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Dainauskas JJ, Vitale P, Moreno S, Marie H, Migliore M, Saudargiene A. Altered synaptic plasticity at hippocampal CA1-CA3 synapses in Alzheimer's disease: integration of amyloid precursor protein intracellular domain and amyloid beta effects into computational models. Front Comput Neurosci 2023; 17:1305169. [PMID: 38130706 PMCID: PMC10733499 DOI: 10.3389/fncom.2023.1305169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 11/07/2023] [Indexed: 12/23/2023] Open
Abstract
Alzheimer's disease (AD) is a progressive memory loss and cognitive dysfunction brain disorder brought on by the dysfunctional amyloid precursor protein (APP) processing and clearance of APP peptides. Increased APP levels lead to the production of AD-related peptides including the amyloid APP intracellular domain (AICD) and amyloid beta (Aβ), and consequently modify the intrinsic excitability of the hippocampal CA1 pyramidal neurons, synaptic protein activity, and impair synaptic plasticity at hippocampal CA1-CA3 synapses. The goal of the present study is to build computational models that incorporate the effect of AD-related peptides on CA1 pyramidal neuron and hippocampal synaptic plasticity under the AD conditions and investigate the potential pharmacological treatments that could normalize hippocampal synaptic plasticity and learning in AD. We employ a phenomenological N-methyl-D-aspartate (NMDA) receptor-based voltage-dependent synaptic plasticity model that includes the separate receptor contributions on long-term potentiation (LTP) and long-term depression (LTD) and embed it into the a detailed compartmental model of CA1 pyramidal neuron. Modeling results show that partial blockade of Glu2NB-NMDAR-gated channel restores intrinsic excitability of a CA1 pyramidal neuron and rescues LTP in AICD and Aβ conditions. The model provides insight into the complex interactions in AD pathophysiology and suggests the conditions under which the synchronous activation of a cluster of synaptic inputs targeting the dendritic tree of CA1 pyramidal neuron leads to restored synaptic plasticity.
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Affiliation(s)
- Justinas J. Dainauskas
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Informatics, Vytautas Magnus University, Kaunas, Lithuania
| | - Paola Vitale
- Institute of Biophysics, National Research Council, Palermo, Italy
| | - Sebastien Moreno
- Université Côte d'Azur, Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Hélène Marie
- Université Côte d'Azur, Centre National de la Recherche Scientifique (CNRS), Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), Valbonne, France
| | - Michele Migliore
- Institute of Biophysics, National Research Council, Palermo, Italy
| | - Ausra Saudargiene
- Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Informatics, Vytautas Magnus University, Kaunas, Lithuania
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2
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Zhang Y, Tan BH, Wu S, Wu CH, Suo JL, Gui Y, Zhou CM, Li YC. Different changes in pre- and postsynaptic components in the hippocampal CA1 subfield after transient global cerebral ischemia. Brain Struct Funct 2021. [PMID: 34626230 DOI: 10.1007/s00429-021-02404-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 09/29/2021] [Indexed: 10/20/2022]
Abstract
To date, ischemia-induced damage to dendritic spines has attracted considerable attention, while the possible effects of ischemia on presynaptic components has received relatively less attention. To further examine ischemia-induced changes in pre- and postsynaptic specializations in the hippocampal CA1 subfield, we modeled global cerebral ischemia with two-stage 4-vessel-occlusion in rats, and found that three postsynaptic markers, microtubule-associated protein 2 (MAP2), postsynaptic density protein 95 (PSD95), and filamentous F-actin (F-actin), were all substantially decreased in the CA1 subfield after ischemia/reperfusion (I/R). Although no significant change was detected in synapsin I, a presynaptic marker, in the CA1 subfield at the protein level, confocal microscopy revealed that the number and size of synapsin I puncta were significantly changed in the CA1 stratum radiatum after I/R. The size of synapsin I puncta became slightly, but significantly reduced on Day 1.5 after I/R. From Days 2 to 7 after I/R, the number of synapsin I puncta became moderately decreased, while the size of synapsin I puncta was significantly increased. Interestingly, some enlarged puncta of synapsin I were observed in close proximity to the dendritic shafts of CA1 pyramidal cells. Due to the more substantial decrease in the number of F-actin puncta, the ratio of synapsin I/F-actin puncta was significantly increased after I/R. The decrease in synapsin I puncta size in the early stage of I/R may be the result of excessive neurotransmitter release due to I/R-induced hyperexcitability in CA3 pyramidal cells, while the increase in synapsin I puncta in the later stage of I/R may reflect a disability of synaptic vesicle release due to the loss of postsynaptic contacts.
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Schmalz JT, Kumar G. A computational model of dopaminergic modulation of hippocampal Schaffer collateral-CA1 long-term plasticity. J Comput Neurosci 2021; 50:51-90. [PMID: 34431067 DOI: 10.1007/s10827-021-00793-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/14/2021] [Accepted: 05/28/2021] [Indexed: 10/20/2022]
Abstract
Dopamine plays a critical role in modulating the long-term synaptic plasticity of the hippocampal Schaffer collateral-CA1 pyramidal neuron synapses (SC-CA1), a widely accepted cellular model of learning and memory. Limited results from hippocampal slice experiments over the last four decades have shown that the timing of the activation of dopamine D1/D5 receptors relative to a high/low-frequency stimulation (HFS/LFS) in SC-CA1 synapses regulates the modulation of HFS/LFS-induced long-term potentiation/depression (LTP/LTD) in these synapses. However, the existing literature lacks a complete picture of how various concentrations of D1/D5 agonists and the relative timing between the activation of D1/D5 receptors and LTP/LTD induction by HFS/LFS, affect the spatiotemporal modulation of SC-CA1 synaptic dynamics. In this paper, we have developed a computational model, a first of its kind, to make quantitative predictions of the temporal dose-dependent modulation of the HFS/LFS induced LTP/LTD in SC-CA1 synapses by various D1/D5 agonists. Our model combines the biochemical effects with the electrical effects at the electrophysiological level. We have estimated the model parameters from the published electrophysiological data, available from diverse hippocampal CA1 slice experiments, in a Bayesian framework. Our modeling results demonstrate the capability of our model in making quantitative predictions of the available experimental results under diverse HFS/LFS protocols. The predictions from our model show a strong nonlinear dependency of the modulated LTP/LTD by D1/D5 agonists on the relative timing between the activated D1/D5 receptors and the HFS/LFS protocol and the applied concentration of D1/D5 agonists.
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Sun P, Liu DG, Ye XM. Nicotinic Acetylcholine Receptor α7 Subunit Is an Essential Regulator of Seizure Susceptibility. Front Neurol 2021; 12:656752. [PMID: 33912128 PMCID: PMC8072353 DOI: 10.3389/fneur.2021.656752] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/12/2021] [Indexed: 01/16/2023] Open
Abstract
A large body of data has confirmed that α7 nicotinic acetylcholine receptors (nAChRs) play a pivotal role in cognition, memory, and other neuropsychiatric diseases, but their effect on seizure susceptibility in C57BL/6 wild-type mice is not fully understood. Here, we showed that decreased activity of α7 nAChRs could increase the excitability of CA1 pyramidal neurons and shorten the onset time of epilepsy in pilocarpine-induced mouse models. However, compared with the control group, there was no apparent effect of increasing the activity of α7 nAChRs. Moreover, the expression of α7 nAChRs is downregulated in human epileptogenic tissues. Taken together, our findings indicate that α7 nAChR is an essential regulator of seizure susceptibility.
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Affiliation(s)
- Peng Sun
- Rehabilitation & Sports Medicine Research Institute of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Da-Gang Liu
- Department of Neurosurgery Medicine, Weihai Central Hospital, Weihai, China
| | - Xiang-Ming Ye
- Rehabilitation & Sports Medicine Research Institute of Zhejiang Province, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
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Uchigashima M, Leung M, Watanabe T, Cheung A, Le T, Pallat S, Dinis ALM, Watanabe M, Kawasawa YI, Futai K. Neuroligin3 splice isoforms shape inhibitory synaptic function in the mouse hippocampus. J Biol Chem 2020; 295:8589-8595. [PMID: 32381505 DOI: 10.1074/jbc.ac120.012571] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 05/01/2020] [Indexed: 01/15/2023] Open
Abstract
Synapse formation is a dynamic process essential for the development and maturation of the neuronal circuitry in the brain. At the synaptic cleft, trans-synaptic protein-protein interactions are major biological determinants of proper synapse efficacy. The balance of excitatory and inhibitory synaptic transmission (E-I balance) stabilizes synaptic activity, and dysregulation of the E-I balance has been implicated in neurodevelopmental disorders, including autism spectrum disorders. However, the molecular mechanisms underlying the E-I balance remain to be elucidated. Here, using single-cell transcriptomics, immunohistochemistry, and electrophysiology approaches to murine CA1 pyramidal neurons obtained from organotypic hippocampal slice cultures, we investigate neuroligin (Nlgn) genes that encode a family of postsynaptic adhesion molecules known to shape excitatory and inhibitory synaptic function. We demonstrate that the NLGN3 protein differentially regulates inhibitory synaptic transmission in a splice isoform-dependent manner at hippocampal CA1 synapses. We also found that distinct subcellular localizations of the NLGN3 isoforms contribute to the functional differences observed among these isoforms. Finally, results from single-cell RNA-Seq analyses revealed that Nlgn1 and Nlgn3 are the major murine Nlgn genes and that the expression levels of the Nlgn splice isoforms are highly diverse in CA1 pyramidal neurons. Our results delineate isoform-specific effects of Nlgn genes on the E-I balance in the murine hippocampus.
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Affiliation(s)
- Motokazu Uchigashima
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA.,Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Ming Leung
- Department of Biochemistry and Molecular Biology and Institute for Personalized Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Takuya Watanabe
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Amy Cheung
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Timmy Le
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Sabine Pallat
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Alexandre Luis Marques Dinis
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan
| | - Yuka Imamura Kawasawa
- Department of Biochemistry and Molecular Biology and Institute for Personalized Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA .,Department of Pharmacology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Kensuke Futai
- Brudnick Neuropsychiatric Research Institute, Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Dougherty KA. Differential developmental refinement of the intrinsic electrophysiological properties of CA1 pyramidal neurons from the rat dorsal and ventral hippocampus. Hippocampus 2019; 30:233-249. [PMID: 31490612 DOI: 10.1002/hipo.23152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 08/07/2019] [Accepted: 08/19/2019] [Indexed: 12/21/2022]
Abstract
The dorsal and ventral regions of the rat longitudinal hippocampal axis are functionally distinct. That is, each region is associated with different behavioral tasks and disease susceptibilities due to underlying anatomical, and physiological differences. These differences are especially pronounced in area CA1, where significant differences in morphology, synaptic physiology, intrinsic excitability, and gene expression have been reported between CA1 pyramidal neurons from the dorsal (DHC) and ventral hippocampus (VHC). However, despite a significant amount of recent attention, a cogent picture of the intrinsic electrophysiological profile of DHC and VHC neurons has remained elusive, due, in part, to experiments performed on rats at different developmental time points. Moreover, the resulting intrinsic electrophysiological profiles are sufficiently different as to warrant a thorough investigation of the spatial and temporal changes in the intrinsic excitability of CA1 pyramidal neurons across developmental time. Accordingly, in this study, I have characterized the intrinsic electrophysiological properties of CA1 pyramidal neurons from acute hippocampal slices prepared from the DHC and VHC throughout an approximately 3-week developmental period (P14-P37). DHC and VHC neurons exhibited distinct intra-region changes (DHC or VHC) and inter-region differences (DHC versus VHC) in their intrinsic electrophysiological properties, which yielded two developmental timelines: (a) a common developmental timeline describing changes observed in both DHC and VHC neurons, and (b) a differential developmental timeline highlighting unique features observed in DHC neurons. Specifically, DHC neurons exhibited significant inter-region differences in RMP, input resistance, threshold, and spike frequency adaptation relative to VHC neurons, as well as an intra-region change in the rebound slope (a proxy for Ih ). These observations both integrate and reconcile previous work performed with rats at different developmental stages and suggest a distinct developmental trajectory for DHC neurons that might shed light on the normal physiological functions and disease susceptibility of the DHC.
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Arnold EC, McMurray C, Gray R, Johnston D. Epilepsy-Induced Reduction in HCN Channel Expression Contributes to an Increased Excitability in Dorsal, But Not Ventral, Hippocampal CA1 Neurons. eNeuro 2019; 6:ENEURO.0036-19.2019. [PMID: 30957013 PMCID: PMC6449163 DOI: 10.1523/eneuro.0036-19.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Accepted: 03/05/2019] [Indexed: 12/31/2022] Open
Abstract
CA1 neurons in epileptic animals are vulnerable to selective changes in ion channel expression, called acquired channelopathies, which can increase the excitability of a neuron. Under normal conditions there is a gradient of ion channel expression and intrinsic excitability along the longitudinal, dorsoventral axis of hippocampal area CA1 of the rodent. Many of these channels, including M-channels, GIRK channels and HCN channels, all have dorsoventral expression gradients that might be altered in rodent models of epilepsy. Here, we show that the excitability of dorsal, but not ventral CA1 neurons, had an increased firing rate, reduced interspike interval (ISI) and increased input resistance in a status epilepticus (SE) model of temporal lobe epilepsy (TLE). As a result, the excitability of CA1 neurons became uniform across the dorsoventral axis of the rat hippocampus post-SE. Using current clamp recordings with pharmacology and immunohistochemistry, we demonstrate that the expression of HCN channels was downregulated in the dorsal CA1 region post-SE, while the expression of M and GIRK channels were unchanged. We did not find this acquired channelopathy in ventral CA1 neurons post-SE. Our results suggest that the excitability of dorsal CA1 neurons post-SE increase to resemble the intrinsic properties of ventral CA1 neurons, which likely makes the hippocampal circuit more permissible to seizures, and contributes to the cognitive impairments associated with chronic epilepsy.
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Affiliation(s)
- Elizabeth C. Arnold
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Calli McMurray
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Richard Gray
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
| | - Daniel Johnston
- Institute for Neuroscience, University of Texas at Austin, Austin, TX 78712
- Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712
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8
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Cui K, Zhang S, Sun J, Zhang X, Ding C, Xu G. Inhibitory effect of ultrasonic stimulation on the voltage-dependent potassium currents in rat hippocampal CA1 neurons. BMC Neurosci 2019; 20:3. [PMID: 30611209 PMCID: PMC6321733 DOI: 10.1186/s12868-018-0485-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 12/26/2018] [Indexed: 12/20/2022] Open
Abstract
Background Transcranial ultrasonic stimulation is a novel noninvasive tool for neuromodulation, and has high spatial resolution and deep penetration. Although it can increase excitation of neurons, its effects on neuron are poorly understood. This study was to evaluate effect of ultrasonic stimulation (US) on neurons in vitro. In this paper, the effect of US on the excitability and voltage-dependent \documentclass[12pt]{minimal}
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\begin{document}$$ K^{ + } $$\end{document}K+ currents of CA1 pyramidal neurons in the rat hippocampus was studied using patch clamp. Results Our results suggest that US increased the spontaneous firing rate and inhibited transient outward potassium current (\documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{A}} $$\end{document}IA) and delayed rectifier potassium current (\documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{K}} ) $$\end{document}IK). Furthermore, US altered the activation of \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{K}} $$\end{document}IK channels, inactivation and recovery properties of \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{A}} $$\end{document}IA channels. After US, the \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{K}} $$\end{document}IK activation curves significantly moved to the negative voltage direction and increased its slope factor. Moreover, the data showed that US moved the inactivation curve of \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{A}} $$\end{document}IA to the negative voltage and increased the slope factor. Besides, US delayed the recovery of \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{A}} $$\end{document}IA channel. Conclusions Our data indicate that US can increase excitation of neurons by inhibiting potassium currents. Different US decreased the voltage sensitivity of \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{K}} $$\end{document}IK activation differentially. Moreover, the more time is needed for US to make the \documentclass[12pt]{minimal}
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\begin{document}$$ \varvec{I}_{\varvec{A}} $$\end{document}IA channels open again after inactivating. US may play a physiological role by inhibiting voltage-dependent potassium currents in neuromodulation. Our research can provide a theoretical basis for the future clinical application of ultrasound in neuromodulation.
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Affiliation(s)
- Kun Cui
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China
| | - Shuai Zhang
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China. .,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China.
| | - Jinyao Sun
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China
| | - Xueying Zhang
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China
| | - Chong Ding
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China
| | - Guizhi Xu
- State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, No. 8 Hongrong Road, Hongqiao District, Tianjin, 300132, China.,Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province, Hebei University of Technology, Tianjin, 300132, China
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9
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Thome C, Roth FC, Obermayer J, Yanez A, Draguhn A, Egorov AV. Synaptic entrainment of ectopic action potential generation in hippocampal pyramidal neurons. J Physiol 2018; 596:5237-5249. [PMID: 30144079 DOI: 10.1113/jp276720] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 08/15/2018] [Indexed: 01/26/2023] Open
Abstract
KEY POINTS Ectopic action potentials (EAPs) arise at distal locations in axonal fibres and are often associated with neuronal pathologies such as epilepsy or nerve injury, but they also occur during physiological network conditions. This study investigates whether initiation of such EAPs is modulated by subthreshold synaptic activity. Somatic subthreshold potentials invade the axonal compartment to considerable distances (>350 μm), whereas spread of axonal subthreshold potentials to the soma is inefficient. Ectopic spike generation is entrained by conventional synaptic signalling mechanisms. Excitatory synaptic potentials promote EAPs, whereas inhibitory synaptic potentials block EAPs. The modulation of ectopic excitability depends on propagation of somatic voltage deflections to the axonal EAP initiation site. Synaptic modulation of EAP initiation challenges the view of the distal axon being independent of synaptic activity and may contribute to mechanisms underlying fast network oscillations and pathological network activity. ABSTRACT While most action potentials are generated at the axon initial segment, they can also be triggered at more distal sites along the axon. Such ectopic action potentials (EAPs) occur during several neuronal pathologies such as epilepsy, nerve injuries and inflammation but have also been observed during physiological network activity. EAPs propagate antidromically towards the somato-dendritic compartment where they modulate synaptic plasticity. Here we investigate the converse signal direction: do somato-dendritic synaptic potentials affect the generation of ectopic spikes? We measured anti- and orthodromic spikes in the soma and axon of mouse hippocampal CA1 pyramidal cells. We found that synaptic potentials propagate reliably through the axon, causing significant voltage transients at distances >350 μm. At these sites, excitatory input efficiently facilitated EAP initiation in distal axons and, conversely, inhibitory input suppressed EAP initiation. Our data reveal a new mechanism by which ectopically generated spikes can be entrained by conventional synaptic signalling during normal and pathological network activity.
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Affiliation(s)
- Christian Thome
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, 69120, Heidelberg, Germany
| | - Fabian C Roth
- Division of Physiology, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317, Oslo, Norway
| | - Joshua Obermayer
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, 69120, Heidelberg, Germany
| | - Antonio Yanez
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, 69120, Heidelberg, Germany
| | - Andreas Draguhn
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, 69120, Heidelberg, Germany
| | - Alexei V Egorov
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, 69120, Heidelberg, Germany
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10
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Hartzell AL, Martyniuk KM, Brigidi GS, Heinz DA, Djaja NA, Payne A, Bloodgood BL. NPAS4 recruits CCK basket cell synapses and enhances cannabinoid-sensitive inhibition in the mouse hippocampus. eLife 2018; 7:35927. [PMID: 30052197 PMCID: PMC6105310 DOI: 10.7554/elife.35927] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 07/19/2018] [Indexed: 12/30/2022] Open
Abstract
Experience-dependent expression of immediate-early gene transcription factors (IEG-TFs) can transiently change the transcriptome of active neurons and initiate persistent changes in cellular function. However, the impact of IEG-TFs on circuit connectivity and function is poorly understood. We investigate the specificity with which the IEG-TF NPAS4 governs experience-dependent changes in inhibitory synaptic input onto CA1 pyramidal neurons (PNs). We show that novel sensory experience selectively enhances somatic inhibition mediated by cholecystokinin-expressing basket cells (CCKBCs) in an NPAS4-dependent manner. NPAS4 specifically increases the number of synapses made onto PNs by individual CCKBCs without altering synaptic properties. Additionally, we find that sensory experience-driven NPAS4 expression enhances depolarization-induced suppression of inhibition (DSI), a short-term form of cannabinoid-mediated plasticity expressed at CCKBC synapses. Our results indicate that CCKBC inputs are a major target of the NPAS4-dependent transcriptional program in PNs and that NPAS4 is an important regulator of plasticity mediated by endogenous cannabinoids.
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Affiliation(s)
- Andrea L Hartzell
- Neuroscience Graduate Program, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States.,Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - Kelly M Martyniuk
- Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - G Stefano Brigidi
- Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - Daniel A Heinz
- Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States.,Biological Sciences Graduate Program, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - Nathalie A Djaja
- Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - Anja Payne
- Neuroscience Graduate Program, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States.,Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
| | - Brenda L Bloodgood
- Neuroscience Graduate Program, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States.,Division of Biological Sciences, Section of Neurobiology, Center for Neural Circuits and Behavior, University of California San Diego, San Diego, United States
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11
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Schroeder A, Vanderlinden J, Vints K, Ribeiro LF, Vennekens KM, Gounko NV, Wierda KD, de Wit J. A Modular Organization of LRR Protein-Mediated Synaptic Adhesion Defines Synapse Identity. Neuron 2018; 99:329-344.e7. [PMID: 29983322 DOI: 10.1016/j.neuron.2018.06.026] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 05/04/2018] [Accepted: 06/14/2018] [Indexed: 10/28/2022]
Abstract
Pyramidal neurons express rich repertoires of leucine-rich repeat (LRR)-containing adhesion molecules with similar synaptogenic activity in culture. The in vivo relevance of this molecular diversity is unclear. We show that hippocampal CA1 pyramidal neurons express multiple synaptogenic LRR proteins that differentially distribute to the major excitatory inputs on their apical dendrites. At Schaffer collateral (SC) inputs, FLRT2, LRRTM1, and Slitrk1 are postsynaptically localized and differentially regulate synaptic structure and function. FLRT2 controls spine density, whereas LRRTM1 and Slitrk1 exert opposing effects on synaptic vesicle distribution at the active zone. All LRR proteins differentially affect synaptic transmission, and their combinatorial loss results in a cumulative phenotype. At temporoammonic (TA) inputs, LRRTM1 is absent; FLRT2 similarly controls functional synapse number, whereas Slitrk1 function diverges to regulate postsynaptic AMPA receptor density. Thus, LRR proteins differentially control synaptic architecture and function and act in input-specific combinations and a context-dependent manner to specify synaptic properties.
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Affiliation(s)
- Anna Schroeder
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium
| | - Jeroen Vanderlinden
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium
| | - Katlijn Vints
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium; Electron Microscopy Platform & VIB BioImaging Core, Herestraat 49, 3000 Leuven, Belgium
| | - Luís F Ribeiro
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium
| | - Kristel M Vennekens
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium
| | - Natalia V Gounko
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium; Electron Microscopy Platform & VIB BioImaging Core, Herestraat 49, 3000 Leuven, Belgium
| | - Keimpe D Wierda
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium
| | - Joris de Wit
- VIB Center for Brain & Disease Research, Herestraat 49, 3000 Leuven, Belgium; KU Leuven, Department of Neurosciences, Leuven Brain Institute, Herestraat 49, 3000 Leuven, Belgium.
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12
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Evans MC, Dougherty KA. Carbamazepine-induced suppression of repetitive firing in CA1 pyramidal neurons is greater in the dorsal hippocampus than the ventral hippocampus. Epilepsy Res 2018; 145:63-72. [PMID: 29913405 DOI: 10.1016/j.eplepsyres.2018.05.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/11/2018] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
Abstract
Medial temporal lobe epilepsy (mTLE)-the most common form of focal epilepsy-is defined by recurrent partial seizures originating within the medial temporal lobe. Such seizures are commonly associated with the anterior hippocampus (as opposed to the posterior hippocampus), and refractory to the currently available anti-epileptic drugs (AED) for about one third of patients. Unfortunately, the mechanisms driving seizure generation and AED efficacy along the longitudinal hippocampal axis remain poorly understood. Recently, several groups investigating differences in excitability along the rodent longitudinal hippocampal axis have demonstrated that CA1 pyramidal neurons from the rodent ventral hippocampus (the rodent homolog of the human anterior hippocampus) are intrinsically more excitable than their dorsal counterparts (the rodent homolog of the human posterior hippocampus). This phenotypic difference is accompanied by significant differences in gene expression along the longitudinal hippocampal axis, which include gene products-such as voltage-gated sodium channel β-subunits-known to influence AED efficacy. Given this phenotypic heterogeneity, and the differential expression of gene products known to influence anti-epileptic drug efficacy, we sought to investigate the efficacy of the classical use-dependent sodium channel blocker, carbamazepine, in CA1 pyramidal neurons across the longitudinal hippocampal axis. Accordingly, we performed whole-cell current-clamp recordings on CA1 pyramidal neurons from acute hippocampal slices prepared from the dorsal and ventral hippocampus, and found that acute exposure to 100 μM carbamazepine induced a significantly greater suppression of repetitive firing for dorsal neurons relative to ventral neurons by inducing profound spike frequency adaptation (SFA). Moreover, we observed a small, but significant depolarization of resting membrane potential (RMP) for dorsal neurons (but not ventral neurons), following exposure to carbamazepine. Together, these observations demonstrate that carbamazepine's effect is concentrated in the dorsal hippocampus, which could provide meaningful insight into the side effect profile of carbamazepine (and related anti-epileptic drugs) in non-epileptic tissue, and inform future work investigating the mechanisms of carbamazepine resistance in epileptic tissue.
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Affiliation(s)
| | - Kelly Ann Dougherty
- Department of Biology, Rhodes College, 2000 N Parkway, Memphis, TN, 38112, USA.
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13
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Li W, Bellot-Saez A, Phillips ML, Yang T, Longo FM, Pozzo-Miller L. A small-molecule TrkB ligand restores hippocampal synaptic plasticity and object location memory in Rett syndrome mice. Dis Model Mech 2018; 10:837-845. [PMID: 28679669 PMCID: PMC5536912 DOI: 10.1242/dmm.029959] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/08/2017] [Indexed: 01/06/2023] Open
Abstract
Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in methyl-CpG-binding protein-2 (MECP2), a transcriptional regulator of many genes, including brain-derived neurotrophic factor (BDNF). BDNF levels are reduced in RTT autopsy brains and in multiple brain areas of Mecp2-deficient mice. Furthermore, experimental interventions that increase BDNF levels improve RTT-like phenotypes in Mecp2 mutant mice. Here, we characterized the actions of a small-molecule ligand of the BDNF receptor TrkB in hippocampal function in Mecp2 mutant mice. Systemic treatment of female Mecp2 heterozygous (HET) mice with LM22A-4 for 4 weeks improved hippocampal-dependent object location memory and restored hippocampal long-term potentiation (LTP). Mechanistically, LM22A-4 acts to dampen hyperactive hippocampal network activity, reduce the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs), and reduce the frequency of spontaneous tetrodotoxin-resistant Ca2+ signals in Mecp2 mutant hippocampal neurons, making them comparable to those features observed in wild-type neurons. Together, these observations indicate that LM22A-4 is a promising therapeutic candidate for the treatment of hippocampal dysfunction in RTT. Editors' choice: The brain-penetrant BDNF loop domain mimetic LM22A-4 improves synaptic plasticity and spatial discrimination memory in Rett syndrome mice, making it a promising therapeutic candidate for the treatment of hippocampal dysfunction.
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Affiliation(s)
- Wei Li
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Alba Bellot-Saez
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Mary L Phillips
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Tao Yang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Lucas Pozzo-Miller
- Department of Neurobiology, Civitan International Research Center, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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14
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Chung BYT, Bignell W, Jacklin DL, Winters BD, Bailey CDC. Postsynaptic nicotinic acetylcholine receptors facilitate excitation of developing CA1 pyramidal neurons. J Neurophysiol 2016; 116:2043-2055. [PMID: 27489367 DOI: 10.1152/jn.00370.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/01/2016] [Indexed: 11/22/2022] Open
Abstract
The hippocampus plays a key role in learning and memory. The normal development and mature function of hippocampal networks supporting these cognitive functions depends on afferent cholinergic neurotransmission mediated by nicotinic acetylcholine receptors. Whereas it is well-established that nicotinic receptors are present on GABAergic interneurons and on glutamatergic presynaptic terminals within the hippocampus, the ability of these receptors to mediate postsynaptic signaling in pyramidal neurons is not well understood. We use whole cell electrophysiology to show that heteromeric nicotinic receptors mediate direct inward currents, depolarization from rest and enhanced excitability in hippocampus CA1 pyramidal neurons of male mice. Measurements made throughout postnatal development provide a thorough developmental profile for these heteromeric nicotinic responses, which are greatest during the first 2 wk of postnatal life and decrease to low adult levels shortly thereafter. Pharmacological experiments show that responses are blocked by a competitive antagonist of α4β2* nicotinic receptors and augmented by a positive allosteric modulator of α5 subunit-containing receptors, which is consistent with expression studies suggesting the presence of α4β2 and α4β2α5 nicotinic receptors within the developing CA1 pyramidal cell layer. These findings demonstrate that functional heteromeric nicotinic receptors are present on CA1 pyramidal neurons during a period of major hippocampal development, placing these receptors in a prime position to play an important role in the establishment of hippocampal cognitive networks.
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Affiliation(s)
- Beryl Y T Chung
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
| | - Warren Bignell
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
| | - Derek L Jacklin
- Department of Psychology, College of Social and Applied Human Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Boyer D Winters
- Department of Psychology, College of Social and Applied Human Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Craig D C Bailey
- Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada; and
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15
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Yang S, Tang CM, Yang S. The Shaping of Two Distinct Dendritic Spikes by A-Type Voltage-Gated K(+) Channels. Front Cell Neurosci 2015; 9:469. [PMID: 26696828 PMCID: PMC4673864 DOI: 10.3389/fncel.2015.00469] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/17/2015] [Indexed: 12/03/2022] Open
Abstract
Dendritic ion channels have been a subject of intense research in neuroscience because active ion channels in dendrites shape input signals. Ca2+-permeable channels including NMDA receptors (NMDARs) have been implicated in supralinear dendritic integration, and the IA conductance in sublinear integration. Despite their essential roles in dendritic integration, it has remained uncertain whether these conductance coordinate with, or counteract, each other in the process of dendritic integration. To address this question, experiments were designed in hippocampal CA1 neurons with a recent 3D digital holography system that has shown excellent performance for spatial photoactivation. The results demonstrated a role of IA as a key modulator for two distinct dendritic spikes, low- and high-threshold Ca2+ spikes, through a preferential action of IA on Ca2+-permeable channel-mediated currents, over fast AMPAR-mediated currents. It is likely that the rapid kinetics of IA provides feed-forward inhibition to counteract the regenerative Ca2+ channel-mediated dendritic excitability. This research reveals one dynamic ionic mechanism of dendritic integration, and may contribute to a new understanding of neuronal hyperexcitability embedded in several neural diseases such as epilepsy, fragile X syndrome and Alzheimer’s disease.
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Affiliation(s)
- Sungchil Yang
- Department of Biomedical Sciences, City University of Hong Kong Kowloon, Hong Kong
| | - Cha-Min Tang
- Department of Neurology and Department of Physiology, University of Maryland School of Medicine Baltimore VAMC, MD, USA
| | - Sunggu Yang
- Department of Nano-Bioengineering, Incheon National University Incheon, South Korea
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16
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Lauderdale K, Murphy T, Tung T, Davila D, Binder DK, Fiacco TA. Osmotic Edema Rapidly Increases Neuronal Excitability Through Activation of NMDA Receptor-Dependent Slow Inward Currents in Juvenile and Adult Hippocampus. ASN Neuro 2015; 7:7/5/1759091415605115. [PMID: 26489684 PMCID: PMC4623564 DOI: 10.1177/1759091415605115] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Cellular edema (cell swelling) is a principal component of numerous brain disorders including ischemia, cortical spreading depression, hyponatremia, and epilepsy. Cellular edema increases seizure-like activity in vitro and in vivo, largely through nonsynaptic mechanisms attributable to reduction of the extracellular space. However, the types of excitability changes occurring in individual neurons during the acute phase of cell volume increase remain unclear. Using whole-cell patch clamp techniques, we report that one of the first effects of osmotic edema on excitability of CA1 pyramidal cells is the generation of slow inward currents (SICs), which initiate after approximately 1 min. Frequency of SICs increased as osmolarity decreased in a dose-dependent manner. Imaging of real-time volume changes in astrocytes revealed that neuronal SICs occurred while astrocytes were still in the process of swelling. SICs evoked by cell swelling were mainly nonsynaptic in origin and NMDA receptor-dependent. To better understand the relationship between SICs and changes in neuronal excitability, recordings were performed in increasingly physiological conditions. In the absence of any added pharmacological reagents or imposed voltage clamp, osmotic edema induced excitatory postsynaptic potentials and burst firing over the same timecourse as SICs. Like SICs, action potentials were blocked by NMDAR antagonists. Effects were more pronounced in adult (8-20 weeks old) compared with juvenile (P15-P21) mice. Together, our results indicate that cell swelling triggered by reduced osmolarity rapidly increases neuronal excitability through activation of NMDA receptors. Our findings have important implications for understanding nonsynaptic mechanisms of epilepsy in relation to cell swelling and reduction of the extracellular space.
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Affiliation(s)
- Kelli Lauderdale
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Thomas Murphy
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
| | - Tina Tung
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - David Davila
- Department of Cell Biology and Neuroscience, Riverside, CA, USA
| | - Devin K Binder
- Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA Division of Biomedical Sciences, UC Riverside School of Medicine, CA, USA
| | - Todd A Fiacco
- Department of Cell Biology and Neuroscience, Riverside, CA, USA Center for Glial-Neuronal Interactions, University of California Riverside, CA, USA
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17
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Kim Y, Hsu CL, Cembrowski MS, Mensh BD, Spruston N. Dendritic sodium spikes are required for long-term potentiation at distal synapses on hippocampal pyramidal neurons. eLife 2015; 4:e06414. [PMID: 26247712 PMCID: PMC4576155 DOI: 10.7554/elife.06414] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 08/05/2015] [Indexed: 12/12/2022] Open
Abstract
Dendritic integration of synaptic inputs mediates rapid neural computation as well as longer-lasting plasticity. Several channel types can mediate dendritically initiated spikes (dSpikes), which may impact information processing and storage across multiple timescales; however, the roles of different channels in the rapid vs long-term effects of dSpikes are unknown. We show here that dSpikes mediated by Nav channels (blocked by a low concentration of TTX) are required for long-term potentiation (LTP) in the distal apical dendrites of hippocampal pyramidal neurons. Furthermore, imaging, simulations, and buffering experiments all support a model whereby fast Nav channel-mediated dSpikes (Na-dSpikes) contribute to LTP induction by promoting large, transient, localized increases in intracellular calcium concentration near the calcium-conducting pores of NMDAR and L-type Cav channels. Thus, in addition to contributing to rapid neural processing, Na-dSpikes are likely to contribute to memory formation via their role in long-lasting synaptic plasticity.
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Affiliation(s)
- Yujin Kim
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Ching-Lung Hsu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Mark S Cembrowski
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Brett D Mensh
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Nelson Spruston
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
- Department of Neurobiology, Northwestern University, Evanston, United States
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18
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Saudargienė A, Graham BP. Inhibitory control of site-specific synaptic plasticity in a model CA1 pyramidal neuron. Biosystems 2015; 130:37-50. [PMID: 25769669 DOI: 10.1016/j.biosystems.2015.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 10/31/2014] [Accepted: 03/06/2015] [Indexed: 11/28/2022]
Abstract
A computational model of a biochemical network underlying synaptic plasticity is combined with simulated on-going electrical activity in a model of a hippocampal pyramidal neuron to study the impact of synapse location and inhibition on synaptic plasticity. The simulated pyramidal neuron is activated by the realistic stimulation protocol of causal and anticausal spike pairings of presynaptic and postsynaptic action potentials in the presence and absence of spatially targeted inhibition provided by basket, bistratified and oriens-lacunosum moleculare (OLM) interneurons. The resulting Spike-timing-dependent plasticity (STDP) curves depend strongly on the number of pairing repetitions, the synapse location and the timing and strength of inhibition.
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Affiliation(s)
- Aušra Saudargienė
- Department of Informatics, Vytautas Magnus University, Kaunas LT-44404, Lithuania.
| | - Bruce P Graham
- Computer Science and Mathematics, School of Natural Sciences, University of Stirling, Stirling FK9 4LA, UK
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19
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Drane L, Ainsley JA, Mayford MR, Reijmers LG. A transgenic mouse line for collecting ribosome-bound mRNA using the tetracycline transactivator system. Front Mol Neurosci 2014; 7:82. [PMID: 25400545 PMCID: PMC4212621 DOI: 10.3389/fnmol.2014.00082] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 10/08/2014] [Indexed: 11/28/2022] Open
Abstract
Acquiring the gene expression profiles of specific neuronal cell-types is important for understanding their molecular identities. Genome-wide gene expression profiles of genetically defined cell-types can be acquired by collecting and sequencing mRNA that is bound to epitope-tagged ribosomes (TRAP; translating ribosome affinity purification). Here, we introduce a transgenic mouse model that combines the TRAP technique with the tetracycline transactivator (tTA) system by expressing EGFP-tagged ribosomal protein L10a (EGFP-L10a) under control of the tetracycline response element (tetO-TRAP). This allows both spatial control of EGFP-L10a expression through cell-type specific tTA expression, as well as temporal regulation by inhibiting transgene expression through the administration of doxycycline. We show that crossing tetO-TRAP mice with transgenic mice expressing tTA under the Camk2a promoter (Camk2a-tTA) results in offspring with cell-type specific expression of EGFP-L10a in CA1 pyramidal neurons and medium spiny neurons in the striatum. Co-immunoprecipitation confirmed that EGFP-L10a integrates into a functional ribosomal complex. In addition, collection of ribosome-bound mRNA from the hippocampus yielded the expected enrichment of genes expressed in CA1 pyramidal neurons, as well as a depletion of genes expressed in other hippocampal cell-types. Finally, we show that crossing tetO-TRAP mice with transgenic Fos-tTA mice enables the expression of EGFP-L10a in CA1 pyramidal neurons that are activated during a fear conditioning trial. The tetO-TRAP mouse can be combined with other tTA mouse lines to enable gene expression profiling of a variety of different cell-types.
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Affiliation(s)
- Laurel Drane
- Department of Neuroscience, School of Medicine, Tufts University Boston, MA, USA ; Graduate Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University Boston, MA, USA
| | - Joshua A Ainsley
- Department of Neuroscience, School of Medicine, Tufts University Boston, MA, USA
| | - Mark R Mayford
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute La Jolla, CA, USA
| | - Leon G Reijmers
- Department of Neuroscience, School of Medicine, Tufts University Boston, MA, USA
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20
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Gómez González JF, Mel BW, Poirazi P. Distinguishing Linear vs. Non-Linear Integration in CA1 Radial Oblique Dendrites: It's about Time. Front Comput Neurosci 2011; 5:44. [PMID: 22171217 PMCID: PMC3214726 DOI: 10.3389/fncom.2011.00044] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Accepted: 09/20/2011] [Indexed: 01/10/2023] Open
Abstract
It was recently shown that multiple excitatory inputs to CA1 pyramidal neuron dendrites must be activated nearly simultaneously to generate local dendritic spikes and supralinear responses at the soma; even slight input desynchronization prevented local spike initiation (Gasparini and Magee, 2006; Losonczy and Magee, 2006). This led to the conjecture that CA1 pyramidal neurons may only express their non-linear integrative capabilities during the highly synchronized sharp waves and ripples that occur during slow wave sleep and resting/consummatory behavior, whereas during active exploration and REM sleep (theta rhythm), inadequate synchronization of excitation would lead CA1 pyramidal cells to function as essentially linear devices. Using a detailed single neuron model, we replicated the experimentally observed synchronization effect for brief inputs mimicking single synaptic release events. When synapses were driven instead by double pulses, more representative of the bursty inputs that occur in vivo, we found that the tolerance for input desynchronization was increased by more than an order of magnitude. The effect depended mainly on paired-pulse facilitation of NMDA receptor-mediated responses at Schaffer collateral synapses. Our results suggest that CA1 pyramidal cells could function as non-linear integrative units in all major hippocampal states.
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21
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Ito HT, Schuman EM. Distance-dependent homeostatic synaptic scaling mediated by a-type potassium channels. Front Cell Neurosci 2009; 3:15. [PMID: 20076774 PMCID: PMC2806179 DOI: 10.3389/neuro.03.015.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 11/09/2009] [Indexed: 11/13/2022] Open
Abstract
Many lines of evidence suggest that the efficacy of synapses on CA1 pyramidal neuron dendrites increases as a function of distance from the cell body. The strength of an individual synapse is also dynamically modulated by activity-dependent synaptic plasticity, which raises the question as to how a neuron can reconcile individual synaptic changes with the maintenance of the proximal-to-distal gradient of synaptic strength along the dendrites. As the density of A-type potassium channels exhibits a similar gradient from proximal (low)-to-distal (high) dendrites, the A-current may play a role in coordinating local synaptic changes with the global synaptic strength gradient. Here we describe a form of homeostatic plasticity elicited by conventional activity blockade (with tetrodotoxin) coupled with a block of the A-type potassium channel. Following A-type potassium channel inhibition for 12 h, recordings from CA1 somata revealed a significantly higher miniature excitatory postsynaptic current (mEPSC) frequency, whereas in dendritic recordings, there was no change in mEPSC frequency. Consistent with mEPSC recordings, we observed a significant increase in AMPA receptor density in stratum pyramidale but not stratum radiatum. Based on these data, we propose that the differential distribution of A-type potassium channels along the apical dendrites may create a proximal-to-distal membrane potential gradient. This gradient may regulate AMPA receptor distribution along the same axis. Taken together, our results indicate that A-type potassium channels play an important role in controlling synaptic strength along the dendrites, which may help to maintain the computational capacity of the neuron.
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Affiliation(s)
- Hiroshi T Ito
- Division of Biology, California Institute of Technology Pasadena, CA, USA
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