1
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Wollet M, Hernandez A, Nip K, Pugh J, Kim JH. Impacts of Perinatal Nicotine Exposure on nAChR Expression and Glutamatergic Synaptic Transmission in the Mouse Auditory Brainstem. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.08.592930. [PMID: 38765998 PMCID: PMC11100749 DOI: 10.1101/2024.05.08.592930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Exposure to nicotine in utero, often due to maternal smoking, significantly elevates the risk of auditory processing deficits in offspring. This study investigated the effects of chronic nicotine exposure during a critical developmental period on the functional expression of nicotinic acetylcholine receptors (nAChRs), glutamatergic synaptic transmission, and auditory processing in the mouse auditory brainstem. We evaluated the functionality of nAChRs at a central synapse and explored the impact of perinatal nicotine exposure (PNE) on synaptic currents and auditory brainstem responses (ABR) in mice. Our findings revealed developmentally regulated changes in nAChR expression in the medial nucleus of the trapezoid body (MNTB) neurons and presynaptic Calyx of Held terminals. PNE was associated with enhanced acetylcholine-evoked postsynaptic currents and compromised glutamatergic neurotransmission, highlighting the critical role of nAChR activity in the early stages of auditory synaptic development. Additionally, PNE resulted in elevated ABR thresholds and diminished peak amplitudes, suggesting significant impairment in central auditory processing without cochlear dysfunction. This study provides novel insights into the synaptic disturbances that contribute to auditory deficits resulting from chronic prenatal nicotine exposure, underlining potential targets for therapeutic intervention.
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2
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Castro EM, Lotfipour S, Leslie FM. Nicotine on the developing brain. Pharmacol Res 2023; 190:106716. [PMID: 36868366 PMCID: PMC10392865 DOI: 10.1016/j.phrs.2023.106716] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/23/2023] [Accepted: 02/28/2023] [Indexed: 03/05/2023]
Abstract
Developmental periods such as gestation and adolescence have enhanced plasticity leaving the brain vulnerable to harmful effects from nicotine use. Proper brain maturation and circuit organization is critical for normal physiological and behavioral outcomes. Although cigarette smoking has declined in popularity, noncombustible nicotine products are readily used. The misperceived safety of these alternatives lead to widespread use among vulnerable populations such as pregnant women and adolescents. Nicotine exposure during these sensitive developmental windows is detrimental to cardiorespiratory function, learning and memory, executive function, and reward related circuitry. In this review, we will discuss clinical and preclinical evidence of the adverse alterations in the brain and behavior following nicotine exposure. Time-dependent nicotine-induced changes in reward related brain regions and drug reward behaviors will be discussed and highlight unique sensitivities within a developmental period. We will also review long lasting effects of developmental exposure persisting into adulthood, along with permanent epigenetic changes in the genome which can be passed to future generations. Taken together, it is critical to evaluate the consequences of nicotine exposure during these vulnerable developmental windows due to its direct impact on cognition, potential trajectories for other substance use, and implicated mechanisms for the neurobiology of substance use disorders.
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Affiliation(s)
- Emily M Castro
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, USA
| | - Shahrdad Lotfipour
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, USA; Department of Emergency Medicine, School of Medicine, University of California, Irvine, Irvine, CA, USA; Department of Pathology and Laboratory Medicine, School of Medicine, University of California, Irvine, Irvine, CA, USA
| | - Frances M Leslie
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, USA.
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3
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Abstract
In mammals, the selective transformation of transient experience into stored memory occurs in the hippocampus, which develops representations of specific events in the context in which they occur. In this review, we focus on the development of hippocampal circuits and the self-organized dynamics embedded within them since the latter critically support the role of the hippocampus in learning and memory. We first discuss evidence that adult hippocampal cells and circuits are sculpted by development as early as during embryonic neurogenesis. We argue that these primary developmental programs provide a scaffold onto which later experience of the external world can be grafted. Next, we review the different sequences in the development of hippocampal cells and circuits at anatomical and functional levels. We cover a period extending from neurogenesis and migration to the appearance of phenotypic diversity within hippocampal cells, and their wiring into functional networks. We describe the progressive emergence of network dynamics in the hippocampus, from sensorimotor-driven early sharp waves to sequences of place cells tracking relational information. We outline the critical turn points and discontinuities in that developmental journey, and close by formulating open questions. We propose that rewinding the process of hippocampal development helps understand the main organization principles of memory circuits.
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Affiliation(s)
- Rosa Cossart
- Inserm, INMED, Turing Center for Living Systems, Aix Marseille University, Marseille, France
| | - Rustem Khazipov
- Inserm, INMED, Turing Center for Living Systems, Aix Marseille University, Marseille, France.,Laboratory of Neurobiology, Kazan Federal University, Kazan Russia
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4
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Stone TW. Does kynurenic acid act on nicotinic receptors? An assessment of the evidence. J Neurochem 2020; 152:627-649. [PMID: 31693759 PMCID: PMC7078985 DOI: 10.1111/jnc.14907] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 10/19/2019] [Accepted: 10/30/2019] [Indexed: 02/06/2023]
Abstract
As a major metabolite of kynurenine in the oxidative metabolism of tryptophan, kynurenic acid is of considerable biological and clinical importance as an endogenous antagonist of glutamate in the central nervous system. It is most active as an antagonist at receptors sensitive to N-methyl-D-aspartate (NMDA) which regulate neuronal excitability and plasticity, brain development and behaviour. It is also thought to play a causative role in hypo-glutamatergic conditions such as schizophrenia, and a protective role in several neurodegenerative disorders, notably Huntington's disease. An additional hypothesis, that kynurenic acid could block nicotinic receptors for acetylcholine in the central nervous system has been proposed as an alternative mechanism of action of kynurenate. However, the evidence for this alternative mechanism is highly controversial, partly because at least eight earlier studies concluded that kynurenic acid blocked NMDA receptors but not nicotinic receptors and five subsequent, independent studies designed to repeat the results have failed to do so. Many studies considered to support the alternative 'nicotinic' hypothesis have been based on the use of analogs of kynurenate such as 7-chloro-kynurenic acid, or putatively nicotinic modulators such as galantamine, but a detailed analysis of the pharmacology of these compounds suggests that the results have often been misinterpreted, especially since the pharmacology of galantamine itself has been disputed. This review examines the evidence in detail, with the conclusion that there is no confirmed, reliable evidence for an antagonist activity of kynurenic acid at nicotinic receptors. Therefore, since there is overwhelming evidence for kynurenate acting at ionotropic glutamate receptors, especially NMDAR glutamate and glycine sites, with some activity at GPR35 sites and Aryl Hydrocarbon Receptors, results with kynurenic acid should be interpreted only in terms of these confirmed sites of action.
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Affiliation(s)
- Trevor W. Stone
- Institute for Neuroscience and PsychologyUniversity of GlasgowGlasgowG12 8QQUK
- Present address:
Kennedy InstituteNDORMSUniversity of OxfordOxfordOX3 7FYUK
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5
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Salmon CK, Pribiag H, Gizowski C, Farmer WT, Cameron S, Jones EV, Mahadevan V, Bourque CW, Stellwagen D, Woodin MA, Murai KK. Depolarizing GABA Transmission Restrains Activity-Dependent Glutamatergic Synapse Formation in the Developing Hippocampal Circuit. Front Cell Neurosci 2020; 14:36. [PMID: 32161521 PMCID: PMC7053538 DOI: 10.3389/fncel.2020.00036] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 02/05/2020] [Indexed: 12/27/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mature brain but has the paradoxical property of depolarizing neurons during early development. Depolarization provided by GABAA transmission during this early phase regulates neural stem cell proliferation, neural migration, neurite outgrowth, synapse formation, and circuit refinement, making GABA a key factor in neural circuit development. Importantly, depending on the context, depolarizing GABAA transmission can either drive neural activity or inhibit it through shunting inhibition. The varying roles of depolarizing GABAA transmission during development, and its ability to both drive and inhibit neural activity, makes it a difficult developmental cue to study. This is particularly true in the later stages of development when the majority of synapses form and GABAA transmission switches from depolarizing to hyperpolarizing. Here, we addressed the importance of depolarizing but inhibitory (or shunting) GABAA transmission in glutamatergic synapse formation in hippocampal CA1 pyramidal neurons. We first showed that the developmental depolarizing-to-hyperpolarizing switch in GABAA transmission is recapitulated in organotypic hippocampal slice cultures. Based on the expression profile of K+−Cl− co-transporter 2 (KCC2) and changes in the GABA reversal potential, we pinpointed the timing of the switch from depolarizing to hyperpolarizing GABAA transmission in CA1 neurons. We found that blocking depolarizing but shunting GABAA transmission increased excitatory synapse number and strength, indicating that depolarizing GABAA transmission can restrain glutamatergic synapse formation. The increase in glutamatergic synapses was activity-dependent but independent of BDNF signaling. Importantly, the elevated number of synapses was stable for more than a week after GABAA inhibitors were washed out. Together these findings point to the ability of immature GABAergic transmission to restrain glutamatergic synapse formation and suggest an unexpected role for depolarizing GABAA transmission in shaping excitatory connectivity during neural circuit development.
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Affiliation(s)
- Christopher K Salmon
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Horia Pribiag
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Claire Gizowski
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - W Todd Farmer
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Scott Cameron
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Emma V Jones
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Vivek Mahadevan
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Charles W Bourque
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - David Stellwagen
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
| | - Melanie A Woodin
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON, Canada
| | - Keith K Murai
- Centre for Research in Neuroscience, Department of Neurology and Neurosurgery, Brain Repair and Integrative Neuroscience Program, The Research Institute of the McGill University Health Centre, Montreal General Hospital, Montreal, QC, Canada
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6
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Chung BYT, Bailey CDC. Similar nicotinic excitability responses across the developing hippocampal formation are regulated by small-conductance calcium-activated potassium channels. J Neurophysiol 2018; 119:1707-1722. [PMID: 29384449 DOI: 10.1152/jn.00426.2017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The hippocampal formation forms a cognitive circuit that is critical for learning and memory. Cholinergic input to nicotinic acetylcholine receptors plays an important role in the normal development of principal neurons within the hippocampal formation. However, the ability of nicotinic receptors to stimulate principal neurons across all regions of the developing hippocampal formation has not been determined. We show in this study that heteromeric nicotinic receptors mediate direct inward current and depolarization responses in principal neurons across the hippocampal formation of the young postnatal mouse. These responses were found in principal neurons of the CA1, CA3, dentate gyrus, subiculum, and entorhinal cortex layer VI, and they varied in magnitude across regions with the greatest responses occurring in the subiculum and entorhinal cortex. Despite this regional variation in the magnitude of passive responses, heteromeric nicotinic receptor stimulation increased the excitability of active principal neurons by a similar amount in all regions. Pharmacological experiments found this similar excitability response to be regulated by small-conductance calcium-activated potassium (SK) channels, which exhibited regional differences in their influence on neuron activity that offset the observed regional differences in passive nicotinic responses. These findings demonstrate that SK channels play a role to coordinate the magnitude of heteromeric nicotinic excitability responses across the hippocampal formation at a time when nicotinic signaling drives the development of this cognitive brain region. This coordinated input may contribute to the normal development, synchrony, and maturation of the hippocampal formation learning and memory network. NEW & NOTEWORTHY This study demonstrates that small-conductance calcium-activated potassium channels regulate similar-magnitude excitability responses to heteromeric nicotinic acetylcholine receptor stimulation in active principal neurons across multiple regions of the developing mouse hippocampal formation. Given the importance of nicotinic neurotransmission for the development of principal neurons within the hippocampal formation, this coordinated excitability response is positioned to influence the normal development, synchrony, and maturation of the hippocampal formation learning and memory network.
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Affiliation(s)
- Beryl Y T Chung
- Department of Biomedical Sciences, University of Guelph , Guelph, Ontario , Canada
| | - Craig D C Bailey
- Department of Biomedical Sciences, University of Guelph , Guelph, Ontario , Canada
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7
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Happ DF, Tasker RA. Effects of α7 Nicotinic Receptor Activation on Cell Survival in Rat Organotypic Hippocampal Slice Cultures. Neurotox Res 2017; 33:887-895. [DOI: 10.1007/s12640-017-9854-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/04/2017] [Accepted: 12/13/2017] [Indexed: 11/28/2022]
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8
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Albiñana E, Luengo JG, Baraibar AM, Muñoz MD, Gandía L, Solís JM, Hernández-Guijo JM. Choline induces opposite changes in pyramidal neuron excitability and synaptic transmission through a nicotinic receptor-independent process in hippocampal slices. Pflugers Arch 2017; 469:779-795. [PMID: 28176016 DOI: 10.1007/s00424-017-1939-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/13/2023]
Abstract
Choline is present at cholinergic synapses as a product of acetylcholine degradation. In addition, it is considered a selective agonist for α5 and α7 nicotinic acetylcholine receptors (nAChRs). In this study, we determined how choline affects action potentials and excitatory synaptic transmission using extracellular and intracellular recording techniques in CA1 area of hippocampal slices obtained from both mice and rats. Choline caused a reversible depression of evoked field excitatory postsynaptic potentials (fEPSPs) in a concentration-dependent manner that was not affected by α7 nAChR antagonists. Moreover, this choline-induced effect was not mimicked by either selective agonists or allosteric modulators of α7 nAChRs. Additionally, this choline-mediated effect was not prevented by either selective antagonists of GABA receptors or hemicholinium, a choline uptake inhibitor. The paired pulse facilitation paradigm, which detects whether a substance affects presynaptic release of glutamate, was not modified by choline. On the other hand, choline induced a robust increase of population spike evoked by orthodromic stimulation but did not modify that evoked by antidromic stimulation. We also found that choline impaired recurrent inhibition recorded in the pyramidal cell layer through a mechanism independent of α7 nAChR activation. These choline-mediated effects on fEPSP and population spike observed in rat slices were completely reproduced in slices obtained from α7 nAChR knockout mice, which reinforces our conclusion that choline modulates synaptic transmission and neuronal excitability by a mechanism independent of nicotinic receptor activation.
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Affiliation(s)
- E Albiñana
- Department of Pharmacology and Therapeutic, University Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain.,Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, 28029, Madrid, Spain
| | - J G Luengo
- Department of Pharmacology and Therapeutic, University Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain.,Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, 28029, Madrid, Spain
| | - A M Baraibar
- Department of Pharmacology and Therapeutic, University Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain.,Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, 28029, Madrid, Spain
| | - M D Muñoz
- Servicio de Neurología Experimental, Hospital Universitario Ramón y Cajal, IRYCIS, 28034, Madrid, Spain
| | - L Gandía
- Department of Pharmacology and Therapeutic, University Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain.,Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, 28029, Madrid, Spain
| | - J M Solís
- Servicio de Neurobiología-Investigación, Hospital Universitario Ramón y Cajal, IRYCIS, 28034, Madrid, Spain
| | - J M Hernández-Guijo
- Department of Pharmacology and Therapeutic, University Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain. .,Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, 28029, Madrid, Spain.
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9
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Duan JJ, Lozada AF, Gou CY, Xu J, Chen Y, Berg DK. Nicotine recruits glutamate receptors to postsynaptic sites. Mol Cell Neurosci 2015; 68:340-9. [PMID: 26365992 DOI: 10.1016/j.mcn.2015.09.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 08/04/2015] [Accepted: 09/07/2015] [Indexed: 01/20/2023] Open
Abstract
Cholinergic neurons project throughout the nervous system and activate nicotinic receptors to modulate synaptic function in ways that shape higher order brain function. The acute effects of nicotinic signaling on long-term synaptic plasticity have been well-characterized. Less well understood is how chronic exposure to low levels of nicotine, such as those encountered by habitual smokers, can alter neural connections to promote addiction and other lasting behavioral effects. We show here that chronic exposure of hippocampal neurons in culture to low levels of nicotine recruits AMPA and NMDA receptors to the cell surface and sequesters them at postsynaptic sites. The receptors include GluA2-containing AMPA receptors, which are responsible for most of the excitatory postsynaptic current mediated by AMPA receptors on the neurons, and include NMDA receptors containing GluN1 and GluN2B subunits. Moreover, we find that the nicotine treatment also increases expression of the presynaptic component synapsin 1 and arranges it in puncta juxtaposed to the additional AMPA and NMDA receptor puncta, suggestive of increases in synaptic contacts. Consistent with increased synaptic input, we find that the nicotine treatment leads to an increase in the excitatory postsynaptic currents mediated by AMPA and NMDA receptors. Further, the increases skew the ratio of excitatory-to-inhibitory input that the cell receives, and this holds both for pyramidal neurons and inhibitory neurons in the hippocampal CA1 region. The GluN2B-containing NMDA receptor redistribution at synapses is associated with a significant increase in GluN2B phosphorylation at Tyr1472, a site known to prevent GluN2B endocytosis. These results suggest that chronic exposure to low levels of nicotine not only alters functional connections but also is likely to change excitability levels across networks. Further, it may increase the propensity for synaptic plasticity, given the increase in synaptic NMDA receptors.
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Affiliation(s)
- Jing-Jing Duan
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; Neurobiology Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357, United States
| | - Adrian F Lozada
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357, United States
| | - Chen-Yu Gou
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China
| | - Jing Xu
- Pain Research Center and Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
| | - Yuan Chen
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China.
| | - Darwin K Berg
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357, United States.
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10
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Cheng Q, Yakel JL. The effect of α7 nicotinic receptor activation on glutamatergic transmission in the hippocampus. Biochem Pharmacol 2015. [PMID: 26212541 DOI: 10.1016/j.bcp.2015.07.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nicotinic acetylcholine receptors (nAChRs) are expressed widely in the CNS, and mediate both synaptic and perisynaptic activities of endogenous cholinergic inputs and pharmacological actions of exogenous compounds (e.g., nicotine and choline). Behavioral studies indicate that nicotine improves such cognitive functions as learning and memory, however the cellular mechanism of these actions remains elusive. With help from newly developed biosensors and optogenetic tools, recent studies provide new insights on signaling mechanisms involved in the activation of nAChRs. Here we will review α7 nAChR's action in the tri-synaptic pathway in the hippocampus. The effects of α7 nAChR activation via either exogenous compounds or endogenous cholinergic innervation are detailed for spontaneous and evoked glutamatergic synaptic transmission and synaptic plasticity, as well as the underlying signaling mechanisms. In summary, α7 nAChRs trigger intracellular calcium rise and calcium-dependent signaling pathways to enhance glutamate release and induce glutamatergic synaptic plasticity.
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Affiliation(s)
- Qing Cheng
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709, USA
| | - Jerrel L Yakel
- Neurobiology Laboratory, 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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11
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Jang MJ, Nam Y. NeuroCa: integrated framework for systematic analysis of spatiotemporal neuronal activity patterns from large-scale optical recording data. NEUROPHOTONICS 2015; 2:035003. [PMID: 26229973 PMCID: PMC4516777 DOI: 10.1117/1.nph.2.3.035003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 06/23/2015] [Indexed: 05/22/2023]
Abstract
Optical recording facilitates monitoring the activity of a large neural network at the cellular scale, but the analysis and interpretation of the collected data remain challenging. Here, we present a MATLAB-based toolbox, named NeuroCa, for the automated processing and quantitative analysis of large-scale calcium imaging data. Our tool includes several computational algorithms to extract the calcium spike trains of individual neurons from the calcium imaging data in an automatic fashion. Two algorithms were developed to decompose the imaging data into the activity of individual cells and subsequently detect calcium spikes from each neuronal signal. Applying our method to dense networks in dissociated cultures, we were able to obtain the calcium spike trains of [Formula: see text] neurons in a few minutes. Further analyses using these data permitted the quantification of neuronal responses to chemical stimuli as well as functional mapping of spatiotemporal patterns in neuronal firing within the spontaneous, synchronous activity of a large network. These results demonstrate that our method not only automates time-consuming, labor-intensive tasks in the analysis of neural data obtained using optical recording techniques but also provides a systematic way to visualize and quantify the collective dynamics of a network in terms of its cellular elements.
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Affiliation(s)
- Min Jee Jang
- Korea Advanced Institute of Science and Technology
(KAIST), Department of Bio and Brain Engineering, 291 Daehak-ro,
Yuseong-gu, Daejeon 305-701, Republic of Korea
| | - Yoonkey Nam
- Korea Advanced Institute of Science and Technology
(KAIST), Department of Bio and Brain Engineering, 291 Daehak-ro,
Yuseong-gu, Daejeon 305-701, Republic of Korea
- Address all correspondence to: Yoonkey Nam, E-mail:
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12
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Neurocognitive effects of acute choline supplementation in low, medium and high performer healthy volunteers. Pharmacol Biochem Behav 2015; 131:119-29. [PMID: 25681529 DOI: 10.1016/j.pbb.2015.02.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 01/20/2015] [Accepted: 02/04/2015] [Indexed: 12/28/2022]
Abstract
Novel pharmacological treatments targeting alpha 7 nicotinic acetylcholine receptor (α7 nAChR) hypofunction in schizophrenia have shown mixed success in ameliorating cognitive impairments associated with this disorder. Choline, a selective agonist at α7 receptors is increased with oral administration of cytidine 5'-diphosphocholine (CDP-choline), the cognitive effects of which were assessed in healthy volunteers. Using the CogState test battery, behavioral performance in schizophrenia-relevant cognitive domains was assessed in 24 male participants following a single low (500mg) and moderate (1000mg) dose of CDP-choline. Relative to placebo, CDP-choline improved processing speed, working memory, verbal learning, verbal memory, and executive function in low baseline performers, while exerting no effects in medium baseline performers, and diminishing cognition in high baseline performers. Dose effects varied with cognitive domain but were evident with both the 500mg and 1000mg doses. These preliminary findings of cognitive enhancement in relatively impaired performers are consistent with the α7 receptor mechanism and support further trials with CDP-choline as a potential pro-cognitive strategy for cognitive impairment in schizophrenia.
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13
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Lin H, Hsu FC, Baumann BH, Coulter DA, Anderson SA, Lynch DR. Cortical parvalbumin GABAergic deficits with α7 nicotinic acetylcholine receptor deletion: implications for schizophrenia. Mol Cell Neurosci 2014; 61:163-75. [PMID: 24983521 DOI: 10.1016/j.mcn.2014.06.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Revised: 05/23/2014] [Accepted: 06/16/2014] [Indexed: 11/25/2022] Open
Abstract
Dysfunction of cortical parvalbumin (PV)-containing GABAergic interneurons has been implicated in cognitive deficits of schizophrenia. In humans microdeletion of the CHRNA7 (α7 nicotinic acetylcholine receptor, nAChR) gene is associated with cortical dysfunction in a broad spectrum of neurodevelopmental and neuropsychiatric disorders including schizophrenia while in mice similar deletion causes analogous abnormalities including impaired attention, working-memory and learning. However, the pathophysiological roles of α7 nAChRs in cortical PV GABAergic development remain largely uncharacterized. In both in vivo and in vitro models, we identify here that deletion of the α7 nAChR gene in mice impairs cortical PV GABAergic development and recapitulates many of the characteristic neurochemical deficits in PV-positive GABAergic interneurons found in schizophrenia. α7 nAChR null mice had decreased cortical levels of GABAergic markers including PV, glutamic acid decarboxylase 65/67 (GAD65/67) and the α1 subunit of GABAA receptors, particularly reductions of PV and GAD67 levels in cortical PV-positive interneurons during late postnatal life and adulthood. Cortical GABAergic synaptic deficits were identified in the prefrontal cortex of α7 nAChR null mice and α7 nAChR null cortical cultures. Similar disruptions in development of PV-positive GABAergic interneurons and perisomatic synapses were found in cortical cultures lacking α7 nAChRs. Moreover, NMDA receptor expression was reduced in GABAergic interneurons, implicating NMDA receptor hypofunction in GABAergic deficits in α7 nAChR null mice. Our findings thus demonstrate impaired cortical PV GABAergic development and multiple characteristic neurochemical deficits reminiscent of schizophrenia in cortical PV-positive interneurons in α7 nAChR gene deletion models. This implicates crucial roles of α7 nAChRs in cortical PV GABAergic development and dysfunction in schizophrenia and other neuropsychiatric disorders.
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Affiliation(s)
- Hong Lin
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States
| | - Fu-Chun Hsu
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States
| | - Bailey H Baumann
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States
| | - Douglas A Coulter
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - Stewart A Anderson
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Child Psychiatry, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
| | - David R Lynch
- Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
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14
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Wang H, Megill A, Wong PC, Kirkwood A, Lee HK. Postsynaptic target specific synaptic dysfunctions in the CA3 area of BACE1 knockout mice. PLoS One 2014; 9:e92279. [PMID: 24637500 PMCID: PMC3956924 DOI: 10.1371/journal.pone.0092279] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 02/20/2014] [Indexed: 11/19/2022] Open
Abstract
Beta-amyloid precursor protein cleaving enzyme 1 (BACE1), a major neuronal β-secretase critical for the formation of β-amyloid (Aβ) peptide, is considered one of the key therapeutic targets that can prevent the progression of Alzheimer's disease (AD). Although a complete ablation of BACE1 gene prevents Aβ formation, we previously reported that BACE1 knockouts (KOs) display presynaptic deficits, especially at the mossy fiber (MF) to CA3 synapses. Whether the defect is specific to certain inputs or postsynaptic targets in CA3 is unknown. To determine this, we performed whole-cell recording from pyramidal cells (PYR) and the stratum lucidum (SL) interneurons in the CA3, both of which receive excitatory MF terminals with high levels of BACE1 expression. BACE1 KOs displayed an enhancement of paired-pulse facilitation at the MF inputs to CA3 PYRs without changes at the MF inputs to SL interneurons, which suggests postsynaptic target specific regulation. The synaptic dysfunction in CA3 PYRs was not restricted to excitatory synapses, as seen by an increase in the paired-pulse ratio of evoked inhibitory postsynaptic currents from SL to CA3 PYRs. In addition to the changes in evoked synaptic transmission, BACE1 KOs displayed a reduction in the frequency of miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) in CA3 PYRs without alteration in mEPSCs recorded from SL interneurons. This suggests that the impairment may be more global across diverse inputs to CA3 PYRs. Our results indicate that the synaptic dysfunctions seen in BACE1 KOs are specific to the postsynaptic target, the CA3 PYRs, independent of the input type.
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Affiliation(s)
- Hui Wang
- Department of Neuroscience, Mind/Brain Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Andrea Megill
- Department of Neuroscience, Mind/Brain Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Philip C. Wong
- Department of Pathology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Alfredo Kirkwood
- Department of Neuroscience, Mind/Brain Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Hey-Kyoung Lee
- Department of Neuroscience, Mind/Brain Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
- * E-mail:
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15
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Baj G, Patrizio A, Montalbano A, Sciancalepore M, Tongiorgi E. Developmental and maintenance defects in Rett syndrome neurons identified by a new mouse staging system in vitro. Front Cell Neurosci 2014; 8:18. [PMID: 24550777 PMCID: PMC3914021 DOI: 10.3389/fncel.2014.00018] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/11/2014] [Indexed: 12/02/2022] Open
Abstract
Rett Syndrome (RTT) is a neurodevelopmental disorder associated with intellectual disability, mainly caused by loss-of-function mutations in the MECP2 gene. RTT brains display decreased neuronal size and dendritic arborization possibly caused by either a developmental failure or a deficit in the maintenance of dendritic arbor structure. To distinguish between these two hypotheses, the development of Mecp2-knockout mouse hippocampal neurons was analyzed in vitro. Since a staging system for the in vitro development of mouse neurons was lacking, mouse and rat hippocampal neurons development was compared between 1–15 days in vitro (DIV) leading to a 6-stage model for both species. Mecp2-knockout hippocampal neurons displayed reduced growth of dendritic branches from stage 4 (DIV4) onwards. At stages 5–6 (DIV9-15), synapse number was lowered in Mecp2-knockout neurons, suggesting increased synapse elimination. These results point to both a developmental and a maintenance setback affecting the final shape and function of neurons in RTT.
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Affiliation(s)
- Gabriele Baj
- Department of Life Sciences, BRAIN Center for Neuroscience, University of Trieste Trieste, Italy
| | - Angela Patrizio
- Department of Life Sciences, BRAIN Center for Neuroscience, University of Trieste Trieste, Italy
| | - Alberto Montalbano
- Department of Life Sciences, BRAIN Center for Neuroscience, University of Trieste Trieste, Italy
| | - Marina Sciancalepore
- Department of Life Sciences, BRAIN Center for Neuroscience, University of Trieste Trieste, Italy
| | - Enrico Tongiorgi
- Department of Life Sciences, BRAIN Center for Neuroscience, University of Trieste Trieste, Italy
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16
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Phasic nicotinic potentiation of frog retinotectal transmission facilitates eliciting of higher activity level of the tectum column. Neurosci Lett 2013; 554:1-5. [PMID: 24012815 DOI: 10.1016/j.neulet.2013.08.053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/07/2013] [Accepted: 08/25/2013] [Indexed: 11/24/2022]
Abstract
Nicotinic acetylcholine receptors contribute to the mediation of cholinergic role in attention, vigilance, orienting and detection of behavioral significant stimuli. We have recently demonstrated an increase of the intrinsic recurrent excitatory activity of the tectum column caused by the phasic (after-burst) nicotinic potentiation of a frog single axon retinotectal transmission to the tectum layer F. We have shown in the present study that the phasic nicotinic potentiation facilitates eliciting of higher activity level of the tectum column featured by generation of output signals from the tectum column. Since these signals can lead to an escape from danger reactions, a functional significance of nicotinic modulation of the neural network has been demonstrated. The phasic nicotinic potentiation that facilitates eliciting of higher activity level of the tectum column can be considered as a mechanism of vigilance and cue detection at the level of small neural network.
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17
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Wang X, Lippi G, Carlson DM, Berg DK. Activation of α7-containing nicotinic receptors on astrocytes triggers AMPA receptor recruitment to glutamatergic synapses. J Neurochem 2013; 127:632-43. [PMID: 24032433 DOI: 10.1111/jnc.12436] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 07/31/2013] [Accepted: 08/26/2013] [Indexed: 02/02/2023]
Abstract
Astrocytes, an abundant form of glia, are known to promote and modulate synaptic signaling between neurons. They also express α7-containing nicotinic acetylcholine receptors (α7-nAChRs), but the functional relevance of these receptors is unknown. We show here that stimulation of α7-nAChRs on astrocytes releases components that induce hippocampal neurons to acquire more α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors post-synaptically at glutamatergic synapses. The increase is specific in that no change is seen in synaptic NMDA receptor clusters or other markers for glutamatergic synapses, or in markers for GABAergic synapses. Moreover, the increases in AMPA receptors on the neuron surface are accompanied by increases in the frequency of spontaneous miniature synaptic currents mediated by the receptors and increases in the ratio of evoked synaptic currents mediated by AMPA versus NMDA receptors. This suggests that stimulating α7-nAChRs on astrocytes can convert 'silent' glutamatergic synapses to functional status. Astrocyte-derived thrombospondin is necessary but not sufficient for the effect, while tumor necrosis factor-α is sufficient but not necessary. The results identify astrocyte α7-nAChRs as a novel pathway through which nicotinic cholinergic signaling can promote the development of glutamatergic networks, recruiting AMPA receptors to post-synaptic sites and rendering the synapses more functional. We find that activation of nicotinic receptors on astrocytes releases a component that specifically recruits AMPA receptors to glutamatergic synapses. The recruitment appears to occur preferentially at what may be 'silent synapses', that is, synapses that have all the components required for glutamatergic transmission (including NMDA receptors) but lack sufficient AMPA receptors to generate a response. The results are unexpected and open up new possibilities for mechanisms underlying network formation and synaptic plasticity.
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Affiliation(s)
- Xulong Wang
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California, USA
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18
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Pizzarelli R, Cherubini E. Developmental regulation of GABAergic signalling in the hippocampus of neuroligin 3 R451C knock-in mice: an animal model of Autism. Front Cell Neurosci 2013; 7:85. [PMID: 23761734 PMCID: PMC3671185 DOI: 10.3389/fncel.2013.00085] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 05/17/2013] [Indexed: 11/24/2022] Open
Abstract
Autism Spectrum Disorders (ASDs) comprise an heterogeneous group of neuro-developmental abnormalities, mainly of genetic origin, characterized by impaired social interactions, communications deficits, and stereotyped behaviors. In a small percentage of cases, ASDs have been found to be associated with single mutations in genes involved in synaptic function. One of these involves the postsynaptic cell adhesion molecule neuroligin (NL) 3. NLs interact with presynaptic neurexins (Nrxs) to ensure a correct cross talk between post and presynaptic specializations. Here, transgenic mice carrying the human R451C mutation of Nlgn3, were used to study GABAergic signaling in the hippocampus early in postnatal life. Whole cell recordings from CA3 pyramidal neurons in slices from NL3R451C knock-in mice revealed an enhanced frequency of Giant Depolarizing Potentials (GDPs), as compared to controls. This effect was probably dependent on an increased GABAergic drive to principal cells as demonstrated by the enhanced frequency of miniature GABAA-mediated (GPSCs), but not AMPA-mediated postsynaptic currents (EPSCs). Changes in frequency of mGPSCs were associated with an acceleration of their decay kinetics, in the absence of any change in unitary synaptic conductance or in the number of GABAA receptor channels, as assessed by peak scaled non-stationary fluctuation analysis. The enhanced GABAergic but not glutamatergic transmission early in postnatal life may change the excitatory/inhibitory balance known to play a key role in the construction and refinement of neuronal circuits during postnatal development. This may lead to behavioral deficits reminiscent of those observed in ASDs patients.
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Affiliation(s)
- Rocco Pizzarelli
- Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati Trieste, Italy
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19
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PrPC controls via protein kinase A the direction of synaptic plasticity in the immature hippocampus. J Neurosci 2013; 33:2973-83. [PMID: 23407955 DOI: 10.1523/jneurosci.4149-12.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The cellular form of prion protein PrP(C) is highly expressed in the brain, where it can be converted into its abnormally folded isoform PrP(Sc) to cause neurodegenerative diseases. Its predominant synaptic localization suggests a crucial role in synaptic signaling. Interestingly, PrP(C) is developmentally regulated and its high expression in the immature brain could be instrumental in regulating neurogenesis and cell proliferation. Here, PrP(C)-deficient (Prnp(0/0)) mice were used to assess whether the prion protein is involved in synaptic plasticity processes in the neonatal hippocampus. To this aim, calcium transients associated with giant depolarizing potentials, a hallmark of developmental networks, were transiently paired with mossy fiber activation in such a way that the two events were coincident. While this procedure caused long-term potentiation (LTP) in wild-type (WT) animals, it caused long-term depression (LTD) in Prnp(0/0) mice. Induction of LTP was postsynaptic and required the activation of cAMP-dependent protein kinase A (PKA) signaling. The induction of LTD was presynaptic and relied on G-protein-coupled GluK1 receptor and protein lipase C. In addition, at emerging CA3-CA1 synapses in WT mice, but not in Prnp(0/0) mice, pairing Schaffer collateral stimulation with depolarization of CA1 principal cells induced LTP, known to be PKA dependent. Postsynaptic infusion of a constitutively active isoform of PKA catalytic subunit Cα into CA1 and CA3 principal cells in the hippocampus of Prnp(0/0) mice caused a persistent synaptic facilitation that was occluded by subsequent pairing. These data suggest that PrP(C) plays a crucial role in regulating via PKA synaptic plasticity in the developing hippocampus.
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20
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Morley BJ, Mervis RF. Dendritic spine alterations in the hippocampus and parietal cortex of alpha7 nicotinic acetylcholine receptor knockout mice. Neuroscience 2012; 233:54-63. [PMID: 23270857 DOI: 10.1016/j.neuroscience.2012.12.025] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 12/10/2012] [Accepted: 12/12/2012] [Indexed: 12/19/2022]
Abstract
The α7 nicotinic acetylcholine receptor (nAChR) is involved in higher cognitive and memory functions, and is associated with the etiology of neurological diseases involving cognitive decline, including Alzheimer's disease (AD). We hypothesized that spine changes in the α7 knockout might help to explain the behavioral deficits observed in α7 knockout mice and prodromal hippocampal changes in AD. We quantified several measures of dendritic morphology in the CA1 region of the mouse hippocampus in Golgi-stained material from wildtype and α7 knockout mice at P24. The most significant difference was a 64% increase in thin (L-type) dendritic spines on the CA1 basilar tree in knockout mice (p<.05). There were small decreases in the number of in N-type (-15%), M-type (-14%) and D-type (-4%) spine densities. The CA1 basilar dendritic tree of knockout mice had significantly less branching in the regions near the soma in comparison with wildtype animals (p<.01), but not in the more distal branching. Changes in the configuration of CA1 basilar dendritic spines have been observed in a number of experimental paradigms, suggesting that basilar dendritic spines are highly plastic. One component of cognitive dysfunction may be through α7-modulated GABAergic interneurons synapsing on CA1 basal dendrites.
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Affiliation(s)
- B J Morley
- Boys Town National Research Hospital, 555 North 30th Street, Omaha, NE 68131, USA.
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21
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Dyeing to be fired: firing order distinguishes two types of bursting activity. Epilepsy Curr 2012; 12:176-7. [PMID: 23118601 DOI: 10.5698/1535-7511-12.5.176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Ben-Ari Y, Woodin MA, Sernagor E, Cancedda L, Vinay L, Rivera C, Legendre P, Luhmann HJ, Bordey A, Wenner P, Fukuda A, van den Pol AN, Gaiarsa JL, Cherubini E. Refuting the challenges of the developmental shift of polarity of GABA actions: GABA more exciting than ever! Front Cell Neurosci 2012; 6:35. [PMID: 22973192 PMCID: PMC3428604 DOI: 10.3389/fncel.2012.00035] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 07/29/2012] [Indexed: 12/12/2022] Open
Abstract
During brain development, there is a progressive reduction of intracellular chloride associated with a shift in GABA polarity: GABA depolarizes and occasionally excites immature neurons, subsequently hyperpolarizing them at later stages of development. This sequence, which has been observed in a wide range of animal species, brain structures and preparations, is thought to play an important role in activity-dependent formation and modulation of functional circuits. This sequence has also been considerably reinforced recently with new data pointing to an evolutionary preserved rule. In a recent “Hypothesis and Theory Article,” the excitatory action of GABA in early brain development is suggested to be “an experimental artefact” (Bregestovski and Bernard, 2012). The authors suggest that the excitatory action of GABA is due to an inadequate/insufficient energy supply in glucose-perfused slices and/or to the damage produced by the slicing procedure. However, these observations have been repeatedly contradicted by many groups and are inconsistent with a large body of evidence including the fact that the developmental shift is neither restricted to slices nor to rodents. We summarize the overwhelming evidence in support of both excitatory GABA during development, and the implications this has in developmental neurobiology.
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Affiliation(s)
- Yehezkel Ben-Ari
- INSERM Unité 901, Université de la Méditerranée, UMR S901 Aix-Marseille 2 and INMED Marseille, France
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23
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Glutamatergic synapse formation is promoted by α7-containing nicotinic acetylcholine receptors. J Neurosci 2012; 32:7651-61. [PMID: 22649244 DOI: 10.1523/jneurosci.6246-11.2012] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Glutamate is the primary excitatory transmitter in adult brain, acting through synapses on dendritic spines and shafts. Early in development, however, when glutamatergic synapses are only beginning to form, nicotinic cholinergic excitation is already widespread; it is mediated by acetylcholine activating nicotinic acetylcholine receptors (nAChRs) that generate waves of activity across brain regions. A major class of nAChRs contributing at this time is a species containing α7 subunits (α7-nAChRs). These receptors are highly permeable to calcium, influence a variety of calcium-dependent events, and are diversely distributed throughout the developing CNS. Here we show that α7-nAChRs unexpectedly promote formation of glutamatergic synapses during development. The dependence on α7-nAChRs becomes clear when comparing wild-type (WT) mice with mice constitutively lacking the α7-nAChR gene. Ultrastructural analysis, immunostaining, and patch-clamp recording all reveal synaptic deficits when α7-nAChR input is absent. Similarly, nicotinic activation of α7-nAChRs in WT organotypic culture, as well as cell culture, increases the number of glutamatergic synapses. RNA interference demonstrates that the α7-nAChRs must be expressed in the neuron being innervated for normal innervation to occur. Moreover, the deficits persist throughout the developmental period of major de novo synapse formation and are still fully apparent in the adult. GABAergic synapses, in contrast, are undiminished in number under such conditions. As a result, mice lacking α7-nAChRs have an altered balance in the excitatory/inhibitory input they receive. This ratio represents a fundamental feature of neural networks and shows for the first time that endogenous nicotinic cholinergic signaling plays a key role in network construction.
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24
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Consequences of inhibiting amyloid precursor protein processing enzymes on synaptic function and plasticity. Neural Plast 2012; 2012:272374. [PMID: 22792491 PMCID: PMC3390164 DOI: 10.1155/2012/272374] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 04/22/2012] [Indexed: 12/21/2022] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disease, one of whose major pathological hallmarks is the accumulation of amyloid plaques comprised of aggregated β-amyloid (Aβ) peptides. It is now recognized that soluble Aβ oligomers may lead to synaptic dysfunctions early in AD pathology preceding plaque deposition. Aβ is produced by a sequential cleavage of amyloid precursor protein (APP) by the activity of β- and γ-secretases, which have been identified as major candidate therapeutic targets of AD. This paper focuses on how Aβ alters synaptic function and the functional consequences of inhibiting the activity of the two secretases responsible for Aβ generation. Abnormalities in synaptic function resulting from the absence or inhibition of the Aβ-producing enzymes suggest that Aβ itself may have normal physiological functions which are disrupted by abnormal accumulation of Aβ during AD pathology. This interpretation suggests that AD therapeutics targeting the β- and γ-secretases should be developed to restore normal levels of Aβ or combined with measures to circumvent the associated synaptic dysfunction(s) in order to have minimal impact on normal synaptic function.
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25
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Lozada AF, Wang X, Gounko NV, Massey KA, Duan J, Liu Z, Berg DK. Induction of dendritic spines by β2-containing nicotinic receptors. J Neurosci 2012; 32:8391-400. [PMID: 22699919 PMCID: PMC3387687 DOI: 10.1523/jneurosci.6247-11.2012] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 04/17/2012] [Accepted: 05/01/2012] [Indexed: 11/21/2022] Open
Abstract
Glutamatergic synapses are located mostly on dendritic spines in the adult nervous system. The spines serve as postsynaptic compartments, containing components that mediate and control the synaptic signal. Early in development, when glutamatergic synapses are initially forming, waves of excitatory activity pass through many parts of the nervous system and are driven in part by a class of heteropentameric β2-containing nicotinic acetylcholine receptors (β2*-nAChRs). These β2*-nAChRs are widely distributed and, when activated, can depolarize the membrane and elevate intracellular calcium levels in neurons. We show here that β2*-nAChRs are essential for acquisition of normal numbers of dendritic spines during development. Mice constitutively lacking the β2-nAChR gene have fewer dendritic spines than do age-matched wild-type mice at all times examined. Activation of β2*-nAChRs by nicotine either in vivo or in organotypic slice culture quickly elevates the number of spines. RNA interference studies both in vivo and in organotypic culture demonstrate that the β2*-nAChRs act in a cell-autonomous manner to increase the number of spines. The increase depends on intracellular calcium and activation of calcium, calmodulin-dependent protein kinase II. Absence of β2*-nAChRs in vivo causes a disproportionate number of glutamatergic synapses to be localized on dendritic shafts, rather than on spines as occurs in wild type. This shift in synapse location is found both in the hippocampus and cortex, indicating the breadth of the effect. Because spine synapses differ from shaft synapses in their signaling capabilities, the shift observed is likely to have significant consequences for network function.
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Affiliation(s)
- Adrian F. Lozada
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
| | - Xulong Wang
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
| | - Natalia V. Gounko
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
- Scripps Research Institute, La Jolla, California 92037
| | - Kerri A. Massey
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
- Amgen, Inc., Thousand Oaks, California 91360
| | - Jingjing Duan
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China, and
| | - Zhaoping Liu
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
- Intellicyt Corporation, Albuquerque, New Mexico 87113
| | - Darwin K. Berg
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357
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26
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Deterministic and stochastic neuronal contributions to distinct synchronous CA3 network bursts. J Neurosci 2012; 32:4743-54. [PMID: 22492030 DOI: 10.1523/jneurosci.4277-11.2012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Computational studies have suggested that stochastic, deterministic, and mixed processes all could be possible determinants of spontaneous, synchronous network bursts. In the present study, using multicellular calcium imaging coupled with fast confocal microscopy, we describe neuronal behavior underlying spontaneous network bursts in developing rat and mouse hippocampal area CA3 networks. Two primary burst types were studied: giant depolarizing potentials (GDPs) and spontaneous interictal bursts recorded in bicuculline, a GABA(A) receptor antagonist. Analysis of the simultaneous behavior of multiple CA3 neurons during synchronous GDPs revealed a repeatable activation order from burst to burst. This was validated using several statistical methods, including high Kendall's coefficient of concordance values for firing order during GDPs, high Pearson's correlations of cellular activation times between burst pairs, and latent class analysis, which revealed a population of 5-6% of CA3 neurons reliably firing very early during GDPs. In contrast, neuronal firing order during interictal bursts appeared homogeneous, with no particular cells repeatedly leading or lagging during these synchronous events. We conclude that GDPs activate via a deterministic mechanism, with distinct, repeatable roles for subsets of neurons during burst generation, while interictal bursts appear to be stochastic events with cells assuming interchangeable roles in the generation of these events.
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27
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Krüger HS, Hanganu-Opatz IL. Neonatal cholinergic lesion alters the acoustic structure of infant rat vocalization but not the early cognitive development. Dev Psychobiol 2012; 55:294-308. [DOI: 10.1002/dev.21029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 03/02/2012] [Indexed: 11/09/2022]
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28
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Nakauchi S, Sumikawa K. Endogenously released ACh and exogenous nicotine differentially facilitate long-term potentiation induction in the hippocampal CA1 region of mice. Eur J Neurosci 2012; 35:1381-95. [PMID: 22462479 DOI: 10.1111/j.1460-9568.2012.08056.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We examined the role of α7- and β2-containing nicotinic acetylcholine receptors (nAChRs) in the induction of long-term potentiation (LTP). Theta-burst stimulation (TBS), mimicking the brain's naturally occurring theta rhythm, induced robust LTP in hippocampal slices from α7 and β2 knockout mice. This suggests TBS is capable of inducing LTP without activation of α7- or β2-containing nAChRs. However, when weak TBS was applied, the modulatory effects of nicotinic receptors on LTP induction became visible. We showed that during weak TBS, activation of α7 nAChRs occurs by the release of ACh, contributing to LTP induction. Additionally, bath-application of nicotine activated β2-containing nAChRs to promote LTP induction. Despite predicted nicotine-induced desensitization, synaptically mediated activation of α7 nAChRs still occurs in the presence of nicotine and contributed to LTP induction. Optical recording of single-stimulation-evoked excitatory activity with a voltage-sensitive dye revealed enhanced excitatory activity in the presence of nicotine. This effect of nicotine was robust during high-frequency stimulation, and was accompanied by enhanced burst excitatory postsynaptic potentials. Nicotine-induced enhancement of excitatory activity was observed in slices from α7 knockout mice, but was absent in β2 knockout mice. These results suggest that the nicotine-induced enhancement of excitatory activity is mediated by β2-containing nAChRs, and is related to the nicotine-induced facilitation of LTP induction. Thus, our study demonstrates that the activation of α7- and β2-containing nAChRs differentially facilitates LTP induction via endogenously released ACh and exogenous nicotine, respectively, in the hippocampal CA1 region of mice.
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Affiliation(s)
- Sakura Nakauchi
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550, USA
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29
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Griguoli M, Cherubini E. Regulation of hippocampal inhibitory circuits by nicotinic acetylcholine receptors. J Physiol 2012; 590:655-66. [PMID: 22124144 PMCID: PMC3381299 DOI: 10.1113/jphysiol.2011.220095] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2011] [Accepted: 11/24/2011] [Indexed: 11/08/2022] Open
Abstract
The hippocampal network comprises a large variety of locally connected GABAergic interneurons exerting a powerful control on network excitability and which are responsible for the oscillatory behaviour crucial for information processing. GABAergic interneurons receive an important cholinergic innervation from the medial septum-diagonal band complex of the basal forebrain and are endowed with a variety of muscarinic and nicotinic acetylcholine receptors (mAChRs and nAChRs) that regulate their activity. Deficits in the cholinergic system lead to the impairment of high cognitive functions, which are particularly relevant in neurodegenerative pathologies such as Alzheimer's and Parkinson's diseases as well as in schizophrenia. Here, we highlight some recent advances in the mechanisms by which cholinergic signalling via nAChRs regulates local inhibitory circuits in the hippocampus, early in postnatal life and in adulthood. We also discuss recent findings concerning the functional role of nAChRs in controlling short- and long-term modifications of synaptic efficacy. Insights into these processes may provide new targets for the therapeutic control of pathological conditions associated with cholinergic dysfunctions.
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Affiliation(s)
- Marilena Griguoli
- Neuroscience Programme, International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste, Italy
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Chronic neonatal nicotine exposure increases excitation in the young adult rat hippocampus in a sex-dependent manner. Brain Res 2011; 1430:8-17. [PMID: 22119395 DOI: 10.1016/j.brainres.2011.10.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 11/21/2022]
Abstract
Smoking during pregnancy exposes the fetus to nicotine, resulting in nicotine-stimulated neurotransmitter release. Recent evidence suggests that the hippocampus develops differently in males and females with delayed maturation in males. We show that chronic nicotine exposure during the first postnatal week has sex-specific long-term effects. Neonatal rat pups were chronically treated with nicotine (6mg/kg/day) (CNN) from postnatal day 1 to 7 or milk only (Controls), and hippocampal slices were prepared from Control- and CNN-treated young adults. Field excitatory postsynaptic potentials (fEPSPs) or population spikes (PSs) were recorded from the CA1 hippocampus following CA1 s. radiatum stimulation. Input/Output curves constructed from fEPSP data indicated that CNN-males, but not females, had significantly increased excitatory responses compared to Controls (p<0.05, n=10 Con, n=11 CNN). Long-term potentiation (LTP) was not significantly changed by CNN. In the presence of bicuculline, which blocks inhibitory GABA(A) receptors, an epileptiform burst consisting of a series of PSs was evoked. The amplitude of the first PS was significantly larger in CNN-males and females compared to Controls (males: p<0.01, n=8 Con, n=8 CNN; females: p<0.05, n=9 Con, n=7 CNN). Only CNN-males also had significantly larger second PSs (p<0.05, n=8 con, n=8 CNN). Epileptiform activity evoked by zero Mg(2+) incubation did not differ in amplitude or duration of bursts in CNN-males or females compared to Controls. These data indicate that neonatal nicotine exposure has long lasting effects and results in increased excitation within the CA1 hippocampus in adulthood, with males showing increased sensitivity to nicotine's effects.
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Campbell NR, Fernandes CC, John D, Lozada AF, Berg DK. Nicotinic control of adult-born neuron fate. Biochem Pharmacol 2011; 82:820-7. [PMID: 21723854 DOI: 10.1016/j.bcp.2011.06.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 06/14/2011] [Accepted: 06/14/2011] [Indexed: 10/18/2022]
Abstract
The hippocampus is one of only two regions in the adult brain where neurons are generated in significant numbers throughout the lifetime of the animal. Numerous studies have demonstrated that these adult-born neurons are essential for optimal cognitive function with unimpaired memory formation and retrieval. The extent to which adult-born neurons survive through an early "critical period" and become integrated into functional networks has been shown to depend on the richness of stimulation they receive during these formative stages. The dentate gyrus in the hippocampus - home of the adult-born neurons - receives extensive cholinergic innervation, and newly generated neurons in the adult hippocampus express substantial numbers of both major types of neuronal nicotinic acetylcholine receptors. Early studies indicated that nicotinic signaling may be important for the development of adult-born neurons: repeated exposure to nicotine impaired their long-term survival. Recent studies with mutant mice lacking either one of the two major nicotinic receptor subtypes demonstrate that receptor loss results in fewer adult-born neurons surviving the critical period and becoming integrated into neural networks. The key nicotinic receptor mediating the largest effects is one that has a high relative permeability to calcium. In view of this feature, it may not be surprising that excessive exposure to nicotine can have detrimental effects on survival and maturation of adult-born neurons in the dentate; these same receptors appear to be key. The results pose serious challenges for therapeutic strategies targeting an individual class of nicotinic receptors for global treatment in the recipient.
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Affiliation(s)
- Nolan R Campbell
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357, United States
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Bis(12)-hupyridone, a novel multifunctional dimer, promotes neuronal differentiation more potently than its monomeric natural analog huperzine A possibly through α7 nAChR. Brain Res 2011; 1401:10-7. [PMID: 21665194 DOI: 10.1016/j.brainres.2011.05.042] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 05/11/2011] [Accepted: 05/17/2011] [Indexed: 11/22/2022]
Abstract
The cause of many neurodegenerative disorders can be ascribed to the loss of functional neurons, and thus agents capable of promoting neuronal differentiation may have therapeutic benefits to patients of these disorders. In this study, the effects and underlying mechanisms of bis(12)-hupyridone (B12H), a novel dimeric acetylcholinesterase inhibitor modified from huperzine A (HA), on neuronal differentiation were investigated using both the rat PC12 pheochromocytoma cell line and adult rat hippocampus neural stem cells. B12H (3-30 μM), characterized by morphological changes and expression of GAP-43, induced neurite outgrowth in a concentration- and time-dependent manner, with almost 3-fold higher efficacy than that of HA in PC12 cells. Furthermore, B12H (2.5-10 μM), but not HA, promoted neuronal differentiation as shown by the percentage increase of βIII-tubulin positive neurons in neural stem cells. The activities of extracellular signal-regulated kinase (ERK), as well as its downstream transcription factors Elk-1 and cAMP response element-binding protein (CREB) were elevated in the B12H-treated PC12 cells. Mitogen-activated protein kinase kinase inhibitors and alpha7-nicotinic acetylcholine receptor (α7nAChR) antagonist blocked the neurite outgrowth and the activation of ERK induced by B12H. All these findings suggest that B12H potently induces pro-neuronal cells into differentiated neurons by activating the ERK pathway possibly via regulating α7nAChR. These findings support the recent proposition that α7nAChR is required for the neuronal dendritic arborization and differentiation in the adult mice hippocampus, and provide insights into the possible therapeutic potential of B12H in treating neurodegenerative disorders.
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Proctor WR, Dobelis P, Moritz AT, Wu PH. Chronic nicotine treatment differentially modifies acute nicotine and alcohol actions on GABA(A) and glutamate receptors in hippocampal brain slices. Br J Pharmacol 2011; 162:1351-63. [PMID: 21133888 PMCID: PMC3058167 DOI: 10.1111/j.1476-5381.2010.01141.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Revised: 11/02/2010] [Accepted: 11/04/2010] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND AND PURPOSE Tobacco and alcohol are often co-abused producing interactive effects in the brain. Although nicotine enhances memory while ethanol impairs it, variable cognitive changes have been reported from concomitant use. This study was designed to determine how nicotine and alcohol interact at synaptic sites to modulate neuronal processes. EXPERIMENTAL APPROACH Acute effects of nicotine, ethanol, and both drugs on synaptic excitatory glutamatergic and inhibitory GABAergic transmission were measured using whole-cell recording in hippocampal CA1 pyramidal neurons from brain slices of mice on control or nicotine-containing diets. KEY RESULTS Acute nicotine (50 nM) enhanced both GABAergic and glutamatergic synaptic transmission; potentiated GABA(A) receptor currents via activation of α7* and α4β2* nAChRs, and increased N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor currents through α7* receptors. While ethanol (80 mM) also increased GABA(A) currents, it inhibited NMDA currents. Although ethanol had no effect on AMPA currents, it blocked nicotine-induced increases in NMDA and AMPA currents. Following chronic nicotine treatment, acute nicotine or ethanol did not affect NMDA currents, while the effects of GABAergic responses were not altered. CONCLUSIONS AND IMPLICATIONS Acute ethanol ingestion selectively attenuated nicotine enhancement of excitatory glutamatergic NMDA and AMPA receptor function, suggesting an overall reduction in excitatory output from the hippocampus. It also indicated that ethanol could decrease the beneficial effects of nicotine on memory performance. In addition, chronic nicotine treatment produced tolerance to the effects of nicotine and cross-tolerance to the effects of ethanol on glutamatergic activity, leading to a potential increase in the use of these drugs.
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Presynaptic nicotinic α7 and non-α7 receptors stimulate endogenous GABA release from rat hippocampal synaptosomes through two mechanisms of action. PLoS One 2011; 6:e16911. [PMID: 21346795 PMCID: PMC3034729 DOI: 10.1371/journal.pone.0016911] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 01/17/2011] [Indexed: 11/19/2022] Open
Abstract
Background Although converging evidence has suggested that nicotinic acetylcholine receptors (nAChR) play a role in the modulation of GABA release in rat hippocampus, the specific involvement of different nAChR subtypes at presynaptic level is still a matter of debate. In the present work we investigated, using selective α7 and α4β2 nAChR agonists, the presence of different nAChR subtypes on hippocampal GABA nerve endings to assess to what extent and through which mechanisms they stimulate endogenous GABA release. Methodology/Findings All agonists elicited GABA overflow. Choline (Ch)-evoked GABA overflow was dependent to external Ca2+, but unaltered in the presence of Cd2+, tetrodotoxin (TTX), dihydro-β-erythroidine (DHβE) and 1-(4,4-Diphenyl-3-butenyl)-3-piperidinecarboxylic acid hydrochloride SKF 89976A. The effect of Ch was blocked by methyllycaconitine (MLA), α-bungarotoxin (α-BTX), dantrolene, thapsigargin and xestospongin C, suggesting that GABA release might be triggered by Ca2+ entry into synaptosomes through the α7 nAChR channel with the involvement of calcium from intracellular stores. Additionally, 5-Iodo-A-85380 dihydrochloride (5IA85380) elicited GABA overflow, which was Ca2+ dependent, blocked by Cd2+, and significantly inhibited by TTX and DHβE, but unaffected by MLA, SKF 89976A, thapsigargin and xestospongin C and dantrolene. These findings confirm the involvement of α4β2 nAChR in 5IA85380-induced GABA release that seems to occur following membrane depolarization and opening calcium channels. Conclusions/Significance Rat hippocampal synaptosomes possess both α7 and α4β2 nAChR subtypes, which can modulate GABA release via two distinct mechanisms of action. The finding that GABA release evoked by the mixture of sub-maximal concentration of 5IA85380 plus sub-threshold concentrations of Ch was significantly larger than that elicited by the sum of the effects of the two agonists is compatible with the possibility that they coexist on the same nerve terminals. These findings would provide the basis for possible selective pharmacological strategies to treat neuronal disorders that involve the dysfunction of hippocampal cholinergic system.
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Cholinergic influences on cortical development and adult neurogenesis. Behav Brain Res 2011; 221:379-88. [PMID: 21272598 DOI: 10.1016/j.bbr.2011.01.021] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 01/10/2011] [Accepted: 01/13/2011] [Indexed: 11/22/2022]
Abstract
In this review, we focus on immature neurons and their regulation by the cholinergic system, both during cortical development as well as during adult neurogenesis. We discuss various studies that indicate roles for acetylcholine in precursor development and neuronal differentiation. Cholinergic neurons projecting from the basal forebrain innervate the cerebral cortex during critical periods of neuronal development. Acetylcholine stimulation may help to promote a favourable environment for neuronal maturation. Afferents and their cortical target cells interact and are likely to influence each other during the establishment and refinement of connections. Intracortical cholinergic interneurons similarly have a local effect on cortical circuits. Reduced cholinergic innervation during development hence leads to reduced cortical thickness and dendritic abnormalities. Acetylcholine is also likely to play a critical role in neuronal plasticity, as shown in the visual and barrel cortices. Spontaneous nicotinic excitation is also important during a brief developmental window in the first postnatal weeks leading to waves of neural activity, likely to have an effect on neurite extension, target selection and synaptogenesis. In the hippocampus such activity plays a role in the maturation of GABAergic synapses during the developmental shift from depolarizing to hyperpolarizing transmission. The cholinergic system also seems likely to regulate hippocampal neurogenesis in the adult, positively promoting proliferation, differentiation, integration and potentially survival of newborn neurons.
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Lateral mobility of nicotinic acetylcholine receptors on neurons is determined by receptor composition, local domain, and cell type. J Neurosci 2010; 30:8841-51. [PMID: 20592206 DOI: 10.1523/jneurosci.6236-09.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The lateral mobility of surface receptors can define the signaling properties of a synapse and rapidly change synaptic function. Here we use single-particle tracking with Quantum Dots to follow nicotinic acetylcholine receptors (nAChRs) on the surface of chick ciliary ganglion neurons in culture. We find that both heteropentameric alpha3-containing receptors (alpha3*-nAChRs) and homopentameric alpha7-containing receptors (alpha7-nAChRs) access synaptic domains by lateral diffusion. They have comparable mobilities and display Brownian motion in extrasynaptic space but are constrained and move more slowly in synaptic space. The two receptor types differ in the nature of their synaptic restraints. Disruption of lipid rafts, PDZ-containing scaffolds, and actin filaments each increase the mobility of alpha7-nAChRs in synaptic space while collapse of microtubules has no effect. The opposite is seen for alpha3*-nAChRs where synaptic mobility is increased only by microtubule collapse and not the other manipulations. Other differences are found for regulation of alpha3*-nAChR and alpha7-nAChR mobilities in extrasynaptic space. Most striking are effects on the immobile populations of alpha7-nAChRs and alpha3*-nAChRs. Disruption of either lipid rafts or PDZ scaffolds renders half of the immobile alpha3*-nAChRs mobile without changing the proportion of immobile alpha7-nAChRs. Similar results were obtained with chick sympathetic ganglion neurons, though regulation of receptor mobility differed in at least one respect from that seen with ciliary ganglion neurons. Control of nAChR lateral mobility, therefore, is determined by mechanisms that are domain specific, receptor subtype dependent, and cell-type constrained. The outcome is a system that could tailor nicotinic signaling capabilities to specific needs of individual locations.
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Juuri J, Clarke VRJ, Lauri SE, Taira T. Kainate receptor-induced ectopic spiking of CA3 pyramidal neurons initiates network bursts in neonatal hippocampus. J Neurophysiol 2010; 104:1696-706. [PMID: 20660426 DOI: 10.1152/jn.00840.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Kainate receptors (KARs) are expressed at high levels in the brain during early development and may be critical for the proper development of neuronal networks. Here we elucidated a physiological role of high-affinity KARs in developing hippocampal network by studying the effects of 25-100 nM kainate (KA) on intrinsic network activity in slice preparations. Whereas 100 nM KA resulted in hyperexcitability of the network and the disruption of natural activity patterns, ≤ 50 nM KA concentrations enhanced the initiation of network bursts yet preserved the characteristic patterns of endogenous activity. This was not dependent on changes in GABAergic transmission or on activation of GluK1 subunit containing KARs. However, the activation of high-affinity KARs increased glutamatergic drive by promoting spontaneous firing of CA3 pyramidal neurons without affecting action potential independent glutamate release. This was not because of changes in the intrinsic somatic properties of pyramidal neurons but seemed to reside in an electrically remote site, most probably in an axonal compartment. Although application of KAR agonists has mainly been used to study pathological type of network activities, this study provides a novel mechanism by which endogenous activity of KARs can modulate intrinsic activities of the emerging neuronal network in a physiologically relevant manner. The results support recent studies that KARs play a central role in the activity-dependent maturation of synaptic circuitries.
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Affiliation(s)
- Juuso Juuri
- Neuroscience Center and Department of Biosciences, University of Helsinki, Finland
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38
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Campbell NR, Fernandes CC, Halff AW, Berg DK. Endogenous signaling through alpha7-containing nicotinic receptors promotes maturation and integration of adult-born neurons in the hippocampus. J Neurosci 2010; 30:8734-44. [PMID: 20592195 PMCID: PMC2905643 DOI: 10.1523/jneurosci.0931-10.2010] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 04/19/2010] [Accepted: 05/12/2010] [Indexed: 12/20/2022] Open
Abstract
Neurogenesis in the dentate gyrus occurs throughout adult mammalian life and is essential for proper hippocampal function. Early in their development, adult-born neurons express homomeric alpha7-containing nicotinic acetylcholine receptors (alpha7-nAChRs) and receive direct cholinergic innervation. We show here that functional alpha7-nAChRs are necessary for normal survival, maturation, and integration of adult-born neurons in the dentate gyrus. Stereotaxic retroviral injection into the dentate gyrus of wild-type and alpha7-knock-out (alpha7KO) male and female mice was used to label and birthdate adult-born neurons for morphological and electrophysiological measures; BrdU (5-bromo-2-deoxyuridine) injections were used to quantify cell survival. In alpha7KO mice, we find that adult-born neurons develop with truncated, less complex dendritic arbors and display GABAergic postsynaptic currents with immature kinetics. The neurons also have a prolonged period of GABAergic depolarization characteristic of an immature state. In this condition, they receive fewer spontaneous synaptic currents and are more prone to die during the critical period when adult-born neurons are normally integrated into behaviorally relevant networks. Even those adult-born neurons that survive the critical period retain long-term dendritic abnormalities in alpha7KO mice. Interestingly, local infection with retroviral constructs to knockdown alpha7-mRNA mimics the alpha7KO phenotype, demonstrating that the relevant alpha7-nAChR signaling is cell autonomous. The results indicate a profound role for alpha7-nAChRs in adult neurogenesis and predict that alpha7-nAChR loss will cause progressive impairment in hippocampal circuitry and function over time as fewer neurons are added to the dentate gyrus and those that are added integrate less well.
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Affiliation(s)
- Nolan R. Campbell
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
| | - Catarina C. Fernandes
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
- Institute of Pharmacology and Neurosciences, Faculty of Medicine and Unit of Neurosciences, Institute of Molecular Medicine, University of Lisbon, 1649-028 Lisbon, Portugal
| | - Andrew W. Halff
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
| | - Darwin K. Berg
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093-0357, and
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Changeux JP. Nicotine addiction and nicotinic receptors: lessons from genetically modified mice. Nat Rev Neurosci 2010; 11:389-401. [PMID: 20485364 DOI: 10.1038/nrn2849] [Citation(s) in RCA: 333] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The past decades have seen a revolution in our understanding of brain diseases and in particular of drug addiction. This has been largely due to the identification of neurotransmitter receptors and the development of animal models, which together have enabled the investigation of brain functions from the molecular to the cognitive level. Tobacco smoking, the principal - yet avoidable - cause of lung cancer is associated with nicotine addiction. Recent studies in mice involving deletion and replacement of nicotinic acetylcholine receptor subunits have begun to identify the molecular mechanisms underlying nicotine addiction and might offer new therapeutic strategies to treat this addiction.
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Affiliation(s)
- Jean-Pierre Changeux
- Collge de France and the Institut Pasteur CNRS URA 2182, 25 rue du Dr Roux, 75015 Paris, France.
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Synchronous and asynchronous transmitter release at nicotinic synapses are differentially regulated by postsynaptic PSD-95 proteins. J Neurosci 2010; 29:15770-9. [PMID: 20016093 DOI: 10.1523/jneurosci.4951-09.2009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The rate and timing of information transfer at neuronal synapses are critical for determining synaptic efficacy and higher network function. Both synchronous and asynchronous neurotransmitter release shape the pattern of synaptic influences on a neuron. The PSD-95 family of postsynaptic scaffolding proteins, in addition to organizing postsynaptic components at glutamate synapses, acts transcellularly to regulate synchronous glutamate release. Here we show that PSD-95 family members at nicotinic synapses on chick ciliary ganglion neurons in culture execute multiple functions to enhance transmission. Together, endogenous PSD-95 and SAP102 in the postsynaptic cell appear to regulate transcellularly the synchronous release of transmitter from presynaptic terminals onto the neuron while stabilizing postsynaptic nicotinic receptor clusters under the release sites. Endogenous SAP97, in contrast, has no effect on receptor clusters but acts transcellularly from the postsynaptic cell through N-cadherin to enhance asynchronous release. These separate and parallel regulatory pathways allow postsynaptic scaffold proteins to dictate the pattern of cholinergic input a neuron receives; they also require balancing of PSD-95 protein levels to avoid disruptive competition that can occur through common binding domains.
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Son JH, Winzer-Serhan UH. Chronic neonatal nicotine exposure increases mRNA expression of neurotrophic factors in the postnatal rat hippocampus. Brain Res 2009; 1278:1-14. [DOI: 10.1016/j.brainres.2009.04.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/21/2009] [Accepted: 04/27/2009] [Indexed: 01/19/2023]
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Suarez SV, Amadon A, Giacomini E, Wiklund A, Changeux JP, Le Bihan D, Granon S. Brain activation by short-term nicotine exposure in anesthetized wild-type and beta2-nicotinic receptors knockout mice: a BOLD fMRI study. Psychopharmacology (Berl) 2009; 202:599-610. [PMID: 18818904 DOI: 10.1007/s00213-008-1338-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 09/10/2008] [Indexed: 01/08/2023]
Abstract
RATIONALE The behavioral effects of nicotine and the role of the beta2-containing nicotinic receptors in these behaviors are well documented. However, the behaviors altered by nicotine rely on the functioning on multiple brain circuits where the high-affinity beta2-containing nicotinic receptors (beta2*nAChRs) are located. OBJECTIVES We intend to see which brain circuits are activated when nicotine is given in animals naïve for nicotine and whether the beta2*nAChRs are needed for its activation of the blood oxygen level dependent (BOLD) signal in all brain areas. MATERIALS AND METHODS We used functional magnetic resonance imaging (fMRI) to measure the brain activation evoked by nicotine (1 mg/kg delivered at a slow rate for 45 min) in anesthetized C57BL/6J mice and beta2 knockout (KO) mice. RESULTS Acute nicotine injection results in a significant increased activation in anterior frontal, motor, and somatosensory cortices and in the ventral tegmental area and the substantia nigra. Anesthetized mice receiving no nicotine injection exhibited a major decreased activation in all cortical and subcortical structures, likely due to prolonged anesthesia. At a global level, beta2 KO mice were not rescued from the globally declining BOLD signal. However, nicotine still activated regions of a meso-cortico-limbic circuit likely via alpha7 nicotinic receptors. CONCLUSIONS Acute nicotine exposure compensates for the drop in brain activation due to anesthesia through the meso-cortico-limbic network via the action of nicotine on beta2*nAChRs. The developed fMRI method is suitable for comparing responses in wild-type and mutant mice.
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Affiliation(s)
- S V Suarez
- Unité de Neurobiologie Intégrative du Système Cholinergique, URA CNRS 2182, Institut Pasteur, Département de Neuroscience, 25 rue du Dr. Roux, 75015 Paris, France
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Manfredi I, Zani AD, Rampoldi L, Pegorini S, Bernascone I, Moretti M, Gotti C, Croci L, Consalez GG, Ferini-Strambi L, Sala M, Pattini L, Casari G. Expression of mutant β2 nicotinic receptors during development is crucial for epileptogenesis. Hum Mol Genet 2009; 18:1075-88. [DOI: 10.1093/hmg/ddp004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
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BACE1 knock-outs display deficits in activity-dependent potentiation of synaptic transmission at mossy fiber to CA3 synapses in the hippocampus. J Neurosci 2008; 28:8677-81. [PMID: 18753368 DOI: 10.1523/jneurosci.2440-08.2008] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
beta-Amyloid precursor protein cleavage enzyme 1 (BACE1) has been identified as a major neuronal beta-secretase critical for the formation of beta-amyloid (Abeta) peptide, which is thought responsible for the pathology of Alzheimer's disease (AD). Therefore, BACE1 is one of the key therapeutic targets that can prevent the progression of AD. Previous studies showed that knocking out the BACE1 gene prevents Abeta formation, but results in behavioral deficits and specific synaptic dysfunctions at Schaffer collateral to CA1 synapses. However, BACE1 protein is most highly expressed at the mossy fiber projections in CA3. Here, we report that BACE1 knock-out mice display reduced presynaptic function, as measured by an increase in paired-pulse facilitation ratio. More dramatically, mossy fiber long-term potentiation (LTP), which is normally expressed via an increase in presynaptic release, was eliminated in the knock-outs. Although long-term depression was slightly larger in the BACE1 knock-outs, it could not be reversed. The specific deficit in mossy fiber LTP was upstream of cAMP signaling and could be "rescued" by transiently elevating extracellular Ca2+ concentration. These results suggest that BACE1 may play a critical role in regulating presynaptic function, especially activity-dependent strengthening of presynaptic release, at mossy fiber synapses.
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Toledano A, Alvarez MI, Caballero I, Carmona P, De Miguel E. Immunohistochemical increase in cyclooxygenase-2 without apoptosis in different brain areas of subchronic nicotine- and D-amphetamine-treated rats. J Neural Transm (Vienna) 2008; 115:1093-108. [PMID: 18351285 DOI: 10.1007/s00702-008-0040-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2007] [Accepted: 02/26/2008] [Indexed: 11/25/2022]
Abstract
Cyclooxygenase-2 (COX-2) upregulation has been related to both neurodegeneration and physiological processes. To clarify whether nicotine-induced upregulation of COX-2 occurs, and to analyse its significance, a comparative immunohistochemical and Western blot study was performed on the frontoparietal cortex, hippocampus and cerebellar cortex of rats treated (14 days) with nicotine, D(+)amphetamine (0.35 and 1.16 mg free base/kg/day, respectively), or both drugs simultaneously. None of these treatments promoted neuronal apoptosis. Lipid peroxidation increased in the hippocampus of the nicotine-treated rats and in all the brain regions examined in the D(+)amphetamine rats, but not in the double-treated animals. Both molecules increased the COX-2 content (as determined by the number of immunopositive neurons and the intensity of their immunodeposits) in an area-, layer- and neuron type-dependent manner, in all brain regions in which a large number of COX-2 immunopositive neurons were observed in controls (the somatosensory cortical areas, CA-1, CA-3, the gyrus dentatus, the ectorhinal/perirhinal areas, and the gyrus cingularis). No increase was seen in the motor cortical areas, while a reduction was recorded in the cerebellar cortex; these regions had only a few immunopositive neurons in controls. Western blot analysis revealed a 50-80% increase in COX-2 in the brain cortex and hippocampus of nicotine-treated rats, and similar increases (150-200%) in the cortex of the D(+)amphetamine- and nicotine + D(+)amphetamine-treated rats. Nicotine-induced upregulation of COX-2 seems to be related to neuronal plasticity rather than neurodegeneration. Nicotine agonists might be useful in the treatment of cognitive disorders.
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Affiliation(s)
- A Toledano
- Instituto Cajal, CSIC, Avda. Dr. Arce 37, 28002, Madrid, Spain.
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Arnaiz-Cot JJ, González JC, Sobrado M, Baldelli P, Carbone E, Gandía L, García AG, Hernández-Guijo JM. Allosteric modulation of alpha 7 nicotinic receptors selectively depolarizes hippocampal interneurons, enhancing spontaneous GABAergic transmission. Eur J Neurosci 2008; 27:1097-110. [PMID: 18312591 DOI: 10.1111/j.1460-9568.2008.06077.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of postsynaptic nicotinic receptors for acetylcholine (nAChRs) in mediating fast neurotransmission processes in the CNS is controversial. Here we have studied the modulation of synaptic transmission by an agonist (choline) and an allosteric modulator (5-OH-indole) of alpha7 nAChRs in rat hippocampal neuronal cultures. Choline evoked a fast inactivating inward current, causing neuron depolarization and action potential discharge, thereby enhancing the spontaneous postsynaptic current activity (sPSCs). This effect was markedly enhanced when both choline and 5-OH-indole were applied together and was blocked by the selective alpha7 nAChR antagonist methyllycaconitine. This choline action was suppressed by the GABA(A) receptor antagonist bicuculline, while the glutamatergic receptor antagonist kynurenic acid had no effect. Frequency, but not amplitude or area, of both excitatory and inhibitory miniature postsynaptic currents (mEPSCs and mIPSCs) were drastically reduced when Ca(2+) influx was blocked by Cd(2+). Additionally, nAChR activation did not modify the mIPSCs. These data suggest that Ca(2+) influx through the highly Ca(2+)-permeablealpha7 nAChRs was insufficient to directly activate neurotransmitter release, suggesting that a tight colocalization of this receptor with secretory hot spots is unlikely. In a few cases, the activation of alpha7 AChRs led to a suppression of spontaneous synaptic transmission. This effect may be related to the potentiation of GABAergic interneurons that inhibit the spontaneous activity of neurons making synapses with the cell under study. We suggest that GABA release is modulated by alpha7 nAChRs. Thus, selective allosteric modulators of alpha7 nAChRs could have potential therapeutic applications in brain disorders such as epilepsy and schizophrenia and in alterations of cognition and sensory processing.
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Affiliation(s)
- J J Arnaiz-Cot
- Instituto Teófilo Hernando, Facultad de Medicina, University Autónoma de Madrid, Avenida Arzobispo Morcillo 4, 28029 Madrid, Spain
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47
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Nicotine modulates the renin-angiotensin system of cultured neurons and glial cells from cardiovascular brain areas of Wistar Kyoto and spontaneously hypertensive rats. J Mol Neurosci 2007; 33:284-93. [PMID: 17952638 DOI: 10.1007/s12031-007-9006-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 08/23/2007] [Indexed: 10/22/2022]
Abstract
Considering the importance of the renin-angiotensin system (RAS) for the central control of blood pressure and that nicotine increases the probability of development of hypertension associated to genetic predisposition, our aims are (1) to determine RAS in cultured neurons and glia from the brainstem and hypothalamus of spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats; (2) to analyze the possibility of nicotine to interact with brain RAS; and (3) to hypothesize any contribution of nicotine and RAS to the development of neurogenic hypertension. This study demonstrated physiological differences in RAS between cultured neuronal and glial cells from the brainstem and hypothalamus of SHR and WKY neonate rats. Our study also featured evidences of direct modulation of the RAS by nicotine in neurons and glia of brainstem and hypothalamus, which seems to be differential between the two rat strains. Such modulation gives us a clue about the mechanisms possibly involved in the genesis of neurogenic hypertension in vivo, for example, increase in angiotensin II type 1 receptor binding and decrease in angiotensin-converting enzyme 2. In conclusion, we demonstrated that neuronal and glial RAS from the brainstem and hypothalamus of SHR differ from WKY rats and nicotine differentially modulates the brain RAS in SHR and WKY.
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48
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Liu Z, Zhang J, Berg DK. Role of endogenous nicotinic signaling in guiding neuronal development. Biochem Pharmacol 2007; 74:1112-9. [PMID: 17603025 PMCID: PMC2116993 DOI: 10.1016/j.bcp.2007.05.022] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 05/09/2007] [Accepted: 05/29/2007] [Indexed: 11/20/2022]
Abstract
Spontaneous nicotinic cholinergic activity is widespread in the developing nervous system. One of the major components mediating this activity is the nicotinic acetylcholine receptor with alpha7 subunits (alpha7-nAChR) and high relative calcium permeability. We recently reported that alpha7-nAChRs co-localize in part with GABA(A) receptors during development, and the sites become co-innervated by cholinergic and GABAergic terminals. Patch-clamp recording either from embryonic chick ciliary ganglion neurons or from early postnatal mouse hippocampal interneurons reveals that alpha7-nAChR activation can impose a rapid and reversible decrease in GABA(A) receptor responses. The effect extends to GABAergic synaptic currents, and depends on intracellular calcium, calcium/calmodulin-dependent protein kinase II, and MAP kinase in the postsynaptic cell. Over the longer term, nicotinic activity has a more profound effect: it determines the time during development when GABAergic signaling converts from excitation to inhibition. It does this by changing the pattern of chloride transporters to establish the mature chloride gradient required for inhibitory GABAergic responses. The excitatory phase of GABAergic signaling is critical for proper development and integration of neurons into circuits. By driving the conversion of GABAergic signaling, nicotinic activity not only terminates one set of developmental instructions, but also initiates another by collaborating with GABAergic inhibition to impose new instructions. The results reveal a multi-layered pattern of activity-dependent controls in development and indicate the significance of nicotinic signaling in shaping these events.
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Affiliation(s)
- Zhaoping Liu
- Neurobiology Section, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0357, USA
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Zhang J, Berg DK. Reversible inhibition of GABAA receptors by alpha7-containing nicotinic receptors on the vertebrate postsynaptic neurons. J Physiol 2007; 579:753-63. [PMID: 17204496 PMCID: PMC2151364 DOI: 10.1113/jphysiol.2006.124578] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) are expressed throughout the central nervous system and influence a variety of higher order functions including learning and memory. While the effects of presynaptic nAChRs on transmitter release have been well documented, little is known about possible postsynaptic actions. A major species of neuronal nAChRs contains the alpha7 gene product and has a high relative permeability to calcium. Both on rodent hippocampal interneurons and on chick ciliary ganglion neurons these alpha7-nAChRs are often closely juxtaposed to GABAA receptors. We show here that in both cases activation of alpha7-nAChRs on the postsynaptic neuron acutely down-regulates GABA-induced currents. Nicotine application to dissociated ciliary ganglion neurons diminished subsequent GABAA receptor responses to GABA. The effect was blocked by alpha7-nAChR antagonists, by chelation of intracellular Ca2+ with BAPTA, and by inhibition of both Ca2+-calmodulin-dependent protein kinase II and mitogen-activated protein kinase. A similar outcome was obtained in the hippocampus where electrical stimulation to activate cholinergic fibres reduced the amplitude of subsequent GABAA receptor-mediated inhibitory postsynaptic currents. The reduction showed the same calcium and kinase dependence seen in ciliary ganglion neurons and was absent in hippocampal slices from alpha7-nAChR knockout mice. Moreover, alpha7-nAChR blockade in hippocampal slices reduced rundown of GABAA receptor-mediated whole-cell responses, indicating ongoing endogenous modulation. The results demonstrate regulation of GABAA receptors by alpha7-nAChRs on the postsynaptic neuron and identify a new mechanism by which nicotinic cholinergic signalling influences nervous system function.
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Affiliation(s)
- Jingming Zhang
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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Liu Z, Neff RA, Berg DK. Sequential interplay of nicotinic and GABAergic signaling guides neuronal development. Science 2006; 314:1610-3. [PMID: 17158331 DOI: 10.1126/science.1134246] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
GABA (gamma-aminobutyric acid), the major inhibitory transmitter in the brain, goes through a transitory phase of excitation during development. The excitatory phase promotes neuronal growth and integration into circuits. We show here that spontaneous nicotinic cholinergic activity is responsible for terminating GABAergic excitation and initiating inhibition. It does so by changing chloride transporter levels, shifting the driving force on GABA-induced currents. The timing of the transition is critical, because the two phases of GABAergic signaling provide contrasting developmental instructions. Synergistic with nicotinic excitation, GABAergic inhibition constrains neuronal morphology and innervation. The results reveal a multitiered activity-dependent strategy controlling neuronal development.
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Affiliation(s)
- Zhaoping Liu
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0357, USA
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