scholarly journals Membrane Ca2+ permeability and IP3R2 dependent Ca2+-induced Ca2+ release are essential for astrocytic intracellular Ca2+ elevation upon neuronal stimulation at the mouse hippocampal CA3 - CA1 excitatory synapses

2020 ◽  
Author(s):  
Jarand B. Hjukse ◽  
Gry Fluge Vindedal ◽  
Rolf Sprengel ◽  
Vidar Jensen ◽  
Erlend A. Nagelhus ◽  
...  
Keyword(s):  
Inositol Triphosphate ◽  
Excitatory Synapses ◽  
Physiological Conditions ◽  
Two Photon ◽  
Reverse Mode ◽  
Neuronal Stimulation ◽  
Intracellular Ca ◽  
Hippocampal Ca3 ◽  
Frequency Stimulation

AbstractAstrocytes are intricately involved in the activity of neural circuits, however, their basic physiology of interacting with neurons remains controversial. Using dual-indicator two-photon imaging of neurons and astrocytes during stimulations of hippocampal CA3 - CA1 Schaffer collateral (Scc) excitatory synapses, we report that under physiological conditions, the increased glutamate released from the higher frequency stimulation of neurons can accelerate local astrocytic Ca2+ levels. As consequences of extracellular glutamate clearance and maintaining of astrocytic intracellular Na+ homeostasis, the increase of astrocytic membrane Ca2+ permeability via Na+/Ca2+ exchanger (NCX) reverse mode is the primary reason of eliciting astrocytic intracellular Ca2+ elevation upon neuronal stimulation. This Ca2+-induced Ca2+ release is dependent on inositol triphosphate receptor type 2 (IP3R2). In addition, ATP released from Scc excitatory synapses can contribute to this molecular mechanism of Ca2+-induced Ca2+ release in astrocytes.

Regulation of intracellular calcium in N1E-115 neuroblastoma cells: the role of Na+/Ca2+exchange

2002 ◽  
Vol 282 (5) ◽  
pp. C1000-C1008 ◽  
Author(s):  
Kara L. Kopper ◽  
Joseph S. Adorante
Keyword(s):  
Membrane Potential ◽  
Intracellular Calcium ◽  
Normal Cell ◽  
Buffer Capacity ◽  
Neuroblastoma Cells ◽  
Fold Increase ◽  
Scorpion Venom ◽  
Reverse Mode ◽  
Intracellular Ca

In fura 2-loaded N1E-115 cells, regulation of intracellular Ca2+ concentration ([Ca2+]i) following a Ca2+ load induced by 1 μM thapsigargin and 10 μM carbonylcyanide p-trifluoromethyoxyphenylhydrazone (FCCP) was Na+ dependent and inhibited by 5 mM Ni2+. In cells with normal intracellular Na+ concentration ([Na+]i), removal of bath Na+, which should result in reversal of Na+/Ca2+exchange, did not increase [Ca2+]i unless cell Ca2+ buffer capacity was reduced. When N1E-115 cells were Na+ loaded using 100 μM veratridine and 4 μg/ml scorpion venom, the rate of the reverse mode of the Na+/Ca2+ exchanger was apparently enhanced, since an ∼4- to 6-fold increase in [Ca2+]ioccurred despite normal cell Ca2+ buffering. In SBFI-loaded cells, we were able to demonstrate forward operation of the Na+/Ca2+ exchanger (net efflux of Ca2+) by observing increases (∼ 6 mM) in [Na+]i. These Ni2+ (5 mM)-inhibited increases in [Na+]i could only be observed when a continuous ionomycin-induced influx of Ca2+ occurred. The voltage-sensitive dye bis-(1,3-diethylthiobarbituric acid) trimethine oxonol was used to measure changes in membrane potential. Ionomycin (1 μM) depolarized N1E-115 cells (∼25 mV). This depolarization was Na+dependent and blocked by 5 mM Ni2+ and 250–500 μM benzamil. These data provide evidence for the presence of an electrogenic Na+/Ca2+ exchanger that is capable of regulating [Ca2+]i after release of Ca2+ from cell stores.

Evaluation of baroreceptor reflex by blood pressure monitoring in unanesthetized cats

1988 ◽  
Vol 254 (2) ◽  
pp. H377-H383 ◽  
Author(s):  
G. Bertinieri ◽  
M. Di Rienzo ◽  
A. Cavallazzi ◽  
A. U. Ferrari ◽  
A. Pedotti ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Regression Coefficient ◽  
Blood Pressure Monitoring ◽  
Sinus Node ◽  
Pulse Interval ◽  
Pressure Monitoring ◽  
Physiological Conditions ◽  
Average Variation

The arterial baroreceptor control of the sinus node operating in unanesthetized conditions was evaluated in 10 cats in which blood pressure was recorded intra-arterially and scanned by a computer to identify the "spontaneous" sequences of three or more consecutive beats in which systolic blood pressure (SBP) progressively rose and pulse interval (PI) progressively lengthened (type 1 sequences) or SBP progressively fell and PI progressively shortened (type 2 sequences). Many type 1 and 2 three-beat sequences were found; four-, five-, and six-beat sequences of either type were progressively less common, and sequences longer than six beats were almost never identified. The regression coefficient was 30% greater for type 1 than for type 2 sequences. However a prominent feature of either regression coefficient was a wide scattering in each cat (average variation coefficient 50.9 +/- 5.5%). The regression coefficient values were related to some extent to the PI but not to the SBP existing at the beginning of the sequence. Sinoaortic denervation dramatically reduced the number of sequences of either type. These data validate a method for collecting a large number of observations on the baroreceptor-heart rate reflex in physiological conditions. This method may improve understanding of baroreflex involvement in integrated cardiovascular regulation.

Bitter stimuli induce Ca2+ signaling and CCK release in enteroendocrine STC-1 cells: role of L-type voltage-sensitive Ca2+ channels

2006 ◽  
Vol 291 (4) ◽  
pp. C726-C739 ◽  
Author(s):  
Monica C. Chen ◽  
S. Vincent Wu ◽  
Joseph R. Reeve ◽  
Enrique Rozengurt
Keyword(s):  
Endocrine Cells ◽  
Bitter Taste ◽  
Dependent Manner ◽  
Gi Tract ◽  
Intracellular Ca ◽  
Α Subunits ◽  
Ca2 Channels ◽  
Cck Release

We previously demonstrated the expression of bitter taste receptors of the type 2 family (T2R) and the α-subunits of the G protein gustducin (Gαgust) in the rodent gastrointestinal (GI) tract and in GI endocrine cells. In this study, we characterized mechanisms of Ca2+ fluxes induced by two distinct T2R ligands: denatonium benzoate (DB) and phenylthiocarbamide (PTC), in mouse enteroendocrine cell line STC-1. Both DB and PTC induced a marked increase in intracellular [Ca2+] ([Ca2+]i) in a dose- and time-dependent manner. Chelating extracellular Ca2+ with EGTA blocked the increase in [Ca2+]i induced by either DB or PTC but, in contrast, did not prevent the effect induced by bombesin. Thapsigargin blocked the transient increase in [Ca2+]i induced by bombesin, but did not attenuate the [Ca2+]i increase elicited by DB or PTC. These results indicate that Ca2+ influx mediates the increase in [Ca2+]i induced by DB and PTC in STC-1 cells. Preincubation with the L-type voltage-sensitive Ca2+ channel (L-type VSCC) blockers nitrendipine or diltiazem for 30 min inhibited the increase in [Ca2+]i elicited by DB or PTC. Furthermore, exposure to the L-type VSCCs opener BAY K 8644 potentiated the increase in [Ca2+]i induced by DB and PTC. Stimulation with DB also induced a marked increase in the release of cholecystokinin from STC-1 cells, an effect also abrogated by prior exposure to EGTA or L-type VSCC blockers. Collectively, our results demonstrate that bitter tastants increase [Ca2+]i and cholecystokinin release through Ca2+ influx mediated by the opening of L-type VSCCs in enteroendocrine STC-1 cells.

Short-Term Potentiation of Miniature Excitatory Synaptic Currents Causes Excitation of Supraoptic Neurons

2000 ◽  
Vol 83 (5) ◽  
pp. 2542-2553 ◽  
Author(s):  
Samuel B. Kombian ◽  
Michiru Hirasawa ◽  
Didier Mouginot ◽  
Xihua Chen ◽  
Quentin J. Pittman
Keyword(s):  
Nmda Receptors ◽  
Postsynaptic Membrane ◽  
High Frequency Stimulation ◽  
Excitatory Synapses ◽  
Short Term ◽  
Cell Excitability ◽  
Term Potentiation ◽  
Before And After ◽  
Frequency Stimulation ◽  
Supraoptic Neurons

Magnocellular neurons (MCNs) of the hypothalamic supraoptic nucleus (SON) secrete vasopressin and oxytocin. With the use of whole-cell and nystatin-perforated patch recordings of MCNs in current- and voltage-clamp modes, we show that high-frequency stimulation (HFS, 10–200 Hz) of excitatory afferents induces increases in the frequency and amplitude of 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo(f)quinoxaline-7-sulfonamide (NBQX)-sensitive miniature excitatory postsynaptic currents (mEPSCs) lasting up to 20 min. This synaptic enhancement, referred to as short-term potentiation (STP), could be induced repeatedly; required tetrodotoxin (TTX)-dependent action potentials to initiate, but not to maintain; and was independent of postsynaptic membrane potential, N-methyl-d-aspartate (NMDA) receptors, or retrograde neurohypophyseal neuropeptide release. STP was not accompanied by changes in the conductance of the MCNs or in the responsiveness of the postsynaptic non-NMDA receptors, as revealed by brief application of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate. mEPSCs showed similar rise times before and after HFS and analysis of amplitude distributions of mEPSCs revealed one or more peaks pre-HFS and the appearance of additional peaks post-HFS, which were equidistant from the first peak. STP of mEPSCs was not associated with enhanced evoked responses, but was associated with an NBQX-sensitive increase in spontaneous activity of MCNs. Thus we have identified a particularly long-lasting potentiation of excitatory synapses in the SON, which has a presynaptic locus, is dissociated from changes in evoked release, and which regulates postsynaptic cell excitability.

scholarly journals Activity and cytosolic Na+ regulates synaptic vesicle endocytosis

2019 ◽  
Author(s):  
Yun Zhu ◽  
Dainan Li ◽  
Hai Huang
Keyword(s):  
Synaptic Transmission ◽  
High Frequency ◽  
Synaptic Vesicles ◽  
Glutamate Uptake ◽  
High Frequencies ◽  
Vesicle Recycling ◽  
Two Photon ◽  
Readily Releasable Pool ◽  
Content Change ◽  
Intracellular Ca

ABSTRACTRetrieval of synaptic vesicles via endocytosis is essential for maintaining sustained synaptic transmission, especially for neurons that fire action potentials at high frequencies. However, how activity regulates synaptic vesicles recycling is largely unknown. Here we report that Na+ substantially accumulated in the mouse calyx of Held terminals during repetitive high-frequency spiking. Elevated presynaptic Na+ accelerated both slow and rapid forms of endocytosis and facilitated endocytosis overshoot but did not affect the readily releasable pool size, Ca2+ influx, or exocytosis. To examine whether this facilitation of endocytosis is related to the Na+-dependent vesicular content change, we dialyzed increasing concentrations of glutamate into the presynaptic cytosol or blocked the vesicular glutamate uptake with bafilomycin and found the rate of endocytosis was not affected by regulating the glutamate content in the presynaptic terminal. Endocytosis is critically dependent on intracellular Ca2+, and the activity of Na+/Ca2+ exchanger (NCX) may be altered when the Na+ gradient is changed. However, neither NCX blocker nor change of extracellular Na+ concentration affected the endocytosis rate. Moreover, two-photon Ca2+ imaging showed that presynaptic Na+ did not affect the action potential-evoked intracellular Ca2+ transient and decay. Therefore, we revealed a novel mechanism of cytosolic Na+ in accelerating vesicle endocytosis. During high-frequency synaptic transmission, when large amounts of synaptic vesicles are fused, Na+ accumulated in terminals, facilitated vesicle recycling and sustained reliable synaptic transmission.

Na+/Ca2+ exchanger isoform 1 takes part to the Ca2+-related prosurvival pathway of SOD1 in primary motor neurons exposed to beta-methylamino-L-alanine

2021 ◽  
Author(s):  
Agnese Secondo ◽  
Tiziana Petrozziello ◽  
Francesca Boscia ◽  
Valentina Tedeschi ◽  
Anna Pannaccione ◽  
...  
Keyword(s):  
Motor Neurons ◽  
P2x7 Receptor ◽  
Nuclear Translocation ◽  
Neuroprotective Effect ◽  
Integrated Approach ◽  
Double Labeling ◽  
Reverse Mode ◽  
Intracellular Ca ◽  
Patch Clamp Electrophysiology ◽  
Enriched Cultures

Abstract Background: The cycad neurotoxin beta-methylamino-L-alanine (L-BMAA), causing the amyotrophic lateral sclerosis/Parkinson-dementia complex (ALS/PDC), may cause neurodegeneration by disrupting organellar Ca2+ homeostasis. By activating Akt/ERK1/2 pathway, the Cu,Zn-superoxide dismutase (SOD1) and its non-metallated form, ApoSOD1, prevent endoplasmic reticulum (ER) stress-induced cell death in motor neurons exposed to LBMAA. This occurs through the rapid increase of intracellular Ca2+ concentration ([Ca2+]i) in part flowing from the extracellular compartment and in part released from ER. However, the molecular components of this mechanism remain uncharacterized.Methods: By an integrated approach consisting on the use of siRNA strategy, Western blotting, confocal double labeling immunofluorescence, patch-clamp electrophysiology, and Fura 2- /SBFI-single-cell imaging, we explored in rat motor neuron-enriched cultures the involvement of plasma membrane Na+/Ca2+ exchanger (NCX) and the purinergic P2X7 receptor as well as of the intracellular cADP-ribose (cADPR) pathway in the rapid and neuroprotective mechanism of SOD1.Results: we showed that SOD1-induced [Ca2+]i rise was prevented by the pan inhibitor of NCX CB-DMB but not by A430879, a P2X7 receptor specific antagonist, or by 8-bromo-cADPR, a cell permeant antagonist of cADP-ribose. The same occurred for the ApoSOD1. Confocal double labeling immunofluorescence showed a huge expression of plasmalemmal NCX1 and intracellular NCX3 isoforms. Furthermore, we identified NCX1 reverse mode as the main mechanism responsible for the neuroprotective ER Ca2+ refilling elicited by SOD1 and ApoSOD1. Furthermore, SOD1 and ApoSOD1 promoted translocation of active Akt in some nuclei of primary motor neurons. Finally, the activation of NCX1 by the specific agonist CNPYB2 protected motor neurons from L-BMAA-induced cell death.Conclusion: collectively, our data indicate that SOD1 and ApoSOD1 exert their neuroprotective effect by modulating ER Ca2+ content through the activation of NCX1 reverse mode and Akt nuclear translocation in a subset of primary motor neurons.

Junctophilin-2  physically interacts with ryanodine receptor type 2 for peripheral coupling of mouse cardiomyocytes

2020 ◽  
Author(s):  
Tianxia Luo ◽  
Ningning Yan ◽  
Mengru Xu ◽  
Fengjuan Dong ◽  
Qian Liang ◽  
...  
Keyword(s):  
Ryanodine Receptor ◽  
Bioinformatic Analysis ◽  
Cardiac Contraction ◽  
Receptor Type ◽  
Immunofluorescent Staining ◽  
Physical Interaction ◽  
C Terminus ◽  
Confocal Immunofluorescence ◽  
Intracellular Ca

Abstract Background: Ryanodine receptor type 2 (RyR2) mediate Ca 2+ release from the endoplasmic and sarcoplasmic reticulum (ER and SR), which is involved in the peripheral coupling of mouse cardiomyocytes, and thereby plays an important role in cardiac contraction. Junctophilin-2 (JPH2, JP2) is anchored to the plasma membrane (PM) and membranes of the ER and SR, and modulates intracellular Ca 2+ handling through regulation of RyR2. However, the potential RyR2 binding region of JPH2 is poorly understood. Methods: The interaction of JPH2 with RyR2 was studied using LC-MS/MS , bioinformatic analysis,co-immunoprecipitation studies in cardiac SR vesicles. GST-pull down analysis was performed to investigate the physical interaction between RyR2 and JPH2 fragments. Immunofluorescent staining was carried out to determine the colocalization of RyR2 and JPH2 in isolated mouse cardiomyocytes. Ion Optix photometry system was used to measure the levels of intracellular Ca 2+ transients in cardiomyocytes isolated from JPH2 knock down mice. Results: We report that (i) JPH2 interacts with RyR2 and (ii) the C terminus of the JPH2 protein can pull down RyR2 receptors. Confocal immunofluorescence imaging indicated that the majority of JPH2 and RyR2 proteins were colocalized near Z-lines. A decrease in the levels of JPH2 expression reduced the amplitude of Ca 2+ transients in cardiomyocytes. Conclusions: This study suggests that the C terminus domain of JPH2 is required for interactions with RyR2 in the context of peripheral coupling of mouse cardiomyocytes, which provide a molecular mechanism for looking for Ca 2+ - related diseases prevention strategies.

scholarly journals Desensitization of angiotensin II: effect on [Ca2+]i, inositol triphosphate, and prolactin in pituitary cells

2001 ◽  
Vol 280 (3) ◽  
pp. E462-E470 ◽  
Author(s):  
Arturo González Iglesias ◽  
Cecilia Suárez ◽  
Claudia Feierstein ◽  
Graciela Dı́az-Torga ◽  
Damasia Becu-Villalobos
Keyword(s):  
Inositol Phosphate ◽  
Prolactin Secretion ◽  
Inositol Triphosphate ◽  
Pituitary Cells ◽  
Partial Recovery ◽  
Ang Ii ◽  
Pretreated Group ◽  
Intracellular Ca ◽  
Heterologous Desensitization

Activation of pituitary angiotensin (ANG II) type 1 receptors (AT1) mobilizes intracellular Ca2+, resulting in increased prolactin secretion. We first assessed desensitization of AT1 receptors by testing ANG II-induced intracellular Ca2+ concentration ([Ca2+]i) response in rat anterior pituitary cells. A period as short as 1 min with 10−7 M ANG II was effective in producing desensitization (remaining response was 66.8 ± 2.1% of nondesensitized cells). Desensitization was a concentration-related event (EC50: 1.1 nM). Although partial recovery was obtained 15 min after removal of ANG II, full response could not be achieved even after 4 h (77.6 ± 2.4%). Experiments with 5 × 10−7 M ionomycin indicated that intracellular Ca2+ stores of desensitized cells had already recovered when desensitization was still significant. The thyrotropin-releasing hormone (TRH)-induced intracellular Ca2+ peak was attenuated in the ANG II-pretreated group. ANG II pretreatment also desensitized ANG II- and TRH-induced inositol phosphate generation (72.8 ± 3.5 and 69.6 ± 6.1%, respectively, for inositol triphosphate) and prolactin secretion (53.4 ± 2.3 and 65.1 ± 7.2%), effects independent of PKC activation. We conclude that, in pituitary cells, inositol triphosphate formation, [Ca2+]i mobilization, and prolactin release in response to ANG II undergo rapid, long-lasting, homologous and heterologous desensitization.

scholarly journals Smooth muscle Ca2+ sensitization causes hypercontractility of middle cerebral arteries in mice bearing the familial hemiplegic migraine type 2 associated mutation

2018 ◽  
Vol 39 (8) ◽  
pp. 1570-1587 ◽  
Author(s):  
Christian Staehr ◽  
Lise Hangaard ◽  
Elena V Bouzinova ◽  
Sukhan Kim ◽  
Rajkumar Rajanathan ◽  
...  
Keyword(s):  
Blood Flow ◽  
Vascular Function ◽  
Cerebral Arteries ◽  
Point Mutations ◽  
Familial Hemiplegic Migraine ◽  
Laser Speckle ◽  
Hemiplegic Migraine ◽  
Middle Cerebral Arteries ◽  
Intracellular Ca

Familial hemiplegic migraine type 2 (FHM2) is associated with inherited point-mutations in the Na,K-ATPase α2 isoform, including G301R mutation. We hypothesized that this mutation affects specific aspects of vascular function, and thus compared cerebral and systemic arteries from heterozygote mice bearing the G301R mutation (Atp1a2+/−G301R) with wild type (WT). Middle cerebral (MCA) and mesenteric small artery (MSA) function was compared in an isometric myograph. Cerebral blood flow was assessed with Laser speckle analysis. Intracellular Ca2+ and membrane potential were measured simultaneously. Protein expression was semi-quantified by immunohistochemistry. Protein phosphorylation was analysed by Western blot. MSA from Atp1a2+/−G301R and WT showed similar contractile responses. The Atp1a2+/−G301R MCA constricted stronger to U46619, endothelin and potassium compared to WT. This was associated with an increased depolarization, although the Ca2+ change was smaller than in WT. The enhanced constriction of Atp1a2+/−G301R MCA was associated with increased cSrc activation, stronger sensitization to [Ca2+]i and increased MYPT1 phosphorylation. These differences were abolished by cSrc inhibition. Atp1a2+/−G301R mice had reduced resting blood flow through MCA in comparison with WT mice . FHM2-associated mutation leads to elevated contractility of MCA due to sensitization of the contractile machinery to Ca2+, which is mediated via Na,K-ATPase/Src-kinase/MYPT1 signalling.

scholarly journals Mitochondrial Ca2+ Dynamics in MCU Knockout C. elegans Worms

2020 ◽  
Vol 21 (22) ◽  
pp. 8622
Author(s):  
Pilar Álvarez-Illera ◽  
Paloma García-Casas ◽  
Rosalba I Fonteriz ◽  
Mayte Montero ◽  
Javier Alvarez
Keyword(s):  
Cell Activation ◽  
Physiological Activity ◽  
Large Cell ◽  
Atp Production ◽  
Physiological Conditions ◽  
C Elegans ◽  
Neuronal Stimulation ◽  
Low Amplitude ◽  
Stimulation Of

Mitochondrial [Ca2+] plays an important role in the regulation of mitochondrial function, controlling ATP production and apoptosis triggered by mitochondrial Ca2+ overload. This regulation depends on Ca2+ entry into the mitochondria during cell activation processes, which is thought to occur through the mitochondrial Ca2+ uniporter (MCU). Here, we have studied the mitochondrial Ca2+ dynamics in control and MCU-defective C. elegans worms in vivo, by using worms expressing mitochondrially-targeted YC3.60 yellow cameleon in pharynx muscle. Our data show that the small mitochondrial Ca2+ oscillations that occur during normal physiological activity of the pharynx were very similar in both control and MCU-defective worms, except for some kinetic differences that could mostly be explained by changes in neuronal stimulation of the pharynx. However, direct pharynx muscle stimulation with carbachol triggered a large and prolonged increase in mitochondrial [Ca2+] that was much larger in control worms than in MCU-defective worms. This suggests that MCU is necessary for the fast mitochondrial Ca2+ uptake induced by large cell stimulations. However, low-amplitude mitochondrial Ca2+ oscillations occurring under more physiological conditions are independent of the MCU and use a different Ca2+ pathway.

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