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Radwitz J, Hausrat TJ, Heisler FF, Janiesch PC, Pechmann Y, Rübhausen M, Kneussel M. Tubb3 expression levels are sensitive to neuronal activity changes and determine microtubule growth and kinesin-mediated transport. Cell Mol Life Sci 2022; 79:575. [DOI: 10.1007/s00018-022-04607-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 10/11/2022] [Accepted: 10/11/2022] [Indexed: 11/03/2022]
Abstract
AbstractMicrotubules are dynamic polymers of α/β-tubulin. They regulate cell structure, cell division, cell migration, and intracellular transport. However, functional contributions of individual tubulin isotypes are incompletely understood. The neuron-specific β-tubulin Tubb3 displays highest expression around early postnatal periods characterized by exuberant synaptogenesis. Although Tubb3 mutations are associated with neuronal disease, including abnormal inhibitory transmission and seizure activity in patients, molecular consequences of altered Tubb3 levels are largely unknown. Likewise, it is unclear whether neuronal activity triggers Tubb3 expression changes in neurons. In this study, we initially asked whether chemical protocols to induce long-term potentiation (cLTP) affect microtubule growth and the expression of individual tubulin isotypes. We found that growing microtubules and Tubb3 expression are sensitive to changes in neuronal activity and asked for consequences of Tubb3 downregulation in neurons. Our data revealed that reduced Tubb3 levels accelerated microtubule growth in axons and dendrites. Remarkably, Tubb3 knockdown induced a specific upregulation of Tubb4 gene expression, without changing other tubulin isotypes. We further found that Tubb3 downregulation reduces tubulin polyglutamylation, increases KIF5C motility and boosts the transport of its synaptic cargo N-Cadherin, which is known to regulate synaptogenesis and long-term potentiation. Due to the large number of tubulin isotypes, we developed and applied a computational model based on a Monte Carlo simulation to understand consequences of tubulin expression changes in silico. Together, our data suggest a feedback mechanism with neuronal activity regulating tubulin expression and consequently microtubule dynamics underlying the delivery of synaptic cargoes.
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Trans-Anethole Alleviates Trimethyltin Chloride-Induced Impairments in Long-Term Potentiation. Pharmaceutics 2022; 14:pharmaceutics14071422. [PMID: 35890317 PMCID: PMC9320999 DOI: 10.3390/pharmaceutics14071422] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/27/2022] [Accepted: 07/04/2022] [Indexed: 12/04/2022] Open
Abstract
Trans-anethole is an aromatic compound that has been studied for its anti-inflammation, anticonvulsant, antinociceptive, and anticancer effects. A recent report found that trans-anethole exerted neuroprotective effects on the brain via multiple pathways. Since noxious stimuli may both induce neuronal cell injury and affect synaptic functions (e.g., synaptic transmission or plasticity), it is important to understand whether the neuroprotective effect of trans-anethole extends to synaptic plasticity. Here, the effects of trimethyltin (TMT), which is a neurotoxic organotin compound, was investigated using the field recording method on hippocampal slice of mice. The influence of trans-anethole on long-term potentiation (LTP) was also studied for both NMDA receptor-dependent and NMDA receptor–independent cases. The action of trans-anethole on TMT-induced LTP impairment was examined, too. These results revealed that trans-anethole enhances NMDA receptor-dependent and -independent LTP and alleviates TMT-induced LTP impairment. These results suggest that trans-anethole modulates hippocampal LTP induction, prompting us to speculate that it may be helpful for improving cognitive impairment arising from neurodegenerative diseases, including Alzheimer’s disease.
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Jung S, Kayser EB, Johnson SC, Li L, Worstman HM, Sun GX, Sedensky MM, Morgan PG. Tetraethylammonium chloride reduces anaesthetic-induced neurotoxicity in Caenorhabditis elegans and mice. Br J Anaesth 2022; 128:77-88. [PMID: 34857359 PMCID: PMC8787783 DOI: 10.1016/j.bja.2021.09.036] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/30/2021] [Accepted: 09/15/2021] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND If anaesthetics cause permanent cognitive deficits in some children, the implications are enormous, but the molecular causes of anaesthetic-induced neurotoxicity, and consequently possible therapies, are still debated. Anaesthetic exposure early in development can be neurotoxic in the invertebrate Caenorhabditis elegans causing endoplasmic reticulum (ER) stress and defects in chemotaxis during adulthood. We screened this model organism for compounds that alleviated neurotoxicity, and then tested these candidates for efficacy in mice. METHODS We screened compounds for alleviation of ER stress induction by isoflurane in C. elegans assayed by induction of a green fluorescent protein (GFP) reporter. Drugs that inhibited ER stress were screened for reduction of the anaesthetic-induced chemotaxis defect. Compounds that alleviated both aspects of neurotoxicity were then blindly tested for the ability to inhibit induction of caspase-3 by isoflurane in P7 mice. RESULTS Isoflurane increased ER stress indicated by increased GFP reporter fluorescence (240% increase, P<0.001). Nine compounds reduced induction of ER stress by isoflurane by 90-95% (P<0.001 in all cases). Of these compounds, tetraethylammonium chloride and trehalose also alleviated the isoflurane-induced defect in chemotaxis (trehalose by 44%, P=0.001; tetraethylammonium chloride by 23%, P<0.001). In mouse brain, tetraethylammonium chloride reduced isoflurane-induced caspase staining in the anterior cortical (-54%, P=0.007) and hippocampal regions (-46%, P=0.002). DISCUSSION Tetraethylammonium chloride alleviated isoflurane-induced neurotoxicity in two widely divergent species, raising the likelihood that it may have therapeutic value. In C. elegans, ER stress predicts isoflurane-induced neurotoxicity, but is not its cause.
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Affiliation(s)
- Sangwook Jung
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Ernst-Bernhard Kayser
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Simon C Johnson
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA; Department of Neurology, University of Washington, Seattle, WA, USA
| | - Li Li
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA
| | - Hailey M Worstman
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Grace X Sun
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA
| | - Margaret M Sedensky
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA
| | - Philip G Morgan
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, USA; Department of Anesthesiology and Pain Medicine, Seattle, WA, USA.
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Chemical Stimulation of Rodent and Human Cortical Synaptosomes: Implications in Neurodegeneration. Cells 2021; 10:cells10051174. [PMID: 34065927 PMCID: PMC8151714 DOI: 10.3390/cells10051174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 04/29/2021] [Accepted: 05/09/2021] [Indexed: 12/14/2022] Open
Abstract
Synaptic plasticity events, including long-term potentiation (LTP), are often regarded as correlates of brain functions of memory and cognition. One of the central players in these plasticity-related phenomena is the α-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor (AMPAR). Increased levels of AMPARs on postsynaptic membranes thus constitute a biochemical measure of LTP. Isolated synaptic terminals (synaptosomes) are an excellent ex vivo tool to monitor synaptic physiology in healthy and diseased brains, particularly in human research. We herein describe three protocols for chemically-induced LTP (cLTP) in synaptosomes from both rodent and human brain tissues. Two of these chemical stimulation protocols are described for the first time in synaptosomes. A pharmacological block of synaptosomal actin dynamics confirmed the efficiency of the cLTP protocols. Furthermore, the study prototypically evaluated the deficiency of cLTP in cortical synaptosomes obtained from human cases of early-onset Alzheimer’s disease (EOAD) and frontotemporal lobar degeneration (FLTD), as well as an animal model that mimics FLTD.
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Paeonol promotes hippocampal synaptic transmission: The role of the Kv2.1 potassium channel. Eur J Pharmacol 2018; 827:227-237. [PMID: 29550337 DOI: 10.1016/j.ejphar.2018.03.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 03/09/2018] [Accepted: 03/14/2018] [Indexed: 12/30/2022]
Abstract
Paeonol is a major constituent of the Chinese herb Moutan cortex radices. Recent studies report that paeonol has neuroprotective effects and improves impaired learning and memory. However, its underlying mechanisms by which paeonol contributes to synaptic transmission remain unclear. In this study, we found that paeonol increased the frequency of miniature excitatory postsynaptic currents (mEPSCs) and spontaneous excitatory postsynaptic currents (sEPSCs), but had no effect on the amplitude in rat hippocampal CA1 neurons. Similarly, the acetylcholinesterase (AChE) inhibitor rivastigmine increased the frequency of mEPSCs, but had no effect upon amplitude in rat hippocampal neurons. Rivastigmine also inhibited the delayed outward K+ currents in rat hippocampal CA1 neurons, but had no effect in nucleus ambiguus (NA) neurons. The Kv2 blocker guangxitoxin-1E increased the frequency of both mEPSCs and sEPSCs of rat hippocampal CA1 neurons, without affecting their amplitude. Our results suggest that paeonol and rivastigmine enhance spontaneous presynaptic transmitter release, which may be associated with the inhibition of the hippocampal Kv2 current and with therapeutic potential in neurotransmitter deficits found in Alzheimer's disease (AD). Moreover, our data also show that paeonol protects against Aβ25-35-induced impairment of long-term potentiation (LTP) in mouse hippocampal neurons. However, guangxitoxin-1E failed to potentiate the evoked field excitatory postsynaptic potentials (fEPSPs), LTP and Aβ25-35-induced impairment of LTP. These results indicate that paeonol may has the potential to improve learning and memory in AD. Interestingly, this effect is not involved in the inhibition of the hippocampal Kv2 current.
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Bastos FC, Corceiro VN, Lopes SA, de Almeida JG, Matias CM, Dionisio JC, Mendes PJ, Sampaio Dos Aidos FDS, Quinta-Ferreira RM, Quinta-Ferreira ME. Effect of tolbutamide on tetraethylammonium-induced postsynaptic zinc signals at hippocampal mossy fiber-CA3 synapses. Can J Physiol Pharmacol 2017; 95:1058-1063. [PMID: 28654763 DOI: 10.1139/cjpp-2016-0379] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The application of tetraethylammonium (TEA), a blocker of voltage-dependent potassium channels, can induce long-term potentiation (LTP) in the synaptic systems CA3-CA1 and mossy fiber-CA3 pyramidal cells of the hippocampus. In the mossy fibers, the depolarization evoked by extracellular TEA induces a large amount of glutamate and also of zinc release. It is considered that zinc has a neuromodulatory role at the mossy fiber synapses, which can, at least in part, be due to the activation of presynaptic ATP-dependent potassium (KATP) channels. The aim of this work was to study properties of TEA-induced zinc signals, detected at the mossy fiber region, using the permeant form of the zinc indicator Newport Green. The application of TEA caused a depression of those signals that was partially blocked by the KATP channel inhibitor tolbutamide. After the removal of TEA, the signals usually increased to a level above baseline. These results are in agreement with the idea that intense zinc release during strong synaptic events triggers a negative feedback action. The zinc depression, caused by the LTP-evoking chemical stimulation, turns into potentiation after TEA washout, suggesting the existence of a correspondence between the observed zinc potentiation and TEA-evoked mossy fiber LTP.
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Affiliation(s)
- Fatima C Bastos
- a Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal
| | - Vanessa N Corceiro
- a Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal
| | - Sandra A Lopes
- a Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal
| | - José G de Almeida
- b Department of Life Sciences, University of Coimbra, P-3000-456 Coimbra, Portugal
| | - Carlos M Matias
- c CNC - Center for Neurosciences and Cell Biology, University of Coimbra, P-3004-504 Coimbra, Portugal.,d UTAD - University of Trás-os-montes and Alto Douro, P-5000-801 Vila Real, Portugal
| | - Jose C Dionisio
- c CNC - Center for Neurosciences and Cell Biology, University of Coimbra, P-3004-504 Coimbra, Portugal.,e Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Paulo J Mendes
- a Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal.,f LIP - Laboratory of Instrumentation and Experimental Particles Physics, P-3004-516 Coimbra, Portugal
| | | | - Rosa M Quinta-Ferreira
- h CIEPQPF - Research Centre of Chemical Process Engineering and Forest Products, Department of Chemical Engineering, University of Coimbra, P-3030-790 Coimbra, Portugal
| | - M Emilia Quinta-Ferreira
- a Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal.,c CNC - Center for Neurosciences and Cell Biology, University of Coimbra, P-3004-504 Coimbra, Portugal
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Fajardo AS, Seca HF, Martins RC, Corceiro VN, Vieira JP, Quinta-Ferreira ME, Quinta-Ferreira RM. Phenolic wastewaters depuration by electrochemical oxidation process using Ti/IrO 2 anodes. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2017; 24:7521-7533. [PMID: 28116623 DOI: 10.1007/s11356-017-8431-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 01/09/2017] [Indexed: 06/06/2023]
Abstract
The electrochemical oxidation (EO) of phenolic wastewaters mimicking olive oil mill effluents was carried out in a batch stirring reactor using Ti/IrO2 anodes, varying the nature (NaCl and Na2SO4) and electrolyte concentration (1.8-20 g L-1), current density (57-119 mA cm-2) and initial pH (3.4-9). Phenolic content (TPh) and chemical oxygen demand (COD) removals were monitored as a function of applied charge and over time. The nature of the electrolyte greatly affected the efficiency of the system, followed by the influence of the current density. The NaCl concentration and the initial pH influenced the process in a lesser extent. The best operating conditions achieved were 10 g L-1 of NaCl, current density of 119 mA cm-2 and initial pH of 3.4. These parameters led to 100 and 84.8% of TPh and COD removal, respectively. Under these conditions, some morphological differences were observed by SEM on the surface of the anode after treatment. To study the potential toxicity of the synthetic effluent in neuronal activity, this mixture was applied to rat brain slices prior to and after EO. The results indicate that although the treated effluent causes a smaller depression of the neuronal reactive oxygen species (ROS) signal than the untreated one, it leads to a potentiation instead of recovery, upon washout. Furthermore, the purification of a real olive mill wastewater (OMW), with the organic load of the synthetic effluent, using the same optimised operating conditions, achieved total phenolic compounds abatement and 62.8% of COD removal.This study demonstrates the applicability of this EO as a pre-treatment process of a real effluent, in order to achieve the legal limit values to be discharged into natural streams regarding its organic load.
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Affiliation(s)
- Ana S Fajardo
- Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, P3030 790, Coimbra, Portugal.
| | - Helga F Seca
- Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, P3030 790, Coimbra, Portugal
| | - Rui C Martins
- Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, P3030 790, Coimbra, Portugal
| | - Vanessa N Corceiro
- Department of Physics, University of Coimbra, P3004 516, Coimbra, Portugal
| | - João P Vieira
- Department of Physics, University of Coimbra, P3004 516, Coimbra, Portugal
| | - M Emília Quinta-Ferreira
- Department of Physics, University of Coimbra, P3004 516, Coimbra, Portugal
- Centre for Neuroscience and Cell Biology, University of Coimbra, P3004 504, Coimbra, Portugal
| | - Rosa M Quinta-Ferreira
- Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, P3030 790, Coimbra, Portugal
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Fajardo AS, Seca HF, Martins RC, Corceiro VN, Freitas IF, Quinta-Ferreira ME, Quinta-Ferreira RM. Electrochemical oxidation of phenolic wastewaters using a batch-stirred reactor with NaCl electrolyte and Ti/RuO 2 anodes. J Electroanal Chem (Lausanne) 2017. [DOI: 10.1016/j.jelechem.2016.12.033] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tan H, Cao J, Zhang J, Zuo Z. Critical role of inflammatory cytokines in impairing biochemical processes for learning and memory after surgery in rats. J Neuroinflammation 2014; 11:93. [PMID: 24884762 PMCID: PMC4046437 DOI: 10.1186/1742-2094-11-93] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Accepted: 05/01/2014] [Indexed: 11/16/2022] Open
Abstract
Background Patients with postoperative cognitive dysfunction have poor outcomes. Neuroinflammation may be the underlying pathophysiology for this dysfunction. We determined whether proinflammatory cytokines affect the trafficking of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors to the plasma membrane, a fundamental biochemical process for learning and memory. Methods Four-month-old male Fischer 344 rats were subjected to right carotid exposure under isoflurane anesthesia. Some rats received intravenous lidocaine infusion during anesthesia. Rats were tested two weeks later by Barnes maze. The hippocampus was harvested six hours after the surgery for western blotting of interleukin (IL)-1β or IL-6. Hippocampal slices were prepared from control rats or rats subjected to surgery two weeks previously. They were incubated with tetraethylammonium, an agent that can induce long term potentiation, for determining the trafficking of GluR1, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunit. Results Surgery or anesthesia increased the time to identify the target box during the Barnes maze test training sessions and one day after the training sessions. Surgery also prolonged the time to identify the target box eight days after the training sessions. Surgery increased IL-1β and IL-6 in the hippocampus. The tetraethylammonium–induced GluR1 phosphorylation and trafficking were abolished in the hippocampal slices of rats after surgery. These surgical effects were partly inhibited by lidocaine. The incubation of control hippocampal slices with IL-1β and IL-6 abolished tetraethylammonium–induced GluR1 trafficking and phosphorylation. Lidocaine minimally affected the effects of IL-1β on GluR1 trafficking. Conclusions Our results suggest that surgery increases proinflammatory cytokines that then inhibit GluR1 trafficking, leading to learning and memory impairment.
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Affiliation(s)
| | | | | | - Zhiyi Zuo
- Department of Anesthesiology, University of Virginia, 1 Hospital Drive, PO Box 800710, Charlottesville, VA 22908-0710, USA.
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Kim SE, Ko IG, Shin MS, Kim CJ, Jin BK, Hong HP, Jee YS. Treadmill exercise and wheel exercise enhance expressions of neutrophic factors in the hippocampus of lipopolysaccharide-injected rats. Neurosci Lett 2013; 538:54-9. [PMID: 23403101 DOI: 10.1016/j.neulet.2013.01.039] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/23/2012] [Accepted: 01/19/2013] [Indexed: 12/25/2022]
Abstract
Brain inflammation plays a pivotal role in the pathogenesis of chronic neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. We investigated the effects of treadmill exercise and wheel exercise on spatial learning ability in relation with long-term potentiation (LTP) using lipopolysaccharide-induced brain inflammation in the rats. Brain inflammation was induced by an injection of LPS into the cerebral ventricle. We found that brain inflammation impaired spatial learning ability and suppressed the induction of LTP in the hippocampus, as well as weakening expressions of brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase B (Trk-B) with the phosphorylated cyclic AMP response element binding protein (p-CREB). Both treadmill exercise and wheel exercise significantly improved spatial learning ability deteriorated by brain inflammation. These effects can be ascribed to the long-lasting effect of exercise on LTP through enhancement of the expressions regarding BDNF, TrkB, and p-CREB. Treadmill exercise and wheel exercise exerted similar effects on these factors. We infer that exercise may alleviate brain inflammation-induced learning impairment.
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Affiliation(s)
- Sung-Eun Kim
- Department of Physiology, College of Medicine, Kyung Hee University, Dongdaemoon-gu, Seoul 130-701, Republic of Korea
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Zhao S, Studer D, Chai X, Graber W, Brose N, Nestel S, Young C, Rodriguez EP, Saetzler K, Frotscher M. Structural plasticity of spines at giant mossy fiber synapses. Front Neural Circuits 2012; 6:103. [PMID: 23264762 PMCID: PMC3524460 DOI: 10.3389/fncir.2012.00103] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 11/22/2012] [Indexed: 11/13/2022] Open
Abstract
The granule cells of the dentate gyrus give rise to thin unmyelinated axons, the mossy fibers. They form giant presynaptic boutons impinging on large complex spines on the proximal dendritic portions of hilar mossy cells and CA3 pyramidal neurons. While these anatomical characteristics have been known for some time, it remained unclear whether functional changes at mossy fiber synapses such as long-term potentiation (LTP) are associated with structural changes. Since subtle structural changes may escape a fine-structural analysis when the tissue is fixed by using aldehydes and is dehydrated in ethanol, rapid high-pressure freezing (HPF) of the tissue was applied. Slice cultures of hippocampus were prepared and incubated in vitro for 2 weeks. Then, chemical LTP (cLTP) was induced by the application of 25 mM tetraethylammonium (TEA) for 10 min. Whole-cell patch-clamp recordings from CA3 pyramidal neurons revealed a highly significant potentiation of mossy fiber synapses when compared to control conditions before the application of TEA. Next, the slice cultures were subjected to HPF, cryosubstitution, and embedding in Epon for a fine-structural analysis. When compared to control tissue, we noticed a significant decrease of synaptic vesicles in mossy fiber boutons and a concomitant increase in the length of the presynaptic membrane. On the postsynaptic side, we observed the formation of small, finger-like protrusions, emanating from the large complex spines. These short protrusions gave rise to active zones that were shorter than those normally found on the thorny excrescences. However, the total number of active zones was significantly increased. Of note, none of these cLTP-induced structural changes was observed in slice cultures from Munc13-1 deficient mouse mutants showing severely impaired vesicle priming and docking. In conclusion, application of HPF allowed us to monitor cLTP-induced structural reorganization of mossy fiber synapses.
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Affiliation(s)
- Shanting Zhao
- Center for Molecular Neurobiology Hamburg, Institute for Structural Neurobiology Hamburg, Germany
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Zhao S, Studer D, Chai X, Graber W, Brose N, Nestel S, Young C, Rodriguez EP, Saetzler K, Frotscher M. Structural plasticity of hippocampal mossy fiber synapses as revealed by high-pressure freezing. J Comp Neurol 2012; 520:2340-51. [PMID: 22237743 DOI: 10.1002/cne.23040] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Despite recent progress in fluorescence microscopy techniques, electron microscopy (EM) is still superior in the simultaneous analysis of all tissue components at high resolution. However, it is unclear to what extent conventional fixation for EM using aldehydes results in tissue alteration. Here we made an attempt to minimize tissue alteration by using rapid high-pressure freezing (HPF) of hippocampal slice cultures. We used this approach to monitor fine-structural changes at hippocampal mossy fiber synapses associated with chemically induced long-term potentiation (LTP). Synaptic plasticity in LTP has been known to involve structural changes at synapses including reorganization of the actin cytoskeleton and de novo formation of spines. While LTP-induced formation and growth of postsynaptic spines have been reported, little is known about associated structural changes in presynaptic boutons. Mossy fiber synapses are assumed to exhibit presynaptic LTP expression and are easily identified by EM. In slice cultures from wildtype mice, we found that chemical LTP increased the length of the presynaptic membrane of mossy fiber boutons, associated with a de novo formation of small spines and an increase in the number of active zones. Of note, these changes were not observed in slice cultures from Munc13-1 knockout mutants exhibiting defective vesicle priming. These findings show that activation of hippocampal mossy fibers induces pre- and postsynaptic structural changes at mossy fiber synapses that can be monitored by EM.
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Affiliation(s)
- Shanting Zhao
- Department for Structural Neurobiology, Center for Molecular Neurobiology Hamburg-ZMNH, University of Hamburg, D-20246 Hamburg, Germany
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CHIBA H, DEGUCHI Y, KANAZAWA E, KAWAI J, NOZAWA K, SHOJI A, SUGAWARA M. In Vitro Measurements of Extracellular L-Glutamate Level in Region CA3 of Mouse Hippocampal Slices under Chemical Stimulation. ANAL SCI 2010; 26:1103-6. [DOI: 10.2116/analsci.26.1103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Hiromi CHIBA
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Yukari DEGUCHI
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Ena KANAZAWA
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Jun KAWAI
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Keiichiro NOZAWA
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Atsushi SHOJI
- Department of Chemistry, College of Humanities and Sciences, Nihon University
| | - Masao SUGAWARA
- Department of Chemistry, College of Humanities and Sciences, Nihon University
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Group I metabotropic glutamate receptors are involved in TEA-induced long-term potentiation at mossy fiber-CA3 synapses in the rat hippocampus. Brain Res 2009; 1313:45-52. [PMID: 19961834 DOI: 10.1016/j.brainres.2009.11.059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/19/2009] [Accepted: 11/21/2009] [Indexed: 11/24/2022]
Abstract
Gq-protein-coupled Group I metabotropic glutamate receptors (mGluR) reportedly activate phospholipase C (PLC), leading to Ca(2+) release from intracellular stores and the formation of diacylglycerol (DAG). We electrophysiologically examined the involvement of the Group I mGluR in tetraethylammonium (TEA)-induced long-term potentiation (LTP) at mossy fiber (MF)-CA3 synapses in the rat hippocampus. TEA-induced LTP was almost completely blocked under the selective blockade of either mGluR1 or mGluR5, both of which are Group I mGluR. This result was supported by the blockade of TEA-induced LTP even in the absence of these blockers under low temperature conditions, in which the activation of Group I mGluR is thought not to be fully effective. In addition, the blockade of mGluR1 resulted in lower short-term potentiation (STP) during TEA application compared with the blockade of mGluR5. These results demonstrate the crucial roles of Group I mGluR in the TEA-induced LTP at MF-CA3 synapses and the different contributions of mGluR1 and mGluR5 to the initial component of plasticity.
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