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Zhang XY, Bi RY, Zhang P, Gan YH. Veratridine modifies the gating of human voltage-gated sodium channel Nav1.7. Acta Pharmacol Sin 2018; 39:1716-1724. [PMID: 29950616 DOI: 10.1038/s41401-018-0065-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/05/2018] [Indexed: 01/22/2023] Open
Abstract
Veratridine is a lipid-soluble neurotoxin derived from plants in the family Liliaceae. It has been broadly investigated for its action as a sodium channel agonist. However, the effects of veratridine on subtypes of sodium channels, especially Nav1.7, remain to be studied. Here, we investigated the effects of veratridine on human Nav1.7 ectopically expressed in HEK293A cells and recorded Nav1.7 currents from the cells using whole-cell patch clamp technique. We found that veratridine exerted a dose-dependent inhibitory effect on the peak current of Nav1.7, with the half-maximal inhibition concentration (IC50) of 18.39 µM. Meanwhile, veratridine also elicited tail current (linearly) and sustained current [half-maximal concentration (EC50): 9.53 µM], also in a dose-dependent manner. Veratridine (75 µM) shifted the half-maximal activation voltage of the Nav1.7 activation curve in the hyperpolarized direction, from -21.64 ± 0.75 mV to -28.14 ± 0.66 mV, and shifted the half-inactivation voltage of the steady-state inactivation curve from -59.39 ± 0.39 mV to -73.78 ± 0.5 mV. An increased frequency of stimulation decreased the peak and tail currents of Nav1.7 for each pulse along with pulse number, and increased the accumulated tail current at the end of train stimulation. These findings reveal the different modulatory effects of veratridine on the Nav1.7 peak current and tail current.
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Atkin TA, Maher CM, Gerlach AC, Gay BC, Antonio BM, Santos SC, Padilla KM, Rader J, Krafte DS, Fox MA, Stewart GR, Petrovski S, Devinsky O, Might M, Petrou S, Goldstein DB. A comprehensive approach to identifying repurposed drugs to treat SCN8A epilepsy. Epilepsia 2018; 59:802-813. [PMID: 29574705 DOI: 10.1111/epi.14037] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/05/2018] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Many previous studies of drug repurposing have relied on literature review followed by evaluation of a limited number of candidate compounds. Here, we demonstrate the feasibility of a more comprehensive approach using high-throughput screening to identify inhibitors of a gain-of-function mutation in the SCN8A gene associated with severe pediatric epilepsy. METHODS We developed cellular models expressing wild-type or an R1872Q mutation in the Nav 1.6 sodium channel encoded by SCN8A. Voltage clamp experiments in HEK-293 cells expressing the SCN8A R1872Q mutation demonstrated a leftward shift in sodium channel activation as well as delayed inactivation; both changes are consistent with a gain-of-function mutation. We next developed a fluorescence-based, sodium flux assay and used it to assess an extensive library of approved drugs, including a panel of antiepileptic drugs, for inhibitory activity in the mutated cell line. Lead candidates were evaluated in follow-on studies to generate concentration-response curves for inhibiting sodium influx. Select compounds of clinical interest were evaluated by electrophysiology to further characterize drug effects on wild-type and mutant sodium channel functions. RESULTS The screen identified 90 drugs that significantly inhibited sodium influx in the R1872Q cell line. Four drugs of potential clinical interest-amitriptyline, carvedilol, nilvadipine, and carbamazepine-were further investigated and demonstrated concentration-dependent inhibition of sodium channel currents. SIGNIFICANCE A comprehensive drug repurposing screen identified potential new candidates for the treatment of epilepsy caused by the R1872Q mutation in the SCN8A gene.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Slavé Petrovski
- Pairnomix, Plymouth, MN, USA.,Florey Institute for Neuroscience and Mental Health and Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, Australia
| | - Orrin Devinsky
- Pairnomix, Plymouth, MN, USA.,Department of Neurology, New York University Medical Center, New York, NY, USA
| | - Matthew Might
- Pairnomix, Plymouth, MN, USA.,University of Alabama at Birmingham, Birmingham, AL, USA
| | - Steven Petrou
- Pairnomix, Plymouth, MN, USA.,Florey Institute for Neuroscience and Mental Health and Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, Victoria, Australia
| | - David B Goldstein
- Pairnomix, Plymouth, MN, USA.,Institute for Genomic Medicine, Columbia University Medical Center, New York, NY, USA
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Takahara K, Yamamoto T, Uchida K, Zhu HL, Shibata A, Inai T, Noguchi M, Yotsu-Yamashita M, Teramoto N. Effects of 4,9-anhydrotetrodotoxin on voltage-gated Na + channels of mouse vas deferens myocytes and recombinant Na V1.6 channels. Naunyn Schmiedebergs Arch Pharmacol 2018; 391:489-499. [PMID: 29453527 DOI: 10.1007/s00210-018-1476-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 01/31/2018] [Indexed: 12/19/2022]
Abstract
Molecular investigations were performed in order to determine the major characteristics of voltage-gated Na+ channel β-subunits in mouse vas deferens. The use of real-time quantitative PCR showed that the expression of Scn1b was significantly higher than that of other β-subunit genes (Scn2b - Scn4b). Immunoreactivity of Scn1b proteins was also detected in the inner circular and outer longitudinal smooth muscle of mouse vas deferens. In whole-cell recordings, the actions of 4,9-anhydroTTX on voltage-gated Na+ current peak amplitude in myocytes (i.e., native INa) were compared with its inhibitory potency on recombinant NaV1.6 channels (expressed in HEK293 cells). A depolarizing rectangular voltage-pulse elicited a fast and transient inward native INa and recombinant NaV1.6 expressed in HEK293 cells (i.e., recombinant INa). The current decay of native INa was similar to the recombinant NaV1.6 current co-expressed with β1-subunits. The current-voltage (I-V) relationships of native INa were similar to those of recombinant NaV1.6 currents co-expressed with β1-subunits. Application of 4,9-anhydroTTX inhibited the peak amplitude of native INa (K i = 510 nM), recombinant INa (K i = 112 nM), and recombinant INa co-expressed with β1-subunits (K i = 92 nM). The half-maximal (Vhalf) activation and inactivation of native INa values were similar to those observed in recombinant INa co-expressed with β1-subunits. These results suggest that β1-subunit proteins are likely to be expressed mainly in the smooth muscle layers of murine vas deferens and that 4,9-anhydroTTX inhibited not only native INa but also recombinant INa and recombinant INa co-expressed with β1-subunits in a concentration-dependent manner.
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Affiliation(s)
- Kohei Takahara
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Tadashi Yamamoto
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Keiichiro Uchida
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Hai-Lei Zhu
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Atsushi Shibata
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Tetsuichiro Inai
- Department of Morphological Biology, Division of Biomedical Sciences, Fukuoka Dental College, Fukuoka, 814-0193, Japan
| | - Mitsuru Noguchi
- Department of Urology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan
| | - Mari Yotsu-Yamashita
- Laboratory of Bioorganic Chemistry of Natural Products, Graduate School of Agricultural Science, Tohoku University, Sendai, 981-8555, Japan
| | - Noriyoshi Teramoto
- Department of Pharmacology, Faculty of Medicine, Saga University, Saga, 849-8501, Japan. .,Laboratory of Biomedical Engineering, Graduate School of Biomedical Engineering, Tohoku University, Sendai, 980-0845, Japan.
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Abstract
Voltage-gated sodium channels (VGSCs) are critical in generation and conduction of electrical signals in multiple excitable tissues. Natural toxins, produced by animal, plant, and microorganisms, target VGSCs through diverse strategies developed over millions of years of evolutions. Studying of the diverse interaction between VGSC and VGSC-targeting toxins has been contributing to the increasing understanding of molecular structure and function, pharmacology, and drug development potential of VGSCs. This chapter aims to summarize some of the current views on the VGSC-toxin interaction based on the established receptor sites of VGSC for natural toxins.
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Affiliation(s)
- Yonghua Ji
- Laboratory of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, China.
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Grubišić V, Gulbransen BD. Enteric glial activity regulates secretomotor function in the mouse colon but does not acutely affect gut permeability. J Physiol 2017; 595:3409-3424. [PMID: 28066889 DOI: 10.1113/jp273492] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 11/30/2016] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS The role of enteric glial cell activity in the acute regulation of epithelial barrier and secretomotor functions of the intestines under physiological conditions is not clear. We used transgenic mice to modify glial activity and found that enteric glia significantly contribute to the neurogenic ion transport while glial activity does not appear to play a major role in the acute regulation of barrier function. The selective activation of glial activity evoked electrogenic ion transport primarily through neural pathways and was sufficient to drive electrogenic ion transport to an extent equal to the direct activation of neurogenic ion transport. These findings provide novel insight into the cellular mechanisms that control fluid transport homeostasis in the intestine and might provide novel therapeutic avenues for functional diarrheal diseases. ABSTRACT Enteric glial cells are often implicated in the regulation of epithelial barrier and secretomotor functions of the intestines. But whether glial cell activity regulates these functions acutely under physiological conditions is not clear. We addressed this issue by using transgenic animal models to modify the activity of enteric glia, either reducing glial expression of connexin 43 in Sox10::CreERT2+/- /Cx43f/f mice or activating glial calcium responses in GFAP::hM3Dq mice, and tested the effects on colonic barrier function and electrogenic ion transport in Ussing chambers. We assessed neuronal-dependent and -independent contributions by activating or inhibiting neurogenic activity with veratridine and tetrodotoxin, respectively. Our results show that the reduction of glial Cx43 expression in Sox10::CreERT2+/- /Cx43f/f mice significantly reduced neurogenic ion transport. The selective glial activation in tissues from GFAP::hM3Dq mice evoked electrogenic ion transport to an extent equal to the direct activation of neurogenic ion transport with veratridine and glial driven responses consisted of both tetrodotoxin-sensitive and -insensitive components. The selective glial stimulation did not affect transmural ion conductance or cell-impermeant dye flux but the baseline ion conductance was more variable in Sox10::CreERT2+/- /Cx43f/f tissues. Together, our findings show that glial activity contributes to the regulation of electrogenic ion transport in the intestine through effects on neurons and possibly direct effects on epithelial cells. However, glial activity does not appear to play a major role in the acute regulation of barrier function. These findings provide novel insight into the cellular mechanisms that control fluid transport homeostasis in the intestine.
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Affiliation(s)
- Vladimir Grubišić
- Neuroscience Program, Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824, USA
| | - Brian D Gulbransen
- Neuroscience Program, Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, MI, 48824, USA
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Deuis JR, Wingerd JS, Winter Z, Durek T, Dekan Z, Sousa SR, Zimmermann K, Hoffmann T, Weidner C, Nassar MA, Alewood PF, Lewis RJ, Vetter I. Analgesic Effects of GpTx-1, PF-04856264 and CNV1014802 in a Mouse Model of NaV1.7-Mediated Pain. Toxins (Basel) 2016; 8:toxins8030078. [PMID: 26999206 PMCID: PMC4810223 DOI: 10.3390/toxins8030078] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/08/2016] [Accepted: 03/10/2016] [Indexed: 12/19/2022] Open
Abstract
Loss-of-function mutations of Na(V)1.7 lead to congenital insensitivity to pain, a rare condition resulting in individuals who are otherwise normal except for the inability to sense pain, making pharmacological inhibition of Na(V)1.7 a promising therapeutic strategy for the treatment of pain. We characterized a novel mouse model of Na(V)1.7-mediated pain based on intraplantar injection of the scorpion toxin OD1, which is suitable for rapid in vivo profiling of Na(V)1.7 inhibitors. Intraplantar injection of OD1 caused spontaneous pain behaviors, which were reversed by co-injection with Na(V)1.7 inhibitors and significantly reduced in Na(V)1.7(-/-) mice. To validate the use of the model for profiling Na(V)1.7 inhibitors, we determined the Na(V) selectivity and tested the efficacy of the reported Na(V)1.7 inhibitors GpTx-1, PF-04856264 and CNV1014802 (raxatrigine). GpTx-1 selectively inhibited Na(V)1.7 and was effective when co-administered with OD1, but lacked efficacy when delivered systemically. PF-04856264 state-dependently and selectively inhibited Na(V)1.7 and significantly reduced OD1-induced spontaneous pain when delivered locally and systemically. CNV1014802 state-dependently, but non-selectively, inhibited Na(V) channels and was only effective in the OD1 model when delivered systemically. Our novel model of Na(V)1.7-mediated pain based on intraplantar injection of OD1 is thus suitable for the rapid in vivo characterization of the analgesic efficacy of Na(V)1.7 inhibitors.
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Affiliation(s)
- Jennifer R Deuis
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia.
| | - Joshua S Wingerd
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Zoltan Winter
- Department of Physiology and Pathophysiology and Department of Anaesthesiology, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany.
| | - Thomas Durek
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Zoltan Dekan
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Silmara R Sousa
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Katharina Zimmermann
- Department of Physiology and Pathophysiology and Department of Anaesthesiology, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany.
| | - Tali Hoffmann
- Department of Physiology and Pathophysiology and Department of Anaesthesiology, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany.
| | - Christian Weidner
- Department of Physiology and Pathophysiology and Department of Anaesthesiology, Friedrich-Alexander University Erlangen-Nuremberg, 91054 Erlangen, Germany.
| | - Mohammed A Nassar
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK.
| | - Paul F Alewood
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Richard J Lewis
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
| | - Irina Vetter
- Centre for Pain Research, Institute for Molecular Biosciences, The University of Queensland, St Lucia, QLD 4072, Australia.
- School of Pharmacy, The University of Queensland, Woolloongabba, QLD 4102, Australia.
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Munasinghe NR, Christie MJ. Conotoxins That Could Provide Analgesia through Voltage Gated Sodium Channel Inhibition. Toxins (Basel) 2015; 7:5386-407. [PMID: 26690478 PMCID: PMC4690140 DOI: 10.3390/toxins7124890] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/23/2015] [Accepted: 11/19/2015] [Indexed: 12/19/2022] Open
Abstract
Chronic pain creates a large socio-economic burden around the world. It is physically and mentally debilitating, and many sufferers are unresponsive to current therapeutics. Many drugs that provide pain relief have adverse side effects and addiction liabilities. Therefore, a great need has risen for alternative treatment strategies. One rich source of potential analgesic compounds that has emerged over the past few decades are conotoxins. These toxins are extremely diverse and display selective activity at ion channels. Voltage gated sodium (NaV) channels are one such group of ion channels that play a significant role in multiple pain pathways. This review will explore the literature around conotoxins that bind NaV channels and determine their analgesic potential.
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Affiliation(s)
- Nehan R Munasinghe
- Discipline of Pharmacology, The University of Sydney, Sydney, NSW 2006, Australia.
| | - MacDonald J Christie
- Discipline of Pharmacology, The University of Sydney, Sydney, NSW 2006, Australia.
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Voltage-gated Na+ Channel Activity Increases Colon Cancer Transcriptional Activity and Invasion Via Persistent MAPK Signaling. Sci Rep 2015; 5:11541. [PMID: 26096612 PMCID: PMC4476109 DOI: 10.1038/srep11541] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/22/2015] [Indexed: 12/27/2022] Open
Abstract
Functional expression of voltage-gated Na+ channels (VGSCs) has been demonstrated in multiple cancer cell types where channel activity induces invasive activity. The signaling mechanisms by which VGSCs promote oncogenesis remain poorly understood. We explored the signal transduction process critical to VGSC-mediated invasion on the basis of reports linking channel activity to gene expression changes in excitable cells. Coincidentally, many genes transcriptionally regulated by the SCN5A isoform in colon cancer have an over-representation of cis-acting sites for transcription factors phosphorylated by ERK1/2 MAPK. We hypothesized that VGSC activity promotes MAPK activation to induce transcriptional changes in invasion-related genes. Using pharmacological inhibitors/activators and siRNA-mediated gene knockdowns, we correlated channel activity with Rap1-dependent persistent MAPK activation in the SW620 human colon cancer cell line. We further demonstrated that VGSC activity induces downstream changes in invasion-related gene expression via a PKA/ERK/c-JUN/ELK-1/ETS-1 transcriptional pathway. This is the first study illustrating a molecular mechanism linking functional activity of VGSCs to transcriptional activation of invasion-related genes.
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9
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Late sodium current (INaL) in pancreatic β-cells. Pflugers Arch 2014; 467:1757-68. [DOI: 10.1007/s00424-014-1613-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 09/01/2014] [Accepted: 09/08/2014] [Indexed: 12/20/2022]
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Yin Y, Wen K, Wu Y, Kang Y, Lou J. Inhibition of sodium current by taurine magnesium coordination compound prevents cesium chloride-induced arrhythmias. Biol Trace Elem Res 2012; 146:192-8. [PMID: 22057978 DOI: 10.1007/s12011-011-9240-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
Abstract
The mechanism(s) by which taurine magnesium coordination compound (TMCC) inhibits experimental arrhythmias remains poorly understood. The purpose of this study was to observe the effects of TMCC against cesium chloride-induced arrhythmia in the rabbit heart and find whether the antiarrhythmic activity is related to inhibition of sodium current. Early afterdepolarization was induced by 1.5 mM cesium chloride (1 ml kg(-1)) through intravenous injection. The monophasic action potentials (MAP) and electrocardiograms were simultaneously recorded. The effect of TMCC on functional refractory periods (FRPs) in the left atrium was also observed in vitro. Arrhythmias onset was significantly retarded by TMCC. The number of ventricular premature contractions and incidence of monophasic ventricular tachycardia and polyphasic ventricular tachycardia in 10 min were decreased by TMCC. These effects can be abolished by veratridine (10 μg kg(-1)). MAP duration at 90% repolarization was significantly prolonged by TMCC, which can be prolonged even longer by veratridine (10 μg kg(-1)). In vitro experiments showed that FRPs was prolonged by TMCC which can be cancelled by veratridine (10 μg kg(-1)). TMCC prevents cesium chloride-induced arrhythmias, and inhibition of sodium current, in part, contributes to the antiarrhythmic effect of TMCC.
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Affiliation(s)
- Yongqiang Yin
- Department of Pharmacology, Tianjin Medical University, Tianjin, China
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11
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Stevens M, Peigneur S, Tytgat J. Neurotoxins and their binding areas on voltage-gated sodium channels. Front Pharmacol 2011; 2:71. [PMID: 22084632 PMCID: PMC3210964 DOI: 10.3389/fphar.2011.00071] [Citation(s) in RCA: 179] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/24/2011] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are large transmembrane proteins that conduct sodium ions across the membrane and by doing so they generate signals of communication between many kinds of tissues. They are responsible for the generation and propagation of action potentials in excitable cells, in close collaboration with other channels like potassium channels. Therefore, genetic defects in sodium channel genes can cause a wide variety of diseases, generally called “channelopathies.” The first insights into the mechanism of action potentials and the involvement of sodium channels originated from Hodgkin and Huxley for which they were awarded the Nobel Prize in 1963. These concepts still form the basis for understanding the function of VGSCs. When VGSCs sense a sufficient change in membrane potential, they are activated and consequently generate a massive influx of sodium ions. Immediately after, channels will start to inactivate and currents decrease. In the inactivated state, channels stay refractory for new stimuli and they must return to the closed state before being susceptible to a new depolarization. On the other hand, studies with neurotoxins like tetrodotoxin (TTX) and saxitoxin (STX) also contributed largely to our today’s understanding of the structure and function of ion channels and of VGSCs specifically. Moreover, neurotoxins acting on ion channels turned out to be valuable lead compounds in the development of new drugs for the enormous range of diseases in which ion channels are involved. A recent example of a synthetic neurotoxin that made it to the market is ziconotide (Prialt®, Elan). The original peptide, ω-MVIIA, is derived from the cone snail Conus magus and now FDA/EMA-approved for the management of severe chronic pain by blocking the N-type voltage-gated calcium channels in pain fibers. This review focuses on the current status of research on neurotoxins acting on VGSC, their contribution to further unravel the structure and function of VGSC and their potential as novel lead compounds in drug development.
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Affiliation(s)
- Marijke Stevens
- Lab of Toxicology, Katholieke Universiteit Leuven Leuven, Belgium
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de Arruda Camargo GMP, de Arruda Camargo LA, Saad WA. On a possible dual role for the lateral septal area 5-HT1A receptor system in the regulation of water intake and urinary excretion. Behav Brain Res 2010; 215:122-8. [DOI: 10.1016/j.bbr.2010.07.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/07/2010] [Accepted: 07/09/2010] [Indexed: 11/29/2022]
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Zhu HL, Shibata A, Inai T, Nomura M, Shibata Y, Brock JA, Teramoto N. Characterization of NaV1.6-mediated Na+ currents in smooth muscle cells isolated from mouse vas deferens. J Cell Physiol 2010; 223:234-43. [PMID: 20054822 DOI: 10.1002/jcp.22032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Patch-clamp experiments were performed to investigate the behavior of voltage-activated inward currents in vas deferens myocytes from Na(V)1.6-null mice (Na(V)1.6(-/-)) lacking the expression of the Na(+) channel gene, Scn8a, and their wild-type littermates (Na(V)1.6(+/+)). Immunohistochemistry confirmed expression of Na(V)1.6 in the muscle of Na(V)1.6(+/+), but not Na(V)1.6(-/-), vas deferens. PCR analysis revealed that the only beta(1)-subunit gene expressed in Na(V)1.6(+/+) vas deferens was Scn1b. In Na(V)1.6(+/+) myocytes, the threshold for membrane currents evoked by 20 msec voltage ramps (-100 mV to 60 mV) was -38.5 +/- 4.6 mV and this was shifted to a more positive potential (-31.2 +/- 4.9 mV) by tetrodotoxin (TTX). In Na(V)1.6(-/-) myocytes, the threshold was -30.4 +/- 3.4 mV and there was no TTX-sensitive current. The Na(+) current (I(Na)) in Na(V)1.6(+/+) myocytes had a bell-shaped current-voltage relationship that peaked at approximately -10 mV. Increasing the duration of the voltage ramps beyond 20 msec reduced the peak amplitude of I(Na). I(Na) displayed both fast (tau approximately 10 msec) and slow (tau approximately 1 sec) recovery from inactivation, the magnitude of the slow component increasing with the duration of the conditioning pulse (5-40 msec). During repetitive activation (5-40 msec pulses), I(Na) declined at stimulation frequencies > 0.5 Hz and at 10 Hz <or= 50% of the current remained. These findings indicate that I(Na) is due solely to Na(V)1.6 in Na(V)1.6(+/+) myocytes. The gating properties of these channels suggest they play a major role in regulating smooth muscle excitability, particularly in response to rapid depolarizing stimuli.
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Affiliation(s)
- Hai-Lei Zhu
- Department of Pharmacology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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