Calcium stores regulate excitability in cultured rat hippocampal neurons

Segal, Menahem

doi:10.1152/jn.00447.2018

Cited by 22 publications

(17 citation statements)

References 35 publications

(46 reference statements)

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“…The depolarizing shift of the threshold as well as the increased velocity and amplitude of the action potential indicate that voltage-gated sodium channels are more difficult to activate, and to desensitize, when extracellular calcium is increased. Our findings are thus broadly consistent with several proposed mechanisms for the effect of extracellular calcium on neuronal excitability, including charge-screening, pore block of voltage-gated sodium channels, and activation of calcium-activated potassium channels (Segal 2018). More in-depth studies will be necessary to delineate the relative importance of these mechanisms to changes in excitability in the physiological range of extracellular calcium.…”

Section: Extracellular Calcium and Intrinsic Excitabilitysupporting

confidence: 89%

Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat

Forsberg

Seth

Björefeldt

et al. 2019

Journal of Neurochemistry

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It is well‐known that the extracellular concentration of calcium affects neuronal excitability and synaptic transmission. Less is known about the physiological concentration of extracellular calcium in the brain. In electrophysiological brain slice experiments, the artificial cerebrospinal fluid traditionally contains relatively high concentrations of calcium (2‐4 mM) to support synaptic transmission and suppress neuronal excitability. Using an ion‐selective electrode, we determined the fraction of ionized calcium in healthy human cerebrospinal fluid to 1.0 mM of a total concentration of 1.2 mM (86%). Using patch‐clamp and extracellular recordings in the CA1 region in acute slices of rat hippocampus, we then compared the effects of this physiological concentration of calcium with the commonly used 2 mM on neuronal excitability, synaptic transmission, and long‐term potentiation (LTP) to examine the magnitude of changes in this range of extracellular calcium. Increasing the total extracellular calcium concentration from 1.2 to 2 mM decreased spontaneous action potential firing, induced a depolarization of the threshold, and increased the rate of both de‐ and repolarization of the action potential. Evoked synaptic transmission was approximately doubled, with a balanced effect between inhibition and excitation. In 1.2 mM calcium high‐frequency stimulation did not result in any LTP, whereas a prominent LTP was observed at 2 or 4 mM calcium. Surprisingly, this inability to induce LTP persisted during blockade of GABAergic inhibition. In conclusion, an increase from the physiological 1.2 mM to 2 mM calcium in the artificial cerebrospinal fluid has striking effects on neuronal excitability, synaptic transmission, and the induction of LTP. Open science badges This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. Read the Editorial Highlight for this article on page 435.

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Section: Extracellular Calcium and Intrinsic Excitabilitysupporting

confidence: 89%

Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat

Forsberg

Seth

Björefeldt

et al. 2019

Journal of Neurochemistry

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“…However, it is possible that it is better suited for other cell types. The suboptimal calcium spikes observed in NEUMO and FluoroBrite media may be related to their formulations driving higher calcium store release, and consequently suppressing neuronal activity by activating calcium-gated potassium currents and increasing action potential thresholds 49 . In a blind comparative analysis, our data show that BPI surpasses alternative photostable basal media when used on functional human PSC-derived neuronal culture.…”

Section: Discussionmentioning

confidence: 99%

BrainPhys neuronal medium optimized for imaging and optogenetics in vitro

et al. 2020

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The capabilities of imaging technologies, fluorescent sensors, and optogenetics tools for cell biology are advancing. In parallel, cellular reprogramming and organoid engineering are expanding the use of human neuronal models in vitro. This creates an increasing need for tissue culture conditions better adapted to live-cell imaging. Here, we identify multiple caveats of traditional media when used for live imaging and functional assays on neuronal cultures (i.e., suboptimal fluorescence signals, phototoxicity, and unphysiological neuronal activity). To overcome these issues, we develop a neuromedium called BrainPhys™ Imaging (BPI) in which we optimize the concentrations of fluorescent and phototoxic compounds. BPI is based on the formulation of the original BrainPhys medium. We benchmark available neuronal media and show that BPI enhances fluorescence signals, reduces phototoxicity and optimally supports the electrical and synaptic activity of neurons in culture. We also show the superior capacity of BPI for optogenetics and calcium imaging of human neurons. Altogether, our study shows that BPI improves the quality of a wide range of fluorescence imaging applications with live neurons in vitro while supporting optimal neuronal viability and function.

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“…The CO and synpo have been implied in regulating local AIS Ca 2+ trafficking (Benedeczky et al, 1994; Sanchez-Ponce et al, 2012b; King et al, 2014). Ca 2+ sensitive channels (Inositol 1,4,5-trisphosphate receptors, ryanodine receptors) and Ca 2+ pumps (i.e., sarco/endoplasmic reticulum Ca 2+ -ATPase) associated with the CO are discussed to boost local cytosolic Ca 2+ transients during action potential firing through Ca 2+ -induced Ca 2+ release from internal Ca 2+ stores (Berridge, 1998; Segal, 2018). This Ca 2+ signaling amplification in turn could impact axonal membrane potential properties and neuronal excitability (Berridge, 1998; Segal, 2018), and thus AIS length.…”

Section: Discussionmentioning

confidence: 99%

Dynamic Regulation of Synaptopodin and the Axon Initial Segment in Retinal Ganglion Cells During Postnatal Development

Schlüter

Roßberger

Dannehl

et al. 2019

Front. Cell. Neurosci.

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A key component allowing a neuron to function properly within its dynamic environment is the axon initial segment (AIS), the site of action potential generation. In visual cortex, AIS of pyramidal neurons undergo periods of activity-dependent structural plasticity during development. However, it remains unknown how AIS morphology is organized during development for downstream cells in the visual pathway (retinal ganglion cells; RGCs) and whether AIS retain the ability to dynamically adjust to changes in network state. Here, we investigated the maturation of AIS in RGCs during mouse retinal development, and tested putative activity-dependent mechanisms by applying visual deprivation with a focus on the AIS-specific cisternal organelle (CO), a presumed Ca 2+ -store. Whole-mount retinae from wildtype and Thy1-GFP transgenic mice were processed for multi-channel immunofluorescence using antibodies against AIS scaffolding proteins ankyrin-G, βIV-spectrin and the CO marker synaptopodin (synpo). Confocal microscopy in combination with morphometrical analysis of AIS length and position as well as synpo cluster size was performed. Data indicated that a subset of RGC AIS contains synpo clusters and that these show significant dynamic regulation in size during development as well as after visual deprivation. Using super resolution microscopy, we addressed the subcellular localization of synpo in RGC axons. Similar to cortical neurons, RGCs show a periodic distribution of AIS scaffolding proteins. A previously reported scaffold-deficient nanodomain correlating with synpo localization is not evident in all RGC AIS. In summary, our work demonstrates a dynamic regulation of both the AIS and synpo in RGCs during retinal development and after visual deprivation, providing first evidence that the AIS and CO in RGCs can undergo structural plasticity in response to changes in network activity.

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Calcium stores regulate excitability in cultured rat hippocampal neurons

Cited by 22 publications

References 35 publications

Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat

Ionized calcium in human cerebrospinal fluid and its influence on intrinsic and synaptic excitability of hippocampal pyramidal neurons in the rat

BrainPhys neuronal medium optimized for imaging and optogenetics in vitro

Dynamic Regulation of Synaptopodin and the Axon Initial Segment in Retinal Ganglion Cells During Postnatal Development

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