scholarly journals Quantal Release of ATP in Mouse Cortex

2007 ◽  
Vol 129 (3) ◽  
pp. 257-265 ◽  
Author(s):  
Yuriy Pankratov ◽  
Ulyana Lalo ◽  
Alexei Verkhratsky ◽  
R. Alan North
Keyword(s):  
Ampa Receptors ◽  
Brain Slices ◽  
Atp Release ◽  
Amplitude Distribution ◽  
P2x Receptor ◽  
Lower Probability ◽  
Quantal Release ◽  
Mouse Cortex ◽  
Lower Amplitude ◽  
Inward Currents

Transient currents occur at rest in cortical neurones that reflect the quantal release of transmitters such as glutamate and γ-aminobutyric acid (GABA). We found a bimodal amplitude distribution for spontaneously occurring inward currents recorded from mouse pyramidal neurones in situ, in acutely isolated brain slices superfused with picrotoxin. Larger events were blocked by glutamate receptor (AMPA, kainate) antagonists; smaller events were partially inhibited by P2X receptor antagonists suramin and PPADS. The decay of the larger events was selectively prolonged by cyclothiazide. Stimulation of single intracortical axons elicited quantal glutamate-mediated currents and also quantal currents with amplitudes corresponding to the smaller spontaneous inward currents. It is likely that the lower amplitude spontaneous events reflect packaged ATP release. This occurs with a lower probability than that of glutamate, and evokes unitary currents about half the amplitude of those mediated through AMPA receptors. Furthermore, the packets of ATP appear to be released from vesicle in a subset of glutamate-containing terminals.

scholarly journals Somatic ATP release from guinea pig sympathetic neurons does not require calcium-induced calcium release from internal stores

2010 ◽  
Vol 299 (4) ◽  
pp. C836-C843 ◽  
Author(s):  
Laura A. Merriam ◽  
Sarah A. Locknar ◽  
Beatrice M. Girard ◽  
Rodney L. Parsons
Keyword(s):  
Guinea Pig ◽  
Calcium Release ◽  
Sympathetic Neurons ◽  
Atp Release ◽  
P2x Receptor ◽  
Slow Inward Current ◽  
Membrane Excitability ◽  
Sodium Influx ◽  
Intracellular Ca ◽  
Inward Currents

Prior studies indicated that a Ca2+-dependent release of ATP can be initiated from the soma of sympathetic neurons dissociated from guinea pig stellate ganglia. Previous studies also indicated that Ca2+-induced Ca2+ release (CICR) can modulate membrane excitability in these same neurons. As Ca2+ release from internal stores is thought to support somatodendritic transmitter release in other neurons, the present study investigated whether CICR is essential for somatic ATP release from dissociated sympathetic neurons. Caffeine increased intracellular Ca2+ and activated two inward currents: a slow inward current (SIC) in 85% of cells, and multiple faster inward currents [asynchronous transient inward currents (ASTICs)] in 40% of cells voltage-clamped to negative potentials. Caffeine evoked both currents when cells were bathed in a Ca2+-deficient solution, indicating that both were initiated by Ca2+ release from ryanodine-sensitive stores in the endoplasmic reticulum. Sodium influx contributed to generation of both SICs and ASTICs, but only ASTICs were inhibited by the presence of the P2X receptor blocker PPADs. Thus ASTICs, but not SICs, resulted from an ATP activation of P2X receptors. Ionomycin induced ASTICs in a Ca2+-containing solution, but not when it was applied in a Ca2+-deficient solution, demonstrating the key requirement for external Ca2+ in initiating ASTICs by ionomycin. Pretreatment with drugs to deplete the internal stores of Ca2+ did not block the ability of ionomycin or long depolarizing voltage steps to initiate ASTICs. Although a caffeine-induced release of Ca2+ from internal stores can elicit both SICs and ASTICs in dissociated sympathetic neurons, CICR is not required for the somatic release of ATP.

scholarly journals Shiga toxin signals via ATP and its effect is blocked by purinergic receptor antagonism

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Karl E. Johansson ◽  
Anne-Lie Ståhl ◽  
Ida Arvidsson ◽  
Sebastian Loos ◽  
Ashmita Tontanahal ◽  
...  
Keyword(s):  
Hela Cells ◽  
Shiga Toxin ◽  
Calcium Influx ◽  
Purinergic Receptor ◽  
Atp Release ◽  
Retrograde Transport ◽  
P2x Receptor ◽  
P2x1 Receptor ◽  
Uremic Syndrome ◽  
Induced Apoptosis

Abstract Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli (EHEC), that cause gastrointestinal infection leading to hemolytic uremic syndrome. The aim of this study was to investigate if Stx signals via ATP and if blockade of purinergic receptors could be protective. Stx induced ATP release from HeLa cells and in a mouse model. Toxin induced rapid calcium influx into HeLa cells, as well as platelets, and a P2X1 receptor antagonist, NF449, abolished this effect. Likewise, the P2X antagonist suramin blocked calcium influx in Hela cells. NF449 did not affect toxin intracellular retrograde transport, however, cells pre-treated with NF449 exhibited significantly higher viability after exposure to Stx for 24 hours, compared to untreated cells. NF449 protected HeLa cells from protein synthesis inhibition and from Stx-induced apoptosis, assayed by caspase 3/7 activity. The latter effect was confirmed by P2X1 receptor silencing. Stx induced the release of toxin-positive HeLa cell- and platelet-derived microvesicles, detected by flow cytometry, an effect significantly reduced by NF449 or suramin. Suramin decreased microvesicle levels in mice injected with Stx or inoculated with Stx-producing EHEC. Taken together, we describe a novel mechanism of Stx-mediated cellular injury associated with ATP signaling and inhibited by P2X receptor blockade.

scholarly journals Modulation of phrenic motoneuron excitability by ATP: consequences for respiratory-related output in vitro

2002 ◽  
Vol 92 (5) ◽  
pp. 1899-1910 ◽  
Author(s):  
Gareth B. Miles ◽  
Marjorie A. Parkis ◽  
Janusz Lipski ◽  
Gregory D. Funk
Keyword(s):  
Pyridoxal Phosphate ◽  
Rapid Onset ◽  
Receptor Activation ◽  
Receptor Expression ◽  
P2x Receptor ◽  
Repetitive Firing ◽  
Burst Amplitude ◽  
Inward Currents ◽  
High Level

On the basis of the high level of P2X receptor expression found in phrenic motoneurons (MN) in rats (Kanjhan et al., J Comp Neurol407: 11–32, 1999) and potentiation of hypoglossal MN inspiratory activity by ATP (Funk et al., J Neurosci 17: 6325–6337, 1997), we tested the hypothesis that ATP receptor activation also modulates phrenic MN activity. This question was examined in rhythmically active brain stem-spinal cord preparations from neonatal rats by monitoring effects of ATP on the activity of spinal C4 nerve roots and phrenic MNs. ATP produced a rapid-onset, dose-dependent, suramin- and pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid 4-sodium-sensitive increase in C4 root tonic discharge and a 22 ± 7% potentiation of inspiratory burst amplitude. This was followed by a slower, 10 ± 5% reduction in burst amplitude. ATPγS, the hydrolysis-resistant analog, evoked only the excitatory response. ATP induced inward currents (57 ± 39 pA) and increased repetitive firing of phrenic MNs. These data, combined with persistence of ATP currents in TTX and immunolabeling for P2X2 receptors in Fluoro-Gold-labeled C4 MNs, implicate postsynaptic P2 receptors in the excitation. Inspiratory synaptic currents, however, were inhibited by ATP. This inhibition differed from that seen in root recordings; it did not follow an excitation, had a faster onset, and was induced by ATPγS. Thus ATP inhibited activity through at least two mechanisms: 1) a rapid P2 receptor-mediated inhibition and 2) a delayed P1 receptor-mediated inhibition associated with hydrolysis of ATP to adenosine. The complex effects of ATP on phrenic MNs highlight the importance of ATP as a modulator of central motor outflows.

scholarly journals Impact of Synaptic Depression on Spike Timing at the Endbulb of Held

2009 ◽  
Vol 102 (3) ◽  
pp. 1699-1710 ◽  
Author(s):  
Hua Yang ◽  
Matthew A. Xu-Friedman
Keyword(s):  
Brain Slices ◽  
Temporal Distribution ◽  
Response Probability ◽  
Spike Timing ◽  
Lower Probability ◽  
Dynamic Clamp ◽  
Timing Information ◽  
Highly Active ◽  
Endbulb Of Held ◽  
Activity Dependent

Many synapses show short-term depression, but it is not well understood what functional purpose depression serves and whether its effects are beneficial or detrimental to information processing. We study this issue at the synapse made by auditory-nerve (AN) fibers onto bushy cells (BCs) of the cochlear nucleus, called the “endbulb of Held.” AN fibers carry timing information about sounds and converge on BCs, which relay timing information to brain areas responsible for sound localization. Dynamic-clamp recordings of BCs in mouse brain slices indicated that nonphase-locked inputs influenced the contribution of phase-locked inputs when all inputs had equal strength. We evaluated whether this situation depended on activity-dependent synaptic plasticity. Voltage-clamp recordings indicated that the amount of depression varied over the population of endbulbs, but sibling endbulbs terminating on the same BC had similar plasticity. We tested the effects of endbulb depression on BC spiking using dynamic clamp. Under most conditions, increasing depression led to lower probability of BC spiking. However, the effects on spike timing were highly context dependent. When all inputs carried uniform timing information, depression indirectly affected BC spike precision, by determining how many inputs were required to cross threshold. Earlier work has indicated that this interacts with the temporal distribution of inputs to determine BC spike precision. When inputs carried different timing information, depression greatly improved BC precision by suppressing highly active inputs carrying little phase-locked information. These data suggest that endbulbs with different depression characteristics could produce BCs that enhance response probability or timing under different stimulus conditions.

scholarly journals Postinhibitory rebound neurons and networks are disrupted in retrovirus-induced spongiform neurodegeneration

2014 ◽  
Vol 112 (3) ◽  
pp. 683-704 ◽  
Author(s):  
Ying Li ◽  
Robert A. Davey ◽  
Shobhana Sivaramakrishnan ◽  
William P. Lynch
Keyword(s):  
Ampa Receptors ◽  
Prion Diseases ◽  
Leukemia Virus ◽  
Brain Slices ◽  
Neuronal Loss ◽  
Cell Loss ◽  
Cell Types ◽  
Calcium Buffer ◽  
Postinhibitory Rebound ◽  
Env Protein

Certain retroviruses induce progressive spongiform motor neuron disease with features resembling prion diseases and amyotrophic lateral sclerosis. With the neurovirulent murine leukemia virus (MLV) FrCasE, Env protein expression within glia leads to postsynaptic vacuolation, cellular effacement, and neuronal loss in the absence of neuroinflammation. To understand the physiological changes associated with MLV-induced spongiosis, and its neuronal specificity, we employed patch-clamp recordings and voltage-sensitive dye imaging in brain slices of the mouse inferior colliculus (IC), a midbrain nucleus that undergoes extensive spongiosis. IC neurons characterized by postinhibitory rebound firing (PIR) were selectively affected in FrCasE-infected mice. Coincident with Env expression in microglia and in glia characterized by NG2 proteoglycan expression (NG2 cells), rebound neurons (RNs) lost PIR, became hyperexcitable, and were reduced in number. PIR loss and hyperexcitability were reversed by raising internal calcium buffer concentrations in RNs. PIR-initiated rhythmic circuits were disrupted, and spontaneous synchronized bursting and prolonged depolarizations were widespread. Other IC neuron cell types and circuits within the same degenerative environment were unaffected. Antagonists of NMDA and/or AMPA receptors reduced burst firing in the IC but did not affect prolonged depolarizations. Antagonists of L-type calcium channels abolished both bursts and slow depolarizations. IC infection by the nonneurovirulent isogenic virus Friend 57E (Fr57E), whose Env protein is structurally similar to FrCasE, showed no RN hyperactivity or cell loss; however, PIR latency increased. These findings suggest that spongiform neurodegeneration arises from the unique excitability of RNs, their local regulation by glia, and the disruption of this relationship by glial expression of abnormal protein.

Serotonergic modulation of neuronal activity in rat midbrain periaqueductal gray

2013 ◽  
Vol 109 (11) ◽  
pp. 2712-2719 ◽  
Author(s):  
Hyo-Jin Jeong ◽  
Karen Lam ◽  
Vanessa A. Mitchell ◽  
Christopher W. Vaughan
Keyword(s):  
Brain Slices ◽  
Periaqueductal Gray ◽  
Membrane Excitability ◽  
Inhibitory Effects ◽  
Whole Cell Patch Clamp ◽  
Outward Currents ◽  
Selective Ligands ◽  
Inward Currents ◽  
Subtype Selective ◽  
Serotonergic Modulation

Serotonin (5-HT) modulates pain and anxiety from within the midbrain periaqueductal gray (PAG). In the present study, the effects of 5-HT- and 5-HT1/2 subtype-selective ligands on rat PAG neurons were examined using whole cell patch-clamp recordings in brain slices. In voltage clamp, 5-HT produced outward and inward currents in distinct subpopulations of neurons that varied throughout different subregions of the PAG. The 5-HT1A agonist R(+)-8-OH-DPAT (1 μM) produced outward currents in subpopulations of PAG neurons. By contrast, sumatriptan (1 μM) and other 5-HT1B, -D, and -F subtype agonists had little or no postsynaptic activity. The 5-HT2A/C agonists DOI (3 μM) and TCB-2 (1 μM) produced inward currents in subpopulations of PAG neurons, and DOI enhanced evoked inhibitory postsynaptic currents via a presynaptic mechanism. In current clamp, both R(+)-8-OH-DPAT and sumatriptan produced an excitatory increase in evoked mixed postsynaptic potentials (PSPs). In addition, R(+)-8-OH-DPAT, but not sumatriptan, directly hyperpolarized PAG neurons. By contrast, the 5-HT2 agonist DOI depolarized subpopulations of neurons and produced an inhibitory decrease in evoked mixed PSPs. These findings indicate that 5-HT1A and 5-HT1B/D ligands have partly overlapping inhibitory effects on membrane excitability and synaptic transmission within the PAG, which are functionally opposed by 5-HT2A/C actions in specific PAG subregions.

scholarly journals Characteristics and Functions of α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionate Receptors Expressed in Mouse Pancreatic α-Cells

Endocrinology ◽  
2010 ◽  
Vol 151 (4) ◽  
pp. 1541-1550 ◽  
Author(s):  
Jung-Hwa Cho ◽  
Liangyi Chen ◽  
Mean-Hwan Kim ◽  
Robert H. Chow ◽  
Bertil Hille ◽  
...  
Keyword(s):  
Glutamate Receptor ◽  
Ampa Receptors ◽  
Islet Cells ◽  
Hormone Secretion ◽  
Cell Types ◽  
Membrane Depolarization ◽  
Voltage Gated ◽  
Mouse Pancreatic Islets ◽  
Inward Currents ◽  
Ca2 Channels

Pancreatic islet cells use neurotransmitters such as l-glutamate to regulate hormone secretion. We determined which cell types in mouse pancreatic islets express ionotropic glutamate receptor channels (iGluRs) and describe the detailed biophysical properties and physiological roles of these receptors. Currents through iGluRs and the resulting membrane depolarization were measured with patch-clamp methods. Ca2+ influx through voltage-gated Ca2+ channels and Ca2+-evoked exocytosis were detected by Ca2+ imaging and carbon-fiber microamperometry. Whereas iGluR2 glutamate receptor immunoreactivity was detected using specific antibodies in immunocytochemically identified mouse α- and β-cells, functional iGluRs were detected only in the α-cells. Fast application of l-glutamate to cells elicited rapidly activating and desensitizing inward currents at −60 mV. By functional criteria, the currents were identified as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors. They were activated and desensitized by AMPA, and were activated only weakly by kainate. The desensitization by AMPA was inhibited by cyclothiazide, and the currents were blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Islet iGluRs showed nonselective cation permeability with a low Ca2+ permeability (PCa/PNa = 0.16). Activation of the AMPA receptors induced a sequence of cellular actions in α-cells: 1) depolarization of the membrane by 27 ± 3 mV, 2) rise in intracellular Ca2+ mainly mediated by voltage-gated Ca2+ channels activated during the membrane depolarization, and 3) increase of exocytosis by the Ca2+ rise. In conclusion, iGluRs expressed in mouse α-cells resemble the low Ca2+-permeable AMPA receptor in brain and can stimulate exocytosis.

scholarly journals Cutting off the power: inhibition of leukemia cell growth by pausing basal ATP release and P2X receptor signaling?

2016 ◽  
Vol 12 (3) ◽  
pp. 439-451 ◽  
Author(s):  
Carola Ledderose ◽  
Tobias Woehrle ◽  
Stephan Ledderose ◽  
Katharina Strasser ◽  
Richard Seist ◽  
...  
Keyword(s):  
Cell Growth ◽  
Leukemia Cell ◽  
Atp Release ◽  
P2x Receptor ◽  
Receptor Signaling

scholarly journals P2X1 receptor activation in HL60 cells

Blood ◽  
1996 ◽  
Vol 87 (7) ◽  
pp. 2659-2664 ◽  
Author(s):  
G Buell ◽  
AD Michel ◽  
C Lewis ◽  
G Collo ◽  
PP Humphrey ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Radioligand Binding ◽  
Atp Release ◽  
Receptor Activation ◽  
P2x Receptor ◽  
Luciferase Assay ◽  
Receptor Protein ◽  
Hl60 Cells ◽  
P2x1 Receptor ◽  
Alpha Beta

Recent cloning of the human P2X1 receptor revealed high levels of its messenger RNA in differentiated promyelocytes (HL60 cells). We found expression of P2X1 receptor protein in HL60 cells by radioligand binding, by immunohistochemistry, using a receptor specific antibody, and by electrophysiology. The currents elicited by adenosine triphosphate (ATP) had the expected properties of P2X1 receptors (rapid desensitization, mimicked by alpha,beta-methylene-ATP). However, these currents were only observed in cells that were pretreated with apyrase, which destroys extracellular ATP, or with suramin, a P2X receptor antagonist. This implies that HL60 cells release ATP, which chronically desensitizes the receptor. ATP release was detected by direct measurement, using the luciferin-luciferase assay. It is concluded that functional P2X1 receptors are present in the membrane of differentiated HL60 cells.

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