scholarly journals Screening for Activity Against AMPA Receptors Among Anticonvulsants—Focus on Phenytoin

2021 ◽  
Vol 12 ◽  
Author(s):  
M. Y. Dron ◽  
A. S. Zhigulin ◽  
D. B. Tikhonov ◽  
O. I. Barygin
Keyword(s):  
Ampa Receptors ◽  
Wistar Rat ◽  
Channel Blockers ◽  
Allosteric Inhibitors ◽  
Voltage Gated Sodium Channels ◽  
Whole Cell Patch Clamp ◽  
Mechanism Of Inhibition ◽  
Selective Channel ◽  
Clonic Seizures ◽  
First Time

The interest in AMPA receptors as a target for epilepsy treatment increased substantially after the approval of perampanel, a negative AMPA receptor allosteric antagonist, for the treatment of partial-onset seizures and generalized tonic-clonic seizures. Here we performed a screening for activity against native calcium-permeable AMPA receptors (CP-AMPARs) and calcium-impermeable AMPA receptors (CI-AMPARs) among different anticonvulsants using the whole-cell patch-clamp method on isolated Wistar rat brain neurons. Lamotrigine, topiramate, levetiracetam, felbamate, carbamazepine, tiagabin, vigabatrin, zonisamide, and gabapentin in 100-µM concentration were practically inactive against both major subtypes of AMPARs, while phenytoin reversibly inhibited them with IC50 of 30 ± 4 μM and 250 ± 60 µM for CI-AMPARs and CP-AMPARs, respectively. The action of phenytoin on CI-AMPARs was attenuated in experiments with high agonist concentrations, in the presence of cyclothiazide and at pH 9.0. Features of phenytoin action matched those of the CI-AMPARs pore blocker pentobarbital, being different from classical competitive inhibitors, negative allosteric inhibitors, and CP-AMPARs selective channel blockers. Close 3D similarity between phenytoin and pentobarbital also suggests a common binding site in the pore and mechanism of inhibition. The main target for phenytoin in the brain, which is believed to underlie its anticonvulsant properties, are voltage-gated sodium channels. Here we have shown for the first time that phenytoin inhibits CI-AMPARs with similar potency. Thus, AMPAR inhibition by phenytoin may contribute to its anticonvulsant properties as well as its side effects.

scholarly journals The mechanism of aquaporin inhibition by gold compounds elucidated by biophysical and computational methods

2017 ◽  
Vol 53 (27) ◽  
pp. 3830-3833 ◽  
Author(s):  
Andreia de Almeida ◽  
Andreia F. Mósca ◽  
Darren Wragg ◽  
Margot Wenzel ◽  
Paul Kavanagh ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Computational Methods ◽  
Density Functional ◽  
Electrochemical Studies ◽  
Functional Theory ◽  
Mechanism Of Inhibition ◽  
Gold Compounds ◽  
First Time

The mechanism of inhibition of water and glycerol permeation via human aquaglyceroporin-3 (AQP3) by gold(iii) complexes has been described, for the first time, using molecular dynamics (MD), combined with density functional theory (DFT) and electrochemical studies.

Ca2+ Currents in Central Insect Neurons: Electrophysiological and Pharmacological Properties

1997 ◽  
Vol 77 (1) ◽  
pp. 186-199 ◽  
Author(s):  
Dieter Wicher ◽  
Heinz Penzlin
Keyword(s):  
Periplaneta Americana ◽  
Low Voltage ◽  
Fast Time ◽  
Channel Blockers ◽  
Pharmacological Properties ◽  
Patch Clamp Technique ◽  
Whole Cell Patch Clamp ◽  
Blocking Effects ◽  
Dum Neurons ◽  
Maximal Peak

Wicher, Dieter, and Heinz Penzlin. Ca2+ currents in central insect neurons: electrophysiological and pharmacological properties. J. Neurophysiol. 77: 186–199, 1997. Ca2+ currents in dorsal unpaired median (DUM) neurons isolated from the fifth abdominal ganglion of the cockroach Periplaneta americana were investigated with the whole cell patch-clamp technique. On the basis of kinetic and pharmacological properties, two different Ca2+ currents were separated in these cells: mid/low-voltage-activated (M-LVA) currents and high-voltage-activated (HVA) currents. M-LVA currents had an activation threshold of −50 mV and reached maximal peak values at −10 mV. They were sensitive to depolarized holding potentials and decayed very rapidly. The decay was largely Ca2+ dependent. M-LVA currents were effectively blocked by Cd2+ median inhibiting concentration (IC50 = 9 μM), but they also had a remarkable sensitivity to Ni2+ (IC50 = 19 μM). M-LVA currents were insensitive to vertebrate LVA channel blockers like flunarizine and amiloride. The currents were, however, potently blocked by ω-conotoxin MVIIC (1 μM) and ω-agatoxin IVA (50 nM). The blocking effects of ω-toxins developed fast (time constant τ = 15 s) and were fully reversible after wash. HVA currents activated positive to −30 mV and showed maximal peak currents at +10 mV. They were resistant to depolarized holding potentials up to −50 mV and decayed in a less pronounced manner than M-LVA currents. HVA currents were potently blocked by Cd2+ (IC50 = 5 μM) but less affected by Ni2+ (IC50 = 40 μM). These currents were reduced by phenylalkylamines like verapamil (10 μM) and benzothiazepines like diltiazem (10 μM), but they were insensitive to dihydropyridines like nifedipine (10 μM) and BAY K 8644 (10 μM). Furthermore, HVA currents were sensitive to ω-conotoxin GVIA (1 μM). The toxin-induced reduction of currents appeared slowly (τ ∼ 120 s) and the recovery after wash was incomplete in most cases. The dihydropyridine insensitivity of the phenylalkylamine-sensitive HVA currents is a property the cockroach DUM cells share with other invertebrate neurons. Compared with Ca2+ currents in vertebrates, the DUM neuron currents differ considerably from the presently known types. Although there are some similarities concerning kinetics, the pharmacological profile of the cockroach Ca2+ currents especially is very different from profiles already described for vertebrate currents.

scholarly journals Effect of Geraniol and Citronellol Essential Oils on the Biophysical Gating Properties of AMPA Receptors

2019 ◽  
Vol 9 (21) ◽  
pp. 4693 ◽  
Author(s):  
Mohammad Qneibi ◽  
Nidal Jaradat ◽  
Nour Emwas
Keyword(s):  
Essential Oils ◽  
Ampa Receptors ◽  
Neurological Diseases ◽  
Whole Cell Patch Clamp ◽  
293 Cells ◽  
Future Drug ◽  
Drug Synthesis ◽  
Patch Clamp Electrophysiology ◽  
Calming Effect ◽  
Natural Template

Essential oils have been advertised endlessly to be very beneficial for the health of humans, and an extensive amount of research examines the validity of such claims. In contribution, the current study evaluates the neuroprotective properties of Citronellol and Geraniol essential oils (EOs). In relationship to the biophysical gating properties of different the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits, the EOs were administered to HEK293 (Human embryonic kidney 293) cells and examined for any inhibition and effect on desensitization or deactivation rates, using whole-cell patch-clamp electrophysiology. Our results demonstrated the highest levels of inhibition from Citronellol oil by four-fold on all AMPARs subunits. Likewise, Geraniol oil had a similar inhibiting impact on the receptors, and both oils decreased the desensitization and deactivation rates of the inhibited receptors. Thus, the examined EOs of this study portray neuroprotective qualities by targeting AMPARs activation and reducing desensitization and deactivation rates. Finally, the results of the current study entail a better understanding of AMPARs, provides a natural template for future drug synthesis to treat neurological diseases associated with excessive AMPAR activation, and offers a possible mechanism by which these essential oils deploy their ‘calming’ effect.

Attenuation of apoptosis in enterocytes by blockade of potassium channels

2005 ◽  
Vol 289 (5) ◽  
pp. G815-G821 ◽  
Author(s):  
Anatoly Grishin ◽  
Henri Ford ◽  
Jin Wang ◽  
Hui Li ◽  
Vicenta Salvador-Recatala ◽  
...  
Keyword(s):  
Apoptotic Cell ◽  
Cell Loss ◽  
Cell Types ◽  
Epithelial Cell Line ◽  
Channel Blockers ◽  
Pharmacological Prevention ◽  
Pharmacological Blockade ◽  
Inflammatory Bowel ◽  
First Time

Apoptosis plays an important role in maintaining the balance between proliferation and cell loss in the intestinal epithelium. Apoptosis rates may increase in intestinal pathologies such as inflammatory bowel disease and necrotizing enterocolitis, suggesting pharmacological prevention of apoptosis as a therapy for these conditions. Here, we explore the feasibility of this approach using the rat epithelial cell line IEC-6 as a model. On the basis of the known role of K+ efflux in apoptosis in various cell types, we hypothesized that K+ efflux is essential for apoptosis in enterocytes and that pharmacological blockade of this efflux would inhibit apoptosis. By probing intracellular [K+] with the K+-sensitive fluorescent dye and measuring the efflux of 86Rb+, we found that apoptosis-inducing treatment with the proteasome inhibitor MG-132 leads to a twofold increase in K+ efflux from IEC-6 cells. Blockade of K+ efflux with tetraethylammonium, 4-aminopyridine, stromatoxin, chromanol 293B, and the recently described K+ channel inhibitor 48F10 prevents DNA fragmentation, caspase activation, release of cytochrome c from mitochondria, and loss of mitochondrial membrane potential. Thus K+ efflux occurs early in the apoptotic program and is required for the execution of later events. Apoptotic K+ efflux critically depends on activation of p38 MAPK. These results demonstrate for the first time the requirement of K+ channel-mediated K+ efflux for progression of apoptosis in enterocytes and suggest the use of K+ channel blockers to prevent apoptotic cell loss occurring in intestinal pathologies.

Anion channel blockers inhibit swelling-activated anion, cation, and nonelectrolyte transport in HeLa cells

1996 ◽  
Vol 271 (2) ◽  
pp. C579-C588 ◽  
Author(s):  
J. A. Hall ◽  
J. Kirk ◽  
J. R. Potts ◽  
C. Rae ◽  
K. Kirk
Keyword(s):  
Hela Cells ◽  
Anion Channel ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Influx Rate ◽  
Cation Permeability ◽  
Transport Component ◽  
Selective Channel ◽  
Substrate Concentrations

The effect of osmotic cell swelling on the permeability of HeLa cells to a range of structurally unrelated solutes including taurine, sorbitol, thymidine, choline, and K+ (96Rb+) was investigated. For each solute tested, reduction in the osmolality of the medium from 300 to 200 mosmol/kgH2O caused a significant increase in the unidirectional influx rate. In each case, the osmotically activated transport component was nonsaturable up to external substrate concentrations of 50 mM. Inhibitors of the swelling-activated anion channel of HeLa cells [quinine, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, niflumate, 1,9-dideoxyforskolin, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and tamoxifen] blocked the osmotically activated influx of each of the different substrates tested, as well as the osmotically activated efflux of taurine and I-. Tamoxifen and NPPB were similarly effective at blocking the osmotically activated efflux of 96Rb+. The simplest of several hypotheses consistent with the data is that the osmotically activated transport of the different solutes tested here is via a swelling-activated anion-selective channel that has a significant cation permeability and a minimum pore diameter of 8-9 A.

Characterization of a swelling-induced chloride conductance in cultured rat epididymal cells

1993 ◽  
Vol 265 (4) ◽  
pp. C997-C1005 ◽  
Author(s):  
H. C. Chan ◽  
W. O. Fu ◽  
Y. W. Chung ◽  
S. J. Huang ◽  
T. S. Zhou ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Induced Current ◽  
Whole Cell ◽  
Cyclic Monophosphate ◽  
Whole Cell Patch Clamp ◽  
Current Activation ◽  
Ethanesulfonic Acid ◽  
Cl Conductance

Swelling-induced Cl- conductance in cultured rat epididymal cells was characterized using whole cell patch-clamp techniques. Activation of whole cell current with an outwardly rectifying current-potential relationship was observed in cells exposed to hyposmotic solutions. This current was determined, from the observed current-reversal potentials at different Cl- concentrations, to be Cl- selective. The anion selectivity sequence of the swelling-induced Cl- conductance was I- approximately NO3- approximately Br- > Cl- > 2-(N-morpholino)ethanesulfonic acid. The swelling-induced Cl- conductance was reversibly inhibited by different Cl- channel blockers. Unlike diphenylamine-2-carboxylate or 5-nitro-2-(3-phenylpropylamino)-benzoate, which showed voltage-independent blockade, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid showed a marked voltage-dependent blockade of the volume-sensitive Cl- current, with a greater effect at depolarizing voltages. The swelling-induced Cl- conductance appeared to be different from the Ca(2+)- or adenosine 3',5'-cyclic monophosphate-activated Cl- conductances on the basis of the following observations: 1) swelling-induced current activation was seen even in the presence of kinase inhibitor (H-8) or absence of external free Ca2+, and 2) further increase in current activation could be produced by swelling after Ca(2+)- or adenosine 3',5'-cyclic monophosphate-induced current activation. The swelling-induced Cl- conductance may be involved in regulating epithelial cell volume as well as serving other important epididymal functions such as facilitating transepithelial secretion of organic compounds.

scholarly journals Vasodilator activity of extracts of field Alpinia purpurata (Vieill) K: Schum and A. zerumbet (Pers.) Burtt et Smith cultured in vitro

2009 ◽  
Vol 45 (3) ◽  
pp. 507-514 ◽  
Author(s):  
Cristiane Pimentel Victório ◽  
Ricardo Machado Kuster ◽  
Roberto Soares de Moura ◽  
Celso Luiz Salgueiro Lage
Keyword(s):  
Phenolic Compounds ◽  
Causes Of Death ◽  
Wistar Rat ◽  
Pharmacological Activities ◽  
Vasodilator Effect ◽  
Vasodilator Activity ◽  
Mesenteric Vascular Bed ◽  
Alpinia Purpurata ◽  
First Time

Nowadays, the high blood pressure is one of the main causes of death and cardiovascular diseases. Vasodilator drugs are frequently used to treat arterial hypertension. Experiments were undertaken to determine whether hydroalcoholic extracts obtained from leaves of field-grown Alpinia purpurata and A. zerumbet cultured in vitro under different plant growth regulators induce a vasodilator effect on Wistar rat mesenteric vascular bed pre-contracted with norepinephrine. Plant extracts were able to induce a long-lasting endothelium-dependent vasodilation. Efficiency on activity of A. purpurata reached 87% at concentration of 60 μg. The extract of A. zerumbet maintained in medium containing IAA, induced the relaxation (17.4%) at 90 μg, as compared to the control (MS0) that showed a better vasodilator effect (60%). These results are in agreement with the quantification of phenolic compounds in the extracts, which were 50% lower for those plants cultured in IAA. A. purpurata was assayed for the first time in relation to its vasodilator activity. This paper showed a strong probability of correlation between the pharmacological activities of A. purpurata with their content in phenolic compounds.

scholarly journals Preferential Pharmacological Inhibition of Nav1.6, but not Nav1.1, Abolishes Epileptiform Activity Induced by 4-AP in Mouse Cortical Slices

2020 ◽  
Author(s):  
Reesha R. Patel ◽  
Xingjie Ping ◽  
Shaun R. Patel ◽  
Jeff S. McDermott ◽  
Jeffrey L. Krajewski ◽  
...  
Keyword(s):  
Expression Patterns ◽  
Epileptiform Activity ◽  
Inhibitory Neurons ◽  
Hek293 Cells ◽  
Functional Roles ◽  
Voltage Gated Sodium Channels ◽  
Whole Cell Patch Clamp ◽  
Epileptic Syndromes ◽  
The Brain ◽  
Cortical Slices

ABSTRACTBrain isoforms of voltage-gated sodium channels (VGSCs) have distinct cellular and subcellular expression patterns as well as functional roles that are critical for normal physiology as aberrations in their expression or activity lead to pathophysiological conditions. In this study, we asked how inhibition of select isoforms of VGSCs alters epileptiform activity to further parse out the roles of VGSCs in the brain. We first determined the relative selectivity of recently discovered small molecule, aryl sulfonamide, inhibitors (ICA-121431 and Compound 801) against Nav1.1, Nav1.2, and Nav1.6 activity using whole-cell patch clamp recordings obtained from HEK293 cells. To test the effects of these inhibitors on epileptiform activity, we obtained multielectrode array (MEA) recordings from mouse cortical slices in the presence of 4-aminopyridine (4-AP) to induce epileptiform activity. We found that the ICA-121431 and Compound 801 compounds are relatively selective for Nav1.1 and Nav1.6, respectively. From the MEA recordings, we found that inhibition of Nav1.6 and Nav1.2 with 500nM of the Compound 801 compound completely abolishes ictal local field potentials induced by 4-AP, whereas inhibition of Nav1.1 with 500nM of the ICA-121431 compound had minimal effect on epileptiform activity induced by 4-AP. Due to the prominent expression of Nav1.1 in inhibitory neurons, we asked whether inhibition of Nav1.1 alone alters activity. We found that, indeed, inhibition of Nav1.1 with the ICA-121431 compound increased basal activity in the absence of 4-AP. These findings expand our current understanding of the roles of VGSC isoforms in the brain and suggest that selective targeting of Nav1.6 may be a more efficacious treatment strategy for epileptic syndromes.

Contribution of Ca2+-Permeable AMPA/KA Receptors to Glutamate-Induced Ca2+ Rise in Embryonic Lumbar Motoneurons In Situ

2000 ◽  
Vol 83 (1) ◽  
pp. 50-59 ◽  
Author(s):  
Friedrich Metzger ◽  
Anna Kulik ◽  
Michael Sendtner ◽  
Klaus Ballanyi
Keyword(s):  
Ampa Receptors ◽  
Cyclopiazonic Acid ◽  
Channel Blockers ◽  
Voltage Gated ◽  
Fura 2 ◽  
Combined Application ◽  
Predominant Component ◽  
Intracellular Ca ◽  
Trophic Signaling

Intracellular Ca2+([Ca2+]i) was fluorometrically measured with fura-2 in lumbar motoneurons of acutely isolated spinal cord slices from embryonic rats. In ester-loaded cells, bath-applied glutamate (3 μM to 1 mM) evoked a [Ca2+]i increase by up to 250 nM that was abolished by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) plus 2-amino-5-phosphonovalerate (APV). CNQX or APV alone reduced the response by 82 and 25%, respectively. The glutamatergic agonists kainate (KA), quisqualate (QUI), and S-α-amino-3-hydroxy-5-methyl-4-isoxalone (S-AMPA) evoked a similar [Ca2+]i transient as glutamate. N-methyl-d-aspartate (NMDA) was only effective to increase [Ca2+]i in Mg2+-free saline, whereas [1S,3R]-1-aminocyclopentane-1,3-dicarboxylic acid ([1S,3R]-ACPD) had no effect. The glutamate-induced [Ca2+]i rise was suppressed in Ca2+-free superfusate. Depletion of Ca2+ stores with cyclopiazonic acid (CPA) did not affect the response. Thirty-six percent of the [Ca2+]i increase in response to membrane depolarization induced by a 50 mM K+ solution persisted on combined application of the voltage-gated Ca2+channel blockers nifedipine, ω-conotoxin-GVIA and ω-agatoxin-IVA. In fura-2 dialyzed motoneurons, the glutamate-induced [Ca2+]i increase was attenuated by ∼70% after changing from current to voltage clamp. Forty percent of the remaining [Ca2+]i transient and 20% of the concomitant inward current of 0.3 nA were blocked by Joro spider toxin-3 (JSTX). The results show that voltage-gated Ca2+channels, including a major portion of R-type channels, constitute the predominant component of glutamate-induced [Ca2+]i rises. NMDA and Ca2+-permeable KA/AMPA receptors contribute about equally to the remaining component of the Ca2+ rise. The results substantiate previous assumptions that Ca2+ influx through JSTX-sensitive KA/AMPA receptors is involved in (trophic) signaling in developing motoneurons.

Swelling-activated efflux of taurine and other organic osmolytes in endothelial cells

1997 ◽  
Vol 273 (1) ◽  
pp. C214-C222 ◽  
Author(s):  
V. G. Manolopoulos ◽  
T. Voets ◽  
P. E. Declercq ◽  
G. Droogmans ◽  
B. Nilius
Keyword(s):  
Endothelial Cells ◽  
Anion Channel ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Organic Osmolytes ◽  
Dependent Manner ◽  
Anion Channels ◽  
Whole Cell Patch Clamp ◽  
Osmolyte Efflux ◽  
Dose Dependent

We used a combined biochemical, pharmacological, and electrophysiological approach to study the effects of hyposmotic swelling on organic osmolyte efflux in endothelial cells (EC). In [3H]taurine-loaded monolayers of calf pulmonary artery EC (CPAEC), hyposmolality activated time- and dose-dependent effluxes of [3H]taurine. Swelling-activated [3H]taurine efflux (Jtau swell)in CPAEC was inhibited by the anion channel blockers tamoxifen, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), fenamates, and also quinine (in a pH-dependent manner), ATP, and the phospholipase A2 inhibitor 4-bromophenacyl bromide. In contrast, Jtau swell was partly or totally insensitive to bumetanide, forskolin, phorbol 12-myristate 13-acetate, and staurosporine. Swelling also activated myo-[3H]inositol efflux that was blocked by tamoxifen, NPPB, DIDS, and niflumic acid. Moreover, the cellular content of taurine and other amino acids was significantly reduced in osmotically activated CPAEC. Finally, in whole cell patch-clamp experiments, taurine, glycine, aspartate, and glutamate exhibited significant permeability for swelling-activated anion channels. In conclusion, hyposmotic swelling activates efflux of taurine and other organic osmolytes in EC. In addition, our results suggest that anion channels may provide a pathway for swelling-activated efflux of organic osmolytes in EC.

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