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Erythromelalgia is a rare pain disorder that is underrecognized and difficult-to-treat. It is characterized by episodes of extremity erythema and pain that can be disabling; it may be genetic, related to an underlying systemic disease, or idiopathic. Considering the prominent cutaneous features characteristic of the condition, dermatologists can play an important role in early recognition and limitation of morbidity. The first article in this 2-part continuing medical education series reviews the epidemiology, pathogenesis, clinical manifestations, evaluation, and complications. [ABSTRACT FROM AUTHOR]

The Thr226Met pathologic variant of the SCN1A gene has been associated with the clinical development of an early infantile developmental and epileptic encephalopathy (EIDEE) different from Dravet's syndrome. The electrophysiological mechanisms of the mutated channel lead to a paradoxical gain and loss of function. The use of sodium channel blockers (SCB) that counteract this gain of function has been described in previous studies and they can be safely administered to patients carrying mutations in other sodium channel subtypes without causing a worsening of seizures. We report the use of SCB in a child harboring the Thr226Met pathologic variant of SCN1A with early-onset pharmaco-resistant migrating seizures, as well as developmental delay. Lacosamide led to a dramatic reduction in seizure frequency; however, only a mild improvement in the epileptic activity depicted by electroencephalography (EEG) was achieved. The introduction of carbamazepine as an add-on therapy led to a notable reduction in epileptic activity via EEG and to an improvement in sensorimotor development. Despite the overall clinical improvement, the patient developed febrile seizures and a nonepileptic jerking of the right hand. In this case of EIDEE with the Thr226Met variant, we demonstrate a beneficial pharmacological intervention of SCB in contrast to findings described in current literature. Our report encourages the cautious use of SCB at early stages of the disease in patients carrying this pathologic variant. [ABSTRACT FROM AUTHOR]

BACKGROUND Pyrethroids are the most widely used insecticides for the control of malaria transmitting Anopheles gambiae mosquitoes and rapid increase in resistance to this insecticide class is of major concern. Pyrethroids target the Voltage Gated Sodium Channels (VGSCs), that have a key role in the normal function of the mosquitoes' nervous system. VGSC mutations L995F and L995S have long been associated with pyrethroid resistance and screening for their presence is routine in insecticide resistance management programs. Recently, a VGSC haplotype containing two amino acid substitutions associated with resistance in other species, V402L and I1527T, was identified. These two VGSC mutations are found in tight linkage and are mutually exclusive to the classical L995F/S mutations. RESULTS: We identify the presence of the V402L‐I1527T haplotype in resistant An. coluzzii colonized strains and in field populations from Burkina Faso, at frequencies higher than previously reported; in some cases almost reaching fixation. Functional validation of V402L in insecticide resistance using a CRISPR/Cas9 genome modified line showed that it confers reduced mortality after exposure to all tested pyrethroids and DDT, but at lower levels compared to L995F. In contrast to L995F however, no fitness costs were identified for mosquitoes carrying V402L under laboratory conditions. CONCLUSION: The V402L substitution confers pyrethroid resistance in An. gambiae in the absence of any other VGSC substitution and/or alternative resistance mechanisms. The lower fitness cost associated with this kdr mutation may provide a selective advantage over the classical kdr in some settings and genotyping at this locus should be added in the list of resistant alleles for routine screening. [ABSTRACT FROM AUTHOR]

Mosquitoes are regularly exposed to adverse effects of insecticides employed in field during vector control campaigns. Its primary goal is to eliminate the vector population; nevertheless, this practise typically ignores the residual impacts and long-term repercussions on the remaining population. Here, the current study analysed how sublethal exposure of insecticides alter the life qualities, genotypic and biochemical characteristics of mosquitoes. The resistance ratio value in Laboratory Resistant (Lab-R) larvae increased 10 times (0.010 mg/l to 0.108 mg/l) compared to Laboratory Susceptible (Lab S) larvae. It also revealed that the surviving mosquitoes had 50% reduction in hatchability but had longer larval and pupal periods (15 days and 2 days), respectively. The survival rates decrease in female by 2 days but increase in male by 7 days which is of concern and necessitates additional study. Moreover, major role of monooxygenase was confirmed behind resistance development which was further supported by piperonyl butoxide assay where reduction in Tolerance Ratio (TR 50) by 12-fold occurred and gene expression profile also showed high expression level of CYP6P12 gene. In resistant strain, cuticular thickness increased by 1.23 times and alteration at codon 1532 (A TC to T TC) on VGSC gene leads to mutation I1532F. The data gleaned from our work highlights the threat of sublethal insecticides on vector control techniques and offers ample evidence that the larval selection alters adult life qualities, metabolic properties and transgenerational features which contributes to the damage caused by resistance. [Display omitted] • Aedes albopictus exposed to permethrin led to increase in RR value by 10 folds. • Resistant strain had reduced hatchability but longer larval and pupal periods. • CYP450 and thickening of cuticle play vital role in resistance development. • No major mutation linked to pyrethroid resistance was observed in resistant strain. [ABSTRACT FROM AUTHOR]

Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials.

Modification of voltage‐gated Na+ channel (NaV) function by intracellular Ca2+ has been a topic of much controversy. Early studies relied on measuring NaV function in the absence or presence of intracellular Ca2+, and generated seemingly disparate results. Subsequent investigations revealed the mechanism(s) of Ca2+‐driven NaV modulation are complex and involve multiple accessory proteins. The Ca2+‐sensing protein calmodulin (CaM) has a central role in tuning NaV function to [Ca2+]i, but the mechanism has been obscured by other proteins (such as fibroblast growth factors (FGF) or CaM‐dependent kinase II (CaMKII)) that can also modify channel function or exert an influence in a Ca2+‐dependent manner. Significant progress has been made in understanding the architecture of full‐length ion channels and the structural and biophysical details of NaV–accessory protein interactions. Interdisciplinary structure–function studies are beginning to resolve the effect each interaction has on NaV gating. Carefully designed structure‐guided or strategically selected disease‐associated mutations are able to impair NaV–accessory protein interactions without altering other properties of channel function. Recently CaM was found to engage part of NaV1.5 that is required for channel inactivation with high affinity. Careful impairment of this interaction disrupted NaV1.5's ability to recover from inactivation. Such results support a paradigm of CaM‐facilitated recovery from inactivation (CFRI). How NaV–CaM, CaMKII and FGF/fibroblast growth factor homologous factor interactions affect the timing or function of CFRI in cardiomyocytes remain open questions that are discussed herein. Moreover whether CFRI dysfunction or premature activation underlie certain NaV channelopathies are important questions that will require further investigation. [ABSTRACT FROM AUTHOR]

Based on recent findings, an increased late sodium current (INa,late) plays an important pathophysiological role in cardiac diseases, including rhythm disorders. The article first describes what is INa,late and how it functions under physiological circumstances. Next, it shows the wide range of cellular mechanisms that can contribute to an increased INa,late in heart diseases, and also discusses how the upregulated INa,late can play a role in the generation of cardiac arrhythmias. The last part of the article is about INa,late inhibiting drugs as potential antiarrhythmic agents, based on experimental and preclinical data as well as in the light of clinical trials. [ABSTRACT FROM AUTHOR]

Marawan Ahmed,1 Horia Jalily Hasani,1,* Aravindhan Ganesan,1,* Michael Houghton,2–4 Khaled Barakat1–3 1Faculty of Pharmacy and Pharmaceutical Sciences, 2Li Ka Shing Institute of Virology, 3Li Ka Shing Applied Virology Institute, 4Department of Medical Microbiology and Immunology, Katz Centre for Health Research, University of Alberta, Edmonton, AB, Canada *These authors contributed equally to this work Abstract: Abnormalities in the human Nav1.5 (hNav1.5) voltage-gated sodium ion channel (VGSC) are associated with a wide range of cardiac problems and diseases in humans. Current structural models of hNav1.5 are still far from complete and, consequently, their ability to study atomistic interactions of this channel is very limited. Here, we report a comprehensive atomistic model of the hNav1.5 ion channel, constructed using homology modeling technique and refined through long molecular dynamics simulations (680 ns) in the lipid membrane bilayer. Our model was comprehensively validated by using reported mutagenesis data, comparisons with previous models, and binding to a panel of known hNav1.5 blockers. The relatively long classical MD simulation was sufficient to observe a natural sodium permeation event across the channel’s selectivity filters to reach the channel’s central cavity, together with the identification of a unique role of the lysine residue. Electrostatic potential calculations revealed the existence of two potential binding sites for the sodium ion at the outer selectivity filters. To obtain further mechanistic insight into the permeation event from the central cavity to the intracellular region of the channel, we further employed “state-of-the-art” steered molecular dynamics (SMD) simulations. Our SMD simulations revealed two different pathways through which a sodium ion can be expelled from the channel. Further, the SMD simulations identified the key residues that are likely to control these processes. Finally, we discuss the potential binding modes of a panel of known hNav1.5 blockers to our structural model of hNav1.5. We believe that the data presented here will enhance our understanding of the structure–property relationships of the hNav1.5 ion channel and the underlying molecular mechanisms in sodium ion permeation and drug interactions. The results presented here could be useful for designing safer drugs that do not block the hNav1.5 channel. Keywords: sodium ion channel, voltage-gated sodium channel, steered molecular dynamics, cardiotoxicity, hNav1.5, channel blockers

Extensive and continuous use of pyrethroid insecticides to prevent the transmission of malaria can lead to mutations in the voltage gate sodium channel gene (VGSC) in mosquito vectors. This gene mutation associated with insensitivity pyrethroid is known as knockdown resistance (kdr). The emergence of resistance to pyrethroid insecticides in vector mosquitoes can be a barrier to the successful termination of malaria transmission. Therefore, detection of mutation is necessary to prevent the resistency from build up. The aim of the study was to determine the resistance status of pyrethroid insecticides and identify mutations in the VGSC gene codon 1014 marker for resistance to Anopheles sp. which is a malaria vector in South Sumatra Province. Samples were taken from three districts in South Sumatra: Muara Enim, OKU, and Lahat. The susceptibility enzymatic test of pyrethroid insecticide (permethrin 0.75%) was preliminarily carried out according to WHO 2016 standard on Anopheles vagus Dönitz species. Identification of VGSC gene mutation was performed on all An. vagus that were previously tested for susceptibility and on An. barbirostris van der Wulp species using seminested-PCR and followed by sequencing. The result showed that samples from Muara Enim regency had resistance, whereas in Lahat and OKU regencies were still susceptible to permethrin. From the sequence analysis it is shown that there are no change in DNA kdr bases in VGSC gene insecticide target sites from all regencies. In conclusion, based on molecular studies, there were no pyrethroid insecticide resistance in South Sumatra Province.

The voltage‐sensitive sodium channel (VSSC) is essential for the generation and propagation of action potentials. VSSC kinetics can be modified by producing different splice variants. The functionality of VSSC depends on features such as the voltage sensors, the selectivity filter and the inactivation loop. Mutations in Vssc conferring resistance to pyrethroid insecticides are known as knockdown resistance (kdr). We analysed the conservation of VSSC in both a broad scope and a narrow scope by three approaches: (1) we compared conservation of sequences and of differential exon use across orders of the Insecta; (2) we determined which kdr mutations were possible with a single nucleotide mutation in nine populations of Aedes aegypti; and (3) we examined the individual VSSC variation that exists within a population of Drosophila melanogaster. There is an increasing amount of transcript diversity possible from Diplura towards Diptera. The residues of the voltage sensors, selectivity filter and inactivation loop are highly conserved. The majority of exon sequences were >88.6% similar. Strain‐specific differences in codon constraints exist for kdr mutations in nine strains of A. aegypti. Three Vssc mutations were found in one population of D. melanogaster. This study shows that, overall, Vssc is highly conserved across Insecta and within a population of an insect, but that important differences do exist. [ABSTRACT FROM AUTHOR]

Abstract Background Anopheles culicifacies s.l. is one of the primary vectors of malaria in India responsible for the highest number of malaria cases. This vector is resistant to DDT in most parts of the country with indication of emerging resistance to pyrethroids. Since knockdown resistance (kdr) is known to confer cross-resistance between DDT and pyrethroids owing to a common target site of action, knowledge of prevalence of knockdown resistance (kdr) alleles is important from insecticide resistance management point of view. Methods Nine populations of An. culicifacies belonging to five states of India, representing northern, western and central-east India, were screened for the presence of two alternative kdr mutations L1014F and L1014S using PCR-based assays. Dead and alive mosquitoes, following WHO standard insecticide susceptibility test against deltamethrin and DDT, were tested for allelic association. Results L1014F mutation was recorded in all populations studied except from Haryana and Rajasthan states in northern India, with low frequencies ranging between 0.012 and 0.076; whereas presence of L1014S mutation was recorded in five populations only belonging to central-east India, with allelic frequencies ranging between 0.010 and 0.046. Both the kdr mutant alleles were found mostly in heterozygous condition without deviating from Hardy-Weinberg equilibrium. Both mutations showed protection against deltamethrin whereas only L1014S mutation showed protection against DDT when tested using additive model. Conclusions The two L1014-kdr mutations, L1014F and L1014S, co-occurred in five populations belonging to Chhattisgarh and Odisha states of India whereas L1014F was present in all populations studied except populations from northern states. Both kdr mutations were found with very low allelic frequencies mostly in heterozygous condition and exhibited protection against deltamethrin.

Graphical abstract Abstract The voltage gated sodium channel Na V 1.8 has been postulated to play a key role in the transmission of pain signals. Core hopping from our previously reported phenylimidazole leads has allowed the identification of a novel series of benzimidazole Na V 1.8 blockers. Subsequent optimization allowed the identification of compound 9 , PF-06305591, as a potent, highly selective blocker with an excellent preclinical in vitro ADME and safety profile. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Na v 1.7 is a complex protein with multiple druggable sites. • Inhibitors of Na v 1.7 are able to produce robust pain relief in preclinical models. • Highly potent and selective (>100×) of Na v 1.7 have been recently disclosed. • More work is needed to understand PK/PD relationships of Na v 1.7 inhibitors. Abstract The voltage gated sodium channel Na v 1.7 plays an essential role in the transmission of pain signals. Strong human genetic validation has motivated extensive efforts to discover potent, selective, and efficacious Na v 1.7 inhibitors for the treatment of chronic pain. This digest will introduce the structure and function of Na v 1.7 and highlight the wealth of recent developments on a diverse array of Na v 1.7 inhibitors, including optimization of their potency, selectivity, and PK/PD relationships. [ABSTRACT FROM AUTHOR]

Erythromelalgia (EM) is a rare disorder characterized by erythematous, warm, painful extremities, which is often precipitated by cold conditions. The pathophysiology of EM is incompletely understood. Recent investigations have identified sodium channelopathy as a genetic cause for this pain condition, classified as primary inherited EM. Other subtypes are idiopathic EM and secondary EM. The management of pain in EM is challenging as no single therapy has been found to be effective. There is varying response to pharmacotherapy and significant variability within this clinical population, resulting in a stepwise trial and error approach. Consequently, EM is often associated with poorer health-related quality of life with higher morbidity. There is currently no consensus or guidelines on management of pain in EM. This is a review of the literature on management of pain using pharmacologic, procedural intervention and nonpharmacologic treatment in children and adults with EM. [ABSTRACT FROM AUTHOR]

Key points Voltage-gated sodium channels play a fundamental role in determining neuronal excitability., Specifically, voltage-gated sodium channel subtype NaV1.7 is required for sensing acute and inflammatory somatic pain in mice and humans but its significance in pain originating from the viscera is unknown., Using comparative behavioural models evoking somatic and visceral pain pathways, we identify the requirement for NaV1.7 in regulating somatic (noxious heat pain threshold) but not in visceral pain signalling., These results enable us to better understand the mechanisms underlying the transduction of noxious stimuli from the viscera, suggest that the investigation of pain pathways should be undertaken in a modality-specific manner and help to direct drug discovery efforts towards novel visceral analgesics., Abstract Voltage-gated sodium channel NaV1.7 is required for acute and inflammatory pain in mice and humans but its significance for visceral pain is unknown. Here we examine the role of NaV1.7 in visceral pain processing and the development of referred hyperalgesia using a conditional nociceptor-specific NaV1.7 knockout mouse (NaV1.7Nav1.8) and selective small-molecule NaV1.7 antagonist PF-5198007. NaV1.7Nav1.8 mice showed normal nociceptive behaviours in response to intracolonic application of either capsaicin or mustard oil, stimuli known to evoke sustained nociceptor activity and sensitization following tissue damage, respectively. Normal responses following induction of cystitis by cyclophosphamide were also observed in both NaV1.7Nav1.8 and littermate controls. Loss, or blockade, of NaV1.7 did not affect afferent responses to noxious mechanical and chemical stimuli in nerve-gut preparations in mouse, or following antagonism of NaV1.7 in resected human appendix stimulated by noxious distending pressures. However, expression analysis of voltage-gated sodium channel α subunits revealed NaV1.7 mRNA transcripts in nearly all retrogradely labelled colonic neurons, suggesting redundancy in function. By contrast, using comparative somatic behavioural models we identify that genetic deletion of NaV1.7 (in NaV1.8-expressing neurons) regulates noxious heat pain threshold and that this can be recapitulated by the selective NaV1.7 antagonist PF-5198007. Our data demonstrate that NaV1.7 (in NaV1.8-expressing neurons) contributes to defined pain pathways in a modality-dependent manner, modulating somatic noxious heat pain, but is not required for visceral pain processing, and advocate that pharmacological block of NaV1.7 alone in the viscera may be insufficient in targeting chronic visceral pain. [ABSTRACT FROM AUTHOR]

Objective To investigate the effect of hypoxia on the expression of voltage gated sodium channels and apoptotic factors in spiral ganglion neurons(SGN). Methods The expression of Nav1.1, Nav1.6 and Nav1.7αsubunit mRNA in SGN were detected by using quantitative polymerase chain reaction(qPCR), after cultured under tradition condition or hypoxia condition. The mRNA level of Caspase-3 was also investigated by using qPCR. Results Hypoxia exposure for 24 hcould increase the mRNA expression levels of Caspase-3, Nav1.1 and Nav1.7αsubunit, and decrease the mRNA expresion level of Nav1. 6αsubunit mRNA(P<0.05). Conclusion Hypoxia could down-regulate the expression levevl of voltage gated sodium channels, and activate the Caspase dependent apoptotic process of SGN, which might be the mechanism of sensorineural hearing loss induce by hypoxia. [ABSTRACT FROM AUTHOR]

The receptor-associated protein of the synapse (rapsyn) is required for anchoring and stabilizing the nicotinic acetylcholine receptor (AChR) in the postsynaptic membrane of the neuromuscular junction (NMJ) during development. Here we studied the role of rapsyn in the maintenance of the adult NMJ by reducing rapsyn expression levels with short hairpin RNA (shRNA). Silencing rapsyn led to the average reduction of the protein levels of rapsyn (31% loss) and AChR (36% loss) at the NMJ within 2 weeks, corresponding to previously reported half life of these proteins. On the other hand, the sodium channel protein expression was augmented (66%) in rapsyn-silenced muscles. Unexpectedly, at the ultrastructural level a significant increase in the amount of secondary folds of the postsynaptic membrane in silenced muscles was observed. The neuromuscular transmission in rapsyn-silenced muscles was mildly impaired. The results suggest that the adult NMJ can rapidly produce postsynaptic folds to compensate for AChR and rapsyn loss.

Objective: To investigate the variations in the expression of voltage-gated sodium (Na v ) channel subunits during development of rat cerebellar Purkinje neurons and their correlation with maturation of electrophysiological characteristics of the neurons., Methods: We observed the changes in the expression levels of Na V 1.1, 1.2, 1.3 and 1.6 during the development of Purkinje neurons using immunohistochemistry in neonatal (5-7 days after birth), juvenile (12-14 days), adolescent (21-24 days), and adult (42-60 days) SD rats. Using whole-cell patch-clamp technique, we recorded the spontaneous electrical activity of the neurons in ex vivo brain slices of rats of different ages to analyze the changes of electrophysiological characteristics of these neurons during development., Results: The expression of Na V subunits in rat cerebellar Purkinje neurons showed significant variations during development. Na V 1.1 subunit was highly expressed throughout the developmental stages and increased progressively with age ( P < 0.05). Na V 1.2 expression was not detected in the neurons in any of the developmental stages ( P > 0.05). The expression level of Na V 1.3 decreased with development and became undetectable after adolescence ( P < 0.05). Na V 1.6 expression was not detected during infancy, but increased with further development ( P < 0.05). Na V 1.1 and Na V 1.3 were mainly expressed in the early stages of development. With the maturation of the rats, Na V 1.3 expression disappeared and Na V 1.6 expression increased in the neurons. Na V 1.1 and Na V 1.6 were mainly expressed after adolescence. The total Na V protein level increased gradually with development ( P < 0.05) and tended to stabilize after adolescence. The spontaneous frequency and excitability of the Purkinje neurons increased gradually with development and reached the mature levels in adolescence. The developmental expression of Na V subunits was positively correlated with discharge frequency ( r =0.9942, P < 0.05) and negatively correlated with the excitatory threshold of the neurons ( r =0.9891, P < 0.05)., Conclusion: The changes in the expression levels of Na V subunits are correlated with the maturation of high frequency electrophysiological properties of the neurons, suggesting thatmature Na V subunit expressions is the basis of maturation of electrophysiological characteristics of the neurons.

The axon initial segment (AIS) is a highly specialized neuronal compartment that plays a key role in neuronal development and excitability. It concentrates multiple membrane proteins such as ion channels and cell adhesion molecules (CAMs) that are recruited to the AIS by the scaffold protein ankyrin G (ankG). The crucial function of ankG in the anchoring of AIS membrane components is well established, but a reciprocal role of membrane partners in ankG targeting and stabilization remained elusive. In rat cultured hippocampal neurons and cortical organotypic slices, we found that shRNA-mediated knockdown of ankG membrane partners (voltage-gated sodium channels (Nav) or neurofascin-186) led to a decrease of ankG concentration and perturbed the AIS formation and maintenance. These effects were rescued by expressing a recombinant AIS-targeted Nav or by a minimal construct containing the ankyrin-binding domain of Nav1.2 and a membrane anchor (mABD). Moreover, overexpressing mABD in mature neurons led to ankG mislocalization. Altogether, these results demonstrate that a tight and precocious association of ankG with its membrane partners is a key step for the establishment and maintenance of the AIS. [ABSTRACT FROM AUTHOR]

Antiepileptic drugs act on voltage gated sodium channels in many different ways: rufinamide is thought to influence the fast inactivation, so its anticonvulsant action could be similar to carbamazepine, whereas lacosamide enhances the slow inactivation; however some antidepressants were also described to act in the same way. Rufinamide, lacosamide, carbamazepine, fluoxetine and imipramine were tested using in vitro models of epileptiform activities. Extracellular local field potentials were recorded using hippocampal slices from immature rats and the pattern of epileptiform activities was analyzed. Seizure-like events (SLE), but not interictal bursts were sensitive to AEDs' action. Rufinamide increased interictal periods by prolonging preictal phase and reducing SLE duration, and was the only tested AED which reduced SLE frequency. Lacosamide's effect resembled that of fluoxetine in the low-Mg model: both drugs reduced markedly the SLE duration, but increased their frequency. Imipramine and fluoxetine irreversibly suppressed SLE in all slices. Some proconvulsive type of action on SLEs such as increasing preictal neuronal activity by rufinamide and increasing SLE frequency by lacosamide, fluoxetine and carbamazepine, were also observed. Newer drugs were more efficient than carbamazepine, and the anticonvulsant action of antidepressants on in vitro epileptiform activities may seem somewhat surprising. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX) and its analogs, the paralytic shellfish toxins (PSTs), are a group of potent neurotoxins well known for their role in acute paralytic poisoning by preventing the generation of action potentials in neuronal cells. They are found in both marine and freshwater environments globally and although acute exposure from the former has previously received more attention, low dose extended exposure from both sources is possible and to date has not been investigated. Given the known role of cellular electrical activity in neurodevelopment this pattern of exposure may be a significant public health concern. Additionally, the presence of PSTs is likely to be an ongoing and possibly increasing problem in the future. This review examines the neurodevelopmental toxicity of STX, the risk of extended or repeated exposure to doses with neurodevelopmental effects, the potential implications of this exposure and briefly, the steps taken and difficulties faced in preventing exposure. [ABSTRACT FROM AUTHOR]

(Arylalkyl)azoles (AAAs) emerged as a novel class of antiepileptic agents with the invention of nafimidone and denzimol. Several AAA derivatives with potent anticonvulsant activities have been reported so far, however neurotoxicity was usually an issue. We prepared a set of ester derivatives of 1-(2-naphthyl)-2-(1H-1,2,4-triazol-1-yl)ethanone oxime and evaluated their anticonvulsant and neurotoxic effects in mice. Most of our compounds were protective against maximal electroshock (MES)- and/or subcutaneous metrazol (s.c. MET)-induced seizures whereas none of them showed neurotoxicity. Nafimidone and denzimol have an activity profile similar to that of phenytoin or carbamazepine, both of which are known to inhibit voltage-gated sodium channels (VGSCs) as well as to enhance γ-aminobutiric acid (GABA)-mediated response. In order to get insights into the effects of our compounds on VGSCs and A-type GABA receptors (GABA A Rs) we performed docking studies using homology model of Na + channel inner pore and GABA A R as docking scaffolds. We found that our compounds bind VGSCs in similar ways as phenytoin, carbamazepine, and lamotrigine. They showed strong affinity to benzodiazepine (BZD) binding site and their binding interactions were mainly complied with the experimental data and the reported BZD binding model. [ABSTRACT FROM AUTHOR]

Background: Anopheles culicifacies s.l. is one of the primary vectors of malaria in India responsible for the highest number of malaria cases. This vector is resistant to DDT in most parts of the country with indication of emerging resistance to pyrethroids. Since knockdown resistance (kdr) is known to confer cross-resistance between DDT and pyrethroids owing to a common target site of action, knowledge of prevalence of knockdown resistance (kdr) alleles is important from insecticide resistance management point of view. Methods: Nine populations of An. culicifacies belonging to five states of India, representing northern, western and central-east India, were screened for the presence of two alternative kdr mutations L1014F and L1014S using PCR-based assays. Dead and alive mosquitoes, following WHO standard insecticide susceptibility test against deltamethrin and DDT, were tested for allelic association. Results: L1014F mutation was recorded in all populations studied except from Haryana and Rajasthan states in northern India, with low frequencies ranging between 0.012 and 0.076; whereas presence of L1014S mutation was recorded in five populations only belonging to central-east India, with allelic frequencies ranging between 0.010 and 0.046. Both the kdr mutant alleles were found mostly in heterozygous condition without deviating from Hardy-Weinberg equilibrium. Both mutations showed protection against deltamethrin whereas only L1014S mutation showed protection against DDT when tested using additive model. Conclusions: The two L1014-kdr mutations, L1014F and L1014S, co-occurred in five populations belonging to Chhattisgarh and Odisha states of India whereas L1014F was present in all populations studied except populations from northern states. Both kdr mutations were found with very low allelic frequencies mostly in heterozygous condition and exhibited protection against deltamethrin. [ABSTRACT FROM AUTHOR]

Scorpion β-neurotoxins represent a pharmacological group that affects voltage-gated sodium channels (Nav). Despite knowing the electrophysiological effect of these toxins on Nav channels, the molecular mechanism by which the union is carried out is still undetermined. In this study, computational techniques such as modeling, docking and molecular dynamics were used to elucidate the mechanism of interaction between scorpion β-neurotoxins using the neurotoxin nCssII and its recombinant variant CssII-RCR, which bind to the site-4, an extracellular receptor, of the human sodium channel hNav1.6. Different modes of interaction were observed for both toxins, where the main distinguishing feature was the interaction generated by the residue E15 on such site-4; that is, E15 in nCssII exhibits an interaction with the voltage-sensing domain II, and the same residue E15 of CssII-RCR exhibits an interaction with domain III. Despite this difference in interaction by E15, it is seen that both neurotoxins interact with similar regions of the voltage sensing domain such as the S3-S4 connecting loop (L834-E838) of the hNav1.6. Our simulations present a first approach to the mode of interaction of scorpion beta-neurotoxins in toxin-receptor complexes, being able to explain at the molecular level the phenomenon of voltage sensor entrapment generated by these toxins.Communicated by Ramaswamy H. Sarma.

Classical accommodation is a form of spike frequency adaptation in neurons whereby excitatory drive results in action potential output of gradually decreasing frequency. Here we describe an essential molecular component underlying classical accommodation in juvenile mouse hippocampal CA1 pyramidal neurons. A-type isoforms of fibroblast growth factor homologous factors (FHFs) bound to axoso-matic voltage-gated sodium channels bear an N-terminal blocking particle that drives some associated channels into a fast-onset, long-term inactivated state. Use-dependent accumulating channel blockade progressively elevates spike voltage threshold and lengthens interspike intervals. The FHF particle only blocks sodium channels from the open state, and mutagenesis studies demonstrate that this particle uses multiple aliphatic and cationic residues to both induce and maintain the long-term inactivated state. The broad expression of A-type FHFs in neurons throughout the vertebrate CNS suggests a widespread role of these sodium channel modulators in the control of neural firing. [ABSTRACT FROM AUTHOR]

Highlights: [•] Voltage gated sodium and calcium channels have major role in inflammatory pain. [•] Chronic inflammatory pain may progress to encompass neuropathic pain. [•] Therapeutic potential of sodium and calcium channel blockers for inflammatory pain. [•] Selective NaV1.7,1.8, N- and T-type blockers may improve chronic pain treatment. [ABSTRACT FROM AUTHOR]

Highlights: [•] CNTF decreases muscle excitability by an early, post-transcriptional effect. [•] This effect is due to a decrease in sodium current and an increase in resting potential. [•] It appears to be mediated by PKC induced phosphorylations. [•] It could be involved in acquired polyneuromyopathy syndrome. [ABSTRACT FROM AUTHOR]

Sodium channel alpha subunit type 1 (SCN1A) is voltage gated ion channel which plays critical role in membrane excitability. A common SCN1A IVS5-91G>A (rs3812718) allele has been attributed to be a possible modifying factor for epilepsy susceptibility and therapeutic response. In the present study, we enrolled 485 epilepsy patients and 298 age-sex matched controls free of neurological deficits. Therapeutic response of carbamazepine/oxcarbamazepine (CBZ/OXC) and other antiepileptic drugs were observed in terms of drug responsiveness and drug resistance. Genotyping of SCN1A IVS5-91G>A is done by Taqman custom designed assay; in a real time7500HT System. We observe highly significant association [(P-values for GA (P = 6.58 × 10−5, OR = 2.13, 95% CI = 1.47–3.09) and AA (P = 4.11 × 10−9, OR = 3.59, 95% CI = 2.35–5.50)] at variant genotypes as well as A allele (P = 6.92 × 10−11), OR = 1.99, 95%, CI = 1.62–2.45) in epilepsy patients versus control subjects. The relative risk for epilepsy susceptibility due to variant containing genotypes (GA + AA) was also significant (P = 1.64 × 10−5; OR = 2.56; 95% CI = 1.80–3.65) when compared with homozygous wild-type GG. The risk in recessive model (P = 1.34 × 10−5; OR = 2.12; 95% CI = 1.51–2.97) was also apparent when compared with GA + GG. In case-only analysis, we evaluated the effect of SCN1A IVS5-91G>A polymorphism with drug resistance of anti-epileptic drug therapies. However, we did not observe significant associations either with patients showing drug resistance to CBZ/OXC monotherapy or polytherapy. In conclusion, we report that SCN1AIVS5-91G>A polymorphism is associated with epilepsy susceptibility but not with drug responsiveness in epilepsy patients from North India. [ABSTRACT FROM AUTHOR]

Abstract: Voltage-gated sodium channels have been shown to play a critical role in neuropathic pain. A series of low molecular weight biaryl substituted pyrazole carboxamides were identified with good in-vitro potency and in-vivo efficacy. Compound 26, a Nav1.7 blocker has excellent efficacy in the Chung model of neuropathic pain. [ABSTRACT FROM AUTHOR]

Abstract: Two different mechanisms by which capsaicin blocks voltage-gated sodium channels (VGSCs) were found by using knockout mice for the transient receptor potential V1 (TRPV1−/−). Similar with cultured rat trigeminal ganglion (TG) neurons, the amplitude of tetrodotoxin-resistant (TTX-R) sodium current was reduced 85% by 1 μM capsaicin in capsaicin sensitive neurons, while only 6% was blocked in capsaicin insensitive neurons of TRPV1+/+ mice. The selective effect of low concentration capsaicin on VGSCs was reversed in TRPV1−/− mice, which suggested that this effect was dependent on TRPV1 receptor. The blockage effect of high concentration capsaicin on VGSCs in TRPV1−/− mice was the same as that in capsaicin insensitive neurons of rats and TRPV1+/+ mice. It is noted that non-selective effect of capsaicin on VGSCs shares many similarities with local anesthetics. That is, firstly, both blockages are concentration-dependent and revisable. Secondly, being accompanied with the reduction of amplitude, voltage-dependent inactivation curve shifts to hyperpolarizing direction without a shift of activation curve. Thirdly, use-dependent blocks are induced at high stimulus frequency. [Copyright &y& Elsevier]

Abstract: Brevetoxins (PbTxs) and ciguatoxins (CTXs) are two suites of dinoflagellate derived marine polyether neurotoxins that target the voltage gated sodium channel (VGSC). PbTxs are commonly responsible for massive fish kills and unusual mortalities in marine mammals. CTXs, more often noted for human intoxication, are suspected causes of fish and marine mammal intoxication, although this has never been reported in the field. VGSCs, present in the membrane of all excitable cells including those found in skeletal muscle, nervous and heart tissues, are found as isoforms with differential expression within species and tissues. To investigate the tissue and species susceptibility to these biotoxins, we determined the relative affinity of PbTx-2 and -3 and P-CTX-1 to native VGSCs in the brain, heart, and skeletal muscle of rat and the marine teleost fish Centropristis striata by competitive binding in the presence of [3H]PbTx-3. No differences between rat and fish were observed in the binding of PbTxs and CTX to either brain or skeletal muscle. However, [3H]PbTx-3 showed substantial lower affinity to rat heart tissue while in the fish it bound with the same affinity to heart than to brain or skeletal muscle. These new insights into PbTxs and CTXs binding in fish and mammalian excitable tissues indicate a species related resistance of heart VGSC in the rat; yet, with comparable sensitivity between the species for brain and skeletal muscle. [Copyright &y& Elsevier]

In the work reported here, we have investigated the changes in the activation and fast inactivation properties of the rat brain voltage-gated sodium channel (rNav 1.2a) α subunit, expressed heterologously in the Chinese Hamster Ovary (CHO) cells, by short depolarizing prepulses (10 – 1000 ms). The time constant of recovery from fast inactivation (τfast) and steady-state parameters for activation and inactivation varied in a pseudo-oscillatory fashion with the duration and amplitude of a sustained prepulse. A consistent oscillation was observed in most of the steady-state and non-inactivating current parameters with a time period close to 225 ms, although a faster oscillation of time period 125 ms was observed in the τfast. The studies on the non-inactivating current and steady-state activation indicate that the phase of oscillation varies from cell to cell. Co-expression of the β1 subunit with the α subunit channel suppressed the oscillation in the charge movement per single channel and free energy of steady-state inactivation, although the oscillation in the half steady-state inactivation potential remained unaltered. Incidentally, the frequencies of oscillation in the sodium channel parameters (4–8 Hz) correspond to the theta component of network oscillation. This fast pseudo-oscillatory mechanism, together with the slow pseudo-oscillatory mechanism found in these channels earlier, may contribute to the oscillations in the firing properties observed in various neuronal subtypes and many pathological conditions. [ABSTRACT FROM AUTHOR]

Voltage-gated sodium (Na V) channels play crucial roles in a range of (patho)physiological processes. Much interest has arisen within the pharmaceutical industry to pursue these channels as analgesic targets following overwhelming evidence that Na V channel subtypes Na V 1.7–Na V 1.9 are involved in nociception. More recently, Na V 1.1, Na V 1.3 and Na V 1.6 have also been identified to be involved in pain pathways. Venom-derived disulfide-rich peptide toxins, isolated from spiders and cone snails, have been used extensively as probes to investigate these channels and have attracted much interest as drug leads. However, few peptide-based leads have made it as drugs due to unfavourable physiochemical attributes including poor in vivo pharmacokinetics and limited oral bioavailability. The present work aims to bridge the gap in the development pipeline between drug leads and drug candidates by downsizing these larger venom-derived Na V inhibitors into smaller, more "drug-like" molecules. Here, we use molecular engineering of small cyclic peptides to aid in the determination of what drives subtype selectivity and molecular interactions of these downsized inhibitors across Na V subtypes. We designed a series of small, stable and novel Na V probes displaying Na V subtype selectivity and potency in vitro coupled with potent in vivo analgesic activity, involving yet to be elucidated analgesic pathways in addition to Na V subtype modulation. [ABSTRACT FROM AUTHOR]