scholarly journals Charge at the local anesthetic binding site modulates steady state inactivation of voltage gated Na channels

2007 ◽  
Vol 21 (6) ◽  
Author(s):  
Megan M McNulty ◽  
Gabrielle B Edgerton ◽  
Harry A Fozzard ◽  
Dorothy A Hanck
Keyword(s):  
Steady State ◽  
Binding Site ◽  
Local Anesthetic ◽  
Na Channels ◽  
Voltage Gated ◽  
Steady State Inactivation

Meperidine and Lidocaine Block of Recombinant Voltage-Dependent Na+Channels 

1999 ◽  
Vol 91 (5) ◽  
pp. 1481-1481 ◽  
Author(s):  
Larry E. Wagner ◽  
Michael Eaton ◽  
Salas S. Sabnis ◽  
Kevin J. Gingrich
Keyword(s):  
Steady State ◽  
Local Anesthesia ◽  
Local Anesthetic ◽  
Voltage Dependence ◽  
Tonic Inhibition ◽  
Na Channel ◽  
Mutant Form ◽  
Na Channels ◽  
Voltage Dependent ◽  
Steady State Inactivation

Background The opioid meperidine induces spinal anesthesia and blocks nerve action potentials, suggesting it is a local anesthetic. However, whether it produces effective clinical local anesthesia in peripheral nerves remains unclear. Classification as a local anesthetic requires clinical local anesthesia but also blockade of voltage-dependent Na+ channels with characteristic features (tonic and phasic blockade and a negative shift in the voltage-dependence of steady-state inactivation) involving an intrapore receptor. The authors tested for these molecular pharmacologic features to explore whether meperidine is a local anesthetic. Methods The authors studied rat skeletal muscle mu1 (RSkM1) voltage-dependent Na+ channels or a mutant form heterologously coexpressed with rat brain Na+ channel accessory beta1, subunit in Xenopus oocytes. Polymerase chain reaction was used for mutagenesis, and mutations were confirmed by sequencing. Na+ currents were measured using a two-microelectrode voltage clamp. Meperidine and the commonly used local anesthetic lidocaine were applied to oocytes in saline solution at room temperature. Results Meperidine and lidocaine produced tonic current inhibition with comparable concentration dependence. Meperidine caused phasic current inhibition in which the concentration-response relationship was shifted to fivefold greater concentration relative to lidocaine. Meperidine and lidocaine negatively shifted the voltage dependence of steady-state inactivation. Mutation of a putative local anesthetic receptor reduced phasic inhibition by meperidine and lidocaine and tonic inhibition by lidocaine, but not meperidine tonic inhibition. Conclusions Meperidine blocks Na+ channels with molecular pharmacologic features of a local anesthetic. The findings support classification of meperidine as a local anesthetic but with less overall potency than lidocaine.

Ketamine Blockade of Voltage-gated Sodium Channels

2001 ◽  
Vol 95 (6) ◽  
pp. 1406-1413 ◽  
Author(s):  
Larry E. Wagner ◽  
Kevin J. Gingrich ◽  
John C. Kulli ◽  
Jay Yang
Keyword(s):  
Binding Site ◽  
Sodium Channels ◽  
Local Anesthetic ◽  
Molecular Pharmacology ◽  
Wild Type ◽  
General Anesthetic ◽  
Voltage Gated ◽  
Aspartate Receptor ◽  
Voltage Gated Sodium Channels ◽  
Steady State Inactivation

Background The general anesthetic ketamine is known to be an N-methyl-D-aspartate receptor blocker. Although ketamine also blocks voltage-gated sodium channels in a local anesthetic-like fashion, little information exists on the molecular pharmacology of this interaction. We measured the effects of ketamine on sodium channels. Methods Wild-type and mutant (F1579A) recombinant rat skeletal muscle sodium channels were expressed in Xenopus oocytes. The F1579A amino acid substitution site is part of the intrapore local anesthetic receptor. The effect of ketamine was measured in oocytes expressing wild-type or mutant sodium channels using two-electrode voltage clamp. Results Ketamine blocked sodium channels in a local anesthetic-like fashion, exhibiting tonic blockade (concentration for half-maximal inhibition [IC50] = 0.8 mm), phasic blockade (IC50 = 2.3 mm), and leftward shift of the steady-state inactivation; the parameters of these actions were strongly modified by alteration of the intrapore local anesthetic binding site (IC50 = 2.1 mm and IC50 = 10.3 mm for tonic and phasic blockade, respectively). Compared with lidocaine, ketamine showed greater tonic inhibition but less phasic blockade. Conclusions Ketamine interacts with sodium channels in a local anesthetic-like fashion, including sharing a binding site with commonly used clinical local anesthetics.

scholarly journals Voltage-Gated Na+ Channels are Modulated by Glucose and Involved in Regulating Cellular Insulin Content of INS-1 Cells

2018 ◽  
Vol 45 (2) ◽  
pp. 446-457 ◽  
Author(s):  
Chong Chen ◽  
Songhua Wang ◽  
Qingjuan Hu ◽  
Lvming Zeng ◽  
Hailong Peng ◽  
...  
Keyword(s):  
Steady State ◽  
Glucose Homeostasis ◽  
Insulin Content ◽  
Enzyme Linked Immunosorbent Assay ◽  
Na Channels ◽  
Β Cells ◽  
Insulin Synthesis ◽  
Voltage Gated ◽  
Glucose Levels ◽  
Extracellular Glucose

Background/Aims: Islet beta cells (β-cells) are unique cells that play a critical role in glucose homeostasis by secreting insulin in response to increased glucose levels. Voltage-gated ion channels in β-cells, such as K+ and Ca2+ channels, contribute to insulin secretion. The response of voltage-gated Na+ channels (VGSCs) in β-cells to the changes in glucose levels remains unknown. This work aims to determine the role of extracellular glucose on the regulation of VGSC. Methods: The effect of glucose on VGSC currents (INa) was investigated in insulin-secreting β-cell line (INS-1) cells of rats using whole-cell patch clamp techniques, and the effects of glucose on insulin content and cell viability were determined using Enzyme-Linked Immunosorbent Assay (ELISA) and Methylthiazolyldiphenyl-tetrazolium Bromide (MTT) assay methods respectively. Results: Our results show that extracellular glucose application can inhibit the peak of INa in a concentration-dependent manner. Glucose concentration of 18 mM reduced the amplitude of INa, suppressed the INa of steady-state activation, shifted the steady-state inactivation curves of INa to negative potentials, and prolonged the time course of INa recovery from inactivation. Glucose also enhanced the activity-dependent attenuation of INa and reduced the fraction of activated channels. Furthermore, 18 mM glucose or low concentration of tetrodotoxin (TTX, a VGSC-specific blocker) partially inhibited the activity of VGSC and also improved insulin synthesis. Conclusion: These results revealed that extracellular glucose application enhances the insulin synthesis in INS-1 cells and the mechanism through the partial inhibition on INa channel is involved. Our results innovatively suggest that VGSC plays a vital role in modulating glucose homeostasis.

scholarly journals p.L1612P, a Novel Voltage-gated Sodium Channel Nav1.7 Mutation Inducing a Cold Sensitive Paroxysmal Extreme Pain Disorder

2015 ◽  
Vol 122 (2) ◽  
pp. 414-423 ◽  
Author(s):  
Marc R. Suter ◽  
Zahurul A. Bhuiyan ◽  
Cédric J. Laedermann ◽  
Thierry Kuntzer ◽  
Muriel Schaller ◽  
...  
Keyword(s):  
Steady State ◽  
Sodium Channel ◽  
Cold Exposure ◽  
Pain Disorder ◽  
Clinical Genetic ◽  
Voltage Gated Sodium Channel ◽  
Voltage Gated ◽  
Recovery From Inactivation ◽  
Steady State Inactivation ◽  
Extreme Pain

Abstract Background: Mutations in the SCN9A gene cause chronic pain and pain insensitivity syndromes. We aimed to study clinical, genetic, and electrophysiological features of paroxysmal extreme pain disorder (PEPD) caused by a novel SCN9A mutation. Methods: Description of a 4-generation family suffering from PEPD with clinical, genetic and electrophysiological studies including patch clamp experiments assessing response to drug and temperature. Results: The family was clinically comparable to those reported previously with the exception of a favorable effect of cold exposure and a lack of drug efficacy including with carbamazepine, a proposed treatment for PEPD. A novel p.L1612P mutation in the Nav1.7 voltage-gated sodium channel was found in the four affected family members tested. Electrophysiologically the mutation substantially depolarized the steady–state inactivation curve (V1/2 from −61.8 ± 4.5 mV to −30.9 ± 2.2 mV, n = 4 and 7, P < 0.001), significantly increased ramp current (from 1.8% to 3.4%, n = 10 and 12) and shortened recovery from inactivation (from 7.2 ± 5.6 ms to 2.2 ± 1.5 ms, n = 11 and 10). However, there was no persistent current. Cold exposure reduced peak current and prolonged recovery from inactivation in wild-type and mutated channels. Amitriptyline only slightly corrected the steady–state inactivation shift of the mutated channel, which is consistent with the lack of clinical benefit. Conclusions: The novel p.L1612P Nav1.7 mutation expands the PEPD spectrum with a unique combination of clinical symptoms and electrophysiological properties. Symptoms are partially responsive to temperature but not to drug therapy. In vitro trials of sodium channel blockers or temperature dependence might help predict treatment efficacy in PEPD.

scholarly journals The Tarantula Venom Peptide Eo1a Binds to the Domain II S3-S4 Extracellular Loop of Voltage-Gated Sodium Channel NaV1.8 to Enhance Activation

2022 ◽  
Vol 12 ◽  
Author(s):  
Jennifer R. Deuis ◽  
Lotten Ragnarsson ◽  
Samuel D. Robinson ◽  
Zoltan Dekan ◽  
Lerena Chan ◽  
...  
Keyword(s):  
Steady State ◽  
Binding Site ◽  
Rational Design ◽  
Voltage Dependence ◽  
Fast Inactivation ◽  
Extracellular Loop ◽  
Peak Current ◽  
Future Studies ◽  
Voltage Gated ◽  
Functional Characterisation

Venoms from cone snails and arachnids are a rich source of peptide modulators of voltage-gated sodium (NaV) channels, however relatively few venom-derived peptides with activity at the mammalian NaV1.8 subtype have been isolated. Here, we describe the discovery and functional characterisation of β-theraphotoxin-Eo1a, a peptide from the venom of the Tanzanian black and olive baboon tarantula Encyocratella olivacea that modulates NaV1.8. Eo1a is a 37-residue peptide that increases NaV1.8 peak current (EC50 894 ± 146 nM) and causes a large hyperpolarising shift in both the voltage-dependence of activation (ΔV50–20.5 ± 1.2 mV) and steady-state fast inactivation (ΔV50–15.5 ± 1.8 mV). At a concentration of 10 μM, Eo1a has varying effects on the peak current and channel gating of NaV1.1–NaV1.7, although its activity is most pronounced at NaV1.8. Investigations into the binding site of Eo1a using NaV1.7/NaV1.8 chimeras revealed a critical contribution of the DII S3-S4 extracellular loop of NaV1.8 to toxin activity. Results from this work may form the basis for future studies that lead to the rational design of spider venom-derived peptides with improved potency and selectivity at NaV1.8.

scholarly journals Potent block of inactivation-deficient Na+ channels by n-3 polyunsaturated fatty acids

2006 ◽  
Vol 290 (2) ◽  
pp. C362-C370 ◽  
Author(s):  
Yong-Fu Xiao ◽  
Li Ma ◽  
Sho-Ya Wang ◽  
Mark E. Josephson ◽  
Ging Kuo Wang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Saturated Fatty Acids ◽  
Inhibitory Effect ◽  
Deficient Mutant ◽  
Na Channels ◽  
Mutant Channel ◽  
Α Subunit ◽  
Voltage Gated ◽  
Steady State Inactivation

A voltage-gated, small, persistent Na+ current ( INa) has been shown in mammalian cardiomyocytes. Hypoxia potentiates the persistent INa that may cause arrhythmias. In the present study, we investigated the effects of n-3 polyunsaturated fatty acids (PUFAs) on INa in HEK-293t cells transfected with an inactivation-deficient mutant (L409C/A410W) of the α-subunit (hH1α) of human cardiac Na+ channels (hNav1.5) plus β1-subunits. Extracellular application of 5 μM eicosapentaenoic acid (EPA; C20:5n-3) significantly inhibited INa. The late portion of INa ( INa late, measured near the end of each pulse) was almost completely suppressed. INa returned to the pretreated level after washout of EPA. The inhibitory effect of EPA on INa was concentration dependent, with IC50 values of 4.0 ± 0.4 μM for INa peak ( INa peak) and 0.9 ± 0.1 μM for INa late. EPA shifted the steady-state inactivation of INa peak by −19 mV in the hyperpolarizing direction. EPA accelerated the process of resting inactivation of the mutant channel and delayed the recovery of the mutated Na+ channel from resting inactivation. Other polyunsaturated fatty acids, docosahexaenoic acid, linolenic acid, arachidonic acid, and linoleic acid, all at 5 μM concentration, also significantly inhibited INa. In contrast, the monounsaturated fatty acid oleic acid or the saturated fatty acids stearic acid and palmitic acid at 5 μM concentration had no effect on INa. Our data demonstrate that the double mutations at the 409 and 410 sites in the D1–S6 region of hH1α induce inactivation-deficient INa and that n-3 PUFAs inhibit mutant INa.

Characterization of the isoform-specific differences in the gating of neuronal and muscle sodium channels

1998 ◽  
Vol 76 (10-11) ◽  
pp. 1041-1050 ◽  
Author(s):  
Michael E O'Leary
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Cultured Cells ◽  
Na Channel ◽  
Na Channels ◽  
Patch Clamp Technique ◽  
Recovery From Inactivation ◽  
Na Currents ◽  
Steady State Inactivation ◽  
Rate Of Recovery

Human heart (hH1), human skeletal muscle (hSkM1), and rat brain (rIIA) Na channels were expressed in cultured cells and the activation and inactivation of the whole-cell Na currents measured using the patch clamp technique. hH1 Na channels were found to activate and inactivate at more hyperpolarized voltages than hSkM1 and rIIA. The conductance versus voltage and steady state inactivation relationships have midpoints of -48 and -92 mV (hH1), -28 and -72 mV (hSkM1), and -22 and -61 mV (rIIA). At depolarized voltages, where Na channels predominately inactivate from the open state, the inactivation of hH1 is 2-fold slower than that of hSkM1 and rIIA. The recovery from fast inactivation of all three isoforms is well described by a single rapid component with time constants at -100 mV of 44 ms (hH1), 4.7 ms (hSkM1), and 7.6 ms (rIIA). After accounting for differences in voltage dependence, the kinetics of activation, inactivation, and recovery of hH1 were found to be generally slower than those of hSkM1 and rIIA. Modeling of Na channel gating at hyperpolarized voltages where the channel does not open suggests that the slow rate of recovery from inactivation of hH1 accounts for most of the differences in the steady-state inactivation of these Na channels.Key words: cardiac, neuronal, skeletal muscle, sodium channel.

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