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Voltage clamp

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https://www.readbyqxmd.com/read/28720714/maxi-k-channel-bkca-activity-veils-the-myogenic-tone-of-mesenteric-artery-in-rats
#1
Eun Yeong Suh, Ming Zhe Yin, Haiyue Lin, Yin Hua Zhang, Hae Young Yoo, Sung Joon Kim
Arterioles and small arteries change their tone in response to transmural pressure changes, called myogenic tone (MT). In comparison to the branches of cerebral arteries (CA) showing prominent MT, the third branches of mesenteric arteries (MA) with similar diameters show weaker MT Here, we aimed to analyze the electrophysiological differences responsible for the weaker MT in MA (MTMA) than MT in CA (MTCA). We measured ionic current using patch clamp in isolated MA smooth muscle cells (MASMCs) and CA smooth muscle cells (CASMCs) of rats...
July 2017: Physiological Reports
https://www.readbyqxmd.com/read/28720590/mechanisms-of-noncovalent-%C3%AE-subunit-regulation-of-nav-channel-gating
#2
Wandi Zhu, Taylor L Voelker, Zoltan Varga, Angela R Schubert, Jeanne M Nerbonne, Jonathan R Silva
Voltage-gated Na(+) (NaV) channels comprise a macromolecular complex whose components tailor channel function. Key components are the non-covalently bound β1 and β3 subunits that regulate channel gating, expression, and pharmacology. Here, we probe the molecular basis of this regulation by applying voltage clamp fluorometry to measure how the β subunits affect the conformational dynamics of the cardiac NaV channel (NaV1.5) voltage-sensing domains (VSDs). The pore-forming NaV1.5 α subunit contains four domains (DI-DIV), each with a VSD...
July 18, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/28716724/the-ppar%C3%AE-activator-fenofibrate-inhibits-voltage-dependent-k-channels-in-rabbit-coronary-arterial-smooth-muscle-cells
#3
Hongliang Li, Sung Eun Shin, Mi Seon Seo, Jin Ryeol An, Won-Kyo Jung, Kwon-Soo Ha, Eun-Taek Han, Seok-Ho Hong, Hyoweon Bang, Young Min Bae, Amy L Firth, Il-Whan Choi, Won Sun Park
We examined the effects of the PPARα activator fenofibrate on voltage-dependent K(+) (Kv) channels using a patch clamp technique in native rabbit coronary arterial smooth muscle cells. Kv current was inhibited by application of fenofibrate in a concentration-dependent manner, with an apparent IC50 value of 6.39 ± 0.53μM and a slope value (Hill coefficient) of 1.63 ± 0.10. Fenofibrate accelerated the decay rate of Kv channel inactivation. The rate constants of association and dissociation for fenofibrate were 0...
July 14, 2017: European Journal of Pharmacology
https://www.readbyqxmd.com/read/28711494/development-of-membrane-ion-channels-during-neural-differentiation-from-human-embryonic-stem-cells
#4
Sara Mirsadeghi, Ebrahim Shahbazi, Katayoun Hemmesi, Shiva Nemati, Hossein Baharvand, Javad Mirnajafi-Zadeh, Sahar Kiani
OBJECTIVE: For human embryonic stem cells (hESCs) to differentiate into neurons, enormous changes has to occur leading to trigger action potential and neurotransmitter release. We attempt to determine the changes in expression of voltage gated channels (VGCs) and their electrophysiological properties during neural differentiation. MATERIALS AND METHODS: The relative expressions of α-subunit of voltage gated potassium, sodium and calcium channels were characterized by qRT-PCR technique...
July 12, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28710864/localized-accumulation-of-cytosolic-calcium-near-the-fused-sperm-is-associated-with-the-calcium-and-voltage-dependent-block-of-sperm-entry-in-the-sea-urchin-egg
#5
Pedro I Ivonnet, Tatsuma Mohri, David H McCulloh
Sperm-egg interaction depolarizes the egg membrane, allowing the sperm to enter; however, if the egg membrane is not allowed to depolarize from its resting potential (e.g. by voltage-clamp), the sperm will not enter. Previous studies demonstrated that sperm entry into sea urchin eggs that are voltage-clamped at negative membrane potentials is regulated both by the egg's membrane potential and a voltage-dependent influx of calcium into the egg. In these cases, electrical or cytoplasmic continuity (sperm-egg membrane fusion) occurs at negative membrane potentials, but subsequent loss of cytoplasmic continuity results in failure of sperm entry (unfusion)...
July 15, 2017: Molecular Reproduction and Development
https://www.readbyqxmd.com/read/28710467/human-ipsc-derived-cardiomyocytes-cultured-in-3d-engineered-heart-tissue-show-physiological-upstroke-velocity-and-sodium-current-density
#6
Marc D Lemoine, Ingra Mannhardt, Kaja Breckwoldt, Maksymilian Prondzynski, Frederik Flenner, Bärbel Ulmer, Marc N Hirt, Christiane Neuber, András Horváth, Benjamin Kloth, Hermann Reichenspurner, Stephan Willems, Arne Hansen, Thomas Eschenhagen, Torsten Christ
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) are a promising tool for drug testing and modelling genetic disorders. Abnormally low upstroke velocity is a current limitation. Here we investigated the use of 3D engineered heart tissue (EHT) as a culture method with greater resemblance to human heart tissue in comparison to standard technique of 2D monolayer (ML) format. INa was measured in ML or EHT using the standard patch-clamp technique. INa density was ~1.8 fold larger in EHT (-18...
July 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28706450/reactive-oxygen-species-increase-neuronal-excitability-via-activation-of-nonspecific-cation-channel-in-rat-medullary-dorsal-horn-neurons
#7
Hae In Lee, Byung Rim Park, Sang Woo Chun
The caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn; MDH) receives direct inputs from small diameter primary afferent fibers that predominantly transmit nociceptive information in the orofacial region. Recent studies indicate that reactive oxygen species (ROS) is involved in persistent pain, primarily through spinal mechanisms. In this study, we aimed to investigate the role of xanthine/xanthine oxidase (X/XO) system, a known generator of superoxide anion (O2(·-)), on membrane excitability in the rat MDH neurons...
July 2017: Korean Journal of Physiology & Pharmacology
https://www.readbyqxmd.com/read/28705808/molecular-basis-of-altered-herg1-channel-gating-induced-by-ginsenoside-rg3
#8
Alison Gardner, Wei Wu, Steven Thomson, Eva-Maria Zangerl-Plessl, Anna Stary-Weinzinger, Michael Sanguinetti
Outward current conducted by human ether-a-g-go-related gene type 1 (hERG1) channels is a major determinant of action potential repolarization in the human ventricle. Ginsenoside 20(S)-Rg3 (Rg3), an alkaloid isolated from the root of Panax ginseng slows the rate of hERG1 deactivation, induces channels to open at more negative potentials than normal and increases current magnitude. The onset of Rg3 action is extremely fast, suggesting that it binds to an extracellular accessible site on the channel to alter its gating...
July 13, 2017: Molecular Pharmacology
https://www.readbyqxmd.com/read/28704758/deconstruction-reconstruction-approach-to-analyze-the-essential-structural-elements-of-tetrahydro-3-benzazepine-based-antagonists-of-glun2b-subunit-containing-nmda-receptors
#9
Sougata Dey, Louisa Temme, Julian A Schreiber, Dirk Schepmann, Bastian Frehland, Kirstin Lehmkuhl, Nathalie Strutz-Seebohm, Guiscard Seebohm, Bernhard Wünsch
The role of the phenolic and benzylic OH moieties for the interaction of tetrahydro-3-benzazepine-1,7-diol 3d with GluN2B subunit containing NMDA receptors was analyzed by their stepwise removal. Elimination of trifluormethanesulfinate from 10 and 13 represent the key steps in the synthesis. Removal of phenolic OH moiety led to 5-fold reduced GluN2B affinity of 4d compared with 3d. Additional removal of the benzylic OH moiety (5d) resulted in further reduced GluN2B affinity but increased σ1 and σ2 affinities...
July 1, 2017: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28701925/postsynaptic-gaba-b-receptors-contribute-to-the-termination-of-giant-depolarizing-potentials-in-ca3-neonatal-rat-hippocampus
#10
Ilgam Khalilov, Marat Minlebaev, Marat Mukhtarov, Elvira Juzekaeva, Roustem Khazipov
During development, hippocampal CA3 network generates recurrent population bursts, so-called Giant Depolarizing Potentials (GDPs). GDPs are characterized by synchronous depolarization and firing of CA3 pyramidal cells followed by afterhyperpolarization (GDP-AHP). Here, we explored the properties of GDP-AHP in CA3 pyramidal cells using gramicidin perforated patch clamp recordings from neonatal rat hippocampal slices. We found that GDP-AHP occurs independently of whether CA3 pyramidal cells fire action potentials (APs) or remain silent during GDPs...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28700658/nanosecond-electric-pulses-differentially-affect-inward-and-outward-currents-in-patch-clamped-adrenal-chromaffin-cells
#11
Lisha Yang, Gale L Craviso, P Thomas Vernier, Indira Chatterjee, Normand Leblanc
This study examined the effect of 5 ns electric pulses on macroscopic ionic currents in whole-cell voltage-clamped adrenal chromaffin cells. Current-voltage (I-V) relationships first established that the early peak inward current was primarily composed of a fast voltage-dependent Na+ current (INa), whereas the late outward current was composed of at least three ionic currents: a voltage-gated Ca2+ current (ICa), a Ca2+-activated K+ current (IK(Ca)), and a sustained voltage-dependent delayed rectifier K+ current (IKV)...
2017: PloS One
https://www.readbyqxmd.com/read/28696213/ca-2-regulation-of-cav3-3-t-type-ca-2-channel-is-mediated-by-calmodulin
#12
Narae Lee, Sua Jeong, Kang-Chang Kim, Jin-Ah Kim, Jin-Yong Park, Ho-Won Kang, Edward Perez-Reyes, Jung-Ha Lee
Numerous investigations reported that increases of internal Ca(2+) (Ca(2+)i) pivotally regulate high voltage-activated (HVA) Ca(2+) channels via calmodulin (CaM). However, it is largely elusive that Ca(2+)i can regulate low voltage-activated T-type Ca(2+) channels. Using whole cell patch clamp, we compared the biophysical properties of Ca(2+) current through T-type Ca(2+) channel Cav3.1, Cav3.2, or Cav3.3 stably expressed in HEK293 cells between internal solutions containing 27 nM and l μM free Ca(2+) Both activation and inactivation kinetics of Cav3...
July 10, 2017: Molecular Pharmacology
https://www.readbyqxmd.com/read/28695626/mucosal-glucagon-like-peptide-1-glp-1-responses-are-mediated-by-calcitonin-gene-related-peptide-cgrp-in-the-mouse-colon-and-both-peptide-responses-are-area-specific
#13
I R Tough, R Moodaley, H M Cox
BACKGROUND: Glucagon-like peptide (GLP)-1 is an incretin hormone and its mimetics are proven antidiabetic and antiobesity drugs. GLP-1 exerts antimotility and mucosal proliferative activities but its epithelial ion transport effects are uncharacterized and these may contribute to the gastrointestinal (GI) disturbance, i.e., diarrhea experienced with some GLP-1 mimetics. Our aim was to establish GLP-1 agonist mechanisms and identify potential mucosal mediator(s) in the colonic tissue from C57BL/6J mice...
July 11, 2017: Neurogastroenterology and Motility: the Official Journal of the European Gastrointestinal Motility Society
https://www.readbyqxmd.com/read/28683073/high-throughput-electrophysiological-assays-for-voltage-gated-ion-channels-using-syncropatch-768pe
#14
Tianbo Li, Gang Lu, Eugene Y Chiang, Tania Chernov-Rogan, Jane L Grogan, Jun Chen
Ion channels regulate a variety of physiological processes and represent an important class of drug target. Among the many methods of studying ion channel function, patch clamp electrophysiology is considered the gold standard by providing the ultimate precision and flexibility. However, its utility in ion channel drug discovery is impeded by low throughput. Additionally, characterization of endogenous ion channels in primary cells remains technical challenging. In recent years, many automated patch clamp (APC) platforms have been developed to overcome these challenges, albeit with varying throughput, data quality and success rate...
2017: PloS One
https://www.readbyqxmd.com/read/28677751/effects-of-rmf-on-bkca-and-kv-channels-in-basilar-arterial-smooth%C3%A2-muscle-cells-of-shr
#15
Yan-Fei Qian, Yang Wang, Wei-Wei Tian, Sheng Wang, Lei Zhao, Li Li, Ke-Tao Ma, Jun-Qiang Si
The current study observed the effects and investigated the mechanism of remifentanil (RMF) on the isolated cerebral basilar arteries of spontaneously hypertensive rats (SHR) and Wistar‑Kyoto (WKY) rats. A pressure myograph system was used to observe and compare the effects of different concentrations of RMF (10‑10‑10‑5 mol/l) on the diameter changes of freshly isolated cerebral basilar arteries, which have been pre‑shrunk by phenylephrine (PE), an endothelium‑independent vasoconstrictor. Vascular smooth‑muscle cells of the cerebral basilar artery (BASMCs) were freshly obtained via enzymolysis...
June 29, 2017: Molecular Medicine Reports
https://www.readbyqxmd.com/read/28676563/melatonin-mediates-vasodilation-through-both-direct-and-indirect-activation-of-bkca-channels
#16
Tengteng Zhao, Huirong Zhang, Cheng Jin, Fang Qiu, Ying Wu, Lijun Shi
Melatonin, synthesized primarily by the pineal gland, is a neuroendocrine hormone with high membrane permeability. The vascular effects of melatonin, including vasoconstriction and vasodilation, have been demonstrated in numerous studies. However, the mechanisms underlying these effects are not fully understood. Large-conductance Ca2+-activated K+ (BKCa) channels are expressed broadly on smooth muscle cells and play an important role in vascular tone regulation. The present study explored the mechanisms of myocyte BKCa channels and endothelial factors underlying the action of melatonin on the mesenteric arteries (MAs)...
July 4, 2017: Journal of Molecular Endocrinology
https://www.readbyqxmd.com/read/28673509/discovery-of-a-new-mexiletine-derived-agonist-of-the-herg-k-channel
#17
Roberta Gualdani, Maria Maddalena Cavalluzzi, Francesco Tadini-Buoninsegni, Giovanni Lentini
The human Ether-a-go-go Related Gene (hERG) potassium channel plays a central role in the rapid component (IKr) of cardiac action potential repolarization phase. A large number of structurally different compounds block hERG and cause a high risk of arrhythmias. Among the drugs that block hERG channel, a few compounds have been identified as hERG channel activators. Such compounds may be useful, at least in theory, for the treatment of long term QT syndrome. Here we describe a new activator of hERG channel, named MC450...
June 19, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28672906/t-lymphocyte-kv1-3-channel-activation-triggers-the-nlrp3-inflammasome-signaling-pathway-in-hypertensive-patients
#18
Jian Zhu, Yan Yang, Si-Gan Hu, Qiu-Bing Zhang, Jie Yu, Yuan-Ming Zhang
The aim of the current study was to investigate the correlation between voltage-gated potassium 1.3 (Kv1.3) channel of peripheral blood T-lymphocytes and the NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway in hypertensive patients. Peripheral blood samples from the hypertensive Kazakh patients (n=30) and healthy Kazakh subjects (n=30) were collected. The T lymphocytes and serum were separated, and the state of Kv1.3 channels was detected using the patch-clamp technique. Reverse transcription-quantitative polymerase chain reaction and western blot analyses were used to detect the mRNA and protein expression levels of key molecules [NLRP3, caspase-1 and interleuking (IL)-β] in the lymphocyte NLRP3 inflammasome pathway, while serum IL-1β content was measured by ELISA assay...
July 2017: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/28672825/maitotoxin-is-a-potential-selective-activator-of-the-endogenous-transient-receptor-potential-canonical-type-1-channel-in-xenopus-laevis-oocytes
#19
Pedro L Flores, Emma Rodríguez, Estrella Zapata, Roxana Carbó, José María Farías, Martín Martínez
Maitotoxin (MTX) is the most potent marine toxin known to date. It is responsible for a particular human intoxication syndrome called ciguatera fish poisoning (CFP). Several reports indicate that MTX is an activator of non-selective cation channels (NSCC) in different cell types. The molecular identity of these channels is still an unresolved topic, and it has been proposed that the transient receptor potential (TRP) channels are involved in this effect. In Xenopus laevis oocytes, MTX at picomolar (pM) concentrations induces the activation of NSCC with functional and pharmacological properties that resemble the activity of TRP channels...
June 25, 2017: Marine Drugs
https://www.readbyqxmd.com/read/28668511/voltage-sensitive-potassium-channels-expressed-after-20-hydroxyecdysone-treatment-of-a-mosquito-cell-line
#20
Lacey J Jenson, Baonan Sun, Jeffrey R Bloomquist
The goal of this research was to express receptors and ion channels in hormone-treated insect cell lines. Treatment of Anopheles gambiae Sua1B cells with 20-hydroxyecdysone showed an inhibition of cell growth over a time course of three days, with no change in cellular morphology. The effect of 20-hydroxyecdysone was enhanced in the presence of the potassium channel blocker 4-aminopyridine, but not tetraethylammonium. Concentration-response curves of 4-aminopyridine in the presence of 42 μM (1 mg/ml) 20-hydroxyecdysone showed similar IC50 values (6-10 μM) across 3 day exposures...
June 28, 2017: Insect Biochemistry and Molecular Biology
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