Looking for online definition of Voltage-gated sodium channel subunit alpha Nav1.6 in the Medical Dictionary? Voltage-gated sodium channel subunit alpha Nav1.6 explanation free. What is Voltage-gated sodium channel subunit alpha Nav1.6? Meaning of Voltage-gated sodium channel subunit alpha Nav1.6 medical term. What does Voltage-gated sodium channel subunit alpha Nav1.6 mean?
Title: Voltage-Gated Sodium Channel Blockers; Target Validation and Therapeutic Potential. VOLUME: 5 ISSUE: 6. Author(s): John N. Wood and James Boorman. Affiliation:Molecular Nociception Group, Biology UCL, Gower Street, London WC1 E 6BT.. Abstract: Voltage-gated sodium channels are encoded by a family of ten structurally-related genes that are expressed in spatially and temporally distinct patterns, mainly in excitable tissues. They underlie electrical signalling in nerve and muscle. It has long been known that sodium channel blockers are anaesthetics as well as powerful analgesics when delivered at low concentrations. In addition, cardiac arrhythmias and epileptic activity can be treated with sodium channel blockers. As we have learned more about the sub-types of sodium channels and their distribution, new therapeutic opportunities have suggested themselves. There are indications that sodium channel blockers may also be useful in affective disorders and schizophrenia. The production of ...
The (−)-gallocatechin-3-gallate (GCG) concentration in some tea beverages can account for as much as 50% of the total catechins. It has been shown that catechins have analgesic properties. Voltage-gated sodium channels (Nav) mediate neuronal action potentials. Tetrodotoxin inhibits all Nav isoforms, but Nav1.8 and Nav1.9 are relatively tetrodotoxin-resistant compared to other isoforms and functionally linked to nociception. In this study, the effects of GCG on tetrodotoxin-resistant Na+ currents were investigated in rat primary cultures of dorsal root ganglion neurons via the whole-cell patch-clamp technique. We found that 1 μM GCG reduced the amplitudes of peak current density of tetrodotoxin-resistant Na+ currents significantly. Furthermore, the inhibition was accompanied by a depolarizing shift of the activation voltage and a hyperpolarizing shift of steady-state inactivation voltage. The percentage block of GCG (1 μM) on tetrodotoxin-resistant Na+ current was 45.1% ± 1.1% in 10 min. In
TY - JOUR. T1 - Gambierol acts as a functional antagonist of neurotoxin site 5 on voltage-gated sodium channels in cerebellar granule neurons. AU - LePage, K. T.. AU - Rainier, J. D.. AU - Johnson, H. W.B.. AU - Baden, D. G.. AU - Murray, Thomas F.. PY - 2007/10/1. Y1 - 2007/10/1. N2 - The marine toxin gambierol, a polyether ladder toxin derived from the marine dinoflagellate Gambierdiscus toxicus, was evaluated for interaction with voltage-gated sodium channels (VGSCs) in cerebellar granule neuron (CGN) cultures. At concentrations ranging from 10 nM to 10 μM, gambierol alone had no effect on the intracellular Ca2+ concentration [Ca 2+]i of exposed CGN cultures. Furthermore, there was no evidence of neurotoxicity in CGN cultures exposed for 2 h to gambierol (1 nM-10 μM). However, gambierol was a potent inhibitor (IC50 = 189 nM) of the elevation of [Ca2+]i that accompanies exposure of CGN cultures to the VGSC activator brevetoxin-2 (PbTx-2). To further explore the potential interaction of ...
The amiloride-sensitive epithelial sodium channel (ENaC) plays a critical role in fluid and electrolyte homeostasis and consists of alpha, beta, and gamma subunits. The carboxyl terminus of each ENaC subunit contains a PPxY, motif which is believed to be important for interaction with the WW domains of the ubiquitin-protein ligase, Nedd4. Disruption of this interaction, as in Liddles syndrome, where mutations delete or alter the PPxY motif of either the beta or gamma subunits, has been proposed to result in increased ENaC activity. Here we present evidence that KIAA0439 protein, a close relative of Nedd4, is also a potential regulator of ENaC. We demonstrate that KIAA0439 WW domains bind all three ENaC subunits. We show that a recombinant KIAA0439 WW domain protein acts as a dominant negative mutant that can interfere with the Na(+)-dependent feedback inhibition of ENaC in whole-cell patch clamp experiments. We propose that KIAA0439 and Nedd4 proteins either play a redundant role in ENaC ...
TY - JOUR. T1 - The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes. T2 - Dipnoi). AU - Uchiyama, Minoru. AU - Maejima, Sho. AU - Yoshie, Sumio. AU - Kubo, Yoshihiro. AU - Konno, Norifumi. AU - Joss, Jean M P. PY - 2012. Y1 - 2012. N2 - Epithelial sodium channel (ENaC) is a Na+-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na+ absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaCα, β and γ proteins. The nENaCα, β and γ subunits are closely related to ...
Experiments are often performed to study the behaviour of a single ion channel in response to a perturbation produced by a step change (jump) in a variable that influences its equilibrium position, for example a voltage jump or jump in agonist concentration. It is also common to apply a rectangular pulse (consisting of an on jump followed by an off jump); for example brief concentration pulses are used to mimic synaptic transmission.. Assuming a general Markov mechanism for channel dynamics, we obtain theoretical probability distributions of observable characteristics that describe the non-stationary behaviour of single ion channels which are subject to a jump, or to a pulse of finite duration. These characteristics are such things as open times, shut times, first latency, burst length and length of activation. We concentrate particularly on jumps to or from a zero level of agonist, which necessitates some modification to the usual arguments to cope with having some absorbing sets of states. ...
Ionic channel activity is involved in fundamental cellular behaviour and participates in cancerous features such as proliferation, migration and invasion which in turn contribute to the metastatic process. In this study, we investigated the expression and role of voltage-gated sodium channels in non-small-cell lung cancer cell lines. Functional voltage-gated sodium channels expression was investigated in normal and non-small-cell lung cancer cell lines. The measurement, in patch-clamp conditions, of tetrodotoxin-inhibitable sodium currents indicated that the strongly metastatic cancerous cell lines H23, H460 and Calu-1 possess functional sodium channels while normal and weakly metastatic cell lines do not. While all the cell lines expressed mRNA for numerous sodium channel isoforms, only H23, H460 and Calu-1 cells had a 250 kDa protein corresponding to the functional channel. The other cell lines also had another protein of 230 kDa which is not addressed to the membrane and might act as a dominant
TY - JOUR. T1 - Neuronal voltage-gated sodium channel subtypes. T2 - Key roles in inflammatory and neuropathic pain. AU - Ekberg, J.. AU - Adams, David J.. PY - 2006. Y1 - 2006. N2 - Voltage-gated sodium channels (VGSCs) play an important role in neuronal excitability. Regulation of VGSC activity is a complex phenomenon that occurs at multiple levels in the cell, including transcriptional regulation, post-translational modification and membrane insertion and retrieval. Multiple VGSC subtypes exist that vary in their biophysical and pharmacological properties and tissue distribution. Any alteration of the VGSC subtype profile of a neuron or the mechanisms that regulate VGSC activity can cause significant changes in neuronal excitability. Inflammatory and neuropathic pain states are characterised by alterations in VGSC subtype composition and activity in sensory neurons. This review focuses on the VGSC subtypes involved in such pain states.. AB - Voltage-gated sodium channels (VGSCs) play an ...
1. Erythrocyte sodium, sodium transport (ouabain-sensitive efflux rate of sodium, oMosNa, and ouabain-sensitive efflux rate constant of sodium, oMosNa), sodium-potassium activated ouabain-sensitive adenosine triphosphatase (Na+, K+-ATPase) activity and [3H]ouabain-binding capacity were measured in 15 patients with chronic renal failure and in 10 healthy subjects.. 2. As a group, patients with chronic renal failure had a lower erythrocyte sodium and oMosNa compared with healthy subjects.. 3. When patients were divided according to their erythrocyte sodium (greater or less than 4 mmol/kg of cells), in the group of patients whose erythrocyte sodium was less than 4 mmol/kg of cells (group A) the oMosNa was higher than that in healthy subjects and the oMosNa, Na+, K+-ATPase activity and [3H]ouabain-binding capacity were the same as those in healthy subjects. In the subgroup of patients with renal failure whose erythrocyte sodium content was greater than 4 mmol/kg of cells (group B) the oMosNa was ...
It has long been known that there is a rapid ion exchange over the cell membrane, but Neher and Sakmann were the first to show that specific ion channels actually exist. To elucidate how an ion channel operates it is necessary to be able to record how the channel opens and closes. This appeared elusive since the ionic current through a single ion channel is extraordinarily small. In addition, the small ion channel molecules are embedded in the cell membrane. Neher and Sakmann succeeded in solving these difficulties. They developed a thin glass micropipette (a thousandths of a millimeter in diameter) as a recording electrode. When it is brought in contact with the cell membrane, it will form a tight seal with the periphery of the pipette orifice (Figure 1A, B). As a consequence the exchange of ions between the inside of the pipette and the outside can only occur through the ion channel in the membrane fragment (Figure 1B). When a single ion channel opens, ions will move through the channel as an ...
Background: Gain-of-function mutations of the nociceptive voltage-gated sodium channel Nav1.7 lead to inherited pain syndromes, such as paroxysmal extreme pain disorder (PEPD). One characteristic of these mutations is slowed fast-inactivation kinetics, which may give rise to resurgent sodium currents. It is long known that toxins from Anemonia sulcata, such as ATX-II, slow fast inactivation and skin contact for example during diving leads to various symptoms such as pain and itch. Here, we investigated if ATX-II induces resurgent currents in sensory neurons of the dorsal root ganglion (DRGs) and how this may translate into human sensations. Results: In large A-fiber related DRGs ATX-II (5 nM) enhances persistent and resurgent sodium currents, but failed to do so in small C-fiber linked DRGs when investigated using the whole-cell patch-clamp technique. Resurgent currents are thought to depend on the presence of the sodium channel beta 4-subunit. Using RT-qPCR experiments, we show that small DRGs ...
TY - JOUR. T1 - Diffusion limitation in the block by symmetric tetraalkylammonium ions of anthrax toxin channels in planar phospholipid bilayer membranes. AU - Blaustein, Robert O.. AU - Finkelstein, Alan. PY - 1990/11. Y1 - 1990/11. N2 - Current flow through the channel formed in planar phospholipid bilayer membranes by the PA65 fragment of anthrax toxin is blocked, in a voltage-dependent manner, by tetraalkylammonium ions (at micromolar concentrations), which bind to a blocking site within the channel lumen. We have presented evidence that diffusion plays a significant role in the kinetics of blocking by tetrabutylammonium ion (Bu4N+) from the cis (toxin-containing) side of the membrane (Blaustein, R. O., E. J. A. Lea, and A. Finkelstein. 1990. J. Gen. Physiol. 96:921-942); in this paper we examine the implications and consequences of diffusion control for binding kinetics. As expected for a diffusion-affected reaction, both the entry rate constant (k1cis) of Bu4N+ from the cis solution to the ...
To study the effect of autoimmunity against the alpha subunit of cardiac voltage-gated sodium channel NaV1.5 in vivo, an autoimmune response was induced in rats through immunization with a NaV1.5-peptide. Consequently, high levels of autoantibodies targeting the third extracellular loop of the first domain could be detected in blood, reflecting successful immunization. Immunized animals developed an exclusively electrical phenotype with conduction defects on the sinoatrial and the atrioventricular level without signs of structural heart disease or myocardial inflammation. On the cellular level, this phenotype is probably caused by a reduced density of INa in cardiomyocytes.. The NaV1.5 is composed of 4 structurally homologous domains (DI-DIV) each consisting of 6 transmembrane segments (S1-S6) (14). The residues between S5 and S6 form the channel pore (P loop) and control ion selectivity and permeation. We chose a peptide sequence between S5 and S6 within the third extracellular loop (residues ...
TY - JOUR. T1 - A sodium channel blocker, pilsicainide, produces atrial post-repolarization refractoriness through the reduction of sodium channel availability. AU - Fukuda, Koji. AU - Watanabe, Jun. AU - Yagi, Takuya. AU - Wakayama, Yuji. AU - Nakano, Makoto. AU - Kondo, Masateru. AU - Kumagai, Koji. AU - Miura, Masahito. AU - Shirato, Kunio. AU - Shimokawa, Hiroaki. PY - 2011/9/2. Y1 - 2011/9/2. N2 - Atrial fibrillation (AF) is the most common tachyarrhythmia. Shortening of atrial action potential duration (APD) and effective refractory period (ERP) is one of the crucial factors in the occurrence and maintenance of AF. ERP is usually shorter than APD, but ERP can be prolonged beyond action potential repolarization in some situations. It is termed as post-repolarization refractoriness (PRR) that is thought to be one of main anti-arrhythmic mechanisms of class I sodium channel blockers (SCBs). Most of anti-arrhythmic agents, including SCBs, have multi-channel blocking effects. It is unknown ...
Sodium movement across the luminal membrane of the toad bladder is the rate-limiting step for active transepithelial transport. Recent studies suggest that changes in intracellular sodium regulate the Na permeability of the luminal border, either directly or indirectly via increases in cell calcium induced by the high intracellular sodium. To test these proposals, we measured Na movement across the luminal membrane (th Na influx) and found that it is reduced when intracellular Na is increased by ouabain or by removal of external potassium. Removal of serosal sodium also reduced the influx, suggesting that the Na gradient across the serosal border rather than the cell Na concentration is the critical factor. Because in tissues such as muscle and nerve a steep transmembrane sodium gradient is necessary to maintain low cytosolic calcium, it is possible that a reduction in the sodium gradient in the toad bladder reduces luminal permeability by increasing the cell calcium activity. We found that the ...
Lithium is the most common cause of nephrogenic diabetes insipidus (Li-NDI). Hydrochlorothiazide (HCTZ) combined with amiloride is the mainstay treatment in Li-NDI. The paradox antidiuretic action of HCTZ in Li-NDI is generally attributed to increased sodium and water uptake in proximal tubules as a compensation for increased volume loss due to HCTZ inhibition of the NaCl-co-transporter (NCC), but alternative actions for HCTZ have been suggested. Here, we investigated whether HCTZ exerted an NCC-independent effect in Li-NDI. In polarized mouse cortical collecting duct (mpkCCD) cells, HCTZ treatment attenuated the Li-induced downregulation of the Aquaporin-2 (AQP2) water channel abundance. In these cells, amiloride reduces cellular Li influx through the epithelial sodium channel ENaC. HCTZ also reduced Li influx, but to a lower extent. HCTZ increased AQP2 abundance on top of that of amiloride and did not affect the ENaC-mediated transcellular voltage. MpkCCD cells did not express NCC mRNA or ...
1. This study was designed to quantify the role of angiotensin II in determining the chronic relationships between arterial pressure, renal haemodynamics and sodium excretion.. 2. In six control dogs sodium balance was achieved during chronic increases in sodium intake from 5 to 495 mmol/day with small increases in arterial pressure (7mmHg), moderate increases in glomerular filtration rate (19%) and decreases in filtration fraction. Similar increases in sodium intake in dogs whose circulating levels of angiotensin II were fixed, due to a constant intravenous infusion of 4.85 pmol of angiotensin II min−1 kg−1, caused large increases in arterial pressure (42%), glomerular filtration rate (31%), filtration fraction and calculated renal sodium reabsorption above control. In six dogs whose angiotensin II formation was blocked by SQ 14 225, sodium balance at intakes of 5-80 mmol/day occurred at reduced arterial pressure, glomerular filtration rate, filtration fraction and sodium reabsorption ...
Request for sample pages. Table of contents. 1 Key Insights. 2 Executive Summary of Dravet Syndrome. 3 SWOT Analysis for Dravet Syndrome. 4 Dravet Syndrome Market Overview at a Glance. 4.1 Market Share (%) Distribution of Dravet Syndrome in 2017. 4.2 Market Share (%) Distribution of Dravet Syndrome in 2030. 5 Dravet Syndrome: Disease Background and Overview. 5.1 Introduction. 5.2 Clinical Features of Dravet Syndrome. 5.2.1 Epilepsy. 5.2.2 Cognition. 5.2.3 Movement disorders. 5.2.4 Sudden Death. 5.3 Genetics of Dravet Syndrome. 5.3.1 Sodium Channel a1 Subunit Gene (SCN1A) and its association with Dravet Syndrome. 5.3.2 Functional aspects of voltage gate sodium channel mutations. 5.3.3 Detection of SCN1A mutations. 5.3.4 Inheritance mode and pattern. 5.3.5 Dravet Syndrome without SCN1A Alterations. 5.4 Signs and Symptoms of Dravet Syndrome. 5.5 Pathophysiology. 5.6 Diagnosis of Dravet Syndrome. 5.6.1 Differential diagnosis. 6 Epidemiology and Patient Population. 6.1 Key Findings. 6.2 Total ...
Looking for online definition of syndrome of inappropriate antidiuretic hormone secretion in the Medical Dictionary? syndrome of inappropriate antidiuretic hormone secretion explanation free. What is syndrome of inappropriate antidiuretic hormone secretion? Meaning of syndrome of inappropriate antidiuretic hormone secretion medical term. What does syndrome of inappropriate antidiuretic hormone secretion mean?
Fingerprint Dive into the research topics of CAP-1A is a novel linker that binds clathrin and the voltage-gated sodium channel Na,sub,v,/sub,1.8. Together they form a unique fingerprint. ...
Purpose: The meibomian gland plays an essential role to maintain ocular surface health and integrity by providing the tear film outer lipid layer. This study was designed to explore the ion and fluid transport activities of rat meibomian gland and to establish a primary rat meibomian gland cell culture system.. Methods: Messenger RNA expression of selected sodium and chloride channels in rat meibomian gland tissues were determined by RT-PCR. Localization of mRNA for the α, β, and γ subunits of the epithelial sodium channel (ENaC) was determined by in situ hybridization. Protein expression and localization of β-ENaC were evaluated by western blot and immunohistochemistry, respectively. Freshly excised rat meibomian gland tissues were enzymatically digested and co-cultured with mitomycin C-treated 3T3 cells. Analyses for ion channels, other biomarkers of cell proliferation and differentiation, and lipid production of rat meibomian gland tissues and primary cell culture were performed with ...
Inside the organism, changes in pH levels occur under pathophysiological conditions such as inflammation, ischemia, cancer, and the like, which are accompanied by pain. The Acid-sensing Ion Channel (ASIC) detects changes in pH levels in the organism and transmits the pain signal to the brain. Biologically, many studies have been conducted regarding the Acid-sensing Ion Channel; however, many areas are still unclear, especially in terms of the operational mechanism and the cell membrane merging mechanism. Professor Suhs research team detected the cell membrane merging mechanisms that modulate the activity of the Acid-sensing Ion Channel at the molecular level, and it is this discovery and identification of the new cell membrane merging mechanism of the Acid-sensing Ion Channel that had remained unknown until now. The research team identified through animal experiments that there is a different cell membrane merging mechanism between subunits of the Acid-sensing Ion Channel. ASIC2a can be merged ...
Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated channel 4 is a protein that in humans is encoded by the HCN4 gene. There are four HCN channels. HCN4 is prominently expressed in the pace maker region of the mammalian heart. Some humans with bradycardia and Sick sinus syndrome have been shown to have mutations in their HCN4 gene. The role of HCN channels in autonomic control of heart rate is currently a matter of ongoing investigation. HCN4 has been shown to interact with HCN2. Cyclic nucleotide-gated ion channel Funny current GRCh38: Ensembl release 89: ENSG00000138622 - Ensembl, May 2017 GRCm38: Ensembl release 89: ENSMUSG00000032338 - Ensembl, May 2017 "Human PubMed Reference:". "Mouse PubMed Reference:". Ludwig A, Zong X, Stieber J, Hullin R, Hofmann F, Biel M (May 1999). "Two pacemaker channels from human heart with profoundly different activation kinetics". The EMBO Journal. 18 (9): 2323-9. doi:10.1093/emboj/18.9.2323. PMC 1171315 . PMID 10228147. Seifert R, Scholten A, ...
The discovery of genetic variants that substantially alter an individuals perception of pain has led to a step-change in our understanding of molecular events underlying the detection and transmission of noxious stimuli by the peripheral nervous system. For example, the voltage-gated sodium ion channel Na v 1.7 is expressed selectively in sensory and autonomic neurons; inactivating mutations in SCN9A, which encodes Na v 1.7, result in congenital insensitivity to pain, whereas gain-of-function mutations in this gene produce distinct pain syndromes such as inherited erythromelalgia, paroxysmal extreme pain disorder, and smal l-fibre neuropathy. Heterozygous mutations in TRPA1, which encodes the transient receptor potential cation channel, can cause familial episodic pain syndromes, and variants of genes coding for the voltage-gated sodium channels Na v 1.8 (SCN10A) and Na v 1.9 (SCN11A) lead to small-fibre neuropathy and congenital insensitivity to pain, respectively. Furthermore, other genetic
TY - JOUR. T1 - Vascular smooth muscle contraction induced by Na+ channel activators, veratridine and batrachotoxin. AU - Shinjo(H), Masayoshi. AU - Toshio, Nakaki. AU - Yukari, Otsuka. AU - Nobuyuki, Sasakawa. AU - Ryuichi, Kato. PY - 1991/11/26. Y1 - 1991/11/26. N2 - The effects of the sodium channel activators veratridine and batrachotoxin on isolated rat aorta were investigated. Veratridine caused gradual contraction, independent of the presence of endolhelium, with an EC50 of 35 μM. Batrachotoxin (1 μM) also induced contraction. Both effects were completely inhibited by the sodium channel blocker tetrodotoxin (1 μM). The veratridine (60 μM)-induced contraction was inhibited by nifedipine (0.1 μM). In the absence of extracellular Ca2+, veratridine (60 μm) did not cause contraction. Sodium nitroprusside (80 nM), acetylcholine (10 μM) and isoproterenol (1 μM) caused relaxation of rings precontracted with veratridine (60 μM). An inhibitor of endothelium-derived relaxing factor (EDRF) ...
1. Intra-erythrocyte sodium, potassium, ATP and (Na+,K+-activated)-ATPase concentrations and urinary aldosterone excretion were compared in 3-month-old spontaneously hypertensive rats (n = 11) and normotensive Wistar-Kyoto control rats (n = 11).. 2. Spontaneously hypertensive rats exhibited significantly higher intra-erythrocyte sodium concentration (5.5 ± 1.3 vs 4.0 ± 1.1 mmol/l of erythrocytes, P , 0.01). No significant difference was found in intra-erythrocyte potassium, ATP or (Na+,K+-activated)-ATPase concentration.. 3. Mean urinary aldosterone excretion was significantly lower in spontaneously hypertensive rats (66.3 ± 6.5 pmol/24 h) than in Wistar-Kyoto rats (90.5 ± 10.6 pmol/24 h, P , 0.01). No significant relationship between urinary aldosterone and intra-erythrocyte sodium concentration was found in spontaneously hypertensive or Wistar-Kyoto rats or in the pooled group.. 4. These results are thus consistent with previous findings of an increased intracellular sodium concentration ...
Amiloride-sensitive cation channel 1, neuronal (degenerin), also known as ACCN1, is a human gene.[1] This gene encodes a member of the degenerin/epithelial sodium channel (DEG/ENaC) superfamily. The members of this family are amiloride-sensitive sodium channels that contain intracellular N and C termini, 2 hydrophobic transmembrane regions, and a large extracellular loop, which has many cysteine residues with conserved spacing. The member encoded by this gene may play a role in neurotransmission. In addition, a heteromeric association between this member and ACCN3 (variant 1) has been observed to co-assemble into proton-gated channels sensitive to gadolinium. Alternative splicing has been observed at this locus and two variants, encoding distinct isoforms, have been identified.[1] ...
Bisphenol A (BPA) has attracted considerable public attention as it leaches from plastic used in food containers, is detectable in human fluids and recent epidemiologic studies link BPA exposure with diseases including cardiovascular disorders. As heart-toxicity may derive from modified cardiac electrophysiology, we investigated the interaction between BPA and hNav1.5, the predominant voltage-gated sodium channel subtype expressed in the human heart. Electrophysiology studies of heterologously-expressed hNav1.5 determined that BPA blocks the channel with a Kd of 25.4±1.3 µM. By comparing the effects of BPA and the local anesthetic mexiletine on wild type hNav1.5 and the F1760A mutant, we demonstrate that both compounds share an overlapping binding site. With a key binding determinant thus identified, an homology model of hNav1.5 was generated based on the recently-reported crystal structure of the bacterial voltage-gated sodium channel NavAb. Docking predictions position both ligands in a cavity
PURPOSE To establish an electrical fingerprint for the gap junction channels between mammalian lens epithelial cells. METHODS The double whole cell patch clamp technique was applied to isolated cell pairs obtained from mouse lens epithelium and a continuous cell line of lens epithelial cells derived from the sheep lens (SLE 2.1). RESULTS The junctional conductance in mouse lens epithelial cells and in cultured SLE 2.1 cells was found to be moderately voltage dependent. SLE 2.1 cells were analyzed in more detail. The voltage dependence could be described by a Boltzmann distribution with Vo = +/- 63.1 mV and Gmin = 0.34. In cell pairs that exhibited spontaneously low junctional conductance, single channel events could be distinguished. Single gap junction channel currents had a linear current-voltage relationship. A frequency histogram of single channel conductances from eight cell pairs had three major peaks of 35, 60 and 97 pS. CONCLUSION The electrical properties of gap junction channels
Changes in intracellular sodium ion activity (aiNa) produced by several cardiac glycosides were correlated with twitch tension in sheep cardiac Purkinje strands. Simultaneous measurements of aiNa and twitch tension were obtained through the use of Na-sensitive intracellular microelectrodes (ETH 227) in Purkinje preparations stimulated at a frequency of 1 Hz. All concentrations of ouabain, acetylstrophanthidin, and actodigin that were tested caused an increase in aiNa immediately before, or coincident with, a positive inotropic effect. No fall in aiNa was observed at any positive inotropic concentration of digitalis in these beating fibers. In all cases, the onset and washout of the positive inotropic effect were paralleled by the rise and fall in aiNa, respectively. No dissociation between changes in aiNa and twitch tension occurred at any concentration of any of the agents used. The relation between changes in aiNa and twitch tension was linear with 1 mM increase in aiNa producing about a 100% ...
Voltage-gated sodium channels (VGSCs) play an important role in the control of membrane excitability. We previously reported that the excitability of nociceptor was increased by hypotonic stimulation. The present study tested the effect of hypotonicity on tetrodotoxin-sensitive sodium current (TTX-S current) in cultured trigeminal ganglion (TG) neurons. Our data show that after hypotonic treatment, TTX-S current was increased. In the presence of hypotonicity, voltage-dependent activation curve shifted to the hyperpolarizing direction, while the voltage-dependent inactivation curve was not affected. Transient Receptor Potential Vanilloid 4 receptor (TRPV4) activator increased TTX-S current and hypotonicity-induced increase was markedly attenuated by TRPV4 receptor blockers. We also demonstrate that inhibition of PKC attenuated hypotonicity-induced inhibition, whereas PKA system was not involved in hypotonic-response. We conclude that hypotonic stimulation enhances TTX-S current, which contributes to
Potassium channels, found throughout the animal and plant kingdoms, play important roles in maintaining membrane potentials and regulating action potential firing, shape, and duration, among other functions. Using the Xenopus laevis (frog) oocyte as model system, we induced high expression of sodium and potassium voltage-gated channels and recorded action potentials by a modification of the two-electrode voltage-clamp recording technique. The voltage-dependent sodium conductance was due to expression of the skeletal muscle NaV channel (NaV1.4) and the delayed rectifier voltage-dependent potassium conductance was due to expression of a Shaker (Kv1) potassium channel. Upon this background, we mixed different potassium-selective ion channels, such as inwardly rectifying potassium (KIR) channels, tandem pore domain (K2P) potassium channels and voltage-gated (KV) channels. We analyzed how these potassium channels affected firing thresholds, reliability of action potential generation, action potential
A calcium channel opener is a type of drug which facilitates ion transmission through calcium channels. An example is Bay K8644, which is an analogue of nifedipine that specifically and directly activates L-type voltage-dependent calcium channels. In contrast to Bay K8644, which is not for clinical use, Ambroxol is a frequently used mucolytic drug that triggers lysosomal secretion by mobilizing calcium from acidic calcium stores. This effect does most likely not occur by a direct interaction between the drug and a lysosomal calcium channel, but indirectly by neutralizing the acidic pH within lysosomes. Calcium permeable ion channels in lysosomal membranes that may be activated by a luminal pH increase include two pore channels (TPCs), mucolipin TRP channels (TRPMLs) and purinergic receptors of the P2X channel type. Calcium channel blocker Schramm M, Thomas G, Towart R, Franckowiak G (1983). "Activation of calcium channels by novel 1,4-dihydropyridines. A new mechanism for positive inotropics or ...
1. The antidiuretic effect of hydrochlorothiazide in diabetes insipidus was investigated in rats with the hereditary hypothalamic form of the disease (Brattleboro rats).. 2. Administration of hydrochlorothiazide in the food resulted in a marked fall in urine volume and a corresponding rise in osmolality. These effects persisted throughout the period of treatment (6-7 days).. 3. Body weight and extracellular volume were significantly reduced in the thiazide-treated rats.. 4. Hydrochlorothiazide caused an increase in urinary sodium excretion only on the first day of treatment. The resulting small negative sodium balance (in comparison with untreated rats) remained statistically significant for 2 days only. Thiazide-treated rats gradually developed a potassium deficit which was statistically significant from the fourth day of treatment.. 5. Total exchangeable sodium, measured after 7 days of thiazide treatment, was not significantly different from that of untreated rats. However, plasma sodium was ...
Lubeluzole is widely reported as a multitarget drug acting at least on voltage-gated calcium and sodium channels. There are, however, only a very few studies reporting direct demonstration of sodium channel blockade by lubeluzole in neuronal and cardiac cells (Osikowska-Evers et al., 1995; Le Grand et al., 2003). The more complete study by Le Grand et al., (2003) described the block of sodium channels in single guinea pig ventricular myocytes. It was shown that lubeluzole produces a concentration-dependent tonic and use-dependent block of cardiac sodium channels in a manner similar to that of class I antiarrhythmic drugs, suggesting a greater affinity for inactivated than for resting channels. In the present study, we observed a similar local anesthetic-like effect of lubeluzole on human skeletal muscle sodium channels, and definitely demonstrated that the drug is a very potent blocker of inactivated sodium channels compared with resting channels. The IC50 values calculated for skeletal muscle ...
TY - JOUR. T1 - Effect of phenolphthalein on in vitro rabbit ileal electrolyte transport. AU - Powell, D. W.. AU - Lawrence, B. A.. AU - Morris, S. M.. AU - Etheridge, D. R.. PY - 1980. Y1 - 1980. N2 - The effect of phenolphthalein on rabbit ileal electrolyte transport was studied to gain insight into the mechanism of cathartic action of this drug. Two separate effects were noted in Ringer solution in the Ussing chamber in vitro. First, when present in either or both the mucosal and serosal solutions, phenolphthalein caused a dose-related inhibition of the potential difference and the short-circuit current. Second, when present only on the mucosal side of the epithelium, phenolphthalein inhibited sodium chloride absorption (or caused sodium chloride secretion); when present only on the serosal side, phenolphthalein stimulated sodium chloride absorption. There was no clear difference between the effects of white and yellow phenolphthalein. In sodium-free solutions, mucosal phenolphthalein ...
Pyrethroid resistance in human head louse populations is widespread in the United States and worldwide. We previously documented that the knockdown resistance of permethrin-resistant head louse populations is associated with the T929I and L932F (T917I and L920F in the numbering of the louse amino acid sequence) mutations in the voltage-sensitive sodium channel a-subunit gene. In order to identify additional sodium channel mutations potentially associated with knockdown resistance, we cloned and sequenced full-length cDNA fragments from insecticide-susceptible (Ecuador) and permethrin-resistant (Florida) head louse populations and from an insecticide-susceptible body louse population (Israel). Sequence comparisons of the complete open reading frames of the sodium channel genes identified one additional novel mutation (M815I), which was located in the IIS1-2 extracellular loopof the a-subunit, from the permethrin-resistant head louse population. Absolute conservation of the Met815 residue at the ...
1) Imaging the brain of m igraine sufferers. Flippen C, Welch KMA. Current Opin Neurol 1997;10:226-230.. 2) The periaqueductal grey matter modulates trigeminovascular input: A role in migraine? Knight YE, Goadsby PJ. Neuroscience 2001;106(4):793-800.. 3) Brain stem activation in spontaneous human migraine attacks. Weiller C, May A Limmroth V, et al. Nature Med 1995 Jul;1(7):658-660.. 4) A positron emission tomographic study in spontaneous migraine. Afridi SK, Giffin NJ, Kaube H, Fiston KJ, Ward NS, Frackowiak RS, Goadsby PJ. Arch Neurol 2005; 62(8): 1270-5.. 5) Familial hemiplegic migraine and episodic ataxia type-2 are caused by mutations in the Ca++ channel gene CACNL1A4. Cell 1996;87:543-552.. 6) Mutations in the neuronal voltage-gated sodium channel SCN1A in familial hemiplegic migraine type 3. van den Maagdenberg A, Vanmolkot KRJ, Welch KMA, et al. Cephalalgia 2005;25:1189-1205.. 7) Familial basilar migraine associated with a new mutation in the ATP1A2 gene. Ambrosini A, DOnofrio M, Grieco ...
The secreted nodulation-signaling protein NodO was purified from the supernatant of cultures of Rhizobium leguminosarum biovar viciae. The native protein has a M(r) of approximately 67,000, suggesting that it exists as a dimer since the DNA sequence predicts a M(r) of 30,002. Pure NodO protein had no protease, pectinase, or cellulase activity, and no binding was observed to lipooligosaccharide nodulation factors. Although NodO is relatively hydrophilic, it appeared to insert into liposomes and was protected by liposomes from proteolytic cleavage. When added to planar lipid bilayers, NodO formed cation-selective channels that allowed the movement of monovalent cations (K+ and Na+) across the membrane. NodO is a Ca(2+)-binding protein; in the presence of high concentrations of Ca2+, channel activity was reduced. We hypothesize that NodO plays a role in nodulation signaling by stimulating uptake of nodulation factors or by forming cation-specific channels that function synergistically with the ...
TY - JOUR. T1 - Adult forms of nicotinic acetylcholine receptors are expressed in the absence of nerve during differentiation of a mouse skeletal muscle cell line. AU - Shepherd, Dawn. AU - Brehm, Paul. PY - 1994. Y1 - 1994. N2 - Changes in the functional properties of acetylcholine receptor (AchR) channels were followed in the C2 muscle cell line over the period of 1 to 17 days following myotube formation. Up to 1 week after myotube formation, the predominant class of channel exhibited low (45 pS) conductance and long mean channel open time (14 msec), characteristic of the major type of AchR in embryonic skeletal muscle. Three additional Ach-activated currents with conductances lower than 45 pS and long channel open times were also observed. Seven to 10 days following myotube formation, channels of 45 pS and 65 pS and short (2-6 msec) mean open duration were observed, characteristic of receptor channels in adult muscle. Increases in ε subunit mRNA levels preceded the functional expression of ...
Local anesthetic nerve block (local anesthetic regional nerve blockade, or often simply nerve block) is a short-term nerve block involving the injection of local anesthetic as close to the nerve as possible for pain relief. The local anesthetic bathes the nerve and numbs the area of the body that is innervated by that nerve. The goal of the nerve block is to prevent pain by blocking the transmission of pain signals from the surgical site. The block provides pain relief during and after the surgery. The advantages of nerve blocks over general anesthesia include faster recovery, monitored anesthesia care vs. intubation with an airway tube, and much less postoperative pain. Local anesthetics act on the voltage-gated sodium channels that conduct electrical impulses and mediate fast depolarization along nerves. Most of the local anesthetics target open channels and prevent ion flow. Local anesthetics also act on potassium channels, but they block sodium channels more. Lidocaine preferentially binds ...
Read "Sodium Channel NaV1.5 Expression is Enhanced in Cultured Adult Rat Skeletal Muscle Fibers, The Journal of Membrane Biology" on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
The effect of sea anemone toxins from Parasicyonis actinostoloides and Anemonia sulcata on the Na conductance in crayfish giant axons was studied under voltage-clamp conditions. The toxin slowed the Na inactivation process without changing the kinetics of Na activation or K activation in an early stage of the toxin effect. An analysis of the Na current profile during the toxin treatment suggested an all-or-none modification of individual Na channels. Toxin-modified Na channels were partially inactivated with a slower time course than that of the normal inactivation. This slow inactivation in steady state decreased in its extent as the membrane was depolarized to above -45 mV, so that practically no inactivation occurred at the membrane potentials as high as +50 mV. In addition to inhibition of the normal Na inactivation, prolonged toxin treatment induced an anomalous closing in a certain population of Na channels, indicated by very slow components of the Na tail current. The observed kinetic ...
TY - JOUR. T1 - Sodium channels and pain. AU - Waxman, S. G.. AU - Dib-Hajj, S.. AU - Cummins, T. R.. AU - Black, J. A.. PY - 1999/7/6. Y1 - 1999/7/6. N2 - Although it is well established that hyperexcitability and/or increased baseline sensitivity of primary sensory neurons can lead to abnormal burst activity associated with pain, the underlying molecular mechanisms are not fully understood. Early studies demonstrated that, after injury to their axons, neurons can display changes in excitability, suggesting increased sodium channel expression, and, in fact, abnormal sodium channel accumulation has been observed at the lips of injured axons. We have used an ensemble of molecular, electrophysiological, and pharmacological techniques to ask: what types of sodium channels underlie hyperexcitability of primary sensory neurons after injury? Our studies demonstrate that multiple sodium channels, with distinct electrophysiological properties, are encoded by distinct mRNAs within small dorsal root ...
Introduction: High sodium intake is an established risk factor for hypertension and cardiovascular diseases. The average sodium intake in Koreans was estimated at 4,645mg/day, which was more than two times compared to the recommended amount, 2000mg/day. We assessed whether people who diagnosed with hypertension or treated for hypertension consume less sodium than those without hypertension.. Methods: The present study analyzed data from a total of 6,577 Koreans (3,816 women and 2,761 men) aged 40 years and older, participated in the Korea National Health and Nutrition Examination Survey (KNHANES IV, 2007-2008). Participants were classified into five groups as follows: normal blood pressure, pre-hypertension, hypertension without treatment, hypertension with treatment, and hypertension with complications. The association between sodium intake and hypertension management status was estimated using exponential regression coefficient, adjusted for potential confounders including age, energy intake, ...
Xenon is developing small molecule inhibitors of the voltage-gated sodium channel Nav1.6 for the treatment of Dravet syndrome. There is a genetic link between
Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other aquatic animals (e.g., in blue-ringed octopuses, rough-skinned newts, and moon snails), it is actually produced by certain infecting or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in animals[citation needed]. Tetrodotoxin is a sodium channel blocker. It inhibits the firing of action potentials in neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions (responsible for the rising phase of an action potential) into the neuron. This prevents the nervous system from carrying messages and thus muscles from flexing in response to nervous stimulation. Its mechanism of action, selective blocking of the ...
Voltage-gated sodium channels play a critical role in the generation and conduction of action potentials - so important for electrical signalling by most excitable cells. Sodium channels are integral membrane proteins and are comprised of a large α subunit, which forms the voltage-sensitive and ion-selective pore, and smaller auxiliary β subunit(s) that can modulate the kinetics and voltage dependence of channel gating. Till 2007, 9 isoforms of the sodium-channel α subunit (Nav1.1- Nav1.9), each with a unique central and peripheral nervous system distribution had been identified. 4 closely related sodium channels (Nav 1.1, -1.2, -1.3, and -1.7) are encoded by a set of 4 genes (SCN1A, SCN2A, SCN3A, and SCN9A, respectively) located within a cluster on chromosome 2q24.3. Mutations in the genes encoding Nav1.1, -1.2, and -1.3 are responsible for a group of epilepsy syndromes with overlapping clinical characteristics but divergent clinical severity, mutation in the gene encoding Nav1.7 has a ...
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