101
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Wang K, Lin MT, Adelman JP, Maylie J. Distinct Ca2+ sources in dendritic spines of hippocampal CA1 neurons couple to SK and Kv4 channels. Neuron 2014; 81:379-87. [PMID: 24462100 DOI: 10.1016/j.neuron.2013.11.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2013] [Indexed: 10/25/2022]
Abstract
Small conductance Ca(2+)-activated K(+) (SK) channels and voltage-gated A-type Kv4 channels shape dendritic excitatory postsynaptic potentials (EPSPs) in hippocampal CA1 pyramidal neurons. Synaptically evoked Ca(2+) influx through N-methyl-D-aspartate receptors (NMDARs) activates spine SK channels, reducing EPSPs and the associated spine head Ca(2+) transient. However, results using glutamate uncaging implicated Ca(2+) influx through SNX-482-sensitive (SNX-sensitive) Cav2.3 (R-type) Ca(2+) channels as the Ca(2+) source for SK channel activation. The present findings show that, using Schaffer collateral stimulation, the effects of SNX and apamin are not mutually exclusive and SNX increases EPSPs independent of SK channel activity. Dialysis with 1,2-bis(o-aminophenoxy)ethane-N'N'N'-tetraacetic acid (BAPTA), application of 4-Aminopyridine (4-AP), expression of a Kv4.2 dominant negative subunit, and dialysis with a KChIPs antibody occluded the SNX-induced increase of EPSPs. The results suggest two distinct Ca(2+) signaling pathways within dendritic spines that link Ca(2+) influx through NMDARs to SK channels and Ca(2+) influx through R-type Ca(2+) channels to Kv4.2-containing channels.
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Affiliation(s)
- Kang Wang
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Mike T Lin
- Department of Physiology, University of South Alabama, Mobile, AL 36688, USA
| | - John P Adelman
- Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA.
| | - James Maylie
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, OR 97239, USA.
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102
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Muñoz W, Rudy B. Spatiotemporal specificity in cholinergic control of neocortical function. Curr Opin Neurobiol 2014; 26:149-60. [PMID: 24637201 DOI: 10.1016/j.conb.2014.02.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 02/16/2014] [Accepted: 02/19/2014] [Indexed: 01/01/2023]
Abstract
Cholinergic actions are critical for normal cortical cognitive functions. The release of acetylcholine (ACh) in neocortex and the impact of this neuromodulator on cortical computations exhibit remarkable spatiotemporal precision, as required for the regulation of behavioral processes underlying attention and learning. We discuss how the organization of the cholinergic projections to the cortex and their release properties might contribute to this specificity. We also review recent studies suggesting that the modulatory influences of ACh on the properties of cortical neurons can have the necessary temporal dynamic range, emphasizing evidence of powerful interneuron subtype-specific effects. We discuss areas that require further investigation and point to technical advances in molecular and genetic manipulations that promise to make headway in understanding the neural bases of cholinergic modulation of cortical cognitive operations.
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Affiliation(s)
- William Muñoz
- NYU Neuroscience Institute, NYU School of Medicine, Smilow Research Building Sixth Floor, 522 First Ave, NY, NY, 10016, United States
| | - Bernardo Rudy
- NYU Neuroscience Institute, NYU School of Medicine, Smilow Research Building Sixth Floor, 522 First Ave, NY, NY, 10016, United States.
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103
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Kang S, Xu M, Cooper EC, Hoshi N. Channel-anchored protein kinase CK2 and protein phosphatase 1 reciprocally regulate KCNQ2-containing M-channels via phosphorylation of calmodulin. J Biol Chem 2014; 289:11536-11544. [PMID: 24627475 DOI: 10.1074/jbc.m113.528497] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
M-type potassium channels, encoded by the KCNQ family genes (KCNQ2-5), require calmodulin as an essential co-factor. Calmodulin bound to the KCNQ2 subunit regulates channel trafficking and stabilizes channel activity. We demonstrate that phosphorylation of calmodulin by protein kinase CK2 (casein kinase 2) rapidly and reversibly modulated KCNQ2 current. CK2-mediated phosphorylation of calmodulin strengthened its binding to KCNQ2 channel, caused resistance to phosphatidylinositol 4,5-bisphosphate depletion, and increased KCNQ2 current amplitude. Accordingly, application of CK2-selective inhibitors suppressed KCNQ2 current. This suppression was prevented by co-expression of CK2 phosphomimetic calmodulin mutants or pretreatment with a protein phosphatase inhibitor, calyculin A. We also demonstrated that functional CK2 and protein phosphatase 1 (PP1) were selectively tethered to the KCNQ2 subunit. We identified a functional KVXF consensus site for PP1 binding in the N-terminal tail of KCNQ2 subunit: mutation of this site augmented current density. CK2 inhibitor treatment suppressed M-current in rat superior cervical ganglion neurons, an effect negated by overexpression of phosphomimetic calmodulin or pretreatment with calyculin A Furthermore, CK2 inhibition diminished the medium after hyperpolarization by suppressing the M-current. These findings suggest that CK2-mediated phosphorylation of calmodulin regulates the M-current, which is tonically regulated by CK2 and PP1 anchored to the KCNQ2 channel complex.
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Affiliation(s)
- Seungwoo Kang
- Departments of Pharmacology and University of California, Irvine, California 92697
| | - Mingxuan Xu
- Departments of Neurology and Baylor College of Medicine, Houston, Texas 77030
| | - Edward C Cooper
- Departments of Neurology and Baylor College of Medicine, Houston, Texas 77030; Departments of Neuroscience, Baylor College of Medicine, Houston, Texas 77030
| | - Naoto Hoshi
- Departments of Pharmacology and University of California, Irvine, California 92697; Departments of Physiology and Biophysics, University of California, Irvine, California 92697 and.
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104
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Different calcium sources control somatic versus dendritic SK channel activation during action potentials. J Neurosci 2014; 33:19396-405. [PMID: 24336706 DOI: 10.1523/jneurosci.2073-13.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Small-conductance calcium-activated potassium (SK) channels play an important role in regulating neuronal excitability. While SK channels at the soma have long been known to contribute to the medium afterhyperpolarization (mAHP), recent evidence indicates they also regulate NMDA receptor activation in dendritic spines. Here we investigate the activation of SK channels in spines and dendrites of rat cortical pyramidal neurons during action potentials (APs), and compare this to SK channel activation at the soma. Using confocal calcium imaging, we demonstrate that the inhibition of SK channels with apamin results in a location-dependent increase in calcium influx into dendrites and spines during backpropagating APs (average increase, ~40%). This effect was occluded by block of R-type voltage-dependent calcium channels (VDCCs), but not by inhibition of N- or P/Q-type VDCCs, or block of calcium release from intracellular stores. During these experiments, we noticed that the calcium indicator (Oregon Green BAPTA-1) blocked the mAHP. Subsequent experiments using low concentrations of EGTA (1 mm) produced the same result, suggesting that somatic SK channels are not tightly colocalized with their calcium source. Consistent with this idea, all known subtypes of VDCCs except R-type were calcium sources for the apamin-sensitive mAHP at the soma. We conclude that SK channels in spines and dendrites of cortical pyramidal neurons regulate calcium influx during backpropagating APs in a distance-dependent manner, and are tightly coupled to R-type VDCCs. In contrast, SK channels activated by APs at the soma of these neurons are weakly coupled to a variety of VDCCs.
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105
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Park SJ, Ahn YJ, Oh SR, Lee Y, Kwon G, Woo H, Lee HE, Jang DS, Jung JW, Ryu JH. Amyrin Attenuates Scopolamine-Induced Cognitive Impairment in Mice. Biol Pharm Bull 2014; 37:1207-13. [DOI: 10.1248/bpb.b14-00113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Se Jin Park
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Young Je Ahn
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Sa Rang Oh
- College of Pharmacy, Keimyung University
| | - Younghwan Lee
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Guyoung Kwon
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Hyun Woo
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Hyung Eun Lee
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
| | - Dae Sik Jang
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
- Department of Pharmaceutical Science, College of Pharmacy, Kyung Hee University
| | - Ji Wook Jung
- Department of Herbal Medicinal Pharmacology, College of Herbal Bio-industry, Daegu Haany University
| | - Jong Hoon Ryu
- Department of Life and Nanopharmaceutical Science, Kyung Hee University
- Department of Oriental Pharmaceutical Science, College of Pharmacy, Kyung Hee University
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106
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Persistent sodium current drives conditional pacemaking in CA1 pyramidal neurons under muscarinic stimulation. J Neurosci 2013; 33:15011-21. [PMID: 24048831 DOI: 10.1523/jneurosci.0577-13.2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hippocampal CA1 pyramidal neurons are normally quiescent but can fire spontaneously when stimulated by muscarinic agonists. In brain slice recordings from mouse CA1 pyramidal neurons, we examined the ionic basis of this activity using interleaved current-clamp and voltage-clamp experiments. Both in control and after muscarinic stimulation, the steady-state current-voltage curve was dominated by inward TTX-sensitive persistent sodium current (I(NaP)) that activated near -75 mV and increased steeply with depolarization. In control, total membrane current was net outward (hyperpolarizing) near -70 mV so that cells had a stable resting potential. Muscarinic stimulation activated a small nonselective cation current so that total membrane current near -70 mV shifted to become barely net inward (depolarizing). The small depolarization triggers regenerative activation of I(NaP), which then depolarizes the cell from -70 mV to spike threshold. We quantified the relative contributions of I(NaP), hyperpolarization-activated cation current (I(h)), and calcium current to pacemaking by using the cell's own firing as a voltage command along with specific blockers. TTX-sensitive sodium current was substantial throughout the entire interspike interval, increasing as the membrane potential approached threshold, while both Ih and calcium current were minimal. Thus, spontaneous activity is driven primarily by activation of I(NaP) in a positive feedback loop starting near -70 mV and providing increasing inward current to threshold. These results show that the pacemaking "engine" from I(NaP) is an inherent property of CA1 pyramidal neurons that can be engaged or disengaged by small shifts in net membrane current near -70 mV, as by muscarinic stimulation.
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107
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Teles-Grilo Ruivo LM, Mellor JR. Cholinergic modulation of hippocampal network function. Front Synaptic Neurosci 2013; 5:2. [PMID: 23908628 PMCID: PMC3726829 DOI: 10.3389/fnsyn.2013.00002] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 07/10/2013] [Indexed: 11/13/2022] Open
Abstract
Cholinergic septohippocampal projections from the medial septal area to the hippocampus are proposed to have important roles in cognition by modulating properties of the hippocampal network. However, the precise spatial and temporal profile of acetylcholine release in the hippocampus remains unclear making it difficult to define specific roles for cholinergic transmission in hippocampal dependent behaviors. This is partly due to a lack of tools enabling specific intervention in, and recording of, cholinergic transmission. Here, we review the organization of septohippocampal cholinergic projections and hippocampal acetylcholine receptors as well as the role of cholinergic transmission in modulating cellular excitability, synaptic plasticity, and rhythmic network oscillations. We point to a number of open questions that remain unanswered and discuss the potential for recently developed techniques to provide a radical reappraisal of the function of cholinergic inputs to the hippocampus.
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Affiliation(s)
- Leonor M Teles-Grilo Ruivo
- Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, University Walk Bristol, UK
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108
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Long-term depression of synaptic kainate receptors reduces excitability by relieving inhibition of the slow afterhyperpolarization. J Neurosci 2013; 33:9536-45. [PMID: 23719820 DOI: 10.1523/jneurosci.0034-13.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Kainate receptors (KARs) are ionotropic glutamate receptors that also activate noncanonical G-protein-coupled signaling pathways to depress the slow afterhyperpolarization (sAHP). Here we show that long-term depression of KAR-mediated synaptic transmission (KAR LTD) at rat hippocampal mossy fiber synapses relieves inhibition of the sAHP by synaptic transmission. KAR LTD is induced by high-frequency mossy fiber stimulation and natural spike patterns and requires activation of adenosine A2A receptors. Natural spike patterns also cause long-term potentiation of NMDA receptor-mediated synaptic transmission that overrides the effects of KAR LTD on the cellular response to low-frequency synaptic input. However, KAR LTD is dominant at higher frequency synaptic stimulation where it decreases the cellular response by relieving inhibition of the sAHP. Thus we describe a form of glutamate receptor plasticity induced by natural spike patterns whose primary physiological function is to regulate cellular excitability.
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109
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Ma TF, Zhou L, Wang Y, Qin SJ, Zhang Y, Hu B, Yan JZ, Ma X, Zhou CH, Gu SL. A selective M1and M3receptor antagonist, penehyclidine hydrochloride, prevents postischemic LTP: Involvement of NMDA receptors. Synapse 2013; 67:865-74. [DOI: 10.1002/syn.21693] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/19/2013] [Indexed: 11/07/2022]
Affiliation(s)
| | - Li Zhou
- Key Laboratory for Anesthesiology of Jiangsu Province; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Yun Wang
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Shou-Jun Qin
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Yuan Zhang
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Bin Hu
- Key Laboratory for Brain Disease Bioinformation of Jiangsu Province; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Jing-Zhi Yan
- Key Laboratory for Brain Disease Bioinformation of Jiangsu Province; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Xing Ma
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Cheng-Hua Zhou
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
| | - Shu-Ling Gu
- Department of Pharmacology; Key Laboratory of new drugs and clinical application; XuZhou Medical College, XuZhou; Jiangsu Province; 221004; People's Republic of China
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110
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Davie BJ, Christopoulos A, Scammells PJ. Development of M1 mAChR allosteric and bitopic ligands: prospective therapeutics for the treatment of cognitive deficits. ACS Chem Neurosci 2013; 4:1026-48. [PMID: 23659787 PMCID: PMC3715844 DOI: 10.1021/cn400086m] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 05/09/2013] [Indexed: 12/22/2022] Open
Abstract
Since the cholinergic hypothesis of memory dysfunction was first reported, extensive research efforts have focused on elucidating the mechanisms by which this intricate system contributes to the regulation of processes such as learning, memory, and higher executive function. Several cholinergic therapeutic targets for the treatment of cognitive deficits, psychotic symptoms, and the underlying pathophysiology of neurodegenerative disorders, such as Alzheimer's disease and schizophrenia, have since emerged. Clinically approved drugs now exist for some of these targets; however, they all may be considered suboptimal therapeutics in that they produce undesirable off-target activity leading to side effects, fail to address the wide variety of symptoms and underlying pathophysiology that characterize these disorders, and/or afford little to no therapeutic effect in subsets of patient populations. A promising target for which there are presently no approved therapies is the M1 muscarinic acetylcholine receptor (M1 mAChR). Despite avid investigation, development of agents that selectively activate this receptor via the orthosteric site has been hampered by the high sequence homology of the binding site between the five muscarinic receptor subtypes and the wide distribution of this receptor family in both the central nervous system (CNS) and the periphery. Hence, a plethora of ligands targeting less structurally conserved allosteric sites of the M1 mAChR have been investigated. This Review aims to explain the rationale behind allosterically targeting the M1 mAChR, comprehensively summarize and critically evaluate the M1 mAChR allosteric ligand literature to date, highlight the challenges inherent in allosteric ligand investigation that are impeding their clinical advancement, and discuss potential methods for resolving these issues.
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Affiliation(s)
- Briana J. Davie
- Medicinal
Chemistry and Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville VIC 3052, Australia
| | - Arthur Christopoulos
- Medicinal
Chemistry and Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville VIC 3052, Australia
| | - Peter J. Scammells
- Medicinal
Chemistry and Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences, Monash University, 381 Royal
Parade, Parkville VIC 3052, Australia
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111
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Affiliation(s)
- Alexander Thiele
- Institute of Neuroscience, Henry Wellcome Building, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom;
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112
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The potent M1 receptor allosteric agonist GSK1034702 improves episodic memory in humans in the nicotine abstinence model of cognitive dysfunction. Int J Neuropsychopharmacol 2013; 16:721-31. [PMID: 22932339 DOI: 10.1017/s1461145712000752] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Episodic memory deficits are a core feature of neurodegenerative disorders. Muscarinic M(1) receptors play a critical role in modulating learning and memory and are highly expressed in the hippocampus. We examined the effect of GSK1034702, a potent M(1) receptor allosteric agonist, on cognitive function, and in particular episodic memory, in healthy smokers using the nicotine abstinence model of cognitive dysfunction. The study utilized a randomized, double-blind, placebo-controlled, cross-over design in which 20 male nicotine abstained smokers were tested following single doses of placebo, 4 and 8 mg GSK1034702. Compared to the baseline (nicotine on-state), nicotine abstinence showed statistical significance in reducing immediate (p=0.019) and delayed (p=0.02) recall. GSK1034702 (8 mg) significantly attenuated (i.e. improved) immediate recall (p=0.014) but not delayed recall. None of the other cognitive domains was modulated by either nicotine abstinence or GSK1034702. These findings suggest that stimulating M(1) receptor mediated neurotransmission in humans with GSK1034702 improves memory encoding potentially by modulating hippocampal function. Hence, selective M(1) receptor allosteric agonists may have therapeutic benefits in disorders of impaired learning including Alzheimer's disease.
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113
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de Oliveira Coelho CA, Ferreira TL, Soares JCK, Oliveira MGM. Hippocampal NMDA receptor blockade impairs CREB phosphorylation in amygdala after contextual fear conditioning. Hippocampus 2013; 23:545-51. [DOI: 10.1002/hipo.22118] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2013] [Indexed: 01/23/2023]
Affiliation(s)
- Cesar Augusto de Oliveira Coelho
- Departamento de Psicobiologia; Universidade Federal de Sao Paulo; 862 Botucatu street, 1st floor; Sao Paulo; Brazil; zip code 04023-062
| | | | - Juliana Carlota Kramer Soares
- Departamento de Psicobiologia; Universidade Federal de Sao Paulo; 862 Botucatu street, 1st floor; Sao Paulo; Brazil; zip code 04023-062
| | - Maria Gabriela Menezes Oliveira
- Departamento de Psicobiologia; Universidade Federal de Sao Paulo; 862 Botucatu street, 1st floor; Sao Paulo; Brazil; zip code 04023-062
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114
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Yakel JL. Cholinergic receptors: functional role of nicotinic ACh receptors in brain circuits and disease. Pflugers Arch 2013; 465:441-50. [PMID: 23307081 PMCID: PMC3633680 DOI: 10.1007/s00424-012-1200-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 12/03/2012] [Accepted: 12/03/2012] [Indexed: 12/13/2022]
Abstract
The neurotransmitter acetylcholine (ACh) can regulate neuronal excitability throughout the nervous system by acting on both the cys-loop ligand-gated nicotinic ACh receptor channels (nAChRs) and the G protein-coupled muscarinic ACh receptors (mAChRs). The hippocampus is an important area in the brain for learning and memory, where both nAChRs and mAChRs are expressed. The primary cholinergic input to the hippocampus arises from the medial septum and diagonal band of Broca, the activation of which can activate both nAChRs and mAChRs in the hippocampus and regulate synaptic communication and induce oscillations that are thought to be important for cognitive function. Dysfunction in the hippocampal cholinergic system has been linked with cognitive deficits and a variety of neurological disorders and diseases, including Alzheimer's disease and schizophrenia. My lab has focused on the role of the nAChRs in regulating hippocampal function, from understanding the expression and functional properties of the various subtypes of nAChRs, and what role these receptors may be playing in regulating synaptic plasticity. Here, I will briefly review this work, and where we are going in our attempts to further understand the role of these receptors in learning and memory, as well as in disease and neuroprotection.
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Affiliation(s)
- Jerrel L Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, P.O. Box 12233, Mail Drop F2-08, Research Triangle Park, NC 27709, USA.
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115
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Toscano-Márquez B, Dunn RJ, Krahe R. Distribution of muscarinic acetylcholine receptor mRNA in the brain of the weakly electric fishApteronotus leptorhynchus. J Comp Neurol 2013; 521:1054-72. [DOI: 10.1002/cne.23218] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 07/18/2012] [Accepted: 08/17/2012] [Indexed: 11/06/2022]
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116
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Uslaner JM, Eddins D, Puri V, Cannon CE, Sutcliffe J, Chew CS, Pearson M, Vivian JA, Chang RK, Ray WJ, Kuduk SD, Wittmann M. The muscarinic M1 receptor positive allosteric modulator PQCA improves cognitive measures in rat, cynomolgus macaque, and rhesus macaque. Psychopharmacology (Berl) 2013; 225:21-30. [PMID: 22825578 DOI: 10.1007/s00213-012-2788-8] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Accepted: 06/20/2012] [Indexed: 12/24/2022]
Abstract
RATIONALE The current standards of care for Alzheimer's disease, acetylcholinesterase inhibitors, have limited efficacy due to a host of mechanism-related side effects arising from indiscriminate activation of muscarinic and nicotinic receptors. The M1 muscarinic receptor is predominantly expressed in the brain in regions involved in cognition, and therefore selective activation of the M1 receptor would be expected to boost cognitive performance with reduced risk of peripheral side effects. OBJECTIVES Here we investigated whether the selective M1 muscarinic receptor positive allosteric modulator, PQCA, improves cognitive performance and cerebral blood flow. RESULTS PQCA attenuated a scopolamine-induced deficit in novel object recognition in rat, self-ordered spatial search in cynomolgus macaque, and the object retrieval detour task in rhesus macaque. Beneficial effects in each of these assays and species were observed at similar plasma drug concentrations. Furthermore, at similar drug concentrations that were effective in the behavioral studies, PQCA increased blood flow in the frontal cortex of mice, providing a translational biomarker that could be used to guide dose selection for clinical studies. CONCLUSIONS These findings provide a framework for appropriately testing an M1 selective compound in patients with Alzheimer's disease.
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Affiliation(s)
- Jason M Uslaner
- Merck Research Laboratories, Merck & Co., Inc., West Point, PA 19486, USA.
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117
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Foster DJ, Jones CK, Conn PJ. Emerging approaches for treatment of schizophrenia: modulation of cholinergic signaling. DISCOVERY MEDICINE 2012; 14:413-420. [PMID: 23272693 PMCID: PMC3726271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Currently available therapeutic agents for treatment of schizophrenia target signaling by monoaminergic neurotransmitters; however, these treatments do not adequately treat the range of symptoms observed in patients. While these therapies treat the positive symptoms, they do not have efficacy in treating the negative symptoms and cognitive deficits that are associated with the disease. Evidence suggests that molecules that modulate signaling by the neurotransmitter acetylcholine (ACh) could provide a more comprehensive treatment of schizophrenia than currently prescribed antipsychotics. Molecules that broadly increase ACh-signaling have been demonstrated to have efficacy in treating numerous symptom clusters in schizophrenia patients. Unfortunately, these compounds induce adverse effects via activation of peripheral receptors that limit their clinical utility. One proposed strategy for retaining the efficacy of cholinergic treatments, without the adverse effects, is to target specific cholinergic receptor subtypes in the brain. Several cholinergic receptors are able to modulate brain circuits that are dysregulated in schizophrenia patients including receptors belonging to both the muscarinic family (i.e., M1, M4, and M5), and the nicotinic family (i.e., α7, α4β2). Recently, great strides have been made in developing small molecules with high specificity for these receptors, and several of these novel molecules have robust efficacy in several preclinical models predictive of both anti-psychotic and pro-cognitive effectiveness. Promising studies suggest that targeting M1 and α7 may be beneficial for pro-cognitive effects, while molecules that target M4 may be ideally suited to address the positive symptoms. Since these receptor subtypes are distinct from those responsible for the adverse effects observed with non-selective cholinergic treatments, there is hope that molecules targeting these receptors could provide novel therapeutics. Further research is needed to examine the utility of such compounds as therapeutics that could be used either alone, or in combination with existing medications, to better treat schizophrenia.
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Affiliation(s)
- Daniel J Foster
- Department of Pharmacology and Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee 37202, USA
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118
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Bueno-Junior LS, Lopes-Aguiar C, Ruggiero RN, Romcy-Pereira RN, Leite JP. Muscarinic and nicotinic modulation of thalamo-prefrontal cortex synaptic plasticity [corrected] in vivo. PLoS One 2012; 7:e47484. [PMID: 23118873 PMCID: PMC3484139 DOI: 10.1371/journal.pone.0047484] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 09/11/2012] [Indexed: 02/06/2023] Open
Abstract
The mediodorsal nucleus of the thalamus (MD) is a rich source of afferents to the medial prefrontal cortex (mPFC). Dysfunctions in the thalamo-prefrontal connections can impair networks implicated in working memory, some of which are affected in Alzheimer disease and schizophrenia. Considering the importance of the cholinergic system to cortical functioning, our study aimed to investigate the effects of global cholinergic activation of the brain on MD-mPFC synaptic plasticity by measuring the dynamics of long-term potentiation (LTP) and depression (LTD) in vivo. Therefore, rats received intraventricular injections either of the muscarinic agonist pilocarpine (PILO; 40 nmol/µL), the nicotinic agonist nicotine (NIC; 320 nmol/µL), or vehicle. The injections were administered prior to either thalamic high-frequency (HFS) or low-frequency stimulation (LFS). Test pulses were applied to MD for 30 min during baseline and 240 min after HFS or LFS, while field postsynaptic potentials were recorded in the mPFC. The transient oscillatory effects of PILO and NIC were monitored through recording of thalamic and cortical local field potentials. Our results show that HFS did not affect mPFC responses in vehicle-injected rats, but induced a delayed-onset LTP with distinct effects when applied following PILO or NIC. Conversely, LFS induced a stable LTD in control subjects, but was unable to induce LTD when applied after PILO or NIC. Taken together, our findings show distinct modulatory effects of each cholinergic brain activation on MD-mPFC plasticity following HFS and LFS. The LTP-inducing action and long-lasting suppression of cortical LTD induced by PILO and NIC might implicate differential modulation of thalamo-prefrontal functions under low and high input drive.
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Affiliation(s)
- Lezio Soares Bueno-Junior
- Department of Neuroscience and Behavioral Sciences, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Cleiton Lopes-Aguiar
- Department of Neuroscience and Behavioral Sciences, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Rafael Naime Ruggiero
- Department of Neuroscience and Behavioral Sciences, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Rodrigo Neves Romcy-Pereira
- Department of Neuroscience and Behavioral Sciences, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
- Brain Institute, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil
- * E-mail:
| | - João Pereira Leite
- Department of Neuroscience and Behavioral Sciences, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
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119
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Novel allosteric agonists of M1 muscarinic acetylcholine receptors induce brain region-specific responses that correspond with behavioral effects in animal models. J Neurosci 2012; 32:8532-44. [PMID: 22723693 DOI: 10.1523/jneurosci.0337-12.2012] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
M(1) muscarinic acetylcholine receptors (mAChRs) represent a viable target for treatment of multiple disorders of the central nervous system (CNS) including Alzheimer's disease and schizophrenia. The recent discovery of highly selective allosteric agonists of M(1) receptors has provided a major breakthrough in developing a viable approach for the discovery of novel therapeutic agents that target these receptors. Here we describe the characterization of two novel M(1) allosteric agonists, VU0357017 and VU0364572, that display profound differences in their efficacy in activating M(1) coupling to different signaling pathways including Ca(2+) and β-arrestin responses. Interestingly, the ability of these agents to differentially activate coupling of M(1) to specific signaling pathways leads to selective actions on some but not all M(1)-mediated responses in brain circuits. These novel M(1) allosteric agonists induced robust electrophysiological effects in rat hippocampal slices, but showed lower efficacy in striatum and no measureable effects on M(1)-mediated responses in medial prefrontal cortical pyramidal cells in mice. Consistent with these actions, both M(1) agonists enhanced acquisition of hippocampal-dependent cognitive function but did not reverse amphetamine-induced hyperlocomotion in rats. Together, these data reveal that M(1) allosteric agonists can differentially regulate coupling of M(1) to different signaling pathways, and this can dramatically alter the actions of these compounds on specific brain circuits important for learning and memory and psychosis.
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120
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Long-term relationships between cholinergic tone, synchronous bursting and synaptic remodeling. PLoS One 2012; 7:e40980. [PMID: 22911726 PMCID: PMC3402441 DOI: 10.1371/journal.pone.0040980] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 06/15/2012] [Indexed: 01/20/2023] Open
Abstract
Cholinergic neuromodulation plays key roles in the regulation of neuronal excitability, network activity, arousal, and behavior. On longer time scales, cholinergic systems play essential roles in cortical development, maturation, and plasticity. Presumably, these processes are associated with substantial synaptic remodeling, yet to date, long-term relationships between cholinergic tone and synaptic remodeling remain largely unknown. Here we used automated microscopy combined with multielectrode array recordings to study long-term relationships between cholinergic tone, excitatory synapse remodeling, and network activity characteristics in networks of cortical neurons grown on multielectrode array substrates. Experimental elevations of cholinergic tone led to the abrupt suppression of episodic synchronous bursting activity (but not of general activity), followed by a gradual growth of excitatory synapses over hours. Subsequent blockage of cholinergic receptors led to an immediate restoration of synchronous bursting and the gradual reversal of synaptic growth. Neither synaptic growth nor downsizing was governed by multiplicative scaling rules. Instead, these occurred in a subset of synapses, irrespective of initial synaptic size. Synaptic growth seemed to depend on intrinsic network activity, but not on the degree to which bursting was suppressed. Intriguingly, sustained elevations of cholinergic tone were associated with a gradual recovery of synchronous bursting but not with a reversal of synaptic growth. These findings show that cholinergic tone can strongly affect synaptic remodeling and synchronous bursting activity, but do not support a strict coupling between the two. Finally, the reemergence of synchronous bursting in the presence of elevated cholinergic tone indicates that the capacity of cholinergic neuromodulation to indefinitely suppress synchronous bursting might be inherently limited.
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121
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Collingridge GL, Volianskis A, Bannister N, France G, Hanna L, Mercier M, Tidball P, Fang G, Irvine MW, Costa BM, Monaghan DT, Bortolotto ZA, Molnár E, Lodge D, Jane DE. The NMDA receptor as a target for cognitive enhancement. Neuropharmacology 2012; 64:13-26. [PMID: 22796429 DOI: 10.1016/j.neuropharm.2012.06.051] [Citation(s) in RCA: 180] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/22/2012] [Accepted: 06/24/2012] [Indexed: 12/31/2022]
Abstract
NMDA receptors (NMDARs) play an important role in neural plasticity including long-term potentiation and long-term depression, which are likely to explain their importance for learning and memory. Cognitive decline is a major problem facing an ageing human population, so much so that its reversal has become an important goal for scientific research and pharmaceutical development. Enhancement of NMDAR function is a core strategy toward this goal. In this review we indicate some of the major ways of potentiating NMDAR function by both direct and indirect modulation. There is good evidence that both positive and negative modulation can enhance function suggesting that a subtle approach correcting imbalances in particular clinical situations will be required. Excessive activation and the resultant deleterious effects will need to be carefully avoided. Finally we describe some novel positive allosteric modulators of NMDARs, with some subunit selectivity, and show initial evidence of their ability to affect NMDAR mediated events. This article is part of a Special Issue entitled 'Cognitive Enhancers'.
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Affiliation(s)
- Graham L Collingridge
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol BS1 3NY, UK.
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122
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López-Pérez S, Morales-Villagrán A, Ventura-Valenzuela J, Medina-Ceja L. Short- and long-term changes in extracellular glutamate and acetylcholine concentrations in the rat hippocampus following hypoxia. Neurochem Int 2012; 61:258-65. [DOI: 10.1016/j.neuint.2012.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 02/08/2012] [Accepted: 03/13/2012] [Indexed: 01/25/2023]
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123
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Stelly CE, Cronin J, Daniel JM, Schrader LA. Long-term oestradiol treatment enhances hippocampal synaptic plasticity that is dependent on muscarinic acetylcholine receptors in ovariectomised female rats. J Neuroendocrinol 2012; 24:887-96. [PMID: 22313316 DOI: 10.1111/j.1365-2826.2012.02287.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Short-term oestradiol treatment modulates hippocampus-dependent memory and synaptic plasticity in the hippocampus. Long-term oestradiol treatment can also enhance hippocampus- dependent memory, although the effects of long-term oestradiol treatment on synaptic plasticity are unknown. We investigated the effects of long-term oestradiol treatment on synaptic plasticity at the Schaeffer Collateral/CA1 synapse in 8-month-old female rats. In addition, we determined the role of endogenous activation of muscarinic acetylcholine receptors (mAChRs) in synaptic transmission and plasticity using scopolamine (1 μm), an antagonist of mAChRs. Hippocampus slices from ovariectomised rats that were treated with oestradiol-containing capsules for 5 months were compared with slices from ovariectomised rats that received cholesterol-containing capsules. Unexpectedly, scopolamine application significantly increased the baseline field excitatory postsynaptic potentials (fEPSP) and decreased paired pulse facilitation (PPF) in slices from cholesterol-treated rats. Baseline fEPSPs and PPF were not significantly modulated in slices from oestradiol-treated rats by scopolamine. Slices from oestradiol-treated rats showed enhanced long-term potentiation relative to slices from cholesterol-treated rats. Scopolamine significantly reduced the magnitude of plasticity in slices from oestradiol-treated rats. Taken together, these results suggest that mAChRs have a significant effect on baseline synaptic transmission through a decrease in the probability of glutamate release in slices from cholesterol-treated rats. Long-term oestradiol treatment blocks this effect and enhances theta-burst stimulation-induced synaptic plasticity in the middle-aged female rat, and this effect is mediated by activation of mAChRs.
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Affiliation(s)
- C E Stelly
- Neuroscience Program, Tulane University, New Orleans, LA, USA
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124
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Kwag J, Paulsen O. Gating of NMDA receptor-mediated hippocampal spike timing-dependent potentiation by mGluR5. Neuropharmacology 2012; 63:701-9. [PMID: 22652057 PMCID: PMC3396853 DOI: 10.1016/j.neuropharm.2012.05.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 05/14/2012] [Accepted: 05/15/2012] [Indexed: 12/21/2022]
Abstract
Hippocampal long-term potentiation (LTP) is believed to be important for learning and memory. Experimentally, the pairing of precisely timed pre- and postsynaptic spikes within a time window of ∼10 ms can induce timing-dependent LTP (tLTP), but the requirements for induction of tLTP change with development: in young rodents single postsynaptic spikes are sufficient to induce tLTP, whereas postsynaptic burst firing appears to be required in the adult. However, hippocampal neurons in vivo show theta-modulated single spike activities also in older hippocampus. Here we investigated the conditions for single spike pairing to induce tLTP at older CA3–CA1 synapses. We found that the pairing of single pre- and postsynaptic spikes could induce tLTP in older hippocampus when the postsynaptic neuronal membrane was depolarized and the pairing frequency exceeded ∼4 Hz. The spike frequency requirement is postsynaptic, as tLTP could still be induced with presynaptic stimulation at 1 Hz as long as the postsynaptic spike frequency exceeded ∼4 Hz, suggesting that postsynaptic theta-frequency activity is required for the successful induction of tLTP at older CA3–CA1 synapses. The induction of tLTP was blocked by an NMDA receptor antagonist and by the selective mGluR5 blockers, MPEP and MTEP, whereas activation of mGluR1 and mGluR5 by DHPG relieved the postsynaptic spike frequency requirement for tLTP induction. These results suggest that activation of mGluR5 during single-spike pairing at older CA3–CA1 synapses gates NMDA receptor-dependent tLTP.
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Affiliation(s)
- Jeehyun Kwag
- Department of Brain and Cognitive Engineering, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul 136-701, Republic of Korea.
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125
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Suzuki E, Okada T. Stratum oriens stimulation-evoked modulation of hippocampal long-term potentiation involves the activation of muscarinic acetylcholine receptors and the inhibition of Kv7/M potassium ion channels. Eur J Neurosci 2012; 36:1984-92. [PMID: 22639893 DOI: 10.1111/j.1460-9568.2012.08127.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Acetylcholine is considered to be an endogenous modulator of hippocampal neurotransmission and synaptic plasticity. The activation of muscarinic acetylcholine receptors (mAChRs) reportedly enhances hippocampal synaptic plasticity, which plays an important role in memory function; however, the mechanism by which it enhances synaptic plasticity remains unclear. Here, we examined the involvement of the inhibition of Kv7/M K(+) channels, which are targets of mAChR modulation, during mAChR activation-induced enhancement of long-term potentiation (LTP) at rat hippocampal Schaffer collateral (SC)-CA1 synapses. When an electrical stimulus was applied to the stratum oriens before tetanic stimulation of the SCs, the magnitude of the induced SC-CA1 synapse LTP was enhanced as compared with that induced without stratum oriens stimulation. In the presence of the mAChR antagonist atropine, tetanic stimulation induced stable LTP, but the stratum oriens stimulation-evoked enhancement of LTP was abolished. The additional application of XE991, a selective blocker of Kv7/M K(+) channels, rescued the atropine-induced inhibition of LTP enhancement. The phospholipase C (PLC) inhibitor U-73122 inhibited the stratum oriens stimulation-evoked enhancement of LTP. Application of the T/R-type voltage-dependent Ca(2+) channel (VDCC) blocker Ni(2+) abolished the stratum oriens stimulation-evoked enhancement of LTP. In addition, tetanic stimulation with preceding stratum oriens stimulation was able to induce LTP during N-methyl-d-aspartate receptor blockade. We therefore propose that stratum oriens stimulation inhibits Kv7/M K(+) channels through mAChR activation-induced PLC activation, which leads to VDCC activation, and hence causes sufficient Ca(2+) influx to enhance LTP.
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Affiliation(s)
- Etsuko Suzuki
- Department of Psychology, Faculty of Human Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan
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126
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Soulé J, Alme M, Myrum C, Schubert M, Kanhema T, Bramham CR. Balancing Arc synthesis, mRNA decay, and proteasomal degradation: maximal protein expression triggered by rapid eye movement sleep-like bursts of muscarinic cholinergic receptor stimulation. J Biol Chem 2012; 287:22354-66. [PMID: 22584581 DOI: 10.1074/jbc.m112.376491] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Cholinergic signaling induces Arc/Arg3.1, an immediate early gene crucial for synaptic plasticity. However, the molecular mechanisms that dictate Arc mRNA and protein dynamics during and after cholinergic epochs are little understood. Using human SH-SY5Y neuroblastoma cells, we show that muscarinic cholinergic receptor (mAchR) stimulation triggers Arc synthesis, whereas translation-dependent RNA decay and proteasomal degradation strictly limit the amount and duration of Arc expression. Chronic application of the mAchR agonist, carbachol (Cch), induces Arc transcription via ERK signaling and release of calcium from IP(3)-sensitive stores. Arc translation requires ERK activation, but not changes in intracellular calcium. Proteasomal degradation of Arc (half-life ∼37 min) was enhanced by thapsigargin, an inhibitor of the endoplasmic calcium-ATPase pump. Similar mechanisms of Arc protein regulation were observed in cultured rat hippocampal slices. Functionally, we studied the impact of cholinergic epoch duration and temporal pattern on Arc protein expression. Acute Cch treatment (as short as 2 min) induces transient, moderate Arc expression, whereas continuous treatment of more than 30 min induces maximal expression, followed by rapid decline. Cholinergic activity associated with rapid eye movement sleep may function to facilitate long term synaptic plasticity and memory. Employing a paradigm designed to mimic intermittent rapid eye movement sleep epochs, we show that application of Cch in a series of short bursts generates persistent and maximal Arc protein expression. The results demonstrate dynamic, multifaceted control of Arc synthesis during mAchR signaling, and implicate cholinergic epoch duration and repetition as critical determinants of Arc expression and function in synaptic plasticity and behavior.
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Affiliation(s)
- Jonathan Soulé
- Department of Biomedicine, KG Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway
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127
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Liu T, Kong D, Shah BP, Ye C, Koda S, Saunders A, Ding JB, Yang Z, Sabatini BL, Lowell BB. Fasting activation of AgRP neurons requires NMDA receptors and involves spinogenesis and increased excitatory tone. Neuron 2012; 73:511-22. [PMID: 22325203 DOI: 10.1016/j.neuron.2011.11.027] [Citation(s) in RCA: 201] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/22/2011] [Indexed: 02/06/2023]
Abstract
AgRP neuron activity drives feeding and weight gain whereas that of nearby POMC neurons does the opposite. However, the role of excitatory glutamatergic input in controlling these neurons is unknown. To address this question, we generated mice lacking NMDA receptors (NMDARs) on either AgRP or POMC neurons. Deletion of NMDARs from AgRP neurons markedly reduced weight, body fat and food intake whereas deletion from POMC neurons had no effect. Activation of AgRP neurons by fasting, as assessed by c-Fos, Agrp and Npy mRNA expression, AMPA receptor-mediated EPSCs, depolarization and firing rates, required NMDARs. Furthermore, AgRP but not POMC neurons have dendritic spines and increased glutamatergic input onto AgRP neurons caused by fasting was paralleled by an increase in spines, suggesting fasting induced synaptogenesis and spinogenesis. Thus glutamatergic synaptic transmission and its modulation by NMDARs play key roles in controlling AgRP neurons and determining the cellular and behavioral response to fasting.
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Affiliation(s)
- Tiemin Liu
- Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
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128
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Zheng F, Wess J, Alzheimer C. M2 muscarinic acetylcholine receptors regulate long-term potentiation at hippocampal CA3 pyramidal cell synapses in an input-specific fashion. J Neurophysiol 2012; 108:91-100. [PMID: 22490561 DOI: 10.1152/jn.00740.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscarinic receptors have long been known as crucial players in hippocampus-dependent learning and memory, but our understanding of the cellular underpinnings and the receptor subtypes involved lags well behind. This holds in particular for the hippocampal CA3 region, where the mechanisms of synaptic plasticity depend on the type of afferent input. Williams and Johnston (Williams S, Johnston D. Science 242: 84-87, 1988; Williams S, Johnston D. J Neurophysiol 64: 1089-1097, 1990) demonstrated muscarinic depression of mossy fiber (MF) long-term potentiation (LTP) through a presynaptic site of action and Maeda et al. (Maeda T, Kaneko S, Satoh M. Brain Res 619: 324-330, 1993) proposed a bidirectional modulation of MF LTP by muscarinic receptor subtypes. Since then, this issue, as well as muscarinic regulation of plasticity at associational/commissural (A/C) fiber-CA3 synapses has remained largely neglected, not least because of the lack of highly selective ligands for the different muscarinic receptor subtypes. In the present study, we performed field potential and whole cell recordings from the hippocampal CA3 region of M(2) receptor knockout mice to determine the role of M(2) receptors in short-term and long-term plasticity at A/C and MF inputs to CA3 pyramidal cells. At the A/C synapse, M(2) receptors promoted short-term facilitation and LTP. Unexpectedly, M(2) receptors mediated the opposite effect on LTP at the MF synapse, which was significantly reduced, most likely involving a depressant effect of M(2) receptors on adenylyl cyclase activity in MF terminals. Our data demonstrate that cholinergic projections recruit M(2) receptors to redistribute the gain of LTP in CA3 pyramidal cells in an input-specific manner.
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Affiliation(s)
- Fang Zheng
- Institute of Physiology, University of Kiel, Kiel, Germany
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129
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Yakel JL. Nicotinic ACh receptors in the hippocampus: role in excitability and plasticity. Nicotine Tob Res 2012; 14:1249-57. [PMID: 22472168 DOI: 10.1093/ntr/nts091] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
INTRODUCTION The nicotinic ACh receptors (nAChRs) are in the cys-loop family of ligand-gated ion channels. They are widely expressed throughout the brain, including in the hippocampus where they are thought to be involved in regulating excitability, plasticity, and cognitive function. In addition, dysfunction in hippocampal nAChRs has been linked to a variety of neurological disorders and diseases, including Alzheimer's disease, schizophrenia, and epilepsy. In order to understand how to treat nAChR-related disorders and diseases, it is critical to understand how these receptors participate in normal brain function; this entails not only understanding the biophysical properties of ion channel function and their pattern of expression but also how these receptors are regulating excitability and circuit behavior. DISCUSSION The primary cholinergic input to the hippocampus comes from the medial septum and diagonal band of Broca; however, the mechanistic details are unknown of how activation of cholinergic receptors, either through exogenous nAChR ligands or the activation of endogenous acetylcholine release, regulates hippocampal network activity. This entails direct study of the excitatory and inhibitory neuronal networks, as well as the role of nonneuronal cells, in regulating hippocampal function. CONCLUSIONS Here, I will review the latest work from my laboratory in which we have attempted to do just that, with the overall goal of learning more about the role of the hippocampal nAChR in synaptic plasticity.
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Affiliation(s)
- Jerrel L Yakel
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, P.O. Box 12233, Mail Drop F2-08, Research Triangle Park, NC 27709, USA.
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130
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Kroker KS, Rast G, Giovannini R, Marti A, Dorner-Ciossek C, Rosenbrock H. Inhibition of acetylcholinesterase and phosphodiesterase-9A has differential effects on hippocampal early and late LTP. Neuropharmacology 2012; 62:1964-74. [DOI: 10.1016/j.neuropharm.2011.12.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 12/12/2011] [Accepted: 12/19/2011] [Indexed: 01/19/2023]
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131
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Signaling in dendritic spines and spine microdomains. Curr Opin Neurobiol 2012; 22:389-96. [PMID: 22459689 DOI: 10.1016/j.conb.2012.03.003] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 03/05/2012] [Accepted: 03/05/2012] [Indexed: 11/20/2022]
Abstract
The specialized morphology of dendritic spines creates an isolated compartment that allows for localized biochemical signaling. Recent studies have revealed complexity in the function of the spine head as a signaling domain and indicate that (1) the spine is functionally subdivided into multiple independent microdomains and (2) not all biochemical signals are equally compartmentalized within the spine. Here we review these findings as well as the developments in fluorescence microscopy that are making possible direct monitoring of signaling within spines and, in the future, within sub-spine microdomains.
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132
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Affiliation(s)
- John P. Adelman
- Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239;
| | - James Maylie
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon 97239;
| | - Pankaj Sah
- The Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, 4072, Australia;
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133
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Daval SB, Valant C, Bonnet D, Kellenberger E, Hibert M, Galzi JL, Ilien B. Fluorescent derivatives of AC-42 to probe bitopic orthosteric/allosteric binding mechanisms on muscarinic M1 receptors. J Med Chem 2012; 55:2125-43. [PMID: 22329602 DOI: 10.1021/jm201348t] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two fluorescent derivatives of the M1 muscarinic selective agonist AC-42 were synthesized by coupling the lissamine rhodamine B fluorophore (in ortho and para positions) to AC42-NH(2). This precursor, prepared according to an original seven-step procedure, was included in the study together with the LRB fluorophore (alone or linked to an alkyl chain). All these compounds are antagonists, but examination of their ability to inhibit or modulate orthosteric [(3)H]NMS binding revealed that para-LRB-AC42 shared several properties with AC-42. Carefully designed experiments allowed para-LRB-AC42 to be used as a FRET tracer on EGFP-fused M1 receptors. Under equilibrium binding conditions, orthosteric ligands, AC-42, and the allosteric modulator gallamine behaved as competitors of para-LRB-AC42 binding whereas other allosteric compounds such as WIN 51,708 and N-desmethylclozapine were noncompetitive inhibitors. Finally, molecular modeling studies focused on putative orthosteric/allosteric bitopic poses for AC-42 and para-LRB-AC42 in a 3D model of the human M1 receptor.
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Affiliation(s)
- Sandrine B Daval
- Unité Biotechnologie et Signalisation Cellulaire, UMR 7242 CNRS, Ecole Supérieure de Biotechnologie de Strasbourg, Université de Strasbourg, BP 10413, 67412 Illkirch, France
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134
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Petrovic MM, Nowacki J, Olivo V, Tsaneva-Atanasova K, Randall AD, Mellor JR. Inhibition of post-synaptic Kv7/KCNQ/M channels facilitates long-term potentiation in the hippocampus. PLoS One 2012; 7:e30402. [PMID: 22348007 PMCID: PMC3278412 DOI: 10.1371/journal.pone.0030402] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 12/20/2011] [Indexed: 12/02/2022] Open
Abstract
Activation of muscarinic acetylcholine receptors (mAChR) facilitates the induction of synaptic plasticity and enhances cognitive function. In the hippocampus, M1 mAChR on CA1 pyramidal cells inhibit both small conductance Ca2+-activated KCa2 potassium channels and voltage-activated Kv7 potassium channels. Inhibition of KCa2 channels facilitates long-term potentiation (LTP) by enhancing Ca2+calcium influx through postsynaptic NMDA receptors (NMDAR). Inhibition of Kv7 channels is also reported to facilitate LTP but the mechanism of action is unclear. Here, we show that inhibition of Kv7 channels with XE-991 facilitated LTP induced by theta burst pairing at Schaffer collateral commissural synapses in rat hippocampal slices. Similarly, negating Kv7 channel conductance using dynamic clamp methodologies also facilitated LTP. Negation of Kv7 channels by XE-991 or dynamic clamp did not enhance synaptic NMDAR activation in response to theta burst synaptic stimulation. Instead, Kv7 channel inhibition increased the amplitude and duration of the after-depolarisation following a burst of action potentials. Furthermore, the effects of XE-991 were reversed by re-introducing a Kv7-like conductance with dynamic clamp. These data reveal that Kv7 channel inhibition promotes NMDAR opening during LTP induction by enhancing depolarisation during and after bursts of postsynaptic action potentials. Thus, during the induction of LTP M1 mAChRs enhance NMDAR opening by two distinct mechanisms namely inhibition of KCa2 and Kv7 channels.
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Affiliation(s)
- Milos M. Petrovic
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- Institute of Medical Physiology, School of Medicine, Belgrade University, Beograd, Serbia
| | - Jakub Nowacki
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Valeria Olivo
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Krasimira Tsaneva-Atanasova
- Bristol Centre for Applied Nonlinear Mathematics, Department of Engineering Mathematics, University of Bristol, Bristol, United Kingdom
| | - Andrew D. Randall
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
| | - Jack R. Mellor
- Medical Research Council Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom
- * E-mail:
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135
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Parfitt GM, Campos RC, Barbosa ÂK, Koth AP, Barros DM. Participation of hippocampal cholinergic system in memory persistence for inhibitory avoidance in rats. Neurobiol Learn Mem 2012; 97:183-8. [DOI: 10.1016/j.nlm.2011.12.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 11/23/2011] [Accepted: 12/01/2011] [Indexed: 10/14/2022]
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136
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Kann O, Taubenberger N, Huchzermeyer C, Papageorgiou IE, Benninger F, Heinemann U, Kovács R. Muscarinic receptor activation determines the effects of store-operated Ca2+-entry on excitability and energy metabolism in pyramidal neurons. Cell Calcium 2012; 51:40-50. [DOI: 10.1016/j.ceca.2011.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 10/14/2011] [Accepted: 10/19/2011] [Indexed: 10/15/2022]
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137
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Muscarinic and nicotinic acetylcholine receptor agonists and allosteric modulators for the treatment of schizophrenia. Neuropsychopharmacology 2012; 37:16-42. [PMID: 21956443 PMCID: PMC3238081 DOI: 10.1038/npp.2011.199] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Muscarinic and nicotinic acetylcholine (ACh) receptors (mAChRs and nAChRs) are emerging as important targets for the development of novel treatments for the symptoms associated with schizophrenia. Preclinical and early proof-of-concept clinical studies have provided strong evidence that activators of specific mAChR (M(1) and M(4)) and nAChR (α(7) and α(2)β(4)) subtypes are effective in animal models of antipsychotic-like activity and/or cognitive enhancement, and in the treatment of positive and cognitive symptoms in patients with schizophrenia. While early attempts to develop selective mAChR and nAChR agonists provided important preliminary findings, these compounds have ultimately failed in clinical development due to a lack of true subtype selectivity and subsequent dose-limiting adverse effects. In recent years, there have been major advances in the discovery of highly selective activators for the different mAChR and nAChR subtypes with suitable properties for optimization as potential candidates for clinical trials. One novel strategy has been to identify ligands that activate a specific receptor subtype through actions at sites that are distinct from the highly conserved ACh-binding site, termed allosteric sites. These allosteric activators, both allosteric agonists and positive allosteric modulators, of mAChR and nAChR subtypes demonstrate unique mechanisms of action and high selectivity in vivo, and may provide innovative treatment strategies for schizophrenia.
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138
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Bubser M, Byun N, Wood MR, Jones CK. Muscarinic receptor pharmacology and circuitry for the modulation of cognition. Handb Exp Pharmacol 2012:121-66. [PMID: 22222698 DOI: 10.1007/978-3-642-23274-9_7] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The muscarinic cholinergic system constitutes an important part of the neuronal circuitry that modulates normal cognition. Muscarinic receptor antagonists are well known to produce or exacerbate impairments in attention, learning, and memory. Conversely, both direct-acting muscarinic receptor agonists and indirect-acting muscarinic cholinergic agonists, such as acetylcholinesterase inhibitors, have shown cognition-enhancing properties, including improvements in normal cognitive function, reversal of cognitive deficits induced by muscarinic receptor antagonists, and attenuation of cognitive deficits in psychiatric and neurological disorders, such as Alzheimer's disease and schizophrenia. However, until recently, the lack of small molecule ligands that antagonize or activate specific muscarinic acetylcholine receptor (mAChR) subtypes with high selectivity has been a major obstacle in defining the relative contributions of individual mAChRs to different aspects of cognitive function and for the development of novel therapeutic agents. These limitations may be potentially overcome by the recent discovery of novel mAChR subtype-selective compounds, notably allosteric agonists and positive allosteric modulators, which exhibit greater selectivity for individual mAChR subtypes than previous mAChR orthosteric agonists. In preclinical studies, these novel ligands have shown promising efficacy in several models for the enhancement of cognition. In this chapter, we will review the muscarinic cholinergic circuitry and pharmacology of mAChR agonists and antagonists relevant to the modulation of different aspects of cognition in animals and clinical populations.
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Affiliation(s)
- Michael Bubser
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, USA
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139
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Caruana DA, Warburton EC, Bashir ZI. Induction of activity-dependent LTD requires muscarinic receptor activation in medial prefrontal cortex. J Neurosci 2011; 31:18464-78. [PMID: 22171048 PMCID: PMC6623881 DOI: 10.1523/jneurosci.4719-11.2011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/02/2011] [Accepted: 11/02/2011] [Indexed: 11/21/2022] Open
Abstract
The medial prefrontal cortex (mPFC) forms part of a neural circuit involved in the formation of lasting associations between objects and places. Cholinergic inputs from the basal forebrain innervate the mPFC and may modulate synaptic processes required for the formation of object-in-place memories. To investigate whether acetylcholine regulates synaptic function in the rat mPFC, whole-cell voltage-clamp recordings were made from pyramidal neurons in layer V. Bath application of the cholinergic agonist carbachol caused a potent and long-term depression (LTD) of synaptic responses that was blocked by the muscarinic receptor antagonist scopolamine and was mimicked, in part, by the M(1) receptor agonists McN-A-343 or AF102B. Furthermore, inhibition of PKC blocked carbachol-mediated LTD. We next determined the requirements for activity-dependent LTD in the prefrontal cortex. Synaptic stimulation that was subthreshold for producing LTD did, however, result in LTD when acetylcholine levels were enhanced by inhibition of acetylcholinesterase or when delivered in the presence of the M(1)-selective positive allosteric modulator BQCA. Increasing the levels of synaptic stimulation resulted in M(1) receptor-dependent LTD without the need for pharmacological manipulation of acetylcholine levels. These results show that synaptic stimulation of muscarinic receptors alone can be critical for plastic changes in excitatory synaptic transmission in the mPFC. In turn, these muscarinic mediated events may be important in the formation of object-in-place memories. A loss of basal forebrain cholinergic neurons is a classic hallmark of Alzheimer's dementia and our results provide a potential explanation for the loss of memory associated with the disease.
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Affiliation(s)
- Douglas A. Caruana
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - E. Clea Warburton
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Zafar I. Bashir
- MRC Centre for Synaptic Plasticity, School of Physiology and Pharmacology, University of Bristol, Bristol BS8 1TD, United Kingdom
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140
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Bartlett TE, Lu J, Wang YT. Slice orientation and muscarinic acetylcholine receptor activation determine the involvement of N-methyl D-aspartate receptor subunit GluN2B in hippocampal area CA1 long-term depression. Mol Brain 2011; 4:41. [PMID: 22082088 PMCID: PMC3226435 DOI: 10.1186/1756-6606-4-41] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Accepted: 11/15/2011] [Indexed: 12/03/2022] Open
Abstract
Background The contribution of different GluN2 subunits of the N-methyl D-aspartate (NMDA) receptor to the induction of bidirectional hippocampal synaptic plasticity is a controversial topic. As both supporting and refuting evidence for the hypothesis of subunit specialization in opposing directions of plasticity has accumulated since it was first proposed a few years ago, we hypothesize that differences in experimental conditions may have in part contributed to some of the inconsistent results from these studies. Here we investigate the controversial hypothesis that long-term depression (LTD) is preferentially induced by GluN2B-containing NMDA receptors in area CA1 of hippocampal slices. Results We find that brain slices from 2-3 week old rats prepared in the sagittal orientation have GluN2B-independent LTD whereas slices prepared in the coronal orientation have GluN2B-dependent LTD. There was no difference between the orientations in the fraction of the NMDAR EPSC sensitive to a GluN2B-selective antagonist, leading us to believe that the intracellular signaling properties of the NMDARs were different in the two preparations. Coronal slices had greater association of LTD-related intracellular signaling protein RasGRF1 with GluN2B relative to sagittal slices. Antagonism of muscarinic acetylcholine receptors (mAChRs) in the sagittal slices returned LTD to a GluN2B-dependent form and increased the association of GluN2B with RasGRF1. Conclusions These results suggest a novel form of NMDAR modulation by mAChRs and clarify some disagreement in the literature.
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Affiliation(s)
- Thomas E Bartlett
- Brain Research Centre, University of British Columbia, 2211 Wesbrook Mall, Vancouver, BC, Canada
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141
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Shoemaker PA. Neural bistability and amplification mediated by NMDA receptors: Analysis of stationary equations. Neurocomputing 2011. [DOI: 10.1016/j.neucom.2011.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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142
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Ripples make waves: binding structured activity and plasticity in hippocampal networks. Neural Plast 2011; 2011:960389. [PMID: 21961073 PMCID: PMC3180853 DOI: 10.1155/2011/960389] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 06/14/2011] [Accepted: 06/23/2011] [Indexed: 11/18/2022] Open
Abstract
Establishing novel episodic memories and stable spatial representations depends on an exquisitely choreographed, multistage process involving the online encoding and offline consolidation of sensory information, a process that is largely dependent on the hippocampus. Each step is influenced by distinct neural network states that influence the pattern of activation across cellular assemblies. In recent years, the occurrence of hippocampal sharp wave ripple (SWR) oscillations has emerged as a potentially vital network phenomenon mediating the steps between encoding and consolidation, both at a cellular and network level by promoting the rapid replay and reactivation of recent activity patterns. Such events facilitate memory formation by optimising the conditions for synaptic plasticity to occur between contingent neural elements. In this paper, we explore the ways in which SWRs and other network events can bridge the gap between spatiomnemonic processing at cellular/synaptic and network levels in the hippocampus.
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143
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Abstract
Synaptic plasticity is widely considered to be a cellular mechanism underlying learning and memory. In this issue of Neuron, Gu and Yakel show that the precise timing of a single cholinergic pulse of activity can determine whether plasticity will occur at a glutamatergic synapse and confer long-term potentiation versus depression.
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144
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Gu Z, Yakel JL. Timing-dependent septal cholinergic induction of dynamic hippocampal synaptic plasticity. Neuron 2011; 71:155-65. [PMID: 21745645 PMCID: PMC3134790 DOI: 10.1016/j.neuron.2011.04.026] [Citation(s) in RCA: 218] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2011] [Indexed: 11/26/2022]
Abstract
Cholinergic modulation of hippocampal synaptic plasticity has been studied extensively by applying receptor agonists or blockers; however, the effect of rapid physiological cholinergic stimuli on plasticity is largely unknown. Here, we report that septal cholinergic input, activated either by electrical stimulation or via an optogenetic approach, induced different types of hippocampal Schaffer collateral (SC) to CA1 synaptic plasticity, depending on the timing of cholinergic input relative to the SC input. When the cholinergic input was activated 100 or 10 ms prior to SC stimulation, it resulted in α7 nAChR-dependent long-term potentiation (LTP) or short-term depression, respectively. When the cholinergic stimulation was delayed until 10 ms after the SC stimulation, a muscarinic AChR-dependent LTP was induced. Moreover, these various forms of plasticity were disrupted by Aβ exposure. These results have revealed the remarkable temporal precision of cholinergic functions, providing a novel mechanism for information processing in cholinergic-dependent higher cognitive functions.
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Affiliation(s)
- Zhenglin Gu
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
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145
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Giessel AJ, Sabatini BL. Boosting of synaptic potentials and spine Ca transients by the peptide toxin SNX-482 requires alpha-1E-encoded voltage-gated Ca channels. PLoS One 2011; 6:e20939. [PMID: 21695265 PMCID: PMC3111456 DOI: 10.1371/journal.pone.0020939] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 05/13/2011] [Indexed: 11/18/2022] Open
Abstract
The majority of glutamatergic synapses formed onto principal neurons of the mammalian central nervous system are associated with dendritic spines. Spines are tiny protuberances that house the proteins that mediate the response of the postsynaptic cell to the presynaptic release of glutamate. Postsynaptic signals are regulated by an ion channel signaling cascade that is active in individual dendritic spines and involves voltage-gated calcium (Ca) channels, small conductance (SK)-type Ca-activated potassium channels, and NMDA-type glutamate receptors. Pharmacological studies using the toxin SNX-482 indicated that the voltage-gated Ca channels that signal within spines to open SK channels belong to the class Ca(V)2.3, which is encoded by the Alpha-1E pore-forming subunit. In order to specifically test this conclusion, we examined the effects of SNX-482 on synaptic signals in acute hippocampal slices from knock-out mice lacking the Alpha-1E gene. We find that in these mice, application of SNX-482 has no effect on glutamate-uncaging evoked synaptic potentials and Ca influx, indicating that that SNX-482 indeed acts via the Alpha-1E-encoded Ca(V)2.3 channel.
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Affiliation(s)
- Andrew J Giessel
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America
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146
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Hosy E, Piochon C, Teuling E, Rinaldo L, Hansel C. SK2 channel expression and function in cerebellar Purkinje cells. J Physiol 2011; 589:3433-40. [PMID: 21521760 DOI: 10.1113/jphysiol.2011.205823] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Small-conductance calcium-activated K(+) channels (SK channels) regulate the excitability of neurons and their responsiveness to synaptic input patterns. SK channels contribute to the afterhyperpolarization (AHP) following action potential bursts, and curtail excitatory postsynaptic potentials (EPSPs) in neuronal dendrites. Here we review evidence that SK2 channels are expressed in rat cerebellar Purkinje cells during development and throughout adulthood, and play a key role in diverse cellular processes such as the regulation of the spike firing frequency and the modulation of calcium transients in dendritic spines. In Purkinje cells as well as in other types of neurons, SK2 channel plasticity seems to provide an important mechanism allowing these cells to adjust their intrinsic excitability and to alter the probabilities for the induction of synaptic learning correlates, such as long-term potentiation (LTP).
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Affiliation(s)
- Eric Hosy
- Laboratoire Physiologie Cellulaire de la Synapse, CNRS, Bordeaux Neuroscience Institute, University of Bordeaux, 33077 Bordeaux Cedex, France
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148
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Maylie J, Adelman JP. Cholinergic signaling through synaptic SK channels: it's a protein kinase but which one? Neuron 2011; 68:809-11. [PMID: 21144995 DOI: 10.1016/j.neuron.2010.11.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Cholinergic signaling modulates synaptic responses and influences cognition. In this issue of Neuron, two groups (Buchanan et al. and Giessel and Sabatini) present evidence that cholinergic signaling enhances postsynaptic responses in CA1 neurons by decreasing synaptic SK channel activity. However, they come to different conclusions about the protein kinases involved in this process.
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Affiliation(s)
- James Maylie
- Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, OR 97239, USA
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