scholarly journals Neurosteroids Allopregnanolone Sulfate and Pregnanolone Sulfate Have Diverse Effect on the α Subunit of the Neuronal Voltage-gated Sodium Channels Nav1.2, Nav1.6, Nav1.7, and Nav1.8 Expressed in Xenopus Oocytes

2014 ◽  
Vol 121 (3) ◽  
pp. 620-631 ◽  
Author(s):  
Takafumi Horishita ◽  
Nobuyuki Yanagihara ◽  
Susumu Ueno ◽  
Yuka Sudo ◽  
Yasuhito Uezono ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Xenopus Oocytes ◽  
Sodium Current ◽  
Dependent Manner ◽  
Sodium Currents ◽  
Concentration Dependent Manner ◽  
Α Subunit ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Α Subunits

Abstract Background: The neurosteroids allopregnanolone and pregnanolone are potent positive modulators of γ-aminobutyric acid type A receptors. Antinociceptive effects of allopregnanolone have attracted much attention because recent reports have indicated the potential of allopregnanolone as a therapeutic agent for refractory pain. However, the analgesic mechanisms of allopregnanolone are still unclear. Voltage-gated sodium channels (Nav) are thought to play important roles in inflammatory and neuropathic pain, but there have been few investigations on the effects of allopregnanolone on sodium channels. Methods: Using voltage-clamp techniques, the effects of allopregnanolone sulfate (APAS) and pregnanolone sulfate (PAS) on sodium current were examined in Xenopus oocytes expressing Nav1.2, Nav1.6, Nav1.7, and Nav1.8 α subunits. Results: APAS suppressed sodium currents of Nav1.2, Nav1.6, and Nav1.7 at a holding potential causing half-maximal current in a concentration-dependent manner, whereas it markedly enhanced sodium current of Nav1.8 at a holding potential causing maximal current. Half-maximal inhibitory concentration values for Nav1.2, Nav1.6, and Nav1.7 were 12 ± 4 (n = 6), 41 ± 2 (n = 7), and 131 ± 15 (n = 5) μmol/l (mean ± SEM), respectively. The effects of PAS were lower than those of APAS. From gating analysis, two compounds increased inactivation of all α subunits, while they showed different actions on activation of each α subunit. Moreover, two compounds showed a use-dependent block on Nav1.2, Nav1.6, and Nav1.7. Conclusion: APAS and PAS have diverse effects on sodium currents in oocytes expressing four α subunits. APAS inhibited the sodium currents of Nav1.2 most strongly.

scholarly journals The neurosteroid allopregnanolone sulfate inhibits Nav1.3 α subunit-containing voltage-gated sodium channels, expressed in Xenopus oocytes

2018 ◽  
Vol 137 (1) ◽  
pp. 93-97 ◽  
Author(s):  
Takafumi Horishita ◽  
Nobuyuki Yanagihara ◽  
Susumu Ueno ◽  
Dan Okura ◽  
Reiko Horishita ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Xenopus Oocytes ◽  
Α Subunit ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels

Resveratrol inhibits Kv2.2 currents through the estrogen receptor GPR30-mediated PKC pathway

2013 ◽  
Vol 305 (5) ◽  
pp. C547-C557 ◽  
Author(s):  
Wen-Hao Dong ◽  
Jia-Chen Chen ◽  
Yan-Lin He ◽  
Jia-Jie Xu ◽  
Yan-Ai Mei
Keyword(s):  
Molecular Mechanisms ◽  
Cerebellar Granule Cells ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Α Subunit ◽  
Inactivation Curve ◽  
Hek 293 ◽  
Nongenomic Action ◽  
Α Subunits

Resveratrol (REV) is a naturally occurring phytoalexin that inhibits neuronal K+ channels; however, the molecular mechanisms behind the effects of REV and the relevant α-subunit are not well defined. With the use of patch-clamp technique, cultured cerebellar granule cells, and HEK-293 cells transfected with the Kv2.1 and Kv2.2 α-subunits, we investigated the effect of REV on Kv2.1 and Kv2.2 α-subunits. Our data demonstrated that REV significantly suppressed Kv2.2 but not Kv2.1 currents with a fast, reversible, and mildly concentration-dependent manner and shifted the activation or inactivation curve of Kv2.2 channels. Activating or inhibiting the cAMP/PKA pathway did not abolish the inhibition of Kv2.2 current by REV. In contrast, activation of PKC with phorbol 12-myristate 13-acetate mimicked the inhibitory effect of REV on Kv2.2 by modifying the activation or inactivation properties of Kv2.2 channels and eliminated any further inhibition by REV. PKC and PKC-α inhibitor completely eliminated the REV-induced inhibition of Kv2.2. Moreover, the effect of REV on Kv2.2 was reduced by preincubation with antagonists of GPR30 receptor and shRNA for GPR30 receptor. Western blotting results indicated that the levels of PKC-α and PKC-β were significantly increased in response to REV application. Our data reveal, for the first time, that REV inhibited Kv2.2 currents through PKC-dependent pathways and a nongenomic action of the oestrogen receptor GPR30.

scholarly journals Neuropathic Pain Develops Normally in Mice Lacking both Nav1.7 and Nav1.8

2005 ◽  
Vol 1 ◽  
pp. 1744-8069-1-24 ◽  
Author(s):  
Mohammed A Nassar ◽  
Alessandra Levato ◽  
L Caroline Stirling ◽  
John N Wood
Keyword(s):  
Neuropathic Pain ◽  
Sodium Channels ◽  
Sensory Neurons ◽  
Inflammatory Pain ◽  
Pain Thresholds ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Pain Symptoms ◽  
Α Subunits

Two voltage gated sodium channel α-subunits, Nav1.7 and Nav1.8, are expressed at high levels in nociceptor terminals and have been implicated in the development of inflammatory pain. Mis-expression of voltage-gated sodium channels by damaged sensory neurons has also been implicated in the development of neuropathic pain, but the role of Nav1.7 and Nav1.8 is uncertain. Here we show that deleting Nav1.7 has no effect on the development of neuropathic pain. Double knockouts of both Nav1.7 and Nav1.8 also develop normal levels of neuropathic pain, despite a lack of inflammatory pain symptoms and altered mechanical and thermal acute pain thresholds. These studies demonstrate that, in contrast to the highly significant role for Nav1.7 in determining inflammatory pain thresholds, the development of neuropathic pain does not require the presence of either Nav1.7 or Nav1.8 alone or in combination.

scholarly journals Block of Voltage-Gated Sodium Channels by Atomoxetine in a State- and Use-dependent Manner

2021 ◽  
Vol 12 ◽  
Author(s):  
Karl Josef Föhr ◽  
Ariadni Nastos ◽  
Michael Fauler ◽  
Thomas Zimmer ◽  
Bettina Jungwirth ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Heart Muscle ◽  
Brain Regions ◽  
Clinical Effects ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Human Embryonic Kidney Cells ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Slow Kinetics

Atomoxetine, a neuroactive drug, is approved for the treatment of attention-deficit/hyperactivity disorder (ADHD). It is primarily known as a high affinity blocker of the noradrenaline transporter, whereby its application leads to an increased level of the corresponding neurotransmitter in different brain regions. However, the concentrations used to obtain clinical effects are much higher than those which are required to block the transporter system. Thus, off-target effects are likely to occur. In this way, we previously identified atomoxetine as blocker of NMDA receptors. As many psychotropic drugs give rise to sudden death of cardiac origin, we now tested the hypothesis whether atomoxetine also interacts with voltage-gated sodium channels of heart muscle type in clinically relevant concentrations. Electrophysiological experiments were performed by means of the patch-clamp technique at human heart muscle sodium channels (hNav1.5) heterogeneously expressed in human embryonic kidney cells. Atomoxetine inhibited sodium channels in a state- and use-dependent manner. Atomoxetine had only a weak affinity for the resting state of the hNav1.5 (Kr: ∼ 120 µM). The efficacy of atomoxetine strongly increased with membrane depolarization, indicating that the inactivated state is an important target. A hallmark of this drug was its slow interaction. By use of different experimental settings, we concluded that the interaction occurs with the slow inactivated state as well as by slow kinetics with the fast-inactivated state. Half-maximal effective concentrations (2–3 µM) were well within the concentration range found in plasma of treated patients. Atomoxetine also interacted with the open channel. However, the interaction was not fast enough to accelerate the time constant of fast inactivation. Nevertheless, when using the inactivation-deficient hNav1.5_I408W_L409C_A410W mutant, we found that the persistent late current was blocked half maximal at about 3 µM atomoxetine. The interaction most probably occurred via the local anesthetic binding site. Atomoxetine inhibited sodium channels at a similar concentration as it is used for the treatment of ADHD. Due to its slow interaction and by inhibiting the late current, it potentially exerts antiarrhythmic properties.

scholarly journals Carvacrol inhibits the neuronal voltage-gated sodium channels Nav1.2, Nav1.6, Nav1.3, Nav1.7, and Nav1.8 expressed in Xenopus oocytes with different potencies

2020 ◽  
Vol 142 (4) ◽  
pp. 140-147
Author(s):  
Takafumi Horishita ◽  
Yuichi Ogata ◽  
Reiko Horishita ◽  
Ryo Fukui ◽  
Kuniaki Moriwaki ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Xenopus Oocytes ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels

Potentiation of rat brain sodium channel currents by PKA inXenopus oocytes involves the I-II linker

2000 ◽  
Vol 278 (4) ◽  
pp. C638-C645 ◽  
Author(s):  
Raymond D. Smith ◽  
Alan L. Goldin
Keyword(s):  
Sodium Channel ◽  
Xenopus Oocytes ◽  
Sodium Current ◽  
Sodium Currents ◽  
Voltage Gated Sodium Channels ◽  
Single Region ◽  
Functional Modulation ◽  
Excitability Of Neurons ◽  
Channel Currents ◽  
The Brain

Functional modulation of voltage-gated sodium channels affects the electrical excitability of neurons. Protein kinase A (PKA) can decrease sodium currents by phosphorylation at consensus sites in the cytoplasmic I-II linker. Once the sites are phosphorylated, however, additional PKA activity can increase sodium currents by an unknown mechanism. When the PKA sites were eliminated by substitutions of alanine for serine, peak sodium current amplitudes were increased by 20–80% when PKA was activated in Xenopus oocytes either by stimulation of a coexpressed β2-adrenergic receptor or by perfusion with reagents that increase cAMP. Potentiation required the I-II linker of the brain channel, in that a chimeric channel in which the brain linker was replaced with the comparable linker from the skeletal muscle channel did not demonstrate potentiation. Using a series of chimeric and deleted channels, we demonstrate that potentiation is not dependent on any single region of the linker and that the extent of potentiation varies depending on the total length and the residues throughout the linker. These data are consistent with the hypothesis that potentiation by PKA is an indirect process involving phosphorylation of an accessory protein that interacts with the I-II linker of the sodium channel.

The Endocannabinoid Anandamide Inhibits Voltage-Gated Sodium Channels Nav1.2, Nav1.6, Nav1.7, and Nav1.8 in Xenopus Oocytes

2014 ◽  
Vol 118 (3) ◽  
pp. 554-562 ◽  
Author(s):  
Dan Okura ◽  
Takafumi Horishita ◽  
Susumu Ueno ◽  
Nobuyuki Yanagihara ◽  
Yuka Sudo ◽  
...  
Keyword(s):  
Sodium Channels ◽  
Xenopus Oocytes ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels

scholarly journals Effect of Oxaliplatin on Voltage-Gated Sodium Channels in Peripheral Neuropathic Pain

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 680 ◽  
Author(s):  
Woojin Kim
Keyword(s):  
Neuropathic Pain ◽  
Action Potential ◽  
Sodium Channels ◽  
Sodium Current ◽  
Voltage Response ◽  
Treatment Schedule ◽  
Voltage Gated ◽  
Peripheral Neurons ◽  
Voltage Gated Sodium Channels ◽  
Current Voltage

Oxaliplatin is a chemotherapeutic drug widely used to treat various types of tumors. However, it can induce a serious peripheral neuropathy characterized by cold and mechanical allodynia that can even disrupt the treatment schedule. Since the approval of the agent, many laboratories, including ours, have focused their research on finding a drug or method to decrease this side effect. However, to date no drug that can effectively reduce the pain without causing any adverse events has been developed, and the mechanism of the action of oxaliplatin is not clearly understood. On the dorsal root ganglia (DRG) sensory neurons, oxaliplatin is reported to modify their functions, such as the propagation of the action potential and induction of neuropathic pain. Voltage-gated sodium channels in the DRG neurons are important, as they play a major role in the excitability of the cell by initiating the action potential. Thus, in this small review, eight studies that investigated the effect of oxaliplatin on sodium channels of peripheral neurons have been included. Its effects on the duration of the action potential, peak of the sodium current, voltage–response relationship, inactivation current, and sensitivity to tetrodotoxin (TTX) are discussed.

scholarly journals Extremely Potent Block of Bacterial Voltage-Gated Sodium Channels by µ-Conotoxin PIIIA

Marine Drugs ◽  
2019 ◽  
Vol 17 (9) ◽  
pp. 510 ◽  
Author(s):  
Rocio K. Finol-Urdaneta ◽  
Jeffrey R. McArthur ◽  
Vyacheslav S. Korkosh ◽  
Sun Huang ◽  
Denis McMaster ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Sodium Channel ◽  
Sodium Channels ◽  
Cell Voltage ◽  
Hill Coefficient ◽  
Dependent Manner ◽  
Binding Modes ◽  
Voltage Gated ◽  
Voltage Gated Sodium Channels ◽  
Conducting Pathway

µ-Conotoxin PIIIA, in the sub-picomolar, range inhibits the archetypal bacterial sodium channel NaChBac (NavBh) in a voltage- and use-dependent manner. Peptide µ-conotoxins were first recognized as potent components of the venoms of fish-hunting cone snails that selectively inhibit voltage-gated skeletal muscle sodium channels, thus preventing muscle contraction. Intriguingly, computer simulations predicted that PIIIA binds to prokaryotic channel NavAb with much higher affinity than to fish (and other vertebrates) skeletal muscle sodium channel (Nav 1.4). Here, using whole-cell voltage clamp, we demonstrate that PIIIA inhibits NavBac mediated currents even more potently than predicted. From concentration-response data, with [PIIIA] varying more than 6 orders of magnitude (10−12 to 10−5 M), we estimated an IC50 = ~5 pM, maximal block of 0.95 and a Hill coefficient of 0.81 for the inhibition of peak currents. Inhibition was stronger at depolarized holding potentials and was modulated by the frequency and duration of the stimulation pulses. An important feature of the PIIIA action was acceleration of macroscopic inactivation. Docking of PIIIA in a NaChBac (NavBh) model revealed two interconvertible binding modes. In one mode, PIIIA sterically and electrostatically blocks the permeation pathway. In a second mode, apparent stabilization of the inactivated state was achieved by PIIIA binding between P2 helices and trans-membrane S5s from adjacent channel subunits, partially occluding the outer pore. Together, our experimental and computational results suggest that, besides blocking the channel-mediated currents by directly occluding the conducting pathway, PIIIA may also change the relative populations of conducting (activated) and non-conducting (inactivated) states.

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