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https://www.readbyqxmd.com/read/28921695/frequency-dependent-regulation-of-intrinsic-excitability-by-voltage-activated-membrane-conductances-computational-modeling-and-dynamic-clamp
#1
Attila Szűcs, Anikó Rátkai, Katalin Schlett, Ramon Huerta
As one of the most unique properties of nerve cells, their intrinsic excitability allows them to transform synaptic inputs into action potentials. This process reflects a complex interplay between the synaptic inputs and the voltage-dependent membrane currents of the postsynaptic neuron. While neurons in natural conditions mostly fire under the action of intense synaptic bombardment and receive fluctuating patterns of excitation and inhibition, conventional techniques to characterize intrinsic excitability mainly utilize static means of stimulation...
September 16, 2017: European Journal of Neuroscience
https://www.readbyqxmd.com/read/28919864/%C3%AE-subunits-control-the-effects-of-human-kv4-3-potassium-channel-phosphorylation
#2
Geoffrey W Abbott
The transient outward K(+) current, Ito, activates early in the cardiac myocyte action potential, to begin repolarization. Human Ito is generated primarily by two Kv4.3 potassium channel α subunit splice variants (Kv4.3L and Kv4.3S) that diverge only by a C-terminal, membrane-proximal, 19-residue stretch unique to Kv4.3L. Protein kinase C (PKC) phosphorylation of threonine 504 within the Kv4.3L-specific 19-residues mediates α-adrenergic inhibition of Ito in human heart. Kv4.3 is regulated in human heart by various β subunits, including cytosolic KChIP2b and transmembrane KCNEs, yet their impact on the functional effects of human Kv4...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28917093/molecular-cloning-and-functional-expression-of-the-k-channel-kv7-1-and-the-regulatory-subunit-kcne1-from-equine-myocardium
#3
Philip J Pedersen, Kirsten B Thomsen, Jon B Flak, Maria A Tejada, Frank Hauser, Dagmar Trachsel, Rikke Buhl, Theodore Kalbfleisch, Michael Scott DePriest, James N MacLeod, Kirstine Calloe, Dan A Klaerke
BACKGROUND: The voltage-gated K(+)-channel KV7.1 and the subunit KCNE1, encoded by the KCNQ1 and KCNE1 genes, respectively, are responsible for termination of the cardiac action potential. In humans, mutations in these genes can predispose patients to arrhythmias and sudden cardiac death (SCD). AIM: To characterize equine KV7.1/KCNE1 currents and compare them to human KV7.1/KCNE1 currents to determine whether KV7.1/KCNE1 plays a similar role in equine and human hearts...
September 11, 2017: Research in Veterinary Science
https://www.readbyqxmd.com/read/28910447/orexin-a-suppresses-signal-transmission-to-dopaminergic-amacrine-cells-from-outer-and-inner-retinal-photoreceptors
#4
Sheng-Nan Qiao, Wei Zhou, Lei-Lei Liu, Dao-Qi Zhang, Yong-Mei Zhong
Purpose: The neuropeptides orexin-A and orexin-B are widely expressed in the vertebrate retina; however, their role in visual function is unclear. This study investigates whether and how orexins modulate signal transmission to dopaminergic amacrine cells (DACs) from both outer retinal photoreceptors (rods and cones) and inner retinal photoreceptors (melanopsin-expressing intrinsically photosensitive retinal ganglion cells [ipRGCs]). Methods: A whole-cell voltage-clamp technique was used to record light-induced responses from genetically labeled DACs in flat-mount mouse retinas...
September 1, 2017: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/28905186/antidepressants-inhibit-nav1-3-nav1-7-and-nav1-8-neuronal-voltage-gated-sodium-channels-more-potently-than-nav1-2-and-nav1-6-channels-expressed-in-xenopus-oocytes
#5
Takafumi Horishita, Nobuyuki Yanagihara, Susumu Ueno, Dan Okura, Reiko Horishita, Tomoko Minami, Yuichi Ogata, Yuka Sudo, Yasuhito Uezono, Takeyoshi Sata, Takashi Kawasaki
Tricyclic antidepressants (TCAs) and duloxetine are used to treat neuropathic pain. However, the mechanisms underlying their analgesic effects remain unclear. Although many investigators have shown inhibitory effects of antidepressants on voltage-gated sodium channels (Nav) as a possible mechanism of analgesia, to our knowledge, no one has compared effects on the diverse variety of sodium channel α subunits. We investigated the effects of antidepressants on sodium currents in Xenopus oocytes expressing Nav1...
September 14, 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/28904098/characterization-of-ion-channels-and-o2-sensitivity-in-gill-neuroepithelial-cells-of-the-anoxia-tolerant-goldfish-carassius-auratus
#6
Peter C Zachar, Wen Pan, Michael G Jonz
The neuroepithelial cell (NEC) of the fish gill is an important model for O2 sensing in vertebrates; however, a complete picture of the chemosensory mechanisms in NECs is lacking, and O2 chemoreception in vertebrates that are tolerant to anoxia has yet not been explored. Using whole-cell patch-clamp recording, we characterized four types of ion channels in NECs isolated from the anoxia-tolerant goldfish. A Ca(2+)-dependent K(+) current (IKCa) peaked at ~20 mV, was potentiated by increased intracellular Ca(2+), and was reduced by 100 μM Cd(2+) A voltage-dependent inward current in Ba(2+) solution, with peak at 0 mV, confirmed the presence of Ca(2+) channels...
September 13, 2017: Journal of Neurophysiology
https://www.readbyqxmd.com/read/28902151/apetx4-a-novel-sea-anemone-toxin-and-a-modulator-of-the-cancer-relevant-potassium-channel-kv10-1
#7
Lien Moreels, Steve Peigneur, Diogo T Galan, Edwin De Pauw, Lászlo Béress, Etienne Waelkens, Luis A Pardo, Loïc Quinton, Jan Tytgat
The human ether-à-go-go channel (hEag1 or KV10.1) is a cancer-relevant voltage-gated potassium channel that is overexpressed in a majority of human tumors. Peptides that are able to selectively inhibit this channel can be lead compounds in the search for new anticancer drugs. Here, we report the activity-guided purification and electrophysiological characterization of a novel KV10.1 inhibitor from the sea anemone Anthopleura elegantissima. Purified sea anemone fractions were screened for inhibitory activity on KV10...
September 13, 2017: Marine Drugs
https://www.readbyqxmd.com/read/28901191/hypoxic-culture-promotes-dopaminergic-neuronal-differentiation-of-nasal-olfactory-mucosa-mesenchymal-stem-cells-via-upregulation-of-hypoxia-inducible-factor-1%C3%AE
#8
Yi Zhuo, Lei Wang, Lite Ge, Xuan Li, Da Duan, Xiaohua Teng, Miao Jiang, Kai Liu, Ting Yuan, Pei Wu, Hao Wang, Yujia Deng, Huali Xie, Ping Chen, Ying Xia, Ming Lu
Olfactory mucosa mesenchymal stem cells (OM-MSCs) display significant clonogenic activity and may be easily propagated for Parkinson's disease therapies. Methods of inducing OM-MSCs to differentiate into dopaminergic (DAergic) neurons using olfactory ensheathing cells (OECs) are thus an attractive topic of research. We designed a hypoxic induction protocol to generate DAergic neurons from OM-MSCs using a physiological oxygen (O2) level of 3% and OEC-conditioned medium (OCM; HI group). The normal induction (NI) group was cultured in O2 at ambient air level (21%)...
August 2017: Cell Transplantation
https://www.readbyqxmd.com/read/28900735/4-chloro-3-nitro-n-butylbenzenesulfonamide-acts-on-kv3-1-channels-by-an-open-channel-blocker-mechanism
#9
Carlos Alberto Zanutto Bassetto Junior, Wamberto Antonio Varanda, Eduardo René Pérez González
The effects of 4-chloro-3-nitro-N-butylbenzenesulfonamide (SMD2) on KV3.1 channels, heterologous expressed in L-929 cells, were studied with the whole cell patch-clamp technique. SMD2 blocks KV3.1 in a reversible and use-dependent manner, with IC50 around 10 µM, and a Hill coefficient around 2. Although the conductance vs. voltage relationship in control condition can be described by a single Boltzmann function, two terms are necessary to describe the data in the presence of SMD2. The activation and deactivation time constants are weakly voltage dependent both for control and in the presence of SMD2...
September 12, 2017: Amino Acids
https://www.readbyqxmd.com/read/28898995/uncovering-the-arrhythmogenic-potential-of-trpm4-activation-in-atrial-derived-hl-1-cells-using-novel-recording-and-numerical-approaches
#10
Yaopeng Hu, Yubin Duan, Ayako Takeuchi, Lin Hai-Kurahara, Jun Ichikawa, Keizo Hiraishi, Tomohiro Numata, Hiroki Ohara, Gentaro Iribe, Michio Nakaya, Masayuki X Mori, Satoshi Matsuoka, Genshan Ma, Ryuji Inoue
Aims: Transient receptor potential cation channel subfamily melastatin member 4 (TRPM4), a Ca2+-activated nonselective cation channel abundantly expressed in the heart, has been implicated in conduction block and other arrhythmic propensities associated with cardiac remodelling and injury. The present study aimed to quantitatively evaluate the arrhythmogenic potential of TRPM4. Methods and results: Patch clamp and biochemical analyses were performed using expression system and an immortalized atrial cardiomyocyte cell line (HL-1), and numerical model simulation was employed...
August 1, 2017: Cardiovascular Research
https://www.readbyqxmd.com/read/28898267/depolarization-of-the-conductance-voltage-relationship-in-the-nav1-5-mutant-e1784k-is-due-to-altered-fast-inactivation
#11
Colin H Peters, Alec Yu, Wandi Zhu, Jonathan R Silva, Peter C Ruben
E1784K is the most common mixed long QT syndrome/Brugada syndrome mutant in the cardiac voltage-gated sodium channel NaV1.5. E1784K shifts the midpoint of the channel conductance-voltage relationship to more depolarized membrane potentials and accelerates the rate of channel fast inactivation. The depolarizing shift in the midpoint of the conductance curve in E1784K is exacerbated by low extracellular pH. We tested whether the E1784K mutant shifts the channel conductance curve to more depolarized membrane potentials by affecting the channel voltage-sensors...
2017: PloS One
https://www.readbyqxmd.com/read/28891257/the-k-channel-kzm2-is-involved-in-stomatal-movement-by-modulating-inward-k-currents-in-maize-guard-cells
#12
Yong-Qiang Gao, Wei-Hua Wu, Yi Wang
Stomata are the major gates in plant leaf that allow water and gas exchange, which is essential for plant transpiration and photosynthesis. Stomatal movement is mainly controlled by the ion channels and transporters in guard cells. In Arabidopsis, the inward Shaker K(+) channels, such as KAT1 and KAT2, are responsible for stomatal opening. However, the characterization of inward K(+) channels in maize guard cells is limited. In the present study, we identified two KAT1-like Shaker K(+) channels, KZM2 and KZM3, which were highly expressed in maize guard cells...
September 11, 2017: Plant Journal: for Cell and Molecular Biology
https://www.readbyqxmd.com/read/28888063/sumo-co-expression-modifies-kv-11-1-channel-activity
#13
Annette Buur Steffensen, Martin Nybo Andersen, Nancy Mutsaers, Amer Mujezinovic, Nicole Schmitt
AIM: The voltage-gated potassium channel KV 11.1 is the molecular basis for the IKr current which plays an important role in cardiac physiology. Its malfunction is associated with both inherited and acquired cardiac arrhythmias. Native currents differ from those in experimental models, suggesting additional regulatory mechanisms. We hypothesised that the post-translational modification sumoylation finetunes channel activity. METHODS: The functional effects of sumoylation on KV 11...
September 9, 2017: Acta Physiologica
https://www.readbyqxmd.com/read/28882890/c-terminal-phosphorylation-of-nav1-5-impairs-fgf13-dependent-regulation-of-channel-inactivation
#14
Sophie Burel, Fabien C Coyan, Maxime Lorenzini, Matthew R Meyer, Cheryl F Lichti, Joan H Brown, Gildas Loussouarn, Flavien Charpentier, Jeanne M Nerbonne, R Reid Townsend, Lars S Maier, Céline Marionneau
Voltage-gated Na(+) (NaV) channels are key regulators of myocardial excitability, and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders, and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1...
September 7, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28880874/discovery-and-mode-of-action-of-a-novel-analgesic-%C3%AE-toxin-from-the-african-spider-ceratogyrus-darlingi
#15
Silmara R Sousa, Joshua S Wingerd, Andreas Brust, Christopher Bladen, Lotten Ragnarsson, Volker Herzig, Jennifer R Deuis, Sebastien Dutertre, Irina Vetter, Gerald W Zamponi, Glenn F King, Paul F Alewood, Richard J Lewis
Spider venoms are rich sources of peptidic ion channel modulators with important therapeutical potential. We screened a panel of 60 spider venoms to find modulators of ion channels involved in pain transmission. We isolated, synthesized and pharmacologically characterized Cd1a, a novel peptide from the venom of the spider Ceratogyrus darlingi. Cd1a reversibly paralysed sheep blowflies (PD50 of 1318 pmol/g) and inhibited human Cav2.2 (IC50 2.6 μM) but not Cav1.3 or Cav3.1 (IC50 > 30 μM) in fluorimetric assays...
2017: PloS One
https://www.readbyqxmd.com/read/28878623/mechanisms-of-spontaneous-climbing-fiber-discharge-evoked-pauses-and-output-modulation-of-cerebellar-purkinje-cell-in-mice
#16
Xian-Hua Jin, Hong-Wei Wang, Xin-Yuan Zhang, Chun-Ping Chu, Yuan-Zhe Jin, Song-Biao Cui, De-Lai Qiu
Climbing fiber (CF) afferents modulate the frequency and patterns of cerebellar Purkinje cell (PC) simple spike (SS) activity, but its mechanism is unclear. In the present study, we investigated the mechanisms of spontaneous CF discharge-evoked pauses and the output modulation of cerebellar PCs in urethane-anesthetized mice using in vivo whole-cell recording techniques and pharmacological methods. Under voltage-clamp recording conditions, spontaneous CF discharge evoked strong inward currents followed by small conductance calcium-activated potassium (SK) channels that mediated outward currents...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28874774/current-direction-amplitude-dependent-single-channel-gating-kinetics-of-mouse-pannexin-1-channel-a-new-concept-for-gating-kinetics
#17
Takeshi Nomura, Akiyuki Taruno, Makoto Shiraishi, Takashi Nakahari, Toshio Inui, Masahiro Sokabe, Douglas C Eaton, Yoshinori Marunaka
The detailed single-channel gating kinetics of mouse pannexin 1 (mPanx1) remains unknown, although mPanx1 is reported to be a voltage-activated anion-selective channel. We investigated characteristics of single-channel conductances and opening and closing rates of mPanx1 using patch-clamp techniques. The unitary current of mPanx1 shows outward rectification with single-channel conductances of ~20 pS for inward currents and ~80 pS for outward currents. The channel open time for outward currents (Cl(-) influx) increases linearly as the amplitude of single channel currents increases, while the open time for inward currents (Cl(-) efflux) is constant irrespective of changes in the current amplitude, as if the direction and amplitude of the unitary current regulates the open time...
September 5, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28871229/gabapentin-modulates-hcn4-channel-voltage-dependence
#18
Han-Shen Tae, Kelly M Smith, A Marie Phillips, Kieran A Boyle, Melody Li, Ian C Forster, Robert J Hatch, Robert Richardson, David I Hughes, Brett A Graham, Steven Petrou, Christopher A Reid
Gabapentin (GBP) is widely used to treat epilepsy and neuropathic pain. There is evidence that GBP can act on hyperpolarization-activated cation (HCN) channel-mediated Ih in brain slice experiments. However, evidence showing that GBP directly modulates HCN channels is lacking. The effect of GBP was tested using two-electrode voltage clamp recordings from human HCN1, HCN2, and HCN4 channels expressed in Xenopus oocytes. Whole-cell recordings were also made from mouse spinal cord slices targeting either parvalbumin positive (PV(+)) or calretinin positive (CR(+)) inhibitory neurons...
2017: Frontiers in Pharmacology
https://www.readbyqxmd.com/read/28868308/phosphodiesterases-3-and-4-differentially-regulate-the-funny-current-if-in-mouse-sinoatrial-node-myocytes
#19
Joshua R St Clair, Eric D Larson, Emily J Sharpe, Zhandi Liao, Catherine Proenza
Cardiac pacemaking, at rest and during the sympathetic fight-or-flight response, depends on cAMP (3',5'-cyclic adenosine monophosphate) signaling in sinoatrial node myocytes (SAMs). The cardiac "funny current" (If) is among the cAMP-sensitive effectors that drive pacemaking in SAMs. If is produced by hyperpolarization-activated, cyclic nucleotide-sensitive (HCN) channels. Voltage-dependent gating of HCN channels is potentiated by cAMP, which acts either by binding directly to the channels or by activating the cAMP-dependent protein kinase (PKA), which phosphorylates them...
September 2017: Journal of Cardiovascular Development and Disease
https://www.readbyqxmd.com/read/28865873/statin-therapy-exacerbates-alcohol-induced-constriction-of-cerebral-arteries-via-modulation-of-ethanol-induced-bk-channel-inhibition-in-vascular-smooth-muscle
#20
Maria N Simakova, Shivantika Bisen, Alex M Dopico, Anna N Bukiya
Statins constitute the most commonly prescribed drugs to decrease cholesterol (CLR). CLR is an important modulator of alcohol-induced cerebral artery constriction (AICAC). Using rats on a high CLR diet (2% CLR) we set to determine whether atorvastatin administration (10mg/kg daily for 18-23weeks) modified AICAC. Middle cerebral arteries were pressurized in vitro at 60mmHg and AICAC was evoked by 50mM ethanol, that is within the range of blood alcohol detected in humans following moderate-to-heavy drinking. AICAC was evident in high CLR+atorvastatin group but not in high CLR diet+placebo...
September 1, 2017: Biochemical Pharmacology
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