1
|
Luo W, Egger M, Cruz-Ochoa N, Tse A, Maloveczky G, Tamás B, Lukacsovich D, Seng C, Amrein I, Lukacsovich T, Wolfer D, Földy C. Activation of feedforward wiring in adult hippocampal neurons by the basic-helix-loop-helix transcription factor Ascl4. PNAS NEXUS 2024; 3:pgae174. [PMID: 38711810 PMCID: PMC11071515 DOI: 10.1093/pnasnexus/pgae174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 04/17/2024] [Indexed: 05/08/2024]
Abstract
Although evidence indicates that the adult brain retains a considerable capacity for circuit formation, adult wiring has not been broadly considered and remains poorly understood. In this study, we investigate wiring activation in adult neurons. We show that the basic-helix-loop-helix transcription factor Ascl4 can induce wiring in different types of hippocampal neurons of adult mice. The new axons are mainly feedforward and reconfigure synaptic weights in the circuit. Mice with the Ascl4-induced circuits do not display signs of pathology and solve spatial problems equally well as controls. Our results demonstrate reprogrammed connectivity by a single transcriptional factor and provide insights into the regulation of brain wiring in adults.
Collapse
Affiliation(s)
- Wenshu Luo
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - Matteo Egger
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
- Adaptive Brain Circuits in Development and Learning (AdaBD), University Research Priority Program (URPP), University of Zürich, Zürich 8057, Switzerland
| | - Natalia Cruz-Ochoa
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
- Adaptive Brain Circuits in Development and Learning (AdaBD), University Research Priority Program (URPP), University of Zürich, Zürich 8057, Switzerland
| | - Alice Tse
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - Gyula Maloveczky
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - Bálint Tamás
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - David Lukacsovich
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - Charlotte Seng
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - Irmgard Amrein
- Institute of Anatomy, Faculty of Medicine, University of Zürich, Zürich 8057, Switzerland
| | - Tamás Lukacsovich
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
| | - David Wolfer
- Institute of Anatomy, Faculty of Medicine, University of Zürich, Zürich 8057, Switzerland
- Institute of Human Movement Sciences and Sport, D-HEST, ETH Zürich, Zürich 8057, Switzerland
| | - Csaba Földy
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zürich, Zürich 8057, Switzerland
- Adaptive Brain Circuits in Development and Learning (AdaBD), University Research Priority Program (URPP), University of Zürich, Zürich 8057, Switzerland
| |
Collapse
|
2
|
Shao LR, Gao F, Chinnasamy V, Kazuki Y, Oshimura M, Reeves RH, Stafstrom CE. Increased propensity for infantile spasms and altered neocortical excitation-inhibition balance in a mouse model of down syndrome carrying human chromosome 21. Neurobiol Dis 2023:106198. [PMID: 37315904 DOI: 10.1016/j.nbd.2023.106198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/30/2023] [Accepted: 06/11/2023] [Indexed: 06/16/2023] Open
Abstract
Children with Down syndrome (DS, trisomy of chromosome 21) have an increased risk of infantile spasms (IS). As an epileptic encephalopathy, IS may further impair cognitive function and exacerbate neurodevelopmental delays already present in children with DS. To investigate the pathophysiology of IS in DS, we induced IS-like epileptic spasms in a genetic mouse model of DS that carries human chromosome 21q, TcMAC21, the animal model most closely representing gene dosage imbalance in DS. Repetitive extensor/flexor spasms were induced by the GABAB receptor agonist γ-butyrolactone (GBL) and occurred predominantly in young TcMAC21 mice (85%) but also in some euploid mice (25%). During GBL application, background electroencephalographic (EEG) amplitude was reduced, and rhythmic, sharp-and-slow wave activity or high-amplitude burst (epileptiform) events emerged in both TcMAC21 and euploid mice. Spasms occurred only during EEG bursts, but not every burst was accompanied by a spasm. Electrophysiological experiments revealed that basic membrane properties (resting membrane potential, input resistance, action-potential threshold and amplitude, rheobase, input-output relationship) of layer V pyramidal neurons were not different between TcMAC21 mice and euploid controls. However, excitatory postsynaptic currents (EPSCs) evoked at various intensities were significantly larger in TcMAC21 mice than euploid controls, while inhibitory postsynaptic currents (IPSCs) were similar between the two groups, resulting in an increased excitation-inhibition (E-I) ratio. These data show that behavioral spasms with epileptic EEG activity can be induced in young TcMAC21 DS mice, providing proof-of-concept evidence for increased IS susceptibility in these DS mice. Our findings also show that basic membrane properties are similar in TcMAC21 and euploid mice, while the neocortical E-I balance is altered to favor increased excitation in TcMAC21 mice, which may predispose to IS generation.
Collapse
Affiliation(s)
- Li-Rong Shao
- Division of Pediatric Neurology, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Feng Gao
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Viveka Chinnasamy
- Division of Pediatric Neurology, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Yasuhiro Kazuki
- Chromosome Engineering Research Center, Tottori University, Tottori, Japan
| | - Mistuo Oshimura
- Chromosome Engineering Research Center, Tottori University, Tottori, Japan; Trans Chromosomics, Inc., Tottori, Japan
| | - Roger H Reeves
- Chromosome Engineering Research Center, Tottori University, Tottori, Japan; Department of Human Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Carl E Stafstrom
- Division of Pediatric Neurology, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| |
Collapse
|
3
|
Shao LR, Dudek FE. Enhanced burst discharges in the CA1 area of the immature versus adult hippocampus: patterns and cellular mechanisms. J Neurophysiol 2022; 128:1566-1577. [PMID: 36382903 PMCID: PMC9744639 DOI: 10.1152/jn.00327.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 10/27/2022] [Accepted: 11/13/2022] [Indexed: 11/17/2022] Open
Abstract
Burst discharges in the immature brain may contribute to its enhanced seizure susceptibility. The cellular mechanisms underlying burst discharges in the CA1 area of the immature versus adult hippocampus were investigated with simultaneous whole-cell and field-potential recordings. When GABAA receptors were blocked pharmacologically, bursts in CA1 were either graded or all-or-none (or mixed) as a function of electrical stimulation intensity. Most CA1 minislices from immature rats displayed all-or-none or mixed bursts, whereas the slices from adult rats predominantly elicited graded bursts. The frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) were greater in CA1 pyramidal cells from the immature than the adult slices. The developmental differences in CA1 bursting were also detected in slices adjusted for maturational changes in brain volume (i.e., 350 µm thick for immature vs. 450 µm thick for adult rats). Neither N-methyl-d-aspartate (NMDA) nor group I metabotropic glutamate (mGlu1) receptor antagonists blocked the network-driven bursts in immature CA1, but an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor blocker abolished them. Robust excitatory postsynaptic potentials (EPSPs) occurred after bursts in some immature CA1 slices (23%) but never in slices from the adult. The input-output (amount of current injected vs. number of action potentials generated) relationship was markedly greater in CA1 pyramidal cells in the immature compared with the adult hippocampus. These data suggest that the CA1 area of the immature brain is capable of generating network-driven bursts, which declines in adult rats. The increased propensity of burst generation in immature CA1 appears to involve a greater AMPA receptor-mediated synaptic network and an increased intrinsic spike-generating ability.NEW & NOTEWORTHY Burst discharges in the developing brain can provide valuable insights into epileptogenesis. We show that the immature hippocampal CA1 area is capable of generating all-or-none (i.e., network) bursts, which transitions to graded (i.e., nonnetwork) bursts in the mature brain via both synaptic and intrinsic mechanisms. Our results provide new clues to help understand possible mechanisms that may be shared in the immature and epileptic brain and how the normal brain becomes seizure prone (i.e., epileptogenesis).
Collapse
Affiliation(s)
- Li-Rong Shao
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - F Edward Dudek
- Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah
| |
Collapse
|
4
|
Nasudi G, Elahdadi Salmani M, Hosseinmardi N, Moradpour F, Lashkarbolouki T, Goudarzi I. Hippocampal orexin-1 and endocannabinoid-1 receptors underlie the kainate-induced occlusion in theta-burst long- term potentiation. Neuropeptides 2022; 95:102263. [PMID: 35716469 DOI: 10.1016/j.npep.2022.102263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 06/02/2022] [Accepted: 06/02/2022] [Indexed: 10/18/2022]
Abstract
INTRODUCTION Seizures may result from the hyperexcitable neuronal activity of the brain. Multiple neurotransmitter receptors, including orexin (OX) and endocannabinoids interfere with forming the synaptic responses linked to the seizures. Therefore, this study investigates the involvement of OX-1 (OX1R) and endocannbinoid-1 (CB1R) receptors in the kainate- induced excitability in the synaptic field responses. MATERIAL AND METHODS Theta pattern used to stimulate Schaffer collaterals and then metal microelectrodes to record the CA1 field excitatory postsynaptic potentials (fEPSPs). Input/ output stimulation and responses and paired- pulse (PP) stimuli employed to measure the state of synaptic activity in normal and kainate- induced seizure-like hyperexcitable activities and the slope of fEPSPs used as a measure of the change in the synaptic activity. Furthermore, agonists and antagonists of OX and endocannabinoids infused to investigate the involvement of their receptors. RESULT The results showed that kainate application increased the fEPSP slope either in input stimuli with different intensities/output synaptic responses (I/O), or test pulse stimulated baseline synaptic responses (BSR) and, hence, increased the excitability of field responses in the CA1 region. However, neither kainate nor theta burst stimulation (TBS) could alter the PP stimuli -induced synaptic responses. TBS increased the fEPSP slope of the kainate-applied I/O and BSR, however, the increase was not high enough in BSR to be classified as long-term potentiation (LTP). The single-antagonist OX1R and CB1R administration prevented TBS- induced potentiation and partially recovered the effect by adding eCB or OX agonists in kainate-injected animals. In contrast, OX or combined eCB-OX antagonist application group demonstrated nearly full recovery of LTP induction. CONCLUSION Our study concludes that blockade of OX1 or CB1 prevents the induction of LTP, and OX infusion or both receptor blockade recovers the LTP.
Collapse
Affiliation(s)
- Giti Nasudi
- School of Biology, Damghan University, Damghan, Iran
| | | | - Narges Hosseinmardi
- Department of Physiology, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Iran
| | - Farshad Moradpour
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Iran
| | | | - Iran Goudarzi
- School of Biology, Damghan University, Damghan, Iran
| |
Collapse
|
5
|
Seng C, Luo W, Földy C. Circuit formation in the adult brain. Eur J Neurosci 2022; 56:4187-4213. [PMID: 35724981 PMCID: PMC9546018 DOI: 10.1111/ejn.15742] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 06/08/2022] [Accepted: 06/09/2022] [Indexed: 11/30/2022]
Abstract
Neurons in the mammalian central nervous system display an enormous capacity for circuit formation during development but not later in life. In principle, new circuits could be also formed in adult brain, but the absence of the developmental milieu and the presence of growth inhibition and hundreds of working circuits are generally viewed as unsupportive for such a process. Here, we bring together evidence from different areas of neuroscience—such as neurological disorders, adult‐brain neurogenesis, innate behaviours, cell grafting, and in vivo cell reprogramming—which demonstrates robust circuit formation in adult brain. In some cases, adult‐brain rewiring is ongoing and required for certain types of behaviour and memory, while other cases show significant promise for brain repair in disease models. Together, these examples highlight that the adult brain has higher capacity for structural plasticity than previously recognized. Understanding the underlying mechanisms behind this retained plasticity has the potential to advance basic knowledge regarding the molecular organization of synaptic circuits and could herald a new era of neural circuit engineering for therapeutic repair.
Collapse
Affiliation(s)
- Charlotte Seng
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zurich, Zürich, Switzerland
| | - Wenshu Luo
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zurich, Zürich, Switzerland
| | - Csaba Földy
- Laboratory of Neural Connectivity, Brain Research Institute, Faculties of Medicine and Science, University of Zurich, Zürich, Switzerland
| |
Collapse
|
6
|
Owen B, Bichler E, Benveniste M. Excitatory synaptic transmission in hippocampal area CA1 is enhanced then reduced as chronic epilepsy progresses. Neurobiol Dis 2021; 154:105343. [PMID: 33753293 DOI: 10.1016/j.nbd.2021.105343] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 03/16/2021] [Accepted: 03/18/2021] [Indexed: 12/27/2022] Open
Abstract
This study examines changes in synaptic transmission with progression of the chronic epileptic state. Male Sprague-Dawley rats (P40-45) were injected with either saline or pilocarpine. In rats injected with pilocarpine, status epilepticus ensued. Hippocampal slices were cut 20-60 days or 80-110 days post-treatment. Evoked and miniature EPSCs (mEPSCs) were recorded from CA1 pyramidal neurons using whole-cell voltage-clamp. Fiber volleys were also recorded from stratum radiatum. Evoked EPSCs from the pilocarpine-treated cohort showed enhanced amplitudes 20-60 days post-treatment compared to the saline-treated cohort, whereas mEPSCs recorded from the same age group showed no change in event frequency and a slight but significant decrease in mEPSC amplitude distribution. In contrast, comparing evoked EPSCs and mEPSCs recorded 80-110 days after treatment indicated reduced amplitudes from pilocarpine-treated animals compared to controls. mEPSC inter-event interval decreased. This could be explained by a partial depletion of the ready releasable pool of neurotransmitter vesicles in Schaffer collateral presynaptic terminals of the pilocarpine-treated rats. In both saline- and pilocarpine-treated cohorts, concomitant decreases in mEPSC amplitudes as time after treatment progressed suggest that age-related changes in CA1 circuitry may be partially responsible for changes in synaptic transmission that may influence the chronic epileptic state.
Collapse
Affiliation(s)
- Benjamin Owen
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA
| | - Edyta Bichler
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA
| | - Morris Benveniste
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, GA 30310, USA.
| |
Collapse
|
7
|
Roh H, Kim W, Kim J, Kim JH, Kim JH. Duration-dependent extensive volume and shape changes of mesolimbic structures in surgically treated unilateral patients with temporal lobe epilepsy. Epilepsy Behav 2021; 114:107517. [PMID: 33257292 DOI: 10.1016/j.yebeh.2020.107517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 09/15/2020] [Accepted: 09/20/2020] [Indexed: 11/16/2022]
Abstract
PURPOSE Although surgical treatment of drug-resistant mesial temporal lobe epilepsy (MTLE) has proven efficacy, surgical referrals are often delayed. Knowledge of the abnormalities of mesolimbic structures beyond the hippocampus may be important for patients with MTLE because of its usefulness in the understanding of progressive disabilities in affected structures. This study aimed to identify volume and shape changes of mesolimbic structures in surgically treated patients with unilateral MTLE and their correlation with various clinical parameters. METHODS Twenty-four patients with unilateral MTLE (12 with left MTLE [LMTLE] and 12 with right MTLE [RMTLE]) who were surgically treated with standard temporal lobectomy, including amygdalohippocampectomy, and 24 age- and sex-matched healthy individuals were enrolled. Preoperatively, volumetric analysis using magnetic resonance imaging (MRI) of 27 mesolimbic substructures (11 from each hemisphere and 5 from the midline) was performed. We also investigated the three-dimensional morphometric differences of the mesolimbic structures between the unilateral MTLE and control groups using shape analyses. RESULTS Patients with LMTLE showed significant volume reductions in various ipsilateral mesolimbic (72.7%, 8/11) and contralateral structures (27.3%, 3/11). Patients with RMTLE had also significant reduced volumes in ipsilateral (63.6%, 7/11) and contralateral structures (73.3%, 3/11). Among the clinical parameters, only the duration of epilepsy had a statistically significant inverse correlation with the volumes of the hippocampus, parahippocampus, entorhinal cortex, cingulate, and corpus callosum. In the shape analysis of the bilateral hippocampus, amygdala, parahippocampus, and entorhinal cortex, after accounting for the effects of age and total intracranial volume, significant shape changes in the anterolateral area of the ipsilateral hippocampus were noted, which corresponds to the cornu ammonis (CA)1 and subiculum of the hippocampus. CONCLUSIONS The extensive volume reductions in the multiple mesolimbic structures and the substantial inverse correlation between the duration of epilepsy and the volumes of the various mesolimbic structures in our study supports that MTLE is not restricted to the hippocampus, but it progressively involves extensive mesolimbic structures. The duration-dependent atrophic changes in multiple subcortical structures seen in this study also suggest a positive role of early surgical intervention for patients with drug-resistant TLE.
Collapse
Affiliation(s)
- Haewon Roh
- The Department of Neurosurgery, Guro Hospital, Korea University Medicine, Republic of Korea
| | - Won Kim
- The Department of Neurosurgery, Guro Hospital, Korea University Medicine, Republic of Korea
| | - Junwon Kim
- The Department of Neurosurgery, Guro Hospital, Korea University Medicine, Republic of Korea
| | - Ji Hyun Kim
- The Department of Neurology, Guro Hospital, Korea University Medicine, Republic of Korea
| | - Jong Hyun Kim
- The Department of Neurosurgery, Guro Hospital, Korea University Medicine, Republic of Korea.
| |
Collapse
|
8
|
Dolleman-van der Weel MJ, Witter MP. The thalamic midline nucleus reuniens: potential relevance for schizophrenia and epilepsy. Neurosci Biobehav Rev 2020; 119:422-439. [PMID: 33031816 DOI: 10.1016/j.neubiorev.2020.09.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 09/03/2020] [Accepted: 09/28/2020] [Indexed: 01/08/2023]
Abstract
Anatomical, electrophysiological and behavioral studies in rodents have shown that the thalamic midline nucleus reuniens (RE) is a crucial link in the communication between hippocampal formation (HIP, i.e., CA1, subiculum) and medial prefrontal cortex (mPFC), important structures for cognitive and executive functions. A common feature in neurodevelopmental and neurodegenerative brain diseases is a dysfunctional connectivity/communication between HIP and mPFC, and disturbances in the cognitive domain. Therefore, it is assumed that aberrant functioning of RE may contribute to behavioral/cognitive impairments in brain diseases characterized by cortico-thalamo-hippocampal circuit dysfunctions. In the human brain the connections of RE are largely unknown. Yet, recent studies have found important similarities in the functional connectivity of HIP-mPFC-RE in humans and rodents, making cautious extrapolating experimental findings from animal models to humans justifiable. The focus of this review is on a potential involvement of RE in schizophrenia and epilepsy.
Collapse
Affiliation(s)
- M J Dolleman-van der Weel
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, NTNU Norwegian University of Science and Technology, Trondheim NO-7491, Norway.
| | - M P Witter
- Kavli Institute for Systems Neuroscience and Centre for Neural Computation, NTNU Norwegian University of Science and Technology, Trondheim NO-7491, Norway.
| |
Collapse
|
9
|
Henke C, Töllner K, van Dijk RM, Miljanovic N, Cordes T, Twele F, Bröer S, Ziesak V, Rohde M, Hauck SM, Vogel C, Welzel L, Schumann T, Willmes DM, Kurzbach A, El-Agroudy NN, Bornstein SR, Schneider SA, Jordan J, Potschka H, Metallo CM, Köhling R, Birkenfeld AL, Löscher W. Disruption of the sodium-dependent citrate transporter SLC13A5 in mice causes alterations in brain citrate levels and neuronal network excitability in the hippocampus. Neurobiol Dis 2020; 143:105018. [PMID: 32682952 DOI: 10.1016/j.nbd.2020.105018] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/08/2020] [Accepted: 07/11/2020] [Indexed: 12/28/2022] Open
Abstract
In addition to tissues such as liver, the plasma membrane sodium-dependent citrate transporter, NaCT (SLC13A5), is highly expressed in brain neurons, but its function is not understood. Loss-of-function mutations in the human SLC13A5 gene have been associated with severe neonatal encephalopathy and pharmacoresistant seizures. The molecular mechanisms of these neurological alterations are not clear. We performed a detailed examination of a Slc13a5 deletion mouse model including video-EEG monitoring, behavioral tests, and electrophysiologic, proteomic, and metabolomic analyses of brain and cerebrospinal fluid. The experiments revealed an increased propensity for epileptic seizures, proepileptogenic neuronal excitability changes in the hippocampus, and significant citrate alterations in the CSF and brain tissue of Slc13a5 deficient mice, which may underlie the neurological abnormalities. These data demonstrate that SLC13A5 is involved in brain citrate regulation and suggest that abnormalities in this regulation can induce seizures. The present study is the first to (i) establish the Slc13a5-knockout mouse model as a helpful tool to study the neuronal functions of NaCT and characterize the molecular mechanisms by which functional deficiency of this citrate transporter causes epilepsy and impairs neuronal function; (ii) evaluate all hypotheses that have previously been suggested on theoretical grounds to explain the neurological phenotype of SLC13A5 mutations; and (iii) indicate that alterations in brain citrate levels result in neuronal network excitability and increased seizure propensity.
Collapse
Affiliation(s)
- Christine Henke
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
| | - R Maarten van Dijk
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University, Munich, Germany
| | - Nina Miljanovic
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University, Munich, Germany
| | - Thekla Cordes
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Friederike Twele
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
| | - Sonja Bröer
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, 30559 Hannover, Germany
| | - Vanessa Ziesak
- Oscar-Langendorff-Institute of Physiology, Rostock University Medical Center, Rostock, Germany
| | - Marco Rohde
- Oscar-Langendorff-Institute of Physiology, Rostock University Medical Center, Rostock, Germany
| | - Stefanie M Hauck
- Research Unit Protein Science, Helmholtz Center Munich, Neuherberg, Germany
| | - Charlotte Vogel
- Department of Biometry, Epidemiology and Information Processing, University of Veterinary Medicine Hannover, Germany
| | - Lisa Welzel
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, 30559 Hannover, Germany; Center for Systems Neuroscience, 30559 Hannover, Germany
| | - Tina Schumann
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Diana M Willmes
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Anica Kurzbach
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Nermeen N El-Agroudy
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Stefan R Bornstein
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany
| | | | - Jens Jordan
- Institute for Aerospace Medicine, German Aerospace Center (DLR) and Chair for Aerospace Medicine, University of Cologne, Cologne, Germany
| | - Heidrun Potschka
- Institute of Pharmacology, Toxicology, and Pharmacy, Ludwig-Maximilians-University, Munich, Germany
| | - Christian M Metallo
- Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA; Moores Cancer Center, University of California, San Diego, La Jolla, CA 92037, USA
| | - Rüdiger Köhling
- Oscar-Langendorff-Institute of Physiology, Rostock University Medical Center, Rostock, Germany
| | - Andreas L Birkenfeld
- Section of Metabolic and Vascular Medicine, Medical Clinic III, Dresden University School of Medicine, Technische Universität Dresden, Germany; Paul Langerhans Institute Dresden of the Helmholtz Center Munich at University Hospital and Faculty of Medicine, TU Dresden, Dresden, Germany
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, 30559 Hannover, Germany; Center for Systems Neuroscience, 30559 Hannover, Germany.
| |
Collapse
|
10
|
Shuman T, Aharoni D, Cai DJ, Lee CR, Chavlis S, Page-Harley L, Vetere LM, Feng Y, Yang CY, Mollinedo-Gajate I, Chen L, Pennington ZT, Taxidis J, Flores SE, Cheng K, Javaherian M, Kaba CC, Rao N, La-Vu M, Pandi I, Shtrahman M, Bakhurin KI, Masmanidis SC, Khakh BS, Poirazi P, Silva AJ, Golshani P. Breakdown of spatial coding and interneuron synchronization in epileptic mice. Nat Neurosci 2020; 23:229-238. [PMID: 31907437 PMCID: PMC7259114 DOI: 10.1038/s41593-019-0559-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 11/19/2019] [Indexed: 12/19/2022]
Abstract
Temporal lobe epilepsy causes severe cognitive deficits, but the circuit mechanisms remain unknown. Interneuron death and reorganization during epileptogenesis may disrupt the synchrony of hippocampal inhibition. To test this, we simultaneously recorded from the CA1 and dentate gyrus in pilocarpine-treated epileptic mice with silicon probes during head-fixed virtual navigation. We found desynchronized interneuron firing between the CA1 and dentate gyrus in epileptic mice. Since hippocampal interneurons control information processing, we tested whether CA1 spatial coding was altered in this desynchronized circuit, using a novel wire-free miniscope. We found that CA1 place cells in epileptic mice were unstable and completely remapped across a week. This spatial instability emerged around 6 weeks after status epilepticus, well after the onset of chronic seizures and interneuron death. Finally, CA1 network modeling showed that desynchronized inputs can impair the precision and stability of CA1 place cells. Together, these results demonstrate that temporally precise intrahippocampal communication is critical for spatial processing.
Collapse
Affiliation(s)
- Tristan Shuman
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
| | - Daniel Aharoni
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
- Integrative Center for Learning and Memory, University of California, Los Angeles, Los Angeles, CA, USA
| | - Denise J Cai
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Christopher R Lee
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Spyridon Chavlis
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece
| | - Lucia Page-Harley
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Lauren M Vetere
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Yu Feng
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Chen Yi Yang
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Irene Mollinedo-Gajate
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Lingxuan Chen
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Zachary T Pennington
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Jiannis Taxidis
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sergio E Flores
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Kevin Cheng
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Milad Javaherian
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Christina C Kaba
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Naina Rao
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Mimi La-Vu
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Ioanna Pandi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece
- School of Medicine, University of Crete, Heraklion, Greece
| | - Matthew Shtrahman
- Department of Neurosciences, University of California, San Diego, La Jolla, CA, USA
| | - Konstantin I Bakhurin
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Sotiris C Masmanidis
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Baljit S Khakh
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology Hellas (FORTH), Heraklion, Greece.
| | - Alcino J Silva
- Integrative Center for Learning and Memory, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA
- Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, USA
- Department of Psychology, University of California, Los Angeles, Los Angeles, CA, USA
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
- Integrative Center for Learning and Memory, University of California, Los Angeles, Los Angeles, CA, USA.
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, USA.
- Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, USA.
- West LA Veterans Affairs Medical Center, Los Angeles, CA, USA.
- Intellectual and Developmental Disabilities Research Center, University of California, Los Angeles, Los Angeles, CA, USA.
| |
Collapse
|
11
|
Brennan EKW, Ahmed OJ. Ripple While You Walk, and You May Get Lost: Pathological High-Frequency Activity Can Alter Spatial Navigation Circuits. Epilepsy Curr 2019; 19:344-346. [PMID: 31476918 PMCID: PMC6864566 DOI: 10.1177/1535759719871275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The Impact of Pathological High-frequency Oscillations on Hippocampal Network Activity in Rats With Chronic Epilepsy. Ewell LA, Fischer KB, Leibold C, Leutgeb S, Leutgeb JK. eLIFE. 2019;8:pii: e42148. doi:10.7554/eLife.42148. PMID: 30794155 In epilepsy, brain networks generate pathological high-frequency oscillations (pHFOs) during interictal periods. To understand how pHFOs differ from normal oscillations in overlapping frequency bands and potentially perturb hippocampal processing, we performed high-density single unit and local field potential recordings from hippocampi of behaving rats with and without chronic epilepsy. In epileptic animals, we observed 2 types of co-occurring fast oscillations that by comparison to control animals could be classified as “ripple-like” or “pHFO.” We compared their spectral characteristics, brain state dependence, and cellular participants. Strikingly, pHFO occurred irrespective of brain state, were associated with interictal spikes, engaged distinct subnetworks of principal neurons compared to ripple-like events, increased the sparsity of network activity, and initiated both general and immediate disruptions in spatial information coding. Taken together, our findings suggest that events that result in pHFOs have an immediate impact on memory processes, corroborating the need for proper classification of pHFOs to facilitate therapeutic interventions that selectively target pathological activity.
Collapse
|
12
|
Cloyd RA, Koren SA, Abisambra JF. Manganese-Enhanced Magnetic Resonance Imaging: Overview and Central Nervous System Applications With a Focus on Neurodegeneration. Front Aging Neurosci 2018; 10:403. [PMID: 30618710 PMCID: PMC6300587 DOI: 10.3389/fnagi.2018.00403] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Accepted: 11/23/2018] [Indexed: 12/16/2022] Open
Abstract
Manganese-enhanced magnetic resonance imaging (MEMRI) rose to prominence in the 1990s as a sensitive approach to high contrast imaging. Following the discovery of manganese conductance through calcium-permeable channels, MEMRI applications expanded to include functional imaging in the central nervous system (CNS) and other body systems. MEMRI has since been employed in the investigation of physiology in many animal models and in humans. Here, we review historical perspectives that follow the evolution of applied MRI research into MEMRI with particular focus on its potential toxicity. Furthermore, we discuss the more current in vivo investigative uses of MEMRI in CNS investigations and the brief but decorated clinical usage of chelated manganese compound mangafodipir in humans.
Collapse
Affiliation(s)
- Ryan A Cloyd
- Department of Physiology, University of Kentucky, Lexington, KY, United States.,College of Medicine, University of Kentucky, Lexington, KY, United States.,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, United States
| | - Shon A Koren
- Department of Physiology, University of Kentucky, Lexington, KY, United States.,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, United States.,Department of Neuroscience & Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, United States
| | - Jose F Abisambra
- Department of Physiology, University of Kentucky, Lexington, KY, United States.,Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, United States.,Department of Neuroscience & Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, FL, United States.,Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY, United States
| |
Collapse
|
13
|
Rami A, Benz A. Exclusive Activation of Caspase-3 in Mossy Fibers and Altered Dynamics of Autophagy Markers in the Mice Hippocampus upon Status Epilepticus Induced by Kainic Acid. Mol Neurobiol 2018; 55:4492-4503. [PMID: 28685385 DOI: 10.1007/s12035-017-0665-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 06/19/2017] [Indexed: 10/19/2022]
Abstract
Epileptic seizures are generally associated with pathological changes in the hippocampus such as astrogliosis, mossy fiber sprouting, and neuronal damage. However, more than 30% of temporal lobe epilepsy in humans shows neither neuronal damage nor mossy fiber sprouting despite chronic epileptic seizures. A similar situation exists in certain commonly used strains of mice, specifically C57BL/6 and BALB/c, which exhibit epileptic seizures, but no neuronal damage upon kainic acid administration. This suggests that intrinsic factors may influence the pathological manifestations of epilepsy. Mechanisms which are behind the resistance of hippocampal cells to KA-induced neuronal death are unknown. Autophagy seems to be involved in the pathogenesis of many brain insults and to have a dual nature in neuroprotection and cell death. This study addresses the role of autophagy upon status epilepticus (SE) that has been induced by kainic acid (KA) in the C57BL/6 strain which is classified as seizure resistant. We analyzed the dynamics in the expression of autophagic and cell death markers in the hippocampus upon SE. Immunofluorescence data show that KA did not induce neuronal death in the hippocampal CA1-CA3 subfields; however, it leads to an exclusive activation of caspase-3 in the mossy fibers. We also found alterations in the expression of core proteins of the autophagic machinery. Levels of MAP1LC3, phospho-mTOR/mTOR, and Beclin 1 were significantly increased after induction of seizures. However, levels of Atg3, Atg14, Atg5-Atg12, Atg7, BAG3, Hsp70, and LAMP1 showed no significant alterations compared to controls. Although KA did not induce neuronal death, this study provides morphological and biochemical evidence that status epilepticus induced by KA activates caspase-3 in mossy fibers and induces autophagy in the C57BL/6 hippocampus. These data indicate that autophagic factors may modulate the sensitivity of pyramidal cells to KA and that autophagy may constitute a part of an endogenous neuroprotective arsenal which might be behind the resistance of C57BL/6-hippocampal cells to KA-induced neuronal death.
Collapse
Affiliation(s)
- A Rami
- Institut für Zelluläre und Molekulare Anatomie (Anatomie III), Universitätsklinikum, Theodor-Stern-Kai 7, 60590, Frankfurt/Main, Germany.
| | - A Benz
- Institut für Zelluläre und Molekulare Anatomie (Anatomie III), Universitätsklinikum, Theodor-Stern-Kai 7, 60590, Frankfurt/Main, Germany
| |
Collapse
|
14
|
Du X, Zhang H, Parent JM. Rabies tracing of birthdated dentate granule cells in rat temporal lobe epilepsy. Ann Neurol 2017; 81:790-803. [PMID: 28470680 DOI: 10.1002/ana.24946] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/08/2017] [Accepted: 04/15/2017] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To understand how monosynaptic inputs onto adult-born dentate granule cells (DGCs) are altered in experimental mesial temporal lobe epilepsy (mTLE) and whether their integration differs from early-born DGCs that are mature at the time of epileptogenesis. METHODS A dual-virus tracing strategy combining retroviral birthdating with rabies virus-mediated putative retrograde trans-synaptic tracing was used to identify and compare presynaptic inputs onto adult-born and early-born DGCs in the rat pilocarpine model of mTLE. RESULTS Our results demonstrate that hilar ectopic DGCs preferentially synapse onto adult-born DGCs after pilocarpine-induced status epilepticus (SE), whereas normotopic DGCs synapse onto both adult-born and early-born DGCs. We also find that parvalbumin- and somatostatin- interneuron inputs are greatly diminished onto early-born DGCs after SE. However, somatostatin- interneuron inputs onto adult-born DGCs are maintained, likely due to preferential sprouting. Intriguingly, CA3 pyramidal cell backprojections that specifically target adult-born DGCs arise in the epileptic brain, whereas axons of interneurons and pyramidal cells in CA1 appear to sprout across the hippocampal fissure to preferentially synapse onto early-born DGCs. INTERPRETATION These data support the presence of substantial hippocampal circuit remodeling after an epileptogenic insult that generates prominent excitatory monosynaptic inputs, both local recurrent and widespread feedback loops, onto DGCs. Both adult-born and early-born DGCs are targets of new inputs from other DGCs as well as from CA3 and CA1 pyramidal cells after pilocarpine treatment, changes that likely contribute to epileptogenesis in experimental mTLE. Ann Neurol 2017;81:790-803.
Collapse
Affiliation(s)
- Xi Du
- Neuroscience Graduate Program.,Medical Scientist Training Program
| | - Helen Zhang
- Department of Neurology, University of Michigan Medical Center and Ann Arbor VA Healthcare System, Ann Arbor, MI
| | - Jack M Parent
- Neuroscience Graduate Program.,Medical Scientist Training Program.,Department of Neurology, University of Michigan Medical Center and Ann Arbor VA Healthcare System, Ann Arbor, MI
| |
Collapse
|
15
|
Shubina L, Aliev R, Kitchigina V. Endocannabinoid-dependent protection against kainic acid-induced long-term alteration of brain oscillations in guinea pigs. Brain Res 2017; 1661:1-14. [DOI: 10.1016/j.brainres.2017.02.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 02/02/2017] [Accepted: 02/03/2017] [Indexed: 01/12/2023]
|
16
|
Kawamura MJ, Ruskin DN, Masino SA. Metabolic Therapy for Temporal Lobe Epilepsy in a Dish: Investigating Mechanisms of Ketogenic Diet using Electrophysiological Recordings in Hippocampal Slices. Front Mol Neurosci 2016; 9:112. [PMID: 27847463 PMCID: PMC5088211 DOI: 10.3389/fnmol.2016.00112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 10/17/2016] [Indexed: 11/13/2022] Open
Abstract
The hippocampus is prone to epileptic seizures and is a key brain region and experimental platform for investigating mechanisms associated with the abnormal neuronal excitability that characterizes a seizure. Accordingly, the hippocampal slice is a common in vitro model to study treatments that may prevent or reduce seizure activity. The ketogenic diet is a metabolic therapy used to treat epilepsy in adults and children for nearly 100 years; it can reduce or eliminate even severe or refractory seizures. New insights into its underlying mechanisms have been revealed by diverse types of electrophysiological recordings in hippocampal slices. Here we review these reports and their relevant mechanistic findings. We acknowledge that a major difficulty in using hippocampal slices is the inability to reproduce precisely the in vivo condition of ketogenic diet feeding in any in vitro preparation, and progress has been made in this in vivo/in vitro transition. Thus far at least three different approaches are reported to reproduce relevant diet effects in the hippocampal slices: (1) direct application of ketone bodies; (2) mimicking the ketogenic diet condition during a whole-cell patch-clamp technique; and (3) reduced glucose incubation of hippocampal slices from ketogenic diet–fed animals. Significant results have been found with each of these methods and provide options for further study into short- and long-term mechanisms including Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels, vesicular glutamate transporter (VGLUT), pannexin channels and adenosine receptors underlying ketogenic diet and other forms of metabolic therapy.
Collapse
Affiliation(s)
| | - David N Ruskin
- Department of Psychology and Neuroscience Program, Trinity College Hartford, CT, USA
| | - Susan A Masino
- Department of Psychology and Neuroscience Program, Trinity College Hartford, CT, USA
| |
Collapse
|
17
|
Sharma AK, Reams RY, Jordan WH, Miller MA, Thacker HL, Snyder PW. Mesial Temporal Lobe Epilepsy: Pathogenesis, Induced Rodent Models and Lesions. Toxicol Pathol 2016; 35:984-99. [PMID: 18098044 DOI: 10.1080/01926230701748305] [Citation(s) in RCA: 177] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mesial temporal lobe epilepsy (MTLE), the most common epilepsy in adults, is generally intractable and is suspected to be the result of recurrent excitation or inhibition circuitry. Recurrent excitation and the development of seizures have been associated with aberrant mossy fiber sprouting in the hippocampus. Of the animal models developed to investigate the pathogenesis of MTLE, post-status epilepticus models have received the greatest acceptance because they are characterized by a latency period, the development of spontaneous motor seizures, and a spectrum of lesions like those of MTLE. Among post-status epilepticus models, induction of systemic kainic acid or pilocarpine-induced epilepsy is less labor-intensive than electrical-stimulation models and these models mirror the clinicopathologic features of MTLE more closely than do kindling, tetanus toxin, hyperthermia, post-traumatic, and perinatal hypoxia/ischemia models. Unfortunately, spontaneous motor seizures do not develop in kindling or adult hyperthermia models and are not a consistent finding in tetanus toxin-induced or perinatal hypoxia/ischemia models. This review presents the mechanistic hypotheses for seizure induction, means of model induction, and associated pathology, especially as compared to MTLE patients. Animal models are valuable tools not only to study the pathogenesis of MTLE, but also to evaluate potential antiepileptogenic drugs.
Collapse
Affiliation(s)
- Alok K. Sharma
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
- Department of Pathology, Covance Laboratories Inc., Madison, WI, 53704, USA
| | - Rachel Y. Reams
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - William H. Jordan
- Department of Pathology, Lilly Research Laboratories, Division of Eli Lilly and Co., Greenfield, IN, 46140, USA
| | - Margaret A. Miller
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - H. Leon Thacker
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| | - Paul W. Snyder
- Department of Comparative Pathobiology, Purdue University, West Lafayette, IN 47907, USA
| |
Collapse
|
18
|
Temporal progression of evoked field potentials in neocortical slices after unilateral hypoxia-ischemia in perinatal rats: Correlation with cortical epileptogenesis. Neuroscience 2015; 316:232-48. [PMID: 26724579 DOI: 10.1016/j.neuroscience.2015.12.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 12/14/2015] [Accepted: 12/14/2015] [Indexed: 11/20/2022]
Abstract
Infarcts of the neonatal cerebral cortex can lead to progressive epilepsy, which is characterized by time-dependent increases in seizure frequency after the infarct and by shifts in seizure-onset zones from focal to multi-focal. Using a rat model of unilateral perinatal hypoxia-ischemia (PHI), where long-term seizure monitoring had previously demonstrated progressive epilepsy, evoked field potentials (EFPs) were recorded in layers II/III of coronal neocortical slices to analyze the underlying time-dependent, network-level alterations ipsilateral vs. contralateral to the infarct. At 3weeks after PHI, EFPs ipsilateral to the infarct were normal in artificial cerebrospinal fluid (ACSF); however, after blocking GABAA receptors with bicuculline methiodide (BMI, 30μM), the slices with an infarct were more hyperexcitable than slices without an infarct. At 3weeks, contralateral PHI slices had responses indistinguishable from controls. Six months after PHI in normal ACSF, both ipsi- and contralateral slices from rats with cortical infarcts showed prolonged afterdischarges, which were only slightly augmented in BMI. These data suggest that the early changes after PHI are localized to the ipsilateral infarcted cortex and masked by GABA-mediated inhibition; however, after 6months, progressive epileptogenesis results in generation of robust bilateral hyperexcitability. Because these afterdischarges were only slightly prolonged by BMI, a time-dependent reduction of GABAergic transmission is hypothesized to contribute to the pronounced hyperexcitability at 6months. These changes in the EFPs coincide with the seizure semiology of the epilepsy and therefore offer an opportunity to study the mechanisms underlying this form of progressive pediatric epilepsy.
Collapse
|
19
|
Kim JB, Suh SI, Kim JH. Volumetric and shape analysis of hippocampal subfields in unilateral mesial temporal lobe epilepsy with hippocampal atrophy. Epilepsy Res 2015; 117:74-81. [DOI: 10.1016/j.eplepsyres.2015.09.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 08/11/2015] [Accepted: 09/07/2015] [Indexed: 11/30/2022]
|
20
|
Parrish RR, Buckingham SC, Mascia KL, Johnson JJ, Matyjasik MM, Lockhart RM, Lubin FD. Methionine increases BDNF DNA methylation and improves memory in epilepsy. Ann Clin Transl Neurol 2015; 2:401-16. [PMID: 25909085 PMCID: PMC4402085 DOI: 10.1002/acn3.183] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 01/20/2015] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE Temporal lobe epilepsy (TLE) patients exhibit signs of memory impairments even when seizures are pharmacologically controlled. Surprisingly, the underlying molecular mechanisms involved in TLE-associated memory impairments remain elusive. Memory consolidation requires epigenetic transcriptional regulation of genes in the hippocampus; therefore, we aimed to determine how epigenetic DNA methylation mechanisms affect learning-induced transcription of memory-permissive genes in the epileptic hippocampus. METHODS Using the kainate rodent model of TLE and focusing on the brain-derived neurotrophic factor (Bdnf) gene as a candidate of DNA methylation-mediated transcription, we analyzed DNA methylation levels in epileptic rats following learning. After detection of aberrant DNA methylation at the Bdnf gene, we investigated functional effects of altered DNA methylation on hippocampus-dependent memory formation in our TLE rodent model. RESULTS We found that behaviorally driven BdnfDNA methylation was associated with hippocampus-dependent memory deficits. Bisulfite sequencing revealed that decreased BdnfDNA methylation levels strongly correlated with abnormally high levels of BdnfmRNA in the epileptic hippocampus during memory consolidation. Methyl supplementation via methionine (Met) increased BdnfDNA methylation and reduced BdnfmRNA levels in the epileptic hippocampus during memory consolidation. Met administration reduced interictal spike activity, increased theta rhythm power, and reversed memory deficits in epileptic animals. The rescue effect of Met treatment on learning-induced BdnfDNA methylation, Bdnf gene expression, and hippocampus-dependent memory, were attenuated by DNA methyltransferase blockade. INTERPRETATION Our findings suggest that manipulation of DNA methylation in the epileptic hippocampus should be considered as a viable treatment option to ameliorate memory impairments associated with TLE.
Collapse
Affiliation(s)
- R Ryley Parrish
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| | - Susan C Buckingham
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| | - Katherine L Mascia
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| | - Jarvis J Johnson
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| | | | - Roxanne M Lockhart
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| | - Farah D Lubin
- Department of Neurobiology, University of Alabama - Birmingham Birmingham, Alabama
| |
Collapse
|
21
|
Ratnadurai-Giridharan S, Stefanescu RA, Khargonekar PP, Carney PR, Talathi SS. Genesis of interictal spikes in the CA1: a computational investigation. Front Neural Circuits 2014; 8:2. [PMID: 24478636 PMCID: PMC3902301 DOI: 10.3389/fncir.2014.00002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 01/07/2014] [Indexed: 11/13/2022] Open
Abstract
Interictal spikes (IISs) are spontaneous high amplitude, short time duration <400 ms events often observed in electroencephalographs (EEG) of epileptic patients. In vitro analysis of resected mesial temporal lobe tissue from patients with refractory temporal lobe epilepsy has revealed the presence of IIS in the CA1 subfield. In this paper, we develop a biophysically relevant network model of the CA1 subfield and investigate how changes in the network properties influence the susceptibility of CA1 to exhibit an IIS. We present a novel template based approach to identify conditions under which synchronization of paroxysmal depolarization shift (PDS) events evoked in CA1 pyramidal (Py) cells can trigger an IIS. The results from this analysis are used to identify the synaptic parameters of a minimal network model that is capable of generating PDS in response to afferent synaptic input. The minimal network model parameters are then incorporated into a detailed network model of the CA1 subfield in order to address the following questions: (1) How does the formation of an IIS in the CA1 depend on the degree of sprouting (recurrent connections) between the CA1 Py cells and the fraction of CA3 Shaffer collateral (SC) connections onto the CA1 Py cells? and (2) Is synchronous afferent input from the SC essential for the CA1 to exhibit IIS? Our results suggest that the CA1 subfield with low recurrent connectivity (absence of sprouting), mimicking the topology of a normal brain, has a very low probability of producing an IIS except when a large fraction of CA1 neurons (>80%) receives a barrage of quasi-synchronous afferent input (input occurring within a temporal window of ≤24 ms) via the SC. However, as we increase the recurrent connectivity of the CA1 (Psprout > 40); mimicking sprouting in a pathological CA1 network, the CA1 can exhibit IIS even in the absence of a barrage of quasi-synchronous afferents from the SC (input occurring within temporal window >80 ms) and a low fraction of CA1 Py cells (≈30%) receiving SC input. Furthermore, we find that in the presence of Poisson distributed random input via SC, the CA1 network is able to generate spontaneous periodic IISs (≈3 Hz) for high degrees of recurrent Py connectivity (Psprout > 70). We investigate the conditions necessary for this phenomenon and find that spontaneous IISs closely depend on the degree of the network's intrinsic excitability.
Collapse
Affiliation(s)
| | - Roxana A Stefanescu
- Department of Otolaryngology, Kresge Hearing Research Institute, University of Michigan Ann Arbor, MI, USA
| | | | - Paul R Carney
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida Gainesville, FL, USA ; Department of Pediatrics, University of Florida Gainesville, FL, USA
| | - Sachin S Talathi
- J Crayton Pruitt Family Department of Biomedical Engineering, University of Florida Gainesville, FL, USA ; Department of Pediatrics, University of Florida Gainesville, FL, USA ; Qualcomm Corp R&D San Diego, CA, USA
| |
Collapse
|
22
|
A reorganized GABAergic circuit in a model of epilepsy: evidence from optogenetic labeling and stimulation of somatostatin interneurons. J Neurosci 2013; 33:14392-405. [PMID: 24005292 DOI: 10.1523/jneurosci.2045-13.2013] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Axonal sprouting of excitatory neurons is frequently observed in temporal lobe epilepsy, but the extent to which inhibitory interneurons undergo similar axonal reorganization remains unclear. The goal of this study was to determine whether somatostatin (SOM)-expressing neurons in stratum (s.) oriens of the hippocampus exhibit axonal sprouting beyond their normal territory and innervate granule cells of the dentate gyrus in a pilocarpine model of epilepsy. To obtain selective labeling of SOM-expressing neurons in s. oriens, a Cre recombinase-dependent construct for channelrhodopsin2 fused to enhanced yellow fluorescent protein (ChR2-eYFP) was virally delivered to this region in SOM-Cre mice. In control mice, labeled axons were restricted primarily to s. lacunosum-moleculare. However, in pilocarpine-treated animals, a rich plexus of ChR2-eYFP-labeled fibers and boutons extended into the dentate molecular layer. Electron microscopy with immunogold labeling demonstrated labeled axon terminals that formed symmetric synapses on dendritic profiles in this region, consistent with innervation of granule cells. Patterned illumination of ChR2-labeled fibers in s. lacunosum-moleculare of CA1 and the dentate molecular layer elicited GABAergic inhibitory responses in dentate granule cells in pilocarpine-treated mice but not in controls. Similar optical stimulation in the dentate hilus evoked no significant responses in granule cells of either group of mice. These findings indicate that under pathological conditions, SOM/GABAergic neurons can undergo substantial axonal reorganization beyond their normal territory and establish aberrant synaptic connections. Such reorganized circuitry could contribute to functional deficits in inhibition in epilepsy, despite the presence of numerous GABAergic terminals in the region.
Collapse
|
23
|
Lakhina V, Subramanian L, Huilgol D, Shetty AS, Vaidya VA, Tole S. Seizure evoked regulation of LIM-HD genes and co-factors in the postnatal and adult hippocampus. F1000Res 2013; 2:205. [PMID: 25110573 PMCID: PMC4111125 DOI: 10.12688/f1000research.2-205.v1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/01/2013] [Indexed: 12/03/2022] Open
Abstract
The LIM-homeodomain (LIM-HD) family of transcription factors is well known for its functions during several developmental processes including cell fate specification, cell migration and axon guidance, and its members play fundamental roles in hippocampal development. The hippocampus is a structure that displays striking activity dependent plasticity. We examined whether LIM-HD genes and their co-factors are regulated during kainic acid induced seizure in the adult rat hippocampus as well as in early postnatal rats, when the hippocampal circuitry is not fully developed. We report a distinct and field-specific regulation of LIM-HD genes
Lhx1,Lhx2, and
Lhx9, LIM-only gene
Lmo4, and cofactor
Clim1a in the adult hippocampus after seizure induction. In contrast none of these genes displayed altered levels upon induction of seizure in postnatal animals. Our results provide evidence of temporal and spatial seizure mediated regulation of LIM-HD family members and suggest that LIM-HD gene function may be involved in activity dependent plasticity in the adult hippocampus
Collapse
Affiliation(s)
- Vanisha Lakhina
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India ; Current affiliation: Lewis Sigler Institute for Integrative Genomics, Princeton University, NJ, USA
| | - Lakshmi Subramanian
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India ; Current affiliation: Department of Neurology, University of California, San Francisco, CA, USA
| | - Dhananjay Huilgol
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India ; Current affiliation: Cold Spring Harbor Laboratory, NY, USA
| | - Ashwin S Shetty
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Vidita A Vaidya
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| | - Shubha Tole
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, India
| |
Collapse
|
24
|
Ryley Parrish R, Albertson AJ, Buckingham SC, Hablitz JJ, Mascia KL, Davis Haselden W, Lubin FD. Status epilepticus triggers early and late alterations in brain-derived neurotrophic factor and NMDA glutamate receptor Grin2b DNA methylation levels in the hippocampus. Neuroscience 2013; 248:602-19. [PMID: 23811393 DOI: 10.1016/j.neuroscience.2013.06.029] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 06/13/2013] [Accepted: 06/17/2013] [Indexed: 10/26/2022]
Abstract
Status epilepticus (SE) triggers abnormal expression of genes in the hippocampus, such as glutamate receptor subunit epsilon-2 (Grin2b/Nr2b) and brain-derived neurotrophic factor (Bdnf), that is thought to occur in temporal lobe epilepsy (TLE). We examined the underlying DNA methylation mechanisms and investigated whether these mechanisms contribute to the expression of these gene targets in the epileptic hippocampus. Experimental TLE was provoked by kainic acid-induced SE. Bisulfite sequencing analysis revealed increased Grin2b/Nr2b and decreased Bdnf DNA methylation levels that corresponded to decreased Grin2b/Nr2b and increased Bdnf mRNA and protein expression in the epileptic hippocampus. Blockade of DNA methyltransferase (DNMT) activity with zebularine decreased global DNA methylation levels and reduced Grin2b/Nr2b, but not Bdnf, DNA methylation levels. Interestingly, we found that DNMT blockade further decreased Grin2b/Nr2b mRNA expression whereas GRIN2B protein expression increased in the epileptic hippocampus, suggesting that a posttranscriptional mechanism may be involved. Using chromatin immunoprecipitation analysis we found that DNMT inhibition restored the decreases in AP2alpha transcription factor levels at the Grin2b/Nr2b promoter in the epileptic hippocampus. DNMT inhibition increased field excitatory postsynaptic potential in hippocampal slices isolated from epileptic rats. Electroencephalography (EEG) monitoring confirmed that DNMT inhibition did not significantly alter the disease course, but promoted the latency to seizure onset or SE. Thus, DNA methylation may be an early event triggered by SE that persists late into the epileptic hippocampus to contribute to gene expression changes in TLE.
Collapse
Affiliation(s)
- R Ryley Parrish
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - A J Albertson
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - S C Buckingham
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - J J Hablitz
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - K L Mascia
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - W Davis Haselden
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| | - F D Lubin
- Evelyn F. McKnight Brain Institute, Department of Neurobiology, University of Alabama at Birmingham, 1825 University Boulevard, Birmingham, AL 35294, USA.
| |
Collapse
|
25
|
Pilli J, Abbasi S, Richardson M, Kumar SS. Diversity and excitability of deep-layer entorhinal cortical neurons in a model of temporal lobe epilepsy. J Neurophysiol 2012; 108:1724-38. [PMID: 22745466 DOI: 10.1152/jn.00364.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The entorhinal cortex (ERC) is critically implicated in temporal lobe epileptogenesis--the most common type of adult epilepsy. Previous studies have suggested that epileptiform discharges likely initiate in seizure-sensitive deep layers (V-VI) of the medial entorhinal area (MEA) and propagate into seizure-resistant superficial layers (II-III) and hippocampus, establishing a lamina-specific distinction between activities of deep- versus superficial-layer neurons and their seizure susceptibilities. While layer II stellate cells in MEA have been shown to be hyperexcitable and hypersynchronous in patients and animal models of temporal lobe epilepsy (TLE), the fate of neurons in the deep layers under epileptic conditions and their overall contribution to epileptogenicity of this region have remained unclear. We used whole cell recordings from slices of the ERC in normal and pilocarpine-treated epileptic rats to characterize the electrophysiological properties of neurons in this region and directly assess changes in their excitatory and inhibitory synaptic drive under epileptic conditions. We found a surprising heterogeneity with at least three major types and two subtypes of functionally distinct excitatory neurons. However, contrary to expectation, none of the major neuron types characterized showed any significant changes in their excitability, barring loss of excitatory and inhibitory inputs in a subtype of neurons whose dendrite extended into layer III, where neurons are preferentially lost during TLE. We confirmed hyperexcitability of layer II neurons in the same slices, suggesting minimal influence of deep-layer input on superficial-layer neuron excitability under epileptic conditions. These data show that deep layers of ERC contain a more diverse population of excitatory neurons than previously envisaged that appear to belie their seizure-sensitive reputation.
Collapse
Affiliation(s)
- Jyotsna Pilli
- Dept. of Biomedical Sciences, College of Medicine, Florida State Univ., 1115 West Call St., Tallahassee, FL 32306-4300, USA
| | | | | | | |
Collapse
|
26
|
Somatostatin and neuropeptide Y neurons undergo different plasticity in parahippocampal regions in kainic acid-induced epilepsy. J Neuropathol Exp Neurol 2012; 71:312-29. [PMID: 22437342 DOI: 10.1097/nen.0b013e31824d9882] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Parahippocampal brain areas including the subiculum, presubiculum and parasubiculum, and entorhinal cortex give rise to major input and output neurons of the hippocampus and exert increased excitability in animal models and human temporal lobe epilepsy. Using immunohistochemistry and in situ hybridization for somatostatin and neuropeptide Y, we investigated plastic morphologic and neurochemical changes in parahippocampal neurons in the kainic acid (KA) model of temporal lobe epilepsy. Although constitutively contained in similar subclasses of γ-aminobutyric acid (GABA)-ergic neurons, both neuropeptide systems undergo distinctly different changes in their expression. Somatostatin messenger RNA (mRNA) is rapidly but transiently expressed de novo in pyramidal neurons of the subiculum and entorhinal cortex 24 hours after KA. Surviving somatostatin interneurons display increased mRNA levels at late intervals (3 months) after KA and increased labeling of their terminals in the outer molecular layer of the subiculum; the labeling correlates with the number of spontaneous seizures, suggesting that the seizures may trigger somatostatin expression. In contrast, neuropeptide Y mRNA is consistently expressed in principal neurons of the proximal subiculum and the lateral entorhinal cortex and labeling for the peptide persistently increased in virtually all major excitatory pathways of the hippocampal formation. The pronounced plastic changes differentially involving both neuropeptide systems indicate marked rearrangement of parahippocampal areas, presumably aiming at endogenous seizure protection. Their receptors may be targets for anticonvulsive drug therapy.
Collapse
|
27
|
BACE1 elevation is associated with aberrant limbic axonal sprouting in epileptic CD1 mice. Exp Neurol 2012; 235:228-37. [PMID: 22265658 DOI: 10.1016/j.expneurol.2012.01.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Revised: 12/25/2011] [Accepted: 01/04/2012] [Indexed: 12/20/2022]
Abstract
The brain is capable of remarkable synaptic reorganization following stress and injury, often using the same molecular machinery that governs neurodevelopment. This form of plasticity is crucial for restoring and maintaining network function. However, neurodegeneration and subsequent reorganization can also play a role in disease pathogenesis, as is seen in temporal lobe epilepsy and Alzheimer's disease. β-Secretase-1 (BACE1) is a protease known for cleaving β-amyloid precursor protein into β-amyloid (Aβ), a major constituent in amyloid plaques. Emerging evidence suggests that BACE1 is also involved with synaptic plasticity and nerve regeneration. Here we examined whether BACE1 immunoreactivity (IR) was altered in pilocarpine-induced epileptic CD1 mice in a manner consistent with the synaptic reorganization seen during epileptogenesis. BACE1-IR increased in the CA3 mossy fiber field and dentate inner molecular layer in pilocarpine-induced epileptic mice, relative to controls (saline-treated mice and mice 24-48 h after pilocarpine-status), and paralleled aberrant expression of neuropeptide Y. Regionally increased BACE1-IR also occurred in neuropil in hippocampal area CA1 and in subregions of the amygdala and temporal cortex in epileptic mice, colocalizing with increased IR for growth associated protein 43 (GAP43) and polysialylated-neural cell adhesion molecule (PSA-NCAM), but reduced IR for microtubule-associated protein 2 (MAP2). These findings suggest that BACE1 is involved in aberrant limbic axonal sprouting in a model of temporal lobe epilepsy, warranting further investigation into the role of BACE1 in physiological vs. pathological neuronal plasticity.
Collapse
|
28
|
Berdichevsky Y, Dzhala V, Mail M, Staley KJ. Interictal spikes, seizures and ictal cell death are not necessary for post-traumatic epileptogenesis in vitro. Neurobiol Dis 2011; 45:774-85. [PMID: 22115940 DOI: 10.1016/j.nbd.2011.11.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 10/27/2011] [Accepted: 11/07/2011] [Indexed: 11/25/2022] Open
Abstract
Clinical studies indicate that phenytoin prevents acute post-traumatic seizures but not subsequent post-traumatic epilepsy. We explored this phenomenon using organotypic hippocampal slice cultures as a model of severe traumatic brain injury. Hippocampal slices were cultured for up to eight weeks, during which acute and chronic electrical recordings revealed a characteristic evolution of spontaneous epileptiform discharges, including interictal spikes, seizure activity and electrical status epilepticus. Cell death exhibited an early peak immediately following slicing, and a later secondary peak that coincided with the peak of seizure-like activity. The secondary peak in neuronal death was abolished by either blockade of glutamatergic transmission with kynurenic acid or by elimination of ictal activity and status epilepticus with phenytoin. Withdrawal of kynurenic acid or phenytoin was followed by a sharp increase in spontaneous seizure activity. Phenytoin's anticonvulsant and neuroprotective effects failed after four weeks of continuous administration. These data support the clinical findings that after brain injury, anticonvulsants prevent seizures but not epilepsy or the development of anticonvulsant resistance. We extend the clinical data by showing that secondary neuronal death is correlated with ictal but not interictal activity, and that blocking all three of these sequelae of brain injury does not prevent epileptogenesis in this in vitro model.
Collapse
Affiliation(s)
- Yevgeny Berdichevsky
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129, USA
| | | | | | | |
Collapse
|
29
|
Fang M, Xi ZQ, Wu Y, Wang XF. A new hypothesis of drug refractory epilepsy: neural network hypothesis. Med Hypotheses 2011; 76:871-6. [PMID: 21429675 DOI: 10.1016/j.mehy.2011.02.039] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 02/16/2011] [Accepted: 02/20/2011] [Indexed: 01/16/2023]
Abstract
Drug refractory is an important clinical problem in epilepsy, affecting a substantial number of patients globally. Mechanisms underlying drug refractory need to be understood to develop rational therapies. Current two prevailing theories on drug refractory epilepsy (DRE) include the target hypothesis and the transporter hypothesis. However, those hypotheses could not be adequate to explain the mechanisms of all the DRE. Thus, we propose another possible mechanism of DRE, which is neural network hypothesis. It is hypothesized that seizure-induced alterations of brain plasticity including axonal sprouting, synaptic reorganization, neurogenesis and gliosis could contribute to the formation of abnormal neural network, which has not only avoided the inhibitory effect of endogenous antiepileptic system but also prevented the traditional antiepileptic drugs from entering their targets, eventually leading to DRE. We will illustrate this hypothesis at molecular and structural level based on our recent studies and other related researches.
Collapse
Affiliation(s)
- Min Fang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, 1 You Yi Road, Chongqing 400016, China
| | | | | | | |
Collapse
|
30
|
Ito M, Seki T, Liu J, Nakamura K, Namba T, Matsubara Y, Suzuki T, Arai H. Effects of repeated electroconvulsive seizure on cell proliferation in the rat hippocampus. Synapse 2011; 64:814-21. [PMID: 20340175 DOI: 10.1002/syn.20796] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Electroconvulsive therapy (ECT) is known as a successful treatment for severe depression. Despite great efforts, the biological mechanisms underlying the beneficial effects of ECT remain largely unclear. In this study, animals received a single, 10, or 20 applications of electroconvulsive seizure (ECS), and then cell proliferation and apoptosis were investigated in the subgranular zone (SGZ) of the dentate gyrus. We analyzed whether a series of ECSs could induce changes in the dentate gyrus in a dose-response fashion. A single-ECS seizure significantly increased cell proliferation in the SGZ by ∼2.3-fold compared to sham treatment. After 10 ECSs, a significant increase in cell proliferation was observed in the SGZ by ∼2.4-fold compared to sham treatment. Moreover, 10 ECSs induced a significant increase in cell proliferation by 1.3-fold compared to a single-ECS group. However, cell proliferation did not differ between the group with 20 ECSs and sham group. In addition, a significant increase in the number of apoptotic cells was found in the group with 10 ECSs, whereas no significant change in it was found in either a single ECS or 20 ECSs group compared to sham treatment. These findings indicate that the optimal number of treatments and duration of stimulation requires investigation. Further studies are needed to elucidate the intracellular mechanisms underlying both effective and excessive ECT.
Collapse
Affiliation(s)
- Masanobu Ito
- Department of Psychiatry, Juntendo University Faculty of Medicine, Tokyo, Japan
| | | | | | | | | | | | | | | |
Collapse
|
31
|
Park KI, Chu K, Jung KH, Kim JH, Kang KM, Lee ST, Park HK, Kim M, Lee SK, Roh JK. Role of cortical dysplasia in epileptogenesis following prolonged febrile seizure. Epilepsia 2010; 51:1809-19. [DOI: 10.1111/j.1528-1167.2010.02676.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
32
|
Cannabinoid-mediated inhibition of recurrent excitatory circuitry in the dentate gyrus in a mouse model of temporal lobe epilepsy. PLoS One 2010; 5:e10683. [PMID: 20498848 PMCID: PMC2871782 DOI: 10.1371/journal.pone.0010683] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Accepted: 04/28/2010] [Indexed: 11/26/2022] Open
Abstract
Temporal lobe epilepsy (TLE) is a neurological condition associated with neuron loss, axon sprouting, and hippocampal sclerosis, which results in modified synaptic circuitry. Cannabinoids appear to be anti-convulsive in patients and animal models of TLE, but the mechanisms of this effect are not known. A pilocarpine-induced status epilepticus mouse model of TLE was used to study the effect of cannabinoid agonists on recurrent excitatory circuits of the dentate gyrus using electrophysiological recordings in hippocampal slices isolated from control mice and mice with TLE. Cannabinoid agonists WIN 55,212-2, anandamide (AEA), or 2-arachydonoylglycerol (2-AG) reduced the frequency of spontaneous and tetrodotoxin-resistant excitatory postsynaptic currents (EPSCs) in mice with TLE, but not in controls. WIN 55,212-2 also reduced the frequency of EPSCs evoked by glutamate-photolysis activation of other granule cells in epileptic mice. Secondary population discharges evoked after antidromic electrical stimulation of mossy fibers in the hilus were also attenuated by cannabinoid agonists. Agonist effects were blocked by the cannabinoid type 1 receptor (CB1R) antagonist AM251. No change in glutamate release was observed in slices from mice that did not undergo status epilepticus. Western blot analysis suggested an up-regulation of CB1R in the dentate gyrus of animals with TLE. These findings indicate that activation of CB1R present on nerve terminals can suppress recurrent excitation in the dentate gyrus of mice with TLE. This suggests a mechanism for the anti-convulsive role of cannabinoids aimed at modulating receptors on synaptic terminals expressed de novo after epileptogenesis.
Collapse
|
33
|
Berdichevsky Y, Staley KJ, Yarmush ML. Building and manipulating neural pathways with microfluidics. LAB ON A CHIP 2010; 10:999-1004. [PMID: 20358106 PMCID: PMC3137909 DOI: 10.1039/b922365g] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Communication between different brain regions, and between local circuits in the same brain region, is an important area of study for basic and translational neuroscience research. Selective and chronic manipulation of one of the components in a given neural pathway is frequently required for development and plasticity studies. We designed an in vitro platform that captures some of the complexity of mammalian brain pathways but permits easy experimental manipulation of their constituent parts. Organotypic cultures of brain slices were carried out in compartments interconnected by microchannels. We show that co-cultures from cortex and hippocampus formed functional connections by extending axons through the microchannels. We report synchronization of neural activity in co-cultures, and demonstrate selective pharmacological manipulation of activity in the constituent slices. Our platform enables chronic, spatially-restricted experimental manipulation of pre- and post-synaptic neurons in organotypic cultures, and will be useful to investigators seeking to understand development, plasticity, and pathologies of neural pathways.
Collapse
|
34
|
Bhaskaran MD, Smith BN. Effects of TRPV1 activation on synaptic excitation in the dentate gyrus of a mouse model of temporal lobe epilepsy. Exp Neurol 2010; 223:529-36. [PMID: 20144892 DOI: 10.1016/j.expneurol.2010.01.021] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 01/08/2010] [Accepted: 01/31/2010] [Indexed: 11/25/2022]
Abstract
Temporal lobe epilepsy (TLE) is a condition characterized by an imbalance between excitation and inhibition in the temporal lobe. Hallmarks of this change are axon sprouting and accompanying synaptic reorganization in the temporal lobe. Synthetic and endogenous cannabinoids have variable therapeutic potential in treating intractable temporal lobe epilepsy, in part because cannabinoid ligands can bind multiple receptor types. This study utilized in vitro electrophysiological methods to examine the effect of transient receptor potential vanilloid type 1 (TRPV1) activation in dentate gyrus granule cells in a murine model of TLE. Capsaicin, a selective TRPV1 agonist had no measurable effect on overall synaptic input to granule cells in control animals, but significantly enhanced spontaneous and miniature EPSC frequency in mice with TLE. Exogenous application of anandamide, an endogenous cannabinoid that acts at both TRPV1 and cannabinoid type 1 receptors (CB1R), also enhanced glutamate release in the presence of a CB1R antagonist. Anandamide reduced the EPSC frequency when TRPV1 were blocked with capsazepine. Western blot analysis of TRPV1 receptor indicated protein expression was significantly greater in the dentate gyrus of mice with TLE compared with control mice. This study indicates that a prominent cannabinoid agonist can increase excitatory circuit activity in the synaptically reorganized dentate gyrus of mice with TLE by activating TRPV1 receptors, and suggests caution in designing anticonvulsant therapy based on modulating the endocannabinoid system.
Collapse
Affiliation(s)
- Muthu D Bhaskaran
- Department of Cell and Molecular Biology, Tulane University, New Orleans, Louisiana 70118, USA
| | | |
Collapse
|
35
|
Hunt RF, Scheff SW, Smith BN. Regionally localized recurrent excitation in the dentate gyrus of a cortical contusion model of posttraumatic epilepsy. J Neurophysiol 2010; 103:1490-500. [PMID: 20089815 DOI: 10.1152/jn.00957.2009] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Posttraumatic epilepsy is a frequent consequence of brain trauma, but relatively little is known about how neuronal circuits are chronically altered after closed head injury. We examined whether local recurrent excitatory synaptic connections form between dentate granule cells in mice 8-12 wk after cortical contusion injury. Mice were monitored for behavioral seizures shortly after brain injury and < or = 10 wk postinjury. Injury-induced seizures were observed in 15% of mice, and spontaneous seizures were observed weeks later in 40% of mice. Timm's staining revealed mossy fiber sprouting into the inner molecular layer of the dorsal dentate gyrus ipsilateral to the injury in 95% of mice but not contralateral to the injury or in uninjured controls. Whole cell patch-clamp recordings were made from granule cells in isolated hippocampal brain slices. Cells in slices with posttraumatic mossy fiber sprouting had an increased excitatory postsynaptic current (EPSC) frequency compared with cells in slices without sprouting from injured and control animals (P < 0.001). When perfused with Mg(2+)-free artificial cerebrospinal fluid containing 100 microM picrotoxin, these cells had spontaneous bursts of EPSCs and action potentials. Focal glutamate photostimulation of the granule cell layer evoked a burst of EPSCs and action potentials indicative of recurrent excitatory connections in granule cells of slices with mossy fiber sprouting. In granule cells of slices without sprouting from injured animals and controls, spontaneous or photostimulation-evoked epileptiform activity was never observed. These results suggest that a new regionally localized excitatory network forms between dentate granule cells near the injury site within weeks after cortical contusion head injury.
Collapse
Affiliation(s)
- Robert F Hunt
- Dept. of Physiology, University of Kentucky, Lexington, KY 40536, USA
| | | | | |
Collapse
|
36
|
Foresti ML, Arisi GM, Katki K, Montañez A, Sanchez RM, Shapiro LA. Chemokine CCL2 and its receptor CCR2 are increased in the hippocampus following pilocarpine-induced status epilepticus. J Neuroinflammation 2009; 6:40. [PMID: 20034406 PMCID: PMC2804573 DOI: 10.1186/1742-2094-6-40] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Accepted: 12/24/2009] [Indexed: 01/06/2023] Open
Abstract
Background Neuroinflammation occurs after seizures and is implicated in epileptogenesis. CCR2 is a chemokine receptor for CCL2 and their interaction mediates monocyte infiltration in the neuroinflammatory cascade triggered in different brain pathologies. In this work CCR2 and CCL2 expression were examined following status epilepticus (SE) induced by pilocarpine injection. Methods SE was induced by pilocarpine injection. Control rats were injected with saline instead of pilocarpine. Five days after SE, CCR2 staining in neurons and glial cells was examined using imunohistochemical analyses. The number of CCR2 positive cells was determined using stereology probes in the hippocampus. CCL2 expression in the hippocampus was examined by molecular assay. Results Increased CCR2 was observed in the hippocampus after SE. Seizures also resulted in alterations to the cell types expressing CCR2. Increased numbers of neurons that expressed CCR2 was observed following SE. Microglial cells were more closely apposed to the CCR2-labeled cells in SE rats. In addition, rats that experienced SE exhibited CCR2-labeling in populations of hypertrophied astrocytes, especially in CA1 and dentate gyrus. These CCR2+ astroctytes were not observed in control rats. Examination of CCL2 expression showed that it was elevated in the hippocampus following SE. Conclusion The data show that CCR2 and CCL2 are up-regulated in the hippocampus after pilocarpine-induced SE. Seizures also result in changes to CCR2 receptor expression in neurons and astrocytes. These changes might be involved in detrimental neuroplasticity and neuroinflammatory changes that occur following seizures.
Collapse
Affiliation(s)
- Maira L Foresti
- Department of Neurosurgery, Scott and White Hospital, Temple, TX 76503, USA.
| | | | | | | | | | | |
Collapse
|
37
|
Hunt RF, Scheff SW, Smith BN. Posttraumatic epilepsy after controlled cortical impact injury in mice. Exp Neurol 2008; 215:243-52. [PMID: 19013458 DOI: 10.1016/j.expneurol.2008.10.005] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2008] [Revised: 10/06/2008] [Accepted: 10/10/2008] [Indexed: 11/28/2022]
Abstract
Many patients develop temporal lobe epilepsy after trauma, but basic mechanisms underlying the development of chronic seizures after head injury remain poorly understood. Using the controlled cortical impact injury model we examined whether mice developed spontaneous seizures after mild (0.5 mm injury depth) or severe (1.0 mm injury depth) brain injury and how subsequent posttraumatic mossy fiber sprouting was associated with excitability in the dentate gyrus 42-71 d after injury. After several weeks, spontaneous behavioral seizures were observed in 20% of mice with mild and 36% of mice with severe injury. Mossy fiber sprouting was typically present in septal slices of the dentate gyrus ipsilateral to the injury, but not in control mice. In slices with mossy fiber sprouting, perforant path stimulation revealed a significant reduction (P<0.01) in paired-pulse ratios in dentate granule cells at 20 ms and 40 ms interpulse intervals, but not at 80 ms or 160 ms intervals. These slices were also characterized by spontaneous and hilar-evoked epileptiform activity in the dentate gyrus in the presence of Mg(2+)-free ACSF containing 100 microM picrotoxin. In contrast, paired-pulse and hilar-evoked responses in slices from injured animals that did not display mossy fiber sprouting were not different from controls. These data suggest the development of spontaneous posttraumatic seizures as well as structural and functional network changes associated with temporal lobe epilepsy in the mouse dentate gyrus by 71 d after CCI injury. Identifying experimental injury models that exhibit similar pathology to injury-induced epilepsy in humans should help to elucidate the mechanisms by which the injured brain becomes epileptic.
Collapse
Affiliation(s)
- Robert F Hunt
- Department of Physiology, University of Kentucky, MS-508 Chandler Medical Center, 800 Rose St., Lexington, KY 40536-0298, USA
| | | | | |
Collapse
|
38
|
Immonen RJ, Kharatishvili I, Sierra A, Einula C, Pitkänen A, Gröhn OH. Manganese enhanced MRI detects mossy fiber sprouting rather than neurodegeneration, gliosis or seizure-activity in the epileptic rat hippocampus. Neuroimage 2008; 40:1718-30. [DOI: 10.1016/j.neuroimage.2008.01.042] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 01/15/2008] [Accepted: 01/22/2008] [Indexed: 10/22/2022] Open
|
39
|
Williams PA, Dudek FE. A chronic histopathological and electrophysiological analysis of a rodent hypoxic-ischemic brain injury model and its use as a model of epilepsy. Neuroscience 2007; 149:943-61. [PMID: 17935893 PMCID: PMC2897748 DOI: 10.1016/j.neuroscience.2007.07.067] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 07/24/2007] [Accepted: 08/15/2007] [Indexed: 11/24/2022]
Abstract
Ischemic brain injury is one of the leading causes of epilepsy in the elderly, and there are currently no adult rodent models of global ischemia, unilateral hemispheric ischemia, or focal ischemia that report the occurrence of spontaneous motor seizures following ischemic brain injury. The rodent hypoxic-ischemic (H-I) model of brain injury in adult rats is a model of unilateral hemispheric ischemic injury. Recent studies have shown that an H-I injury in perinatal rats causes hippocampal mossy fiber sprouting and epilepsy. These experiments aimed to test the hypothesis that a unilateral H-I injury leading to severe neuronal loss in young-adult rats also causes mossy fiber sprouting and spontaneous motor seizures many months after the injury, and that the mossy fiber sprouting induced by the H-I injury forms new functional recurrent excitatory synapses. The right common carotid artery of 30-day old rats was permanently ligated, and the rats were placed into a chamber with 8% oxygen for 30 min. A quantitative stereologic analysis revealed that the ipsilateral hippocampus had significant hilar and CA1 pyramidal neuronal loss compared with the contralateral and sham-control hippocampi. The septal region from the ipsilateral and contralateral hippocampus had small but significantly increased amounts of Timm staining in the inner molecular layer compared with the sham-control hippocampi. Three of 20 lesioned animals (15%) were observed to have at least one spontaneous motor seizure 6-12 months after treatment. Approximately 50% of the ipsilateral and contralateral hippocampal slices displayed abnormal electrophysiological responses in the dentate gyrus, manifest as all-or-none bursts to hilar stimulation. This study suggests that H-I injury is associated with synaptic reorganization in the lesioned region of the hippocampus, and that new recurrent excitatory circuits can predispose the hippocampus to abnormal electrophysiological activity and spontaneous motor seizures.
Collapse
|
40
|
Fink AE, Sariñana J, Gray EE, O'dell TJ. Activity-Dependent Depression of Local Excitatory Connections in the CA1 Region of Mouse Hippocampus. J Neurophysiol 2007; 97:3926-36. [PMID: 17409173 DOI: 10.1152/jn.00213.2007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The existence of recurrent excitatory synapses between pyramidal cells in the hippocampal CA1 region has been known for some time yet little is known about activity-dependent forms of plasticity at these synapses. Here we demonstrate that under certain experimental conditions, Schaffer collateral/commissural fiber stimulation can elicit robust polysynaptic excitatory postsynaptic potentials due to recurrent synaptic inputs onto CA1 pyramidal cells. In contrast to CA3 pyramidal cell inputs, recurrent synapses onto CA1 pyramidal cells exhibited robust paired-pulse depression and a sustained, but rapidly reversible, depression in response to low-frequency trains of Schaffer collateral fiber stimulation. Blocking GABAB receptors abolished paired-pulse depression but had little effect on low-frequency stimulation (LFS)-induced depression. Instead, LFS-induced depression was significantly attenuated by an inhibitor of A1 type adenosine receptors. Blocking the postsynaptic effects of GABAB and A1 receptor activation on CA1 pyramidal cell excitability with an inhibitor of G-protein-activated inwardly rectifying potassium channels had no effect on either paired-pulse depression or LFS-induced depression. Thus activation of presynaptic GABAB and adenosine receptors appears to have an important role in activity-dependent depression at recurrent synapses. Together, our results indicate that CA3-CA1 and CA1-CA1 synapses exhibit strikingly different forms of short-term synaptic plasticity and suggest that activity-dependent changes in recurrent synaptic transmission can transform the CA1 region from a sparsely connected recurrent network into a predominantly feedforward circuit.
Collapse
Affiliation(s)
- Ann E Fink
- Interdepartmental Ph.D. Program for Neuroscience, David Geffen School of Medicine, University of California, Los Angeles, California 90095-1751, USA
| | | | | | | |
Collapse
|
41
|
Dudek FE, Sutula TP. Epileptogenesis in the dentate gyrus: a critical perspective. PROGRESS IN BRAIN RESEARCH 2007; 163:755-73. [PMID: 17765749 DOI: 10.1016/s0079-6123(07)63041-6] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The dentate gyrus has long been a focal point for studies on the molecular, cellular, and network mechanisms responsible for epileptogenesis in temporal lobe epilepsy (TLE). Although several hypothetical mechanisms are considered in this chapter, two that have garnered particular interest and experimental support are: (1) the selective loss of vulnerable interneurons in the region of the hilus and (2) the formation of new recurrent excitatory circuits after mossy fiber sprouting. Histopathological data show that specific GABAergic interneurons in the hilus are lost in animal models of TLE, and several lines of electrophysiological evidence, including intracellular analyses of postsynaptic currents, support this hypothesis. In particular, whole-cell recordings have demonstrated a reduction in the frequency of miniature inhibitory postsynaptic currents in the dentate gyrus and other areas (e.g., CA1 pyramidal cells), which provides relatively specific evidence for a reduction in GABAergic input to granule cells. These studies support the viewpoint that modest alterations in GABAergic inhibition can have significant functional impact in the dentate gyrus, and suggest that dynamic activity-dependent mechanisms of GABAergic regulation add complexity to this local synaptic circuitry and to analyses of epileptogenesis. In regard to mossy fiber sprouting, a wide variety of experiments involving intracellular or whole-cell recordings during electrical stimulation of the hilus, glutamate microstimulation, and dual recordings from granule cells support the hypothesis that mossy fiber sprouting forms new recurrent excitatory circuits in the dentate gyrus in animal models of TLE. Similar to previous studies on recurrent excitation in the CA3 area, GABA-mediated inhibition and the intrinsic high threshold of granule cells in the dentate gyrus tends to mask the presence of the new recurrent excitatory circuits and reduce the likelihood that reorganized circuits will generate seizure-like activity. How cellular alterations such as neuron loss in the hilus and mossy fiber sprouting influence functional properties is potentially important for understanding fundamental aspects of epileptogenesis, such as the consequences of primary initial injuries, mechanisms underlying network synchronization, and progression of intractability. The continuous nature of the axonal sprouting and formation of recurrent excitation could account for aspects of the latent period and the progressive nature of the epileptogenesis. Future studies will need to identify precisely how these hypothetical mechanisms and others contribute to the process whereby epileptic seizures are initiated or propagated through an area such as the dentate gyrus. Finally, in addition to its unique features and potential importance in epileptogenesis, the dentate gyrus may also serve as a model for other cortical structures in acquired epilepsy.
Collapse
Affiliation(s)
- F Edward Dudek
- Department of Physiology, University of Utah School of Medicine, Salt Lake City, UT 84108, USA.
| | | |
Collapse
|
42
|
Sutula TP, Dudek FE. Unmasking recurrent excitation generated by mossy fiber sprouting in the epileptic dentate gyrus: an emergent property of a complex system. PROGRESS IN BRAIN RESEARCH 2007; 163:541-63. [PMID: 17765737 DOI: 10.1016/s0079-6123(07)63029-5] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Seizure-induced sprouting of the mossy fiber pathway in the dentate gyrus has been observed nearly universally in experimental models of limbic epilepsy and in the epileptic human hippocampus. The observation of progressive mossy fiber sprouting induced by kindling demonstrated that even a few repeated seizures are sufficient to alter synaptic connectivity and circuit organization. As it is now recognized that seizures induce synaptic reorganization in hippocampal and cortical pathways, the implications of seizure-induced synaptic reorganization for circuit properties and function have been subjects of intense interest. Detailed anatomical characterization of the sprouted mossy fiber pathway has revealed that the overwhelming majority of sprouted synapses in the inner molecular layer of the dentate gyrus form recurrent excitatory connections, and are thus likely to contribute to recurrent excitation and potentially to enhanced susceptibility to seizures. Nevertheless, difficulties in detecting functional abnormalities in circuits reorganized by mossy fiber sprouting and the fact that some sprouted axons appear to form synapses with inhibitory interneurons have been cited as evidence that sprouting may not contribute to seizure susceptibility, but could form recurrent inhibitory circuits and be a compensatory response to prevent seizures. Quantitative analysis of the synaptic connections of the sprouted mossy fiber pathway, assessment of the functional features of sprouted circuitry using reliable physiological measures, and the perspective of complex systems analysis of neural circuits strongly support the view that the functional effects of the recurrent excitatory circuits formed by mossy fiber sprouting after seizures or injury emerge only conditionally and intermittently, as observed with spontaneous seizures in human epilepsy. The recognition that mossy fiber sprouting is induced after hippocampal injury and seizures and contributes conditionally to emergence of recurrent excitation has provided a conceptual framework for understanding how injury and seizure-induced circuit reorganization may contribute to paroxysmal network synchronization, epileptogenesis, and the consequences of repeated seizures, and thus has had a major influence on understanding of fundamental aspects of the epilepsies.
Collapse
Affiliation(s)
- Thomas P Sutula
- Department of Neurology H6/570 CSC, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792, USA.
| | | |
Collapse
|
43
|
Altrup U, Häder M, Cáceres JLH, Malcharek S, Meyer M, Galla HJ. Epileptogenic drugs in a model nervous system: Electrophysiological effects and incorporation into a phospholipid layer. Brain Res 2006; 1122:65-77. [PMID: 17049497 DOI: 10.1016/j.brainres.2006.09.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 08/28/2006] [Accepted: 09/06/2006] [Indexed: 11/20/2022]
Abstract
Mechanisms of epileptiform activity in a model nervous system (buccal ganglia of Helix pomatia) are presented. The ganglia contain the identified giant neurons B1 through B4. For epileptiform activity, pentylenetetrazol (1 mmol/L to 40 mmol/L) or etomidate (12.5 micromol/L to 500 micromol/L) were applied. Membrane pressure was measured using a Wilhelmy film balance. In electrophysiological experiments, both drugs induced several effects in all studied neurons: membrane resistance increased, down-stroke of action potentials declined, and all types of chemical synaptic potentials decreased (the latter concerns pentylenetetrazol only). The threshold was 1 mmol/L of pentylenetetrazol and 12.5 micromol/L of etomidate. Epileptiform potentials developed in neurons that had expressed the membrane mechanisms underlying pacemaker potentials. The threshold of this development was again 1 mmol/L of pentylenetetrazol and 12.5 micromol/L of etomidate. Epileptiform depolarizations appeared with 40 mmol/L of pentylenetetrazol and 500 micromol/L of etomidate. In biochemical experiments, both drugs incorporated into an artificial phospholipids membrane and increased pressure in the membrane. The threshold of pressure increase was 1 mmol/L of pentylenetetrazol and 12.5 micromol/L of etomidate. Pressure increased dose-dependently and was 69% and 63% above starting pressure of 10 mN/m with epileptogenic concentrations of pentylenetetrazol (40 mmol/L) and of etomidate (500 micromol/L), respectively. It is postulated that amphiphilic substances incorporate into cell membranes and increase intramembranous pressure, and that this disturbs several membrane processes mechanically and leads to epileptic depolarizations in pacemaker neurons.
Collapse
Affiliation(s)
- Ulrich Altrup
- Institute of Experimental Epilepsy Research, University of Münster, Hüfferstr. 68, 48149 Münster, Germany.
| | | | | | | | | | | |
Collapse
|
44
|
Cross DJ, Cavazos JE. Synaptic reorganization in subiculum and CA3 after early-life status epilepticus in the kainic acid rat model. Epilepsy Res 2006; 73:156-65. [PMID: 17070016 PMCID: PMC1876715 DOI: 10.1016/j.eplepsyres.2006.09.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 09/13/2006] [Accepted: 09/22/2006] [Indexed: 11/23/2022]
Abstract
PURPOSE The immature rat brain is highly susceptible to seizures, but has a resistance to pathological changes induced by seizures as compared to adult rats. However, prolonged seizures during early-life enhance cellular injury and hyperexcitability induced by convulsive insults later in adulthood. The mechanisms underlying these phenomena are not understood. In adult models, the CA1 axons reorganize their projections to subiculum. Seizure induced plasticity in this pathway has not been investigated in immature seizure models, and may contribute to the vulnerability to later seizures. METHODS On postnatal day 15, rats experienced convulsive status epilepticus with kainic acid (KA). Seizure induced plasticity was examined with Timm histochemistry and iontophoretic injections of sodium selenite, a retrograde tracer. Cellular injury was evaluated with Fluoro-Jade B histochemistry. RESULTS Retrograde tracing experiments determined a 67% larger dorsoventral extent of retrograde labeling in the CA1 pyramidal region after tracer injections in subiculum. The synaptic reorganization of the CA1 projection to subiculum was noted in the absence of overt neuronal injury in subiculum or CA1. In contrast, mossy fiber sprouting was detected into the stratum oriens of CA3 with limited neuronal injury to CA3 pyramidal neurons. No mossy fiber sprouting into the inner molecular layer of the dentate gyrus, or CA1 sprouting into the stratum moleculare of CA1 were noted. CONCLUSIONS The results indicate that the developing brain has distinct mechanisms of seizure induced reorganization as compared to the adult brain. Our experiments show that the concept of "resistance of the immature brain to excitotoxicity" is considerably more complicated than generally believed. Morphological plasticity in the immature brain appears more extensive in distal, but not proximal, projections of hippocampal pathways, and across hippocampal lamellae. The abnormal connectivity between hippocampal lamellae might play a role in the increased susceptibility to injury and hyperexcitability associated with later convulsive insults.
Collapse
Affiliation(s)
- Devin J Cross
- Department of Medicine (Neurology), University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA
| | | |
Collapse
|
45
|
El-Hassar L, Milh M, Wendling F, Ferrand N, Esclapez M, Bernard C. Cell domain-dependent changes in the glutamatergic and GABAergic drives during epileptogenesis in the rat CA1 region. J Physiol 2006; 578:193-211. [PMID: 17008374 PMCID: PMC2075107 DOI: 10.1113/jphysiol.2006.119297] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
An increased ratio of the glutamatergic drive to the overall glutamatergic/GABAergic drive characterizes the chronic stage of temporal lobe epilepsy (TLE), but it is unclear whether this modification is present during the latent period that often precedes the epileptic stage. Using the pilocarpine model of TLE in rats, we report that this ratio is decreased in hippocampal CA1 pyramidal cells during the early phase of the latent period (3-5 days post pilocarpine). It is, however, increased during the late phase of the latent period (7-10 days post pilocarpine), via cell domain-dependent alterations in synaptic current properties, concomitant with the occurrence of interictal-like activity in vivo. During the late latent period, the glutamatergic drive was increased in somata via an enhancement in EPSC decay time constant and in dendrites via an increase in EPSC frequency and amplitude. The GABAergic drive remained unchanged in the soma but was decreased in dendrites, since the drop off in IPSC frequency was more marked than the increase in IPSC kinetics. Theoretical considerations suggest that these modifications are sufficient to produce interictal-like activity. In epileptic animals, the ratio of the glutamatergic drive to the overall synaptic drive was not further modified, despite additional changes in synaptic current frequency and kinetics. These results show that the global changes to more glutamatergic and less GABAergic activities in the CA1 region precede the chronic stage of epilepsy, possibly facilitating the occurrence and/or the propagation of interictal activity.
Collapse
Affiliation(s)
- Lynda El-Hassar
- INMED-INSERM U29-Université de la Méditerranée, 163 Route de Luminy BP13, 13273 Marseille Cedex 09, France
| | | | | | | | | | | |
Collapse
|
46
|
Jenrow KA, Ratkewicz AE, Zalinski DN, Roszka KM, Lemke NW, Elisevich KV. Influence of ionizing radiation on the course of kindled epileptogenesis. Brain Res 2006; 1094:207-16. [PMID: 16762327 DOI: 10.1016/j.brainres.2006.03.096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Revised: 03/29/2006] [Accepted: 03/30/2006] [Indexed: 10/24/2022]
Abstract
Several clinical and experimental reports suggest that low-dose irradiation of an established epileptic focus can reduce the occurrence of spontaneous seizures. Conversely, some recent reports suggest that under some conditions low-dose irradiation may have disinhibitory effects on seizure expression. Here, we have investigated mechanistic aspects of this phenomenon in the kindling model of epilepsy by applying focal irradiation at various points during kindling development. Rats were kindled to stage 5 by afterdischarge-threshold electrostimulation of the left amygdala. Treatment groups were irradiated using a collimated X-ray beam (18 MV) either prior to kindling, at kindling stage 3, or at kindling stage 5, by exposure of the left amygdala to a single-fraction central-axis dose of 25 Gy. Generalized seizure thresholds (GSTs) were subsequently assayed at weekly intervals for 10 weeks and at monthly intervals for an additional 3 months, along with the severity of the evoked seizures. Irradiation produced no significant effects on seizure threshold, but did produce persistent changes in seizure severity which varied as a function of the timing of irradiation. Relative to sham irradiated controls, the occurrence of stage 6 seizures was significantly increased by irradiation prior to kindling, but was unaffected by irradiation at kindling stage 3, and significantly reduced by irradiation at kindling stage 5. Quantitative immunohistochemical assays for neuron and astrocyte densities within the amygdala and hippocampus revealed only subtle changes in neuronal density within the dentate granule cell layer. These results are discussed in relation to mechanisms of seizure- and radiation-induced plasticity.
Collapse
Affiliation(s)
- Kenneth A Jenrow
- Department of Neurosurgery, Henry Ford Health Sciences Center, Henry Ford Hospital, Detroit, MI 48202, USA.
| | | | | | | | | | | |
Collapse
|
47
|
Ikegaya Y. [Potential roles for mossy fiber sprouting in temporal lobe epilepsy]. Nihon Yakurigaku Zasshi 2006; 127:355-61. [PMID: 16819240 DOI: 10.1254/fpj.127.355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
|
48
|
Cavazos JE, Cross DJ. The role of synaptic reorganization in mesial temporal lobe epilepsy. Epilepsy Behav 2006; 8:483-93. [PMID: 16500154 PMCID: PMC2829602 DOI: 10.1016/j.yebeh.2006.01.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2005] [Revised: 01/10/2006] [Accepted: 01/10/2006] [Indexed: 11/21/2022]
Abstract
The mechanisms underlying mesial temporal lobe epilepsy (MTLE) remain uncertain. Putative mechanisms should account for several features characteristic of the clinical presentation and the neurophysiological and neuropathological abnormalities observed in patients with intractable MTLE. Synaptic reorganization of the mossy fiber pathway has received considerable attention over the past two decades as a potential mechanism that increases the excitability of the hippocampal network through the formation of new recurrent excitatory collaterals. Morphological plasticity beyond the mossy fiber pathway has not been as thoroughly investigated. Recently, plasticity of the CA1 pyramidal axons has been demonstrated in acute and chronic experimental models of MTLE. As the hippocampal formation is topographically organized in stacks of slices (lamellae), synaptic reorganization of CA1 axons projecting to subiculum appears to increase the connectivity between lamellae, providing a mechanism for translamellar synchronization of cellular hyperexcitability, leading to pharmacologically intractable seizures.
Collapse
Affiliation(s)
- Jose E Cavazos
- South Texas Comprehensive Epilepsy Center and Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
| | | |
Collapse
|
49
|
Perez Y, Ratté S, Sanon N, Lapointe V, Lacaille JC. Cell type-specific changes in spontaneous and minimally evoked excitatory synaptic activity in hippocampal CA1 interneurons of kainate-treated rats. Epilepsy Res 2006; 68:241-54. [PMID: 16368225 DOI: 10.1016/j.eplepsyres.2005.11.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 10/06/2005] [Accepted: 11/10/2005] [Indexed: 11/29/2022]
Abstract
The epileptiform activity in the kainic acid (KA) model of epilepsy arises from complex changes in excitation and inhibition. To assess the involvement of excitatory drive onto inhibitory interneurons in this epileptiform activity, we examined changes in spontaneous and minimally evoked excitatory post-synaptic currents (sEPSCs and eEPSCs) in CA1 interneurons in stratum oriens/alveus (O/A) and stratum radiatum (RAD) in rat hippocampal slices after KA treatment. The frequency and amplitude of sEPSCs and the amplitude of eEPSCs were unchanged in O/A interneurons, but the EPSC kinetics were significantly slower. These changes appear to be due to altered kinetics and voltage-dependent properties of the NMDA component of EPSCs in O/A interneurons. In contrast, sEPSCs and eEPSCs in RAD interneurons did not change after KA treatment. The distinct changes in excitatory synaptic activity in interneurons differentially involved in feedback (O/A) versus feedforward (RAD) inhibition suggest a cell type-specific reorganization of excitatory synapses after KA treatment. These modifications in excitatory input to interneurons could contribute to the maintenance of inhibition of CA1 pyramidal cells after KA treatment, or may also create network conditions favourable to epileptiform activity.
Collapse
Affiliation(s)
- Yaël Perez
- Département de Physiologie et Centre de Recherche en Sciences Neurologiques, Université de Montréal, Qué., Canada H3C 3J7.
| | | | | | | | | |
Collapse
|
50
|
Siddiqui AH, Joseph SA. CA3 axonal sprouting in kainate-induced chronic epilepsy. Brain Res 2006; 1066:129-46. [PMID: 16359649 DOI: 10.1016/j.brainres.2005.10.066] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 10/17/2005] [Accepted: 10/20/2005] [Indexed: 11/25/2022]
Abstract
Latency between an early neurological insult and development of spontaneous recurrent seizures suggests aberrant chronological reorganization in patients with mesial temporal sclerosis associated epilepsy. Kainate-induced status similarly results in delayed development of spontaneous recurrent seizures. Mossy fiber sprouting by the dentate granule cells is a well-characterized manifestation of such temporal structural reorganization in both patients and animal models. However, alterations in other components of hippocampal circuitry have not been evaluated. We present results from studies using precise anterograde and retrograde tract tracing methodologies to evaluate the reorganization of outflow of the CA3 pyramidal cells. Although septotemporal relationships of the normal CA3 outflow tract through the Schaffer collaterals are well known, their aberrant reorganization following kainate-induced spontaneous recurrent seizures is not known. We provide the first definitive evidence of widespread CA3 structural reorganization in the form of sprouting of CA3 axons to widespread areas throughout the hippocampus and entorhinal cortex. This includes an apparent increase in the density of projection to areas that normally receive CA3 outflow such as CA1 and subiculum as well as novel projections beyond the confines of the hippocampus to the pre and parasubiculum and medial and lateral entorhinal cortex. We provide the first evidence of novel CA3 Schaffer collateral projection to the entorhinal cortex. The sprouting of CA3 outflow to widespread regions of the hippocampus and the entorhinal cortex may provide insight into how the injured hippocampus propagates unconventional impulse excitation to cortical fields which have a critical role in providing excitatory inputs into the hippocampus possibly setting up reverberating excitatory circuits as well as widespread connections throughout the cortical mantle. Sprouting-related mechanisms may also explain the latency associated with development of spontaneous recurrent seizures, the hallmark of temporal lobe epilepsy.
Collapse
Affiliation(s)
- Adnan H Siddiqui
- Department of Neurosurgery, Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
| | | |
Collapse
|