scholarly journals Loss of Cdc42 leads to defects in synaptic plasticity and remote memory recall

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Il Hwan Kim ◽  
Hong Wang ◽  
Scott H Soderling ◽  
Ryohei Yasuda
Keyword(s):  
Synaptic Plasticity ◽  
Dendritic Spines ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Conditional Knockout ◽  
Remote Memory ◽  
Memory Recall ◽  
Ca1 Pyramidal Neurons ◽  
Memory Acquisition

Cdc42 is a signaling protein important for reorganization of actin cytoskeleton and morphogenesis of cells. However, the functional role of Cdc42 in synaptic plasticity and in behaviors such as learning and memory are not well understood. Here we report that postnatal forebrain deletion of Cdc42 leads to deficits in synaptic plasticity and in remote memory recall using conditional knockout of Cdc42. We found that deletion of Cdc42 impaired LTP in the Schaffer collateral synapses and postsynaptic structural plasticity of dendritic spines in CA1 pyramidal neurons in the hippocampus. Additionally, loss of Cdc42 did not affect memory acquisition, but instead significantly impaired remote memory recall. Together these results indicate that the postnatal functions of Cdc42 may be crucial for the synaptic plasticity in hippocampal neurons, which contribute to the capacity for remote memory recall.

scholarly journals Hippocampal CA1 Pyramidal Neurons ofMecp2Mutant Mice Show a Dendritic Spine Phenotype Only in the Presymptomatic Stage

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Christopher A. Chapleau ◽  
Elena Maria Boggio ◽  
Gaston Calfa ◽  
Alan K. Percy ◽  
Maurizio Giustetto ◽  
...  
Keyword(s):  
Dendritic Spines ◽  
Dendritic Spine ◽  
Pyramidal Neurons ◽  
Mutant Mice ◽  
Spine Density ◽  
Ca1 Pyramidal Neurons ◽  
Dendritic Spine Density ◽  
Presymptomatic Stage ◽  
Deficient Mice

Alterations in dendritic spines have been documented in numerous neurodevelopmental disorders, including Rett Syndrome (RTT). RTT, an X chromosome-linked disorder associated with mutations inMECP2, is the leading cause of intellectual disabilities in women. Neurons inMecp2-deficient mice show lower dendritic spine density in several brain regions. To better understand the role of MeCP2 on excitatory spine synapses, we analyzed dendritic spines of CA1 pyramidal neurons in the hippocampus ofMecp2tm1.1Jaemale mutant mice by either confocal microscopy or electron microscopy (EM). At postnatal-day 7 (P7), well before the onset of RTT-like symptoms, CA1 pyramidal neurons from mutant mice showed lower dendritic spine density than those from wildtype littermates. On the other hand, at P15 or later showing characteristic RTT-like symptoms, dendritic spine density did not differ between mutant and wildtype neurons. Consistently, stereological analyses at the EM level revealed similar densities of asymmetric spine synapses in CA1stratum radiatumof symptomatic mutant and wildtype littermates. These results raise caution regarding the use of dendritic spine density in hippocampal neurons as a phenotypic endpoint for the evaluation of therapeutic interventions in symptomaticMecp2-deficient mice. However, they underscore the potential role of MeCP2 in the maintenance of excitatory spine synapses.

scholarly journals Loss of Ryanodine Receptor 2 impairs neuronal activity-dependent remodeling of dendritic spines and triggers compensatory neuronal hyperexcitability

2020 ◽  
Vol 27 (12) ◽  
pp. 3354-3373
Author(s):  
Fabio Bertan ◽  
Lena Wischhof ◽  
Liudmila Sosulina ◽  
Manuel Mittag ◽  
Dennis Dalügge ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Neuronal Activity ◽  
Dendritic Spines ◽  
Pyramidal Neurons ◽  
Excitatory Synapses ◽  
Structural And Functional Properties ◽  
Intracellular Ca ◽  
Memory Acquisition ◽  
Activity Dependent

AbstractDendritic spines are postsynaptic domains that shape structural and functional properties of neurons. Upon neuronal activity, Ca2+ transients trigger signaling cascades that determine the plastic remodeling of dendritic spines, which modulate learning and memory. Here, we study in mice the role of the intracellular Ca2+ channel Ryanodine Receptor 2 (RyR2) in synaptic plasticity and memory formation. We demonstrate that loss of RyR2 in pyramidal neurons of the hippocampus impairs maintenance and activity-evoked structural plasticity of dendritic spines during memory acquisition. Furthermore, post-developmental deletion of RyR2 causes loss of excitatory synapses, dendritic sparsification, overcompensatory excitability, network hyperactivity and disruption of spatially tuned place cells. Altogether, our data underpin RyR2 as a link between spine remodeling, circuitry dysfunction and memory acquisition, which closely resemble pathological mechanisms observed in neurodegenerative disorders.

scholarly journals Attenuation of the extracellular matrix increases the number of synapses but suppresses synaptic plasticity

2020 ◽  
Author(s):  
Yulia Dembitskaya ◽  
Nikolay Gavrilov ◽  
Igor Kraev ◽  
Maxim Doronin ◽  
Olga Tyurikova ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Synaptic Plasticity ◽  
Dendritic Spines ◽  
Pyramidal Neurons ◽  
Long Term Potentiation ◽  
Excitatory Postsynaptic Potential ◽  
Sk Channels ◽  
Ca1 Pyramidal Neurons ◽  
Section Electron ◽  
Serial Section Electron Microscopy

AbstractThe brain extracellular matrix (ECM) is a proteoglycan complex that occupies the extracellular space between brain cells and regulates brain development, brain wiring, and synaptic plasticity. However, the action of the ECM on synaptic plasticity remains controversial. Here, we employed serial section electron microscopy to show that enzymatic attenuation of ECM with chondroitinase ABC (ChABC) triggers the appearance of new glutamatergic synapses onto thin dendritic spines of CA1 pyramidal neurons. The appearance of new synapses increased the ratio of the field excitatory postsynaptic potential (fEPSP) to presynaptic fiber volley (PrV), suggesting that these new synapses are formed on existing axonal fibers. However, both the mean miniature excitatory postsynaptic current (mEPSC) amplitude and AMPA/NMDA ratio were decreased, suggesting that ECM attenuation increased the proportion of ‘unpotentiated’ synapses. A higher proportion of unpotentiated synapses would be expected to promote long-term potentiation (LTP). Surprisingly, theta-burst induced LTP was suppressed by ChABC treatment. The suppression of LTP was accompanied by decreased excitability of CA1 pyramidal neurons due to the upregulation of small conductance Ca2+-activated K+ (SK) channels. A pharmacological blockade of SK channels restored cell excitability and, expectedly, enhanced LTP above the level of control. This enhancement of LTP was abolished by a blockade of Rho-associated protein kinase (ROCK), which is involved in the maturation of dendritic spines. Thus, ECM attenuation enables the appearance of new synapses in the hippocampus, which is compensated for by a reduction in the excitability of postsynaptic neurons, thereby preventing network overexcitation at the expense of synaptic plasticity.

scholarly journals Microglia mediate synaptic plasticity induced by 10 Hz repetitive magnetic stimulation

2021 ◽  
Author(s):  
Amelie Eichler ◽  
Dimitrios Kleidonas ◽  
Zsolt Turi ◽  
Matthias Kirsch ◽  
Dietmar Pfeifer ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Functional Properties ◽  
Magnetic Stimulation ◽  
Pyramidal Neurons ◽  
Therapeutic Effects ◽  
Tissue Cultures ◽  
Ca1 Pyramidal Neurons ◽  
Structural And Functional Properties ◽  
Repetitive Magnetic Stimulation

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique that is widely used in clinical practice for therapeutic purposes. Nevertheless, the mechanisms that mediate its therapeutic effects remain poorly understood. Recent work implicates that microglia, the resident immune cells of the central nervous system, have a defined role in the regulation of physiological brain function, e.g. the expression of synaptic plasticity. Despite this observation, no evidence exists for a role of microglia in excitatory synaptic plasticity induced by rTMS. Here, we used repetitive magnetic stimulation of organotypic entorhino-hippocampal tissue cultures to test for the role of microglia in synaptic plasticity induced by 10 Hz repetitive magnetic stimulation (rMS). For this purpose, we performed PLX3397 (Pexidartinib) treatment to deplete microglia from tissue culture preparations. Using whole-cell patch-clamp recordings, live-cell microscopy, immunohistochemistry and transcriptome analysis, we assessed structural and functional properties of both CA1 pyramidal neurons and microglia to correlate the microglia phenotype to synaptic plasticity. PLX3397 treatment over 18 days reliably depletes microglia in tissue cultures, without affecting structural and functional properties of CA1 pyramidal neurons. Microglia-depleted cultures display defects in the ability of CA1 pyramidal neurons to express plasticity of excitatory synapses upon rMS. Notably, rMS induces a moderate release of proinflammatory and plasticity-promoting factors, while microglial morphology stays unaltered. We conclude that microglia play a crucial role in rMS-induced excitatory synaptic plasticity.

scholarly journals Local autocrine signaling of IGF1 synthesized and released by CA1 pyramidal neurons regulates plasticity of dendritic spines

2021 ◽  
Author(s):  
Xun Tu ◽  
Anant Jain ◽  
Helena Decker ◽  
Ryohei Yasuda
Keyword(s):  
Synaptic Plasticity ◽  
Dendritic Spines ◽  
Pyramidal Neurons ◽  
Receptor Activation ◽  
Brain Regions ◽  
Dependent Manner ◽  
Autocrine Signaling ◽  
Ca1 Pyramidal Neurons ◽  
Igf1 Receptor ◽  
Activity Dependent

Insulin-like growth factor 1 (IGF1) regulates hippocampal plasticity, learning, and memory. While circulating, liver-derived IGF1 is known to play an essential role in hippocampal function and plasticity, IGF1 is also synthesized in multiple brain regions, including the hippocampus. However, little is known about the role of hippocampus-derived IGF1 in synaptic plasticity, the type of cells that may provide relevant IGF1, and the spatiotemporal dynamics of IGF1 signaling. Here, using a new FRET sensor for IGF1 signaling, we show that IGF1 in the hippocampus is primarily synthesized in CA1 pyramidal neurons and released in an activity-dependent manner in mice. The local IGF1 release from dendritic spines triggers local autocrine IGF1 receptor activation on the same spine, regulating structural and electrophysiological plasticity of the activated spine. Thus, our study demonstrates a novel mechanism underlying synaptic plasticity by the synthesis and autocrine signaling of IGF1 specific to CA1 pyramidal neurons.

scholarly journals Rapid synaptic plasticity contributes to a learned conjunctive code of position and choice-related information in the hippocampus

2021 ◽  
Author(s):  
Nelson Spruston ◽  
Xinyu Zhao ◽  
Ching-Lung Hsu
Keyword(s):  
Synaptic Plasticity ◽  
Hippocampal Neurons ◽  
Pyramidal Neurons ◽  
Brain Regions ◽  
Induced Response ◽  
Population Code ◽  
Ca1 Pyramidal Neurons ◽  
Related Information ◽  
Plateau Potential ◽  
Whole Cell Recordings

To successfully perform goal-directed navigation, animals must know where they are and what they are doing, e.g., looking for water, bringing food back to the nest, or escaping from a predator. Hippocampal neurons code for these critical variables conjunctively, but little is known about how this where/what code is formed or flexibly routed to other brain regions. To address these questions, we performed intracellular whole-cell recordings in mouse CA1 during a cued, two-choice virtual navigation task. We demonstrate that plateau potentials in CA1 pyramidal neurons rapidly strengthen synaptic inputs carrying conjunctive information about position and choice. Plasticity-induced response fields were modulated by cues only in animals previously trained to collect rewards based on these cues. Thus, we reveal that gradual learning is required for the formation of a conjunctive population code, upstream of CA1, while plateau-potential-induced synaptic plasticity in CA1 enables flexible routing of the code to downstream brain regions.

scholarly journals Early Life Vitamin C Deficiency Does Not Alter Morphology of Hippocampal CA1 Pyramidal Neurons or Markers of Synaptic Plasticity in a Guinea Pig Model

Nutrients ◽  
2018 ◽  
Vol 10 (6) ◽  
pp. 749 ◽  
Author(s):  
Stine Hansen ◽  
Jane Jørgensen ◽  
Jens Nyengaard ◽  
Jens Lykkesfeldt ◽  
Pernille Tveden-Nyborg
Keyword(s):  
Synaptic Plasticity ◽  
Vitamin C ◽  
Guinea Pig ◽  
Early Life ◽  
Pyramidal Neurons ◽  
Pig Model ◽  
Vitamin C Deficiency ◽  
Ca1 Pyramidal Neurons ◽  
Hippocampal Ca1 ◽  
Guinea Pig Model

scholarly journals Chemical LTD, but not LTP, induces transient accumulation of gelsolin in dendritic spines

2019 ◽  
Vol 400 (9) ◽  
pp. 1129-1139 ◽  
Author(s):  
Iryna Hlushchenko ◽  
Pirta Hotulainen
Keyword(s):  
Synaptic Plasticity ◽  
Dendritic Spines ◽  
Hippocampal Neurons ◽  
Long Term Potentiation ◽  
Excitatory Synapses ◽  
Signal Molecule ◽  
Brain Functions ◽  
Dendritic Shaft ◽  
Term Potentiation

Abstract Synaptic plasticity underlies central brain functions, such as learning. Ca2+ signaling is involved in both strengthening and weakening of synapses, but it is still unclear how one signal molecule can induce two opposite outcomes. By identifying molecules, which can distinguish between signaling leading to weakening or strengthening, we can improve our understanding of how synaptic plasticity is regulated. Here, we tested gelsolin’s response to the induction of chemical long-term potentiation (cLTP) or long-term depression (cLTD) in cultured rat hippocampal neurons. We show that gelsolin relocates from the dendritic shaft to dendritic spines upon cLTD induction while it did not show any relocalization upon cLTP induction. Dendritic spines are small actin-rich protrusions on dendrites, where LTD/LTP-responsive excitatory synapses are located. We propose that the LTD-induced modest – but relatively long-lasting – elevation of Ca2+ concentration increases the affinity of gelsolin to F-actin. As F-actin is enriched in dendritic spines, it is probable that increased affinity to F-actin induces the relocalization of gelsolin.

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