d-Serine inhibits AMPA receptor-mediated current in rat hippocampal neurons

2007 ◽  
Vol 85 (5) ◽  
pp. 546-555 ◽  
Author(s):  
Xiang-Qun Gong ◽  
Rebecca L. Zabek ◽  
Donglin Bai
Keyword(s):  
Amino Acids ◽  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Binding Pocket ◽  
Maximal Response ◽  
Competitive Antagonist ◽  
The Right ◽  
Concentration Response Curve ◽  
Native Ligand

d-Serine, a recently identified gliotransmitter, serves as an endogenous coagonist binding to the glycine site of N-methyl-d-aspartate (NMDA) receptors. However, it is not clear whether this native ligand is able to bind to and modulate α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) receptors. In the present study, we showed that d-serine was able to concentration-dependently inhibit kainate-induced AMPA receptor-mediated current in acutely isolated hippocampal neurons. The blocking action of d-serine on AMPA receptors was characterized by a shift in concentration–response curve of kainate-induced current to the right with no change in the maximal response and independent of holding potential in the range of –80 to +60 mV. This is consistent with a model that d-serine is a competitive antagonist on AMPA receptors. In contrast, l-serine did not exert such an inhibitory action. Consistent with this observation, we found that several d-isoforms, but not l-isoforms, of endogenous and exogenous amino acids were able to block AMPA receptors. These results indicate that there is a low affinity and stereo-selective site at the agonist binding pocket of AMPA receptors for these d-amino acids. More importantly, vesicular-released endogenous d-serine from astrocytes could potentially modulate AMPA receptors in synaptic transmission in hippocampus.

Mechanisms and determinants of anaesthetic drug action

2017 ◽  
Author(s):  
David G. Lambert
Keyword(s):  
Drug Target ◽  
Drug Action ◽  
Acetylcholinesterase Inhibition ◽  
Receptor Interaction ◽  
General Description ◽  
Anaesthetic Drug ◽  
Competitive Antagonist ◽  
Pharmacological Interactions ◽  
The Right ◽  
Concentration Response Curve

This chapter is broken into two main sections: a general description of the principles of ligand receptor interaction and a discussion of the main groups of ‘targets’; and explanation of some common pharmacological interactions in anaesthesia, critical care, and pain management. Agonists bind to and activate receptors while antagonists bind to receptors and block the effects of agonists. Antagonists can be competitive (most common) or non-competitive/irreversible. The main classes of drug target are enzymes, carriers, ion channels, and receptors with examples of anaesthetic relevance interacting with all classes. There are many examples in anaesthesia where multiple interacting drugs are co-administered—polypharmacology. To give an example: neuromuscular blockade. Rocuronium is a non-depolarizing neuromuscular blocker acting as a competitive antagonist at the nicotinic acetylcholine receptor. Rocuronium competes with endogenous acetylcholine to shift the concentration–response curve for contraction to the right. The degree of contractility is less for a given concentration of acetylcholine (agonist) in the presence of rocuronium. Using the same principle, the rightward shift can be compensated by increasing the amount of acetylcholine (as long as the amount of rocuronium presented to the receptor as an antagonist remains unchanged, its action can be overcome by increased agonist). Acetylcholine at the effect site is increased by acetylcholinesterase inhibition with neostigmine. One of the side-effects of neostigmine is that it acts as an indirect parasympathomimetic. In the cardiovascular system this would lead to muscarinic receptor-mediated bradycardia; these effects are routinely reversed by the competitive muscarinic antagonist glycopyrrolate.

Positive Allosteric Modulators of AMPA Receptors Reduce Proton-Induced Receptor Desensitization in Rat Hippocampal Neurons

2001 ◽  
Vol 85 (5) ◽  
pp. 2030-2038 ◽  
Author(s):  
Saobo Lei ◽  
Beverley A. Orser ◽  
Gregory R. L. Thatcher ◽  
James N. Reynolds ◽  
John F. MacDonald
Keyword(s):  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Organic Nitrate ◽  
Receptor Desensitization ◽  
Open Probability ◽  
Ca1 Neurons ◽  
Hippocampal Ca1 ◽  
Rate Of Recovery ◽  
Kinetics Of

Whole-cell or outside-out patch recordings were used to investigate the effects of protons and positive modulators of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors on the desensitization of glutamate-evoked AMPA receptor currents in isolated hippocampal CA1 neurons. Protons inhibited glutamate-evoked currents (IC50 of 6.2 pH units) but also enhanced the apparent rate and extent of AMPA receptor desensitization. The proton-induced enhancement of desensitization could not be attributed to a reduction in the rate of recovery from desensitization or to a change in the kinetics of deactivation. Non-stationary variance analysis indicated that protons reduced maximum open probability without changing the conductance of AMPA channels. The positive modulators of AMPA receptor desensitization, cyclothiazide and GT-21-005 (an organic nitrate), reduced the proton sensitivity of AMPA receptor desensitization, which suggests that they interact with protons to diminish desensitization. In contrast, the effects of wheat germ agglutinin and aniracetam on AMPA receptor desensitization were independent of pH. These results demonstrate that a reduction in the proton sensitivity of receptor desensitization contributes to the mechanism of action of some positive modulators of AMPA receptors.

II. Pharmacology of Angiotensin Antagonists

1973 ◽  
Vol 51 (2) ◽  
pp. 114-121 ◽  
Author(s):  
D. Regoli ◽  
W. K. Park ◽  
F. Rioux
Keyword(s):  
Slow Rate ◽  
Response Curve ◽  
Receptor Site ◽  
Maximal Response ◽  
Pharmacological Properties ◽  
Response Curves ◽  
Onset Of Action ◽  
Competitive Antagonist ◽  
Long Acting ◽  
The Right

The pharmacological properties of three antagonists of angiotensin II (ATII) have been characterized on the rat isolated stomach strip.(8-Gly)-ATII, a newly synthesized antagonist of ATII, as well as (8-Leu)-ATII and (1-Sar-8-Leu)-ATII displace to the right the dose–response curve of ATII and the displacement is proportional to the dose of antagonist.Dose–response curves of ATII remain parallel to that of the control in the presence of (8-Gly)-ATII and (8-Leu)-ATII, while parallelism is lost with (1-Sar-8-Leu)-ATII. This antagonist also depresses the maximal response to ATII.All data presented in this paper indicate that (8-Gly)-ATII and (8-Leu)-ATII are competitive antagonists of ATII with different affinities for the receptors, (8-Gly)-ATII being about 12 times less potent than (8-Leu)-ATII. This compound competes with ATII on a one to one basis: pA2 of (8-Leu)-ATII has the same value as pD2 of ATII.(1-Sar-8-Leu)-ATII does not fulfil the criteria of a competitive antagonist. This compound is very potent and the onset of action is as rapid (5 min) as for the other two compounds. All data obtained with (1-Sar-8-Leu)-ATII are consistent with the assumption that this compound is competitive in the sense that it acts on the same receptor site as ATII, but owing probably to slow rate of inactivation by tissue aminopeptidases, it dissociates slowly from the receptors and it acts as a specific long-acting antagonist.

scholarly journals Sustained postsynaptic kainate receptor activation downregulates AMPA receptor surface expression and induces hippocampal LTD

2020 ◽  
Author(s):  
Jithin D. Nair ◽  
Ellen Braksator ◽  
Busra P Yucel ◽  
Richard Seager ◽  
Jack R. Mellor ◽  
...  
Keyword(s):  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Hippocampal Slices ◽  
Surface Expression ◽  
Receptor Activation ◽  
Kainate Receptors ◽  
Receptor Surface Expression ◽  
Acute Hippocampal Slices

AbstractHere we report that sustained activation of GluK2 subunit-containing kainate receptors leads to AMPA receptor endocytosis and a novel form of long-term depression (KAR-LTDAMPAR) in hippocampal neurons. The KAR-evoked loss of surface AMPA receptors requires KAR channel activity and is occluded by the blockade of PKC or PKA. Moreover, in acute hippocampal slices, kainate invoked LTD of AMPA EPSCs. These data, together with our previously reported KAR-LTPAMPAR, demonstrate that KARs bidirectionally regulate synaptic AMPARs and synaptic plasticity.

scholarly journals Class I HDAC Inhibitor Rescues Synaptic Damage and Neuron Loss in APP-Transfected Cells and APP/Ps1 Mice through the GRIP1/AMPA Pathway

2021 ◽  
Author(s):  
Ying Han ◽  
Le Chen ◽  
Jingyun Liu ◽  
Chunyang Wang ◽  
Yu Guo ◽  
...  
Keyword(s):  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Cell Model ◽  
Cytoskeletal Proteins ◽  
Synaptic Proteins ◽  
Human Neuroblastoma ◽  
Transfected Cells ◽  
Related Proteins

Abstract As a neurodegenerative disease, Alzheimer's disease (AD) seriously affects the health of older people. It is now known that changes in synapses occur first in the course of disease, perhaps even before the formation of Aβ plaques. Histone deacetylase (HDAC) can mediate the damage of Aβ oligomers to dendritic spines. Therefore, we examined the relationship between HDAC activity and synaptic defects by using an HDACI, BG45 in Human neuroblastoma SH-SY5Y cell line with stable overexpression of Swedish mutant APP (APPsw) and in APP/Ps1 transgenic mice during this study. The cells were treated with 15µM BG45 and the APP/Ps1 mice 30mg/kg BG45. We detected the level of synapse-related proteins, HDACs, tau phosphorylation and AMPA receptors by western bloting and immunohistochemistry. We also measured the expression of cytoskeletal proteins in the cell model. The mRNA level of GRIK2, SCN3B, SYNPR, Grm2, Grid2IP, GRIP1,GRIP2 were. to explore the effects of HDACi on regulating the synaptic proteins and AMPA receptors. Our studies demonstrated that the expression of HDAC1、HDAC2 and HDAC3 was increased, which was accompanied by the downregulation of the synapse-related proteins synaptophysin (SYP), postsynaptic dendritic protein (PSD-95) and spinophilin as early as 24 h after transfection with APPsw gene. BG45 upregulated the expression of synapse-related proteins and repaired cytoskeletal damage. In vivo, BG45 alleviated the apoptotic loss of hippocampal neurons, upregulated synapse-related proteins, reduced Aβ deposition and phosphorylation of tau and increased the level of the synapse-related genes GRIK2, SCN3B, SYNPR, Grm2, and Grid2IP. BG45 increased the expression of the AMPA receptor subunits GluA1, GluA2 and GluA3 on APPsw-transfected cells and increased GRIP1 and GRIP2 expression and AMPA receptor phosphorylation in vivo. These results suggest that HDACs are involved in the early process of synaptic defects of AD and that BG45 may rescue synaptic damage and loss of hippocampal neurons by specifically inhibiting HDAC1、HDAC2 and HDAC3, thereby modulating AMPA receptor transduction, increasing synapse-related gene expression and finally improving excitatory synapses. BG45 may be considered as a potential drug for the treatment of early AD for further study.

scholarly journals MicroRNA-186-5p controls GluA2 surface expression and synaptic scaling in hippocampal neurons

2019 ◽  
Vol 116 (12) ◽  
pp. 5727-5736 ◽  
Author(s):  
Mariline M. Silva ◽  
Beatriz Rodrigues ◽  
Joana Fernandes ◽  
Sandra D. Santos ◽  
Laura Carreto ◽  
...  
Keyword(s):  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Surface Expression ◽  
Receptor Expression ◽  
Synaptic Activity ◽  
Synaptic Scaling ◽  
Posttranscriptional Control ◽  
Direct Target ◽  
Activity Dependent

Homeostatic synaptic scaling is a negative feedback response to fluctuations in synaptic strength induced by developmental or learning-related processes, which maintains neuronal activity stable. Although several components of the synaptic scaling apparatus have been characterized, the intrinsic regulatory mechanisms promoting scaling remain largely unknown. MicroRNAs may contribute to posttranscriptional control of mRNAs implicated in different stages of synaptic scaling, but their role in these mechanisms is still undervalued. Here, we report that chronic blockade of glutamate receptors of the AMPA and NMDA types in hippocampal neurons in culture induces changes in the neuronal mRNA and miRNA transcriptomes, leading to synaptic upscaling. Specifically, we show that synaptic activity blockade persistently down-regulates miR-186-5p. Moreover, we describe a conserved miR-186-5p-binding site within the 3′UTR of the mRNA encoding the AMPA receptor GluA2 subunit, and demonstrate that GluA2 is a direct target of miR-186-5p. Overexpression of miR-186 decreased GluA2 surface levels, increased synaptic expression of GluA2-lacking AMPA receptors, and blocked synaptic scaling, whereas inhibition of miR-186-5p increased GluA2 surface levels and the amplitude and frequency of AMPA receptor-mediated currents, and mimicked excitatory synaptic scaling induced by synaptic inactivity. Our findings elucidate an activity-dependent miRNA-mediated mechanism for regulation of AMPA receptor expression.

AMPA receptor heterogeneity in rat hippocampal neurons revealed by differential sensitivity to cyclothiazide

1996 ◽  
Vol 75 (6) ◽  
pp. 2322-2333 ◽  
Author(s):  
M. W. Fleck ◽  
R. Bahring ◽  
D. K. Patneau ◽  
M. L. Mayer
Keyword(s):  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Splice Variants ◽  
Differential Sensitivity ◽  
Stratum Radiatum ◽  
Receptor Subtypes ◽  
Receptor Desensitization ◽  
B Subunits ◽  
Kinetics Of

1. The kinetics of onset of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor desensitization by glutamate, and the extent of attenuation of AMPA receptor desensitization by cyclothiazide, showed pronounced cell-to-cell variation in cultures of rat hippocampal neurons. Cultures prepared from area CA1 stratum radiatum tended to show weaker modulation by cyclothiazide than cultures prepared from the whole hippocampus. 2. Kinetic analysis of concentration jump responses to glutamate revealed multiple populations of receptors with fast (approximately 400 ms), intermediate (approximately 2-4 s), and slow (> 20 s) time constants for recovery from modulation by cyclothiazide. The amplitudes of these components varied widely between cells, suggesting the existence of at least three populations of AMPA receptor subtypes, the relative density of which varied from cell to cell. 3. The complex patterns of sensitivity to cyclothiazide seen in hippocampal neurons could be reconstituted by assembly of recombinant AMPA receptor subunits generated from cDNAs encoding the flip (i) and flop (o) splice variants of the GluR-A and GluR-B subunits. Recovery from modulation by cyclothiazide was slower for GluR-AiBi and GluR-AoBi than for GluR-AiBo and GluR-AoBo. 4. Coexpression of the flip and flop splice variants of GluR-A, in the absence of GluR-B, revealed that heteromeric AMPA receptors with intermediate sensitivity to cyclothiazide, similar to responses observed for the combinations GluR-AoBi or GluR-AiBo, could be generated independently of the presence of the GluR-B subunit. However, recovery from modulation by cyclothiazide was twofold slower for GluR-AiBi than for homomeric GluR-Ai, indicating that the GluR-A and GluR-B subunits are not functionally equivalent in controlling sensitivity to cyclothiazide. 5. These results demonstrate that AMPA receptors expressed in hippocampal neurons are assembled in a variety of subunit and splice variant combinations that might serve as a mechanism to fine-tune the kinetics of synaptic transmission.

A selective LTP of NMDA receptor-mediated currents induced by anoxia in CA1 hippocampal neurons

1993 ◽  
Vol 70 (5) ◽  
pp. 2045-2055 ◽  
Author(s):  
V. Crepel ◽  
C. Hammond ◽  
P. Chinestra ◽  
D. Diabira ◽  
Y. Ben-Ari
Keyword(s):  
Nmda Receptor ◽  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Long Term Potentiation ◽  
Peak Amplitude ◽  
Excitatory Postsynaptic Potential ◽  
Physiological Concentration ◽  
Term Potentiation

1. The possibility of long-lasting modifications of glutamatergic responses after anoxic-aglycemic (AA) episodes was investigated in CA1 hippocampal neurons of adult slices. Bicuculline (10 microM) was continuously bath applied to block GABAA receptor-mediated currents. AA episodes were induced by brief (1.30-3 min) perfusions with a glucose free artificial-cerebro-spinal-fluid (ACSF) saturated with 95% N2-5% CO2. 2. In presence of (0.6 mM) Mg2+ and a low concentration of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 1 microM), the Schaffer collateral field EPSPs consisted of an early AMPA receptor-mediated component and a late N-methyl-D-aspartate (NMDA) receptor-mediated component. The former was blocked by (10 microM) CNQX and the latter by (50) microM D-2-amino-5-phosphonovalerate (D-APV). The AA episode induced a selective long-term potentiation (LTP) of the NMDA receptor-mediated component [+70 +/- 13% (mean +/- SE), P < or = 0.008, n = 9] without affecting significantly the AMPA receptor-mediated component (+2 +/- 4, P < or = 0.86 n = 9). This selective LTP is due to an enhanced efficacy of synaptic transmission and will be referred to as anoxic LTP. 3. In slices perfused with an ACSF containing a physiological concentration of (1.3 mM) Mg2+ and no CNQX, the intracellularly recorded excitatory postsynaptic potential (EPSP) was mixed (AMPA/NMDA) at -65 mV and exclusively mediated by AMPA receptors at -100 mV. At -65 mV, the AA episode induced a persistent potentiation of the EPSP (peak amplitude potentiated by 43 +/- 6%, P < or = 0.008, n = 9, 1 h after return to control ACSF). This potentiated component of the EPSP was fully sensitive to (50 microM) D-APV. The CNQX-sensitive AMPA receptor-mediated component was not affected by the AA episode (-5.7 +/- 6%, P < or = 0.123, n = 9). Furthermore, at -100 mV a large APV-sensitive component appeared after the AA episode (+58 +/- 18% of the peak amplitude, P < or = 0.018, n = 9). Therefore, the AA episode induced a selective LTP of the NMDA receptor-mediated component of the EPSP. 4. A robust LTP (+50.0 +/- 7.5%, P < or = 0.008, n = 12) of the NMDA receptor-mediated intracellular EPSP was also observed when AMPA receptors were fully and continuously blocked by (15 microM) CNQX.(ABSTRACT TRUNCATED AT 400 WORDS)

Antagonist actions of bicuculline methiodide and picrotoxin on extrasynaptic γ-aminobutyric acid receptors

1985 ◽  
Vol 63 (11) ◽  
pp. 1465-1470 ◽  
Author(s):  
A. W. Barolet ◽  
A. Li ◽  
S. Liske ◽  
M. E. Morris
Keyword(s):  
Membrane Conductance ◽  
Aminobutyric Acid ◽  
Maximal Response ◽  
Bicuculline Methiodide ◽  
Low Concentrations ◽  
Agonist And Antagonist ◽  
High Concentrations ◽  
The Right ◽  
Transmitter Uptake ◽  
Concentration Response Curve

The effects of picrotoxin and bicuculline methiodide to block depolarizing responses of extrasynaptic receptors for γ-aminobutyric acid (GABA) are compared using excitability testing of myelinated axons in amphibian peripheral nerve. The actions of the antagonists appear both complex and dissimilar. Picrotoxin (10–1000 μM) produces large reversible depressions of the maximal response to GABA (0.01–10 mM) and increases the EC50 from 0.33 to 12.6 mM. With high concentrations of agonist and antagonist an insensitive component is apparent. The action of picrotoxin is not classically noncompetitive: it may represent a mixed antagonism (competitive and noncompetitive) or a noncompetitive one, masked by the presence of receptor reserve and (or) secondary depolarizing influences (e.g., GABA-evoked [K+]o accumulation). Bicuculline methiodide (10–200 μM) shifts the GABA concentration–response curve to the right; maximal responses persist and are even enhanced. The impression that bicuculline methiodide has a competitive action is supported by analysis of its inhibition of responses to low concentrations of the agonist. It is suggested that the enhancement of GABA responses by bicuculline methiodide and their apparent resistance to block by picrotoxin may be due to a common secondary effect of the antagonists such as a decrease in membrane conductance to K+ and (or) block of transmitter uptake.

scholarly journals Constitutive ghrelin receptor activity modulates AMPA receptor traffic and supports memory formation

2020 ◽  
Author(s):  
Luís F. Ribeiro ◽  
Tatiana Catarino ◽  
Mário Carvalho ◽  
Sandra D. Santos ◽  
Luísa Cortes ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Ampa Receptor ◽  
Ampa Receptors ◽  
Hippocampal Neurons ◽  
Physiological Role ◽  
Long Term Potentiation ◽  
Receptor Activity ◽  
Constitutive Activity ◽  
Ghrelin Receptor

AbstractThe ability of animals to store and retrieve food caches in the wild requires the integration of biological signals of hunger, satiety and memory. The role of ghrelin in regulating feeding and memory makes ghrelin receptors an important target to shape the required cellular and molecular responses. We investigated the effects of the high ligand-independent activity of the ghrelin receptor on the physiology of excitatory synapses. Blocking this type of activity produced a decrease in the synaptic content of AMPA receptors in hippocampal neurons and a reduction in GluA1 phosphorylation at Ser845. Impaired constitutive activity from the ghrelin receptor increased surface diffusion of AMPA receptors and impaired AMPA receptor synaptic delivery mediated by chemical long-term potentiation. These observations support a role for the constitutive activity of the ghrelin receptor in regulating AMPA receptor trafficking under basal conditions and synaptic plasticity. Accordingly, we found that blocking the ghrelin receptor constitutive activity impairs spatial and recognition memory.Impact statementThis work uncovers a role for the constitutive activity of the ghrelin receptor in memory, and in the regulation of the synaptic levels of AMPA receptors, their mobility and synaptic plasticity. Underscoring the importance of deciphering the physiological role of constitutive ghrelin receptor activity, ghrelin receptor inverse agonism is now being considered as a therapy to treat alcohol use disorder.

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