLUSIONS Results suggest that the loss of NR2A subunit-containing NMDA receptors impairs the ability to form or express learned reward-related responses to ethanol and causes deficits in motor coordination. However, the loss of NR2A does not alter other measures of acute ethanol intoxication or ethanol consumption, possibly implicating other NMDA subunits in these effects. These data provide novel insight into the role of NMDA receptors in modulating the behavioral effects of ethanol.
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Affiliation(s)
- Janel M Boyce-Rustay
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD 20852, USA.
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24
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Kishimoto Y, Kano M. Endogenous cannabinoid signaling through the CB1 receptor is essential for cerebellum-dependent discrete motor learning. J Neurosci 2006; 26:8829-37. [PMID: 16928872 PMCID: PMC6674369 DOI: 10.1523/jneurosci.1236-06.2006] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 07/03/2006] [Accepted: 07/19/2006] [Indexed: 01/14/2023] Open
Abstract
Cannabinoids exert their psychomotor actions through the CB1 cannabinoid receptor in the brain. Genetic deletion of CB1 in mice causes various symptoms, including changes in locomotor activity, increased ring catalepsy, supraspinal hypoalgesia, and impaired memory extinction. Although the cerebellar cortex contains the highest level of CB1, severe cerebellum-related functional deficits have not been reported in CB1 knock-out mice. To clarify the roles of CB1 in cerebellar function, we subjected CB1 knock-out mice to a delay version of classical eyeblink conditioning. This paradigm is a test for cerebellum-dependent discrete motor learning, in which conditioned stimulus (CS) (352 ms tone) and unconditioned stimulus (US) (100 ms periorbital electrical shock) are coterminated. We found that delay eyeblink conditioning performance was severely impaired in CB1 knock-out mice. In contrast, they exhibited normal performance in a trace version of eyeblink conditioning with 500 ms stimulus-free interval intervened between the CS offset and the US onset. This paradigm is a test for hippocampus-dependent associative learning. Sensitivity of CB1 knock-out mice to CS or US was normal, suggesting that impaired delay eyeblink conditioning is attributable to defects in association of responses to CS and US. We also found that intraperitoneal injection of the CB1 antagonist SR141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole carboxamide] to wild-type mice caused severe impairment in acquisition but not extinction of delay eyeblink conditioning. SR141716A treatment had no effect on trace eyeblink conditioning with a 500 or 750 ms trace interval. These results indicate that endogenous cannabinoid signaling through CB1 is essential for cerebellum-dependent discrete motor learning, especially for its acquisition.
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Affiliation(s)
- Yasushi Kishimoto
- Department of Cellular Neuroscience, Graduate School of Medicine, Osaka University, Suita 565-0871, Japan, and
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8640, Japan
| | - Masanobu Kano
- Department of Cellular Neuroscience, Graduate School of Medicine, Osaka University, Suita 565-0871, Japan, and
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-8640, Japan
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Powell CM, Miyakawa T. Schizophrenia-relevant behavioral testing in rodent models: a uniquely human disorder? Biol Psychiatry 2006; 59:1198-207. [PMID: 16797265 PMCID: PMC3928106 DOI: 10.1016/j.biopsych.2006.05.008] [Citation(s) in RCA: 274] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Revised: 05/08/2006] [Accepted: 05/15/2006] [Indexed: 11/26/2022]
Abstract
Animal models are extremely useful tools in defining pathogenesis and treatment of human disease. Creating adequate animal models of complex neuropsychiatric disorders such as schizophrenia represents a particularly difficult challenge. In the case of schizophrenia, little is certain regarding the etiology or pathophysiology of the human disease. In addition, many symptoms of the disorder are difficult to measure directly in rodents. These challenges have not daunted neuroscientists who are capitalizing on even subtle overlaps between this uniquely human disorder and rodent behavior. In this perspective, we detail the features of ideal animal models of schizophrenia, the potential utility of such models, and the rodent behaviors used to model certain aspects of schizophrenia. The development of such models will provide critical tools to understand the pathogenesis of schizophrenia and novel insights into therapeutic approaches to this complex disorder.
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Affiliation(s)
- Craig M Powell
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-8813, USA.
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26
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Kishimoto Y, Nakazawa K, Tonegawa S, Kirino Y, Kano M. Hippocampal CA3 NMDA receptors are crucial for adaptive timing of trace eyeblink conditioned response. J Neurosci 2006; 26:1562-70. [PMID: 16452679 PMCID: PMC6675508 DOI: 10.1523/jneurosci.4142-05.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Classical conditioning of the eyeblink reflex is a simple form of associative learning for motor responses. To examine the involvement of hippocampal CA3 NMDA receptors (NRs) in nonspatial associative memory, mice lacking an NR1 subunit selectively in adult CA3 pyramidal cells [CA3-NR1 knock-out (KO) mice] were subjected to eyeblink conditioning paradigms. Mice received paired presentations of an auditory conditioned stimulus (CS) and a periorbital shock unconditioned stimulus (US). With repeated presentation of the CS followed by the US, wild-type mice learned to blink in anticipation of the US before its onset. We first confirmed that wild-type mice require an intact hippocampus in the trace version of eyeblink conditioning in which the CS and US do not overlap, creating a stimulus-free time gap of 500 ms. Under the same condition, CA3-NR1 KO mice successfully acquired conditioned responses (CRs) during the 10 d acquisition sessions, whereas the extinction of CRs was impaired on the first day of extinction sessions. Importantly, CA3-NR1 KO mice were impaired in the formation of an adaptively timed CR during the first five trials in the daily acquisition sessions. The aberrantly timed CR was also observed in the extinction sessions in accordance with the impaired extinction of CRs. These results indicate that CA3-NR1 KO mice are unable to rapidly retrieve adaptive CR timing, suggesting that CA3 NRs play a crucial role in the memory of adaptive CR timing in trace conditioning.
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Burman MA, Starr MJ, Gewirtz JC. Dissociable effects of hippocampus lesions on expression of fear and trace fear conditioning memories in rats. Hippocampus 2006; 16:103-13. [PMID: 16261555 DOI: 10.1002/hipo.20137] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The role of the hippocampus in memory is commonly investigated by comparing fear conditioning paradigms that differ in their reliance on the hippocampus. For example, the dorsal (septal) portion of the hippocampus is involved in trace, but not delay fear conditioning, two Pavlovian paradigms in which only the relative timing of stimulus presentation is varied. However, a growing literature implicates the ventral (temporal) portion of the hippocampus in the expression of fear, irrespective of prior training. The current experiments evaluated the relative contributions of the dorsal and ventral portions of the hippocampus to trace fear conditioning specifically vs. the expression of conditioned fear in general. Lesions restricted to the dorsal hippocampus blocked acquisition of trace fear conditioning. Larger lesions, also including an adjacent portion of the ventral hippocampus, were required to impair retrieval of trace fear conditioning. Delay fear conditioning was not disrupted in either case. In contrast, lesions that encompassed almost the entire dorsal and ventral hippocampus disrupted expression of both trace and delay fear conditioning. The current data suggest distinct roles in fear conditioning for three regions of the hippocampus: the septal zone is required for acquisition of trace fear conditioning, a larger portion of the hippocampus is critical for memory retrieval, and a region including the temporal zone is required for expression of both trace and delay fear conditioning. These findings are consistent with evidence suggesting the neuroanatomical and functional segregation of the hippocampus into three zones along its septal-temporal axis.
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Affiliation(s)
- Michael A Burman
- Department of Psychology, University of Minnesota, Minneapolis, Minnesota, USA
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28
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Gruart A, Muñoz MD, Delgado-García JM. Involvement of the CA3-CA1 synapse in the acquisition of associative learning in behaving mice. J Neurosci 2006; 26:1077-87. [PMID: 16436593 PMCID: PMC6674570 DOI: 10.1523/jneurosci.2834-05.2006] [Citation(s) in RCA: 360] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
One of the brain sites more directly related with learning and memory processes is the hippocampus. We recorded, in conscious mice, the activity-dependent changes taking place at the hippocampal CA3-CA1 synapse during the acquisition, extinction, recall, and reconditioning of an associative task. Mice were classically conditioned to evoke eyelid responses using a trace [conditioned stimuli (CS), tone; unconditioned stimuli (US), shock] paradigm. A single electrical pulse presented to the Schaffer collateral-commissural pathway during the CS-US interval evoked a monosynaptic field EPSP (fEPSP) at ipsilateral CA1 pyramidal cells. The slope of evoked fEPSPs increased across conditioning sessions and decreased during extinction, being linearly related to learning evolution. In contrast, fEPSPs were not modified when evoked in control mice in the absence of a conditioning protocol. Long-term potentiation (LTP) evoked by high-frequency stimulation of Schaffer collaterals prevented acquisition, extinction, recall, or reconditioning, depending on the moment when it was triggered. Learning and memory impairments evoked by LTP induction resulted probably from the functional saturation of the CA3-CA1 synapse, although an additional disturbance of the subsequent information transfer toward postsynaptic circuits cannot be discarded. CGP 39551 [(E)-(+/-)-2-amino-4-methyl-5-phosphono-3-pentenoic acid ethyl ester] (an NMDA antagonist) prevented LTP induction in behaving mice, as well as the acquisition of an eyelid learned response, and the synaptic changes taking place at the CA3-CA1 synapse across conditioning. In conclusion, the responsivity of the CA3-CA1 synapse seems to be modulated during associative learning, and both processes are prevented by experimental LTP or NMDA-receptor inactivation. Our results provide evidence of a relationship between activity-dependent synaptic plasticity and associative learning in behaving mice.
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Affiliation(s)
- Agnès Gruart
- División de Neurociencias, Universidad Pablo de Olavide, 41013 Sevilla, Spain.
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29
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Takehara-Nishiuchi K, Kawahara S, Kirino Y. NMDA receptor-dependent processes in the medial prefrontal cortex are important for acquisition and the early stage of consolidation during trace, but not delay eyeblink conditioning. Learn Mem 2006; 12:606-14. [PMID: 16322362 PMCID: PMC1356179 DOI: 10.1101/lm.5905] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Permanent lesions in the medial prefrontal cortex (mPFC) affect acquisition of conditioned responses (CRs) during trace eyeblink conditioning and retention of remotely acquired CRs. To clarify further roles of the mPFC in this type of learning, we investigated the participation of the mPFC in mnemonic processes both during and after daily conditioning using local microinfusion of the GABA(A) receptor agonist muscimol or the NMDA receptor antagonist APV into the rat mPFC. Muscimol infusions into the mPFC before daily conditioning significantly retarded CR acquisition and reduced CR expression if applied after sufficient learning. APV infusion also impaired acquisition of CRs, but not expression of well-learned CRs. When infusions were made immediately after daily conditioning, acquisition of the CR was partially impaired in both the muscimol and APV infusion groups. In contrast, rats that received muscimol infusions 3 h after daily conditioning exhibited improvement in their CR performance comparable to that of the control group. Both the pre- and post-conditioning infusion of muscimol had no effect on acquisition in the delay paradigm. These results suggest that the mPFC participates in both acquisition of a CR and the early stage of consolidation of memory in trace, but not delay eyeblink conditioning by NMDA receptor-mediated operations.
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Affiliation(s)
- Kaori Takehara-Nishiuchi
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, Japan
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Miyamoto E. Molecular Mechanism of Neuronal Plasticity: Induction and Maintenance of Long-Term Potentiation in the Hippocampus. J Pharmacol Sci 2006; 100:433-42. [PMID: 16799259 DOI: 10.1254/jphs.cpj06007x] [Citation(s) in RCA: 217] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Recent studies have demonstrated that activation of enzymes can be observed in living cells in response to stimulation with neurotransmitters, hormones, growth factors, and so forth. Thus, the activation of enzymes was shown to be closely related to the dynamic states of various cell functions. The development of new experimental methodologies has enabled researchers to study the molecular basis of neuronal plasticity in living cells. In 1973, Bliss and his associates identified the phenomena of long-term potentiation (LTP). Since it was thought to be a model for neuronal plasticity such as learning and memory, its molecular mechanism has been extensively investigated. The mechanism was found to involve a signal transduction cascade that includes release of glutamate, activation of the NMDA glutamate receptors, Ca(2+) entry, and activations of Ca(2+)/calmodulin-dependent protein kinases (CaM kinases) II and IV and mitogen-activated protein kinase (MAPK). Consequently, AMPA glutamate receptors were activated by phosphorylation by CaM kinase II, resulting in an increase of Ca(2+) entry into postsynaptic neurons. Furthermore, activation of CaM kinase IV and MAPK increased phosphorylation of CREB (cyclic AMP response element binding protein) and expression of c-Fos by stimulation of gene expression. These results suggest that LTP induction and maintenance would be models of short- and long-term memory, respectively.
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Affiliation(s)
- Eishichi Miyamoto
- Department of Electrical Engineering and Bioscience, Graduate School of Science and Engineering, Waseda University, Tokyo, Japan.
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Dumas TC. Developmental regulation of cognitive abilities: modified composition of a molecular switch turns on associative learning. Prog Neurobiol 2005; 76:189-211. [PMID: 16181726 DOI: 10.1016/j.pneurobio.2005.08.002] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2005] [Revised: 06/14/2005] [Accepted: 08/09/2005] [Indexed: 01/18/2023]
Abstract
N-methyl-D-aspartate receptors (NMDARs) act as molecular coincidence detectors and allow for association or dissociation between pre- and postsynaptic neurons. NMDA receptors are central to remodeling of synaptic connections during postnatal development and associative learning abilities in adults. The ability to remodel neural networks is altered during postnatal development, possibly due to a change in the composition of NMDARs. That is, as forebrain systems (and cerebellum) develop, synaptic NR2B-containing NMDARs (NR2B-NMDARs) are replaced by NR2A-containing NMDARs (NR2A-NMDARs) and NR2B-NMDARs move to extrasynaptic sites. During the initial phase of the switch, synapses contain both NR2A- and NR2B-NMDARs and both long-term potentiation and long-term depression are enhanced. As NMDAR subunit expression decreases and NR2A-NMDARs come to predominate in the synapse, channel function and synaptic plasticity are reduced, and remodeling ability dissipates. The end result is a balance of plasticity and stability that is optimal for information processing and storage. Associative learning abilities involving different sensory modalities emerge sequentially, in accordance with synaptic maturation in related cortical and underlying brain structures. Thus, developmental alterations in NMDAR composition that occur at different ages in various brain structures may explain the protracted nature of the maturation of various associative learning abilities.
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Affiliation(s)
- Theodore C Dumas
- Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403-1254, USA.
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Hizue M, Pang CH, Yokoyama M. Involvement of N-methyl-D-aspartate-type glutamate receptor epsilon1 and epsilon4 subunits in tonic inflammatory pain and neuropathic pain. Neuroreport 2005; 16:1667-70. [PMID: 16189474 DOI: 10.1097/01.wnr.0000183328.05994.9e] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
N-methyl-D-aspartate receptors play an important role in nociceptive transmissions in various types of pain. In this study, we investigated the pain-related response in mice lacking the N-methyl-D-aspartate-type glutamate receptor epsilon1 or epsilon4 subunit in the formalin test and in the partial sciatic nerve ligation-induced neuropathic pain model. The second tonic inflammatory phase response in the formalin test was significantly reduced in glutamate receptor epsilon1 knockout epsilon1(-/-) mice, but not in glutamate receptor epsilon4(-/-) when compared with wild-type mice. In the partial sciatic nerve ligation model, glutamate receptor epsilon1(-/-) mice exhibited no difference in mechanical allodynia compared with wild-type mice. Glutamate receptor epsilon4(-/-) mice, however, failed to develop allodynia after the nerve ligation. These results suggest that glutamate receptor epsilon1 and epsilon4 subunits are involved in tonic inflammatory pain and neuropathic allodynia, respectively.
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Affiliation(s)
- Masanori Hizue
- Discovery Biology Research, Nagoya Laboratories, Pfizer Global Research and Development, Pfizer Inc., Aichi, Japan.
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Kato Y, Takatsuki K, Kawahara S, Fukunaga S, Mori H, Mishina M, Kirino Y. N-methyl-D-aspartate receptors play important roles in acquisition and expression of the eyeblink conditioned response in glutamate receptor subunit delta2 mutant mice. Neuroscience 2005; 135:1017-23. [PMID: 16165299 DOI: 10.1016/j.neuroscience.2005.07.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2005] [Revised: 07/08/2005] [Accepted: 07/13/2005] [Indexed: 11/15/2022]
Abstract
Classical eyeblink conditioning has been known to depend critically on the cerebellum. Apparently consistent with this, glutamate receptor subunit delta2 null mutant mice, which have serious morphological and functional deficiencies in the cerebellar cortex, are severely impaired in delay paradigm. However, these mutant mice successfully learn in trace paradigm, even in '0-trace paradigm,' in which the unconditioned stimulus starts just after the conditioned stimulus terminates. Our previous studies revealed that the hippocampus and the muscarinic acetylcholine receptors play crucial roles in 0-trace paradigm in glutamate receptor subunit delta2 null mutant mice unlike in wild-type mice, suggesting a large contribution of the forebrain to 0-trace conditioning in this type of mutant mice. In the present study, we investigated the role of N-methyl-D-aspartate receptors in 0-trace eyeblink conditioning in glutamate receptor subunit delta2 null mutant mice. Mice were injected intraperitoneally with the noncompetitive N-methyl-d-aspartate receptor antagonist (+)MK-801 (0.1mg/kg) or saline, and conditioned with 350-ms tone conditioned stimulus followed by 100-ms periorbital shock unconditioned stimulus. Glutamate receptor subunit delta2 null mutant mice that received (+)MK-801 injection exhibited a severe impairment in acquisition of the conditioned response, compared with the saline-injected glutamate receptor subunit delta2 null mutant mice. In contrast, wild-type mice were not impaired in acquisition of 0-trace conditioned response by (+)MK-801 injection. After the injection solution was changed from (+)MK-801 to saline, glutamate receptor subunit delta2 null mutant mice showed a rapid and partial recovery of performance of the conditioned response. On the other hand, when the injection solution was changed from saline to (+)MK-801, glutamate receptor subunit delta2 null mutant mice showed a marked impairment in expression of the pre-acquired conditioned response, whereas impairment of the expression was small in wild-type mice. Injection of (+)MK-801 had no significant effects on spontaneous eyeblink frequency or startle eyeblink frequency to the tone conditioned stimulus in either glutamate receptor subunit delta2 null mutant mice or wild-type mice. These results suggest that N-methyl-D-aspartate receptors play critical roles both in acquisition and expression of the conditioned response in 0-trace eyeblink conditioning in glutamate receptor subunit delta2 null mutant mice.
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Affiliation(s)
- Y Kato
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, and Core Research for Evolution Science and Technology, Japan Science and Technology Agency, Tokyo 113-0033, Japan
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Quinn JJ, Loya F, Ma QD, Fanselow MS. Dorsal hippocampus NMDA receptors differentially mediate trace and contextual fear conditioning. Hippocampus 2005; 15:665-74. [PMID: 15959918 DOI: 10.1002/hipo.20088] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The dorsal hippocampus (DH) is critically involved in the acquisition and expression of trace and contextual fear conditioning. NMDA/glutamate receptor-mediated transmission is thought to be one mechanism mediating the plastic changes that support long-term memories in the DH. However, their precise involvement in acquisition and expression processes has not been defined. To examine this issue, the NMDA receptor antagonist, D,L-2-amino-5-phosphonovaleric acid (APV; 10 microg/microl; 0.5 microl), was infused into the DH prior to conditioning and/or testing, using a trace fear conditioning procedure. All rats were tested for freezing to both tone and context in separate, counterbalanced sessions. The three sessions (1 training and 2 test) were separated by approximately 24 h. Using this design, it was possible to assess the role for DH NMDA receptors in the acquisition versus expression of trace and contextual fear conditioning. APV disrupted acquisition, but not expression, of contextual fear conditioning. By contrast, APV attenuated both acquisition and expression of trace fear memories. Thus, DH NMDA receptors appear to contribute to retrieval of some, but not all, fear memories.
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Affiliation(s)
- Jennifer J Quinn
- Department of Psychology and Brain Research Institute, University of California, Los Angeles, Los Angeles, California, USA.
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Sakamoto T, Takatsuki K, Kawahara S, Kirino Y, Niki H, Mishina M. Role of hippocampal NMDA receptors in trace eyeblink conditioning. Brain Res 2005; 1039:130-6. [PMID: 15781054 DOI: 10.1016/j.brainres.2005.01.068] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2004] [Revised: 01/19/2005] [Accepted: 01/19/2005] [Indexed: 11/29/2022]
Abstract
We examined the effects of acute injections of competitive N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovaleric acid (APV) into the dorsal hippocampus on contextual fear conditioning and classical eyeblink conditioning in C57BL/6 mice. When injected 10 to 40 min before training, APV severely impaired contextual fear conditioning. Thus, APV injection under these conditions was sufficient to suppress hippocampal NMDA receptors. To investigate the role of hippocampal NMDA receptors on eyeblink conditioning, we carried out daily training of mice during 10-40 min after injection of APV. In the delay eyeblink conditioning, in which the unconditioned stimulus (US) is delayed and terminates simultaneously with the conditioned stimulus (CS), APV-injected mice acquired the conditioned responses (CRs) as well as artificial cerebrospinal fluid (aCSF)-injected control mice did. However, in the trace eyeblink conditioning, in which the CS and US were separated by a stimulus-free trace interval of 500 ms, APV-injected mice showed severe impairment in acquisition of the CR. There was no significant difference in pseudo-conditioning between APV- and aCSF-injected mice. These results provide evidence that the NMDA receptor in the dorsal hippocampus is critically involved in acquisition of the CR in long trace eyeblink conditioning.
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Affiliation(s)
- Toshiro Sakamoto
- Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, The University of Tokyo, and SORST, Japan Science and Technology Corporation, Tokyo 113-0033, Japan
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Steuber V, Willshaw D. A biophysical model of synaptic delay learning and temporal pattern recognition in a cerebellar Purkinje cell. J Comput Neurosci 2004; 17:149-64. [PMID: 15306737 DOI: 10.1023/b:jcns.0000037678.26155.b5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
It has been suggested that information in the brain is encoded in temporal spike patterns which are decoded by a combination of time delays and coincidence detection. Here, we show how a multi-compartmental model of a cerebellar Purkinje cell can learn to recognise temporal parallel fibre activity patterns by adapting latencies of calcium responses after activation of metabotropic glutamate receptors (mGluRs). In each compartment of our model, the mGluR signalling cascade is represented by a set of differential equations that reflect the underlying biochemistry. Phosphorylation of the mGluRs changes the concentration of receptors which are available for activation by glutamate and thereby adjusts the time delay between mGluR stimulation and voltage response. The adaptation of a synaptic delay as opposed to a weight represents a novel non-Hebbian learning mechanism that can also implement the adaptive timing of the classically conditioned eye-blink response.
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Affiliation(s)
- Volker Steuber
- Institute for Adaptive and Neural Computation, University of Edinburgh, 5 Forrest Hill, Edinburgh EH1 2QL, Scotland, UK.
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Takehara K, Kawahara S, Munemoto Y, Kuriyama H, Mori H, Mishina M, Kirino Y. The N-methyl-D-aspartate (NMDA)-type glutamate receptor GluRepsilon2 is important for delay and trace eyeblink conditioning in mice. Neurosci Lett 2004; 364:43-7. [PMID: 15193753 DOI: 10.1016/j.neulet.2004.04.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2004] [Revised: 03/30/2004] [Accepted: 04/08/2004] [Indexed: 10/26/2022]
Abstract
It has been proposed that the N-methyl-d-aspartate (NMDA)-type glutamate receptor (GluR) plays an important role in synaptic plasticity, learning, and memory. The four GluRepsilon (NR2) subunits, which constitute NMDA receptors with a GluRzeta (NR1) subunit, differ both in their expression patterns in the brain and in their functional properties. In order to specify the distinct participation of each of these subunits, we focused on the GluRepsilon2 subunits, which are expressed mainly in the forebrain. We investigated delay and trace eyeblink conditioning in GluRepsilon2 heterozygous mutant mice whose content of GluRepsilon2 protein was decreased to about half of that in wild-type mice. GluRepsilon2 mutant mice exhibited severe impairment of the attained level of conditioned response (CR) in the delay paradigm, for which the cerebellum is essential and modulation by the forebrain has been suggested. Moreover, GluRepsilon2 mutant mice showed no trend toward CR acquisition in the trace paradigm with a trace interval of 500 ms, in which the forebrain is critically involved in successful learning. On the other hand, the reduction of GluRepsilon2 proteins did not disturb any basic sensory and motor functions which might have explained the observed impairment. These results are different from those obtained with GluRepsilon1 null mutant mice, which attain a normal level of the CR but at a slower rate in the delay paradigm, and showed a severe impairment in the trace paradigm. Therefore, the NMDA receptor GluRepsilon2 plays a more critical role than the GluRepsilon1 subunit in classical eyeblink conditioning.
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Affiliation(s)
- Kaori Takehara
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Mori H, Mishina M. Roles of diverse glutamate receptors in brain functions elucidated by subunit-specific and region-specific gene targeting. Life Sci 2004; 74:329-36. [PMID: 14607261 DOI: 10.1016/j.lfs.2003.09.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glutamate receptor (GluR) channels play a major role in fast excitatory synaptic transmission in vertebrate central nervous system. We revealed the molecular diversity of the GluR channel by molecular cloning and investigated their physiological roles by subunit-specific gene targeting. NMDA receptor GluRepsilon1 KO mice showed increase in thresholds for hippocampal long-term potentiation and hippocampus-dependent contextual learning. The mutant mice performed delay eyeblink conditioning, but failed to learn trace eyeblink conditioning. GluRepsilon1 mutant suffered less brain injury after focal cerebral ischemia. NMDA receptor GluRepsilon2 KO mice showed impairment of the whisker-related neural pattern formation and suckling response, and died shortly after birth. Heterozygous (+/-) GluRepsilon2 mutant mice were viable and showed enhanced startle response to acoustic stimuli. GluRdelta2, a member of novel GluR channel subfamily we found by molecular cloning, is selectively expressed in the Purkinje cells of the cerebellum. GluRdelta2 KO mice showed impairments of cerebellar synaptic plasticity and synapse stability. GluRdelta2 KO mice exhibited impairment in delay eyeblink conditioning, but learned normally trace eyeblink conditioning. The phenotypes of NMDA receptor subunits and GluRdelta2 mutant mice suggest that diverse GluR subunits play differential roles in the brain functions.
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Affiliation(s)
- Hisashi Mori
- Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, and SORST, Japan Science and Technology Corporation, Hongo 7-3-1, Tokyo 113-0033, Bunkyo, Japan.
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Locus-specific rescue of GluRepsilon1 NMDA receptors in mutant mice identifies the brain regions important for morphine tolerance and dependence. J Neurosci 2003. [PMID: 12878694 DOI: 10.1523/jneurosci.23-16-06529.2003] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Tolerance and physical dependence caused by chronic treatment of narcotics are good models to study basic neuronal plasticity. Activation of the NMDA subtype of the glutamate receptor has been implicated as an anti-opioid system in the development of morphine analgesic tolerance and dependence. The present study examines the specific role of the epsilon1 subunit of the NMDA receptor using mice lacking the gene encoding epsilon1 subunit of the NMDA receptor (GluRepsilon1-/- mice). GluRepsilon1-/- mice showed significant enhancement and prolongation of morphine anti-nociception, compared with wild-type GluRepsilon1+/+ mice. GluRepsilon1-/- mice also showed a marked loss of the analgesic tolerance after repeated morphine treatments. In C57BL/6J mice treated with chronic morphine after tolerance paradigm, the GluRepsilon1 protein expression significantly increased in periaqueductal gray matter (PAG), ventral tegmental area (VTA) and nucleus accumbens (NAc), but not amygdala or hippocampus. The rescue of GluRepsilon1 protein by electroporation into the PAG and VTA, but not NAc of GluRepsilon1-/- mice significantly reversed morphine analgesic tolerance liability. Similar attempts were also performed in the naloxone-precipitated physical dependence paradigm. GluRepsilon1-/- mice showed marked loss of typical withdrawal abstinence behaviors, and significant enhancement of GluRepsilon1 protein expression was only observed in NAc by chronic morphine treatments after dependence paradigm. The rescue of GluRepsilon1 protein by electroporation into the NAc of GluRepsilon1-/- mice significantly reversed the loss of abstinence behaviors. These findings suggest that GluRepsilon1 has locus-specific roles in the development of morphine analgesic tolerance and physical dependence.
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Abstract
We investigated the trace eyeblink conditioning in decerebrate guinea pigs to elucidate the possible role of the cerebellum and brainstem in this hippocampus-dependent task. A 350-ms tone conditioned stimulus was paired with a 100-ms periorbital shock unconditioned stimulus with a trace interval of either 0, 100, 250 or 500 ms. Decerebrate animals readily acquired the conditioned response with a trace interval of 0 or 100 ms. Even in the paradigm with a 500-ms trace interval, which is known to depend critically on the hippocampus in all animal species examined, the decerebrate guinea pigs acquired the conditioned response, which had adaptive timing as well as in the other paradigms with a shorter trace interval. However, it took many more trials to learn in the 500-ms trace paradigm than in the shorter trace interval paradigms, and the conditioned response expression was unstable from trial to trial. When decerebrate animals were conditioned step by step with a trace interval of 100, 250 and 500 ms, sequentially, they easily acquired the adaptive conditioned response to a 500-ms trace interval. However, the frequency of conditioned responses decreased after the trace interval was shifted from 250 ms to 500 ms, which was not observed after the shift from 100 ms to 250 ms. These results suggest that the cerebellum and brainstem could maintain the 'trace' of the conditioned stimulus and associate it with the unconditioned stimulus even in the 500-ms trace paradigm, but that the forebrain might be required for facilitating and stabilizing the association.
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Affiliation(s)
- Sadaharu Kotani
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Kishimoto Y, Fujimichi R, Araishi K, Kawahara S, Kano M, Aiba A, Kirino Y. mGluR1 in cerebellar Purkinje cells is required for normal association of temporally contiguous stimuli in classical conditioning. Eur J Neurosci 2002; 16:2416-24. [PMID: 12492436 DOI: 10.1046/j.1460-9568.2002.02407.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In metabotropic glutamate receptor-subtype 1 (mGluR1)-null (mGluR1-/-) mice, cerebellar long-term depression (LTD) and several forms of memory are impaired. However, because mGluR1 is expressed in various brain regions in wild-type mice, it has been difficult to identify which type of memory depends on mGluR1 expressed in a given brain region. Furthermore, severe ataxia in mGluR1-/- mice complicated interpretation of the data from non-cerebellum-dependent tasks. We have generated mGluR1-rescue mice, which express mGluR1 only in Purkinje cells (PCs) of their cerebellum, by introducing the mGluR1alpha transgene into mGluR1-/- mice under the control of a PC-specific promoter. The mGluR1-rescue mouse has normal LTD and displays no apparent ataxia. Therefore, this mouse is the first animal model in which effects of mGluR1 deficiency outside PCs can be studied without cerebellar dysfunction. We used three eyeblink conditioning paradigms with different temporal specificities between conditioned stimulus (CS) and unconditioned stimulus (US). Delay conditioning, in which CS and US coterminate, was impaired in mGluR1-/- mice but normal in mGluR1-rescue mice. However, both strains of mice displayed severe impairment in trace conditionings, in which a stimulus-free interval of 250 or 500 ms intervened between CS and US. We also examined social transmission of food-preference and novel-object-recognition memory tests. In these tasks, mGluR1-rescue mice showed normal short-term but impaired long-term memory. We conclude that mGluR1 in PCs is indispensable for normal learning of association of temporally contiguous stimuli in associative conditioning. In contrast, mGluR1 in other cell types is required for associating discontiguous stimuli and long-term memory formation in nonspatial hippocampus-dependent learning.
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Affiliation(s)
- Yasushi Kishimoto
- Department of Cellular Neurophysiology, Graduate School of Medical Science, Kanazawa University, 13-1, Takaramachi, Kanazawa 920-8640, Japan
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Takehara K, Kawahara S, Takatsuki K, Kirino Y. Time-limited role of the hippocampus in the memory for trace eyeblink conditioning in mice. Brain Res 2002; 951:183-90. [PMID: 12270496 DOI: 10.1016/s0006-8993(02)03159-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We examined the role of the hippocampus in memory retention after trace eyeblink conditioning in mice. After establishing the conditioned response (CR) in the trace paradigm, mice received a bilateral aspiration of the dorsal hippocampus and its overlying neocortex on the next day (1-day group) or after 4 weeks (4-week group). Control mice received a neocortical aspiration on the same schedule as the hippocampal-lesion group. After 2 weeks of recovery, these groups received additional conditioning for 3 days. Frequency of the CR of the 1-day group was as low as spontaneous values on the first day in the post-lesion session and never reached pre-surgical level during the post-lesion sessions, while that of the control group did reach pre-surgical level during the post-lesion sessions although there was a transient decline just after lesion. In contrast to the 1-day group, the 4-week-hippocampal lesion group retained the CR and showed a further increase, without significant difference from the control group. The temporal pattern of the CR also was unchanged by the hippocampal lesion 4 weeks after learning. These results suggest a time-limited role for the hippocampus in memory retention after trace conditioning in mice: the CR acquired recently requires an intact hippocampus for its retention, but the CR acquired remotely does not. This is similar to the result reported in rabbits. Therefore, the mechanism and time course of memory consolidation after trace eyeblink conditioning may be similar in mice and rabbits.
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Affiliation(s)
- Kaori Takehara
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
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Sakamoto T, Mishina M, Niki H. Mutation of NMDA receptor subunit epsilon 1: effects on audiogenic-like seizures induced by electrical stimulation of the inferior colliculus in mice. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 102:113-7. [PMID: 12191501 DOI: 10.1016/s0169-328x(02)00189-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It has been shown that the N-methyl-D-asparate (NMDA) receptor in the inferior colliculus is involved in the induction of audiogenic seizures (AGS). In the present study we examined audiogenic-like seizure susceptibility in GluR epsilon 1 null KO adult mice (n=32) and wild-type adult mice (n=28) by electrically stimulating the inferior colliculus (IC). Threshold current intensities of the GluR epsilon 1 KO mice for wild running, clonic and tonic seizures were higher than those of wild-type mice. In addition, the incidence rates of each seizure syndrome in GluR epsilon 1 KO mice were lower than in wild-type mice at each current intensity. These results show that GluR epsilon 1 KO mice were more resistant to audiogenic-like seizures induced by stimulating the IC. Thus, our findings suggest that the GluR epsilon 1 subunit plays an important role in regulating AGS.
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Affiliation(s)
- Toshiro Sakamoto
- Laboratory for Neurobiology of Emotion, Brain Science Institute (BSI), RIKEN, Wako-city, Saitama, Japan.
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Kishimoto Y, Kawahara S, Fujimichi R, Mori H, Mishina M, Kirino Y. Impairment of eyeblink conditioning in GluRdelta2-mutant mice depends on the temporal overlap between conditioned and unconditioned stimuli. Eur J Neurosci 2001; 14:1515-21. [PMID: 11722613 DOI: 10.1046/j.0953-816x.2001.01772.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mice lacking the glutamate receptor subunit delta2 (GluRdelta2) are deficient in cerebellar long-term depression (LTD) at the parallel fibre-Purkinje cell synapses. We conducted delay and trace eyeblink conditioning with these mice, using various temporal intervals between the conditioned stimulus (CS) and unconditioned stimulus (US). During trace conditioning in which a stimulus-free trace interval (TI) of 250, 100 or 50 ms intervened between the 352-ms tone CS and 100-ms US, GluRdelta2-mutant mice learned as successfully as wild-type mice. Even in the paradigm with TI = 0 ms, in which the end of CS and onset of US are simultaneous, there was no difference between the GluRdelta2-mutant and wild-type mice in their acquisition of a conditioned response. However, in the delay paradigm in which the 452-ms CS overlapped temporally with the coterminating 100-ms US, GluRdelta2-mutant mice exhibited severe learning impairment. The present study together with our previous work [Kishimoto, Y., Kawahara, S., Suzuki, M., Mori, H., Mishina, M. & Kirino, Y. (2001) Eur. J. Neurosci., 13, 1249-1254], indicates that cerebellar LTD-independent learning is possible in paradigms without temporal overlap between the CS and US. On the other hand, GluRdelta2 and cerebellar LTD are essential for learning when there is CS-US temporal overlap, suggesting that the cerebellar neural substrates underlying eyeblink conditioning may change, depending on the temporal overlap of the CS and US.
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Affiliation(s)
- Y Kishimoto
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
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46
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Kishimoto Y, Suzuki M, Kawahara S, Kirino Y. Age-dependent impairment of delay and trace eyeblink conditioning in mice. Neuroreport 2001; 12:3349-52. [PMID: 11711884 DOI: 10.1097/00001756-200110290-00040] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The age effect on classical eyeblink conditioning in unrestrained mice (C57BL/6J strain) was evaluated. Mice were trained at one of three age periods (8, 45-50 or 85-90 weeks). In the delay paradigm, significant learning deficits were evident in the 85-90 week-old group, but no deficits were observed in the behavior of the 45-50 week-old group. On the other hand, in the trace paradigm with a stimulus-free trace interval of 500 ms, significant deficits became apparent at the age of 45-50 weeks. These results indicate that trace eyeblink conditioning is more susceptible to age-related deterioration of memory in mice than delay eyeblink conditioning.
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Affiliation(s)
- Y Kishimoto
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
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47
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Wainai T, Takeuchi T, Seo N, Mishina M. Regulation of acute nociceptive responses by the NMDA receptor GluRepsilon2 subunit. Neuroreport 2001; 12:3169-72. [PMID: 11711849 DOI: 10.1097/00001756-200110290-00005] [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: 11/25/2022]
Abstract
Heterozygous mice mutant for the NMDA-type glutamate receptor (GluR) epsilon2 subunit with a highly homogeneous genetic background showed exaggerated responses to various acute noxious stimuli in the footshock, tail-flick, hot-plate and tail-pinch tests. Because the noxious stimuli in these behavioral tests were electrical, thermal and mechanical, the reduction of GluRepsilon2 proteins exerted stimulatory effects on acute nociceptive responses across modalities. Previous studies showed that GluRepsilon1 and GluRepsilon4 subunit mutant mice exhibited no alteration in the responses to acute noxious stimuli. Thus, among NMDA receptor subunits, the GluRepsilon2 subunit specifically plays an important role in the regulation of the acute nociceptive responses.
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Affiliation(s)
- T Wainai
- Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, Japan
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Takatsuki K, Kawahara S, Takehara K, Kishimoto Y, Kirino Y. Effects of the noncompetitive NMDA receptor antagonist MK-801 on classical eyeblink conditioning in mice. Neuropharmacology 2001; 41:618-28. [PMID: 11587717 DOI: 10.1016/s0028-3908(01)00113-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
N-methyl-D-aspartate (NMDA) receptors are involved in synaptic plasticity and play a critical role in learning and memory. We investigated the effects of the noncompetitive NMDA receptor antagonist (+)MK-801 on classical eyeblink conditioning of mice, using various interstimulus intervals between the conditioned stimulus (CS) and unconditioned stimulus (US). A tone was used for the CS and a periorbital shock was used for the US. In the delay paradigm, in which the US coterminated with the CS or started immediately after CS offset, the effect of (+)MK-801 (0.1mg/kg, i.p.) was a slight impairment in the acquisition of the conditioned response (CR). During subsequent CS-alone trials, the responses of (+)MK-801-injected mice were extinguished as easily as those of saline-injected mice. In the trace paradigm, (+)MK-801 impaired acquisition of the CR with a trace interval of 250 ms more than it did with a trace interval of 100 ms, and more than in the delay paradigm. (+)MK-801 injected after acquisition of 250-ms trace conditioning did not impair expression or extinction of the CR. These results suggest that NMDA receptors are involved in acquisition of the CR during longer trace interval conditioning more than during shorter trace interval conditioning or delay conditioning, and that their contribution to extinction is much smaller than their contribution to acquisition in mouse eyeblink conditioning.
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Affiliation(s)
- K Takatsuki
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, 113-0033, Tokyo, Japan
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Kishimoto Y, Hirono M, Sugiyama T, Kawahara S, Nakao K, Kishio M, Katsuki M, Yoshioka T, Kirino Y. Impaired delay but normal trace eyeblink conditioning in PLCbeta4 mutant mice. Neuroreport 2001; 12:2919-22. [PMID: 11588603 DOI: 10.1097/00001756-200109170-00033] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To elucidate the functional role of phospholipase Cbeta4 (PLCbeta4), which is highly expressed in the Purkinje cells of the rostral cerebellum, cerebellar long-term depression (LTD) and delay and trace eyeblink conditioning were investigated in PLCbeta4-deficient mice. Rostral cerebellar LTD and delay eyeblink conditioning were severely impaired, whereas trace eyeblink conditioning was not. These results indicate that PLCbeta4 is essential for LTD in the rostral cerebellum and delay conditioning, but not trace conditioning. Rostral cerebellar LTD may be required as a neural substrate for delay conditioning, but is not required for trace conditioning.
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Affiliation(s)
- Y Kishimoto
- Laboratory of Neurobiophysics, School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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Abstract
The neurobiology of schizophrenia remains poorly understood. Symptoms of schizophrenia are classically thought to be associated with an imbalance of the dopaminergic system. However, the contribution of other neurotransmitters, in particular glutamate, has been increasingly appreciated. The role of individual components of neurotransmitter systems in aberrant behaviors can be experimentally tested in transgenic animals. Dopamine transporter knockout mice display persistently elevated dopaminergic tone and therefore might be appropriate substrates to evaluate the dopamine hypothesis. Similarly, NMDA receptor-deficient mice can be used to evaluate the glutamate hypothesis of schizophrenia. In this review we discuss how such animal models might be relevant for understanding the neurochemical underpinnings of certain manifestations of schizophrenia.
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Affiliation(s)
- R R Gainetdinov
- Howard Hughes Medical Institute Laboratories, Dept. of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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