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Zheng Q, Li N, Zhang Y, Li J, Zhang E, Xu Z. Fat-Diets in Perinatal Stages Altered Nr3c2-Mediated Ca 2+ Currents in Mesenteric Arteries of Offspring Rats. Mol Nutr Food Res 2023; 67:e2200722. [PMID: 37366318 DOI: 10.1002/mnfr.202200722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 04/12/2023] [Indexed: 06/28/2023]
Abstract
SCOPE Perinatal high-fat diets (PHF) can influence fetal/neonate development, resulting in cardiovascular pathogenesis, but precise mechanisms remain unclear. This study tests aldosterone receptor-mediated Ca2+ influx and the underlying mechanisms influenced by PHF. METHODS AND RESULTS Maternal S.D. rats receive PHF during pregnancy and lactation periods. Their male offspring are fed normal diets after weaning for four months. Mesenteric arteries (MA) are for electrophysiological testing, Ca2+ imaging, target gene expression, and promotor methylation. PHF increases aldosterone receptor gene Nr3c2-mediated Ca2+ currents in the smooth muscle cells (SMCs) of the MA via L-type Ca2+ channels (LTCC) in the offspring. The increased expression of aldosterone-receptors and LTCC are responsible for an activated Nr3c2-LTCC pathway in the vasculature, eventually predisposes an increase of Ca2+ influx in the myocytes of resistance arteries. The inhibitor of aldosterone-receptors suppresses the increased Ca2+ currents in the SMCs. Nr3c2 and LTCC are upregulated through the transcriptional mechanism in methylation, which can be reversed in the functional changes by methylation inhibitor 5AZA. CONCLUSION The results firstly demonstrate that aldosterone-receptor activation can stimulate Ca2+ currents via LTCC in vascular myocytes, which can be altered by perinatal foods via epigenetic changes of DNA methylation in the promoters of Nr3c2 and LTCC.
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Affiliation(s)
- Qiutong Zheng
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
| | - Na Li
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
| | - Yingying Zhang
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
| | - Jingyang Li
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
| | - Eryun Zhang
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
| | - Zhice Xu
- Maternal and Child Health Care Hospital of Wuxi & First Hospital of Soochow University, Jiangsu, 215000, China
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2
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Quiroz-Acosta T, Bermeo K, Arenas I, Garcia DE. G-protein tonic inhibition of calcium channels in pancreatic β-cells. Am J Physiol Cell Physiol 2023; 325:C592-C598. [PMID: 37458440 DOI: 10.1152/ajpcell.00447.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 06/30/2023] [Accepted: 07/03/2023] [Indexed: 08/17/2023]
Abstract
Voltage-gated calcium channels (CaV) conduct Ca2+ influx promoting neurotransmitters and hormone release. CaV are finely regulated by voltage-dependent and independent pathways either by G-protein-coupled receptors (GPCRs) or intramembrane lipids, respectively, in neurons and glands. Interestingly, pancreatic β-cells are abundantly innervated by both sympathetic and parasympathetic neurons, while a variety of high-voltage activated (HVA) Ca2+ channels are present in these cells. Thus, autonomic system seems to exert a tonic inhibition on HVA Ca2+ channels throughout GPCRs, constitutively preventing hormone secretion. Therefore, this work aimed to investigate noradrenergic and cholinergic inhibition of HVA Ca2+ channels in pancreatic β-cells. Experiments were conducted in pancreatic β-cells of rat by using patch-clamping methods, immunocytochemistry, pharmacological probes, and biochemical reagents. A voltage-clamp protocol with a strong depolarizing prepulse was used to unmask tonic inhibition. Herein, we consistently find a basal tonic inhibition of HVA Ca2+ channels according to a GPCRs regulation. Facilitation ratio is enhanced by noradrenaline (NA) according to a voltage-dependent regulation and a membrane-delimited mechanism, while no facilitation changes are observed with carbachol or phosphatidylinositol 4,5-bisphosphate (PIP2). Furthermore, carbachol or intramembrane lipids, such as PIP2, do not change facilitation ratio according to a voltage-independent regulation. Together, HVA Ca2+ channels of pancreatic β-cells are constitutively inhibited by GPCRs, suggesting a natural brake preventing cells from exhaustive insulin secretion.NEW & NOTEWORTHY Our results support the hypothesis that GPCRs tonically inhibit HVA Ca2+ channels in pancreatic β-cells. A voltage-clamp protocol with a strong depolarizing prepulse was used to unmask voltage-dependent inhibition of Ca2+ channels. The novelty of these results strengthens the critical role of Gβγ's in Ca2+ channel regulation, highlighting kinetic slowing and increased facilitation ratio. Together, HVA Ca2+ channels of pancreatic β-cells are constitutively inhibited by GPCRs underlying fine-tuning modulation of insulin secretion.
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Affiliation(s)
- Tayde Quiroz-Acosta
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - Karina Bermeo
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - Isabel Arenas
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
| | - David E Garcia
- Department of Physiology, Faculty of Medicine, Universidad Nacional Autónoma de México, UNAM, Ciudad de México, Mexico
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3
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Zhou M, Yang M, Wen H, Xu S, Han C, Wu Y. O1-conotoxin Tx6.7 cloned from the genomic DNA of Conus textile that inhibits calcium currents. J Venom Anim Toxins Incl Trop Dis 2023; 29:e20220085. [PMID: 37283723 PMCID: PMC10241523 DOI: 10.1590/1678-9199-jvatitd-2022-0085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 04/13/2023] [Indexed: 06/08/2023] Open
Abstract
Background Conotoxins exhibit great potential as neuropharmacology tools and therapeutic candidates due to their high affinity and specificity for ion channels, neurotransmitter receptors or transporters. The traditional methods to discover new conotoxins are peptide purification from the crude venom or gene amplification from the venom duct. Methods In this study, a novel O1 superfamily conotoxin Tx6.7 was directly cloned from the genomic DNA of Conus textile using primers corresponding to the conserved intronic sequence and 3' UTR elements. The mature peptide of Tx6.7 (DCHERWDWCPASLLGVIYCCEGLICFIAFCI) was synthesized by solid-phase chemical synthesis and confirmed by mass spectrometry. Results Patch clamp experiments on rat DRG neurons showed that Tx6.7 inhibited peak calcium currents by 59.29 ± 2.34% and peak potassium currents by 22.33 ± 7.81%. In addition, patch clamp on the ion channel subtypes showed that 10 μM Tx6.7 inhibited 56.61 ± 3.20% of the hCaV1.2 currents, 24.67 ± 0.91% of the hCaV2.2 currents and 7.30 ± 3.38% of the hNaV1.8 currents. Tx6.7 had no significant toxicity to ND7/23 cells and increased the pain threshold from 0.5 to 4 hours in the mouse hot plate assay. Conclusion Our results suggested that direct cloning of conotoxin sequences from the genomic DNA of cone snails would be an alternative approach to obtaining novel conotoxins. Tx6.7 could be used as a probe tool for ion channel research or a therapeutic candidate for novel drug development.
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Affiliation(s)
- Maojun Zhou
- Department of Oncology, NHC Key Laboratory of Cancer Proteomics,
State Local Joint Engineering Laboratory for Anticancer Drugs, Xiangya Hospital,
Central South University, Changsha, Hunan, China
| | - Manyi Yang
- Department of Hepatobiliary and Pancreatic Surgery, NHC Key
Laboratory of Nanobiological Technology, Xiangya Hospital, Central South University,
Changsha, Hunan, China
| | - Huiling Wen
- School of Pharmacy, Gannan Medical University, Ganzhou, Jiangxi,
China
| | - Shun Xu
- Guangdong Provincial Key Laboratory of Medical Molecular
Diagnostics, Guangdong Medical University, Dongguan, China
| | - Cuifang Han
- Guangdong Provincial Key Laboratory of Medical Molecular
Diagnostics, Guangdong Medical University, Dongguan, China
| | - Yun Wu
- Guangdong Provincial Key Laboratory of Medical Molecular
Diagnostics, Guangdong Medical University, Dongguan, China
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4
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Baraibar AM, de Pascual R, Carretero VJ, Liccardi N, Juárez NH, Hernández-Guijo JM. Aluminum alters excitability by inhibiting calcium, sodium, and potassium currents in bovine chromaffin cells. J Neurochem 2023; 165:162-176. [PMID: 36800503 DOI: 10.1111/jnc.15784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 01/20/2023] [Accepted: 02/06/2023] [Indexed: 02/19/2023]
Abstract
Aluminum (Al3+ ) has long been related to neurotoxicity and neurological diseases. This study aims to describe the specific actions of this metal on cellular excitability and neurotransmitter release in primary culture of bovine chromaffin cells. Using voltage-clamp and current-clamp recordings with the whole-cell configuration of the patch clamp technique, online measurement of catecholamine release, and measurements of [Ca2+ ]c with Fluo-4-AM, we have observed that Al3+ reduced intracellular calcium concentrations around 25% and decreased catecholamine secretion in a dose-dependent manner, with an IC50 of 89.1 μM. Al3+ blocked calcium currents in a time- and concentration-dependent manner with an IC50 of 560 μM. This blockade was irreversible since it did not recover after washout. Moreover, Al3+ produced a bigger blockade on N-, P-, and Q-type calcium channels subtypes (69.5%) than on L-type channels subtypes (50.5%). Sodium currents were also inhibited by Al3+ in a time- and concentration-dependent manner, 24.3% blockade at the closest concentration to the IC50 (399 μM). This inhibition was reversible. Voltage-dependent potassium currents were low affected by Al3+ . Nonetheless, calcium/voltage-dependent potassium currents were inhibited in a concentration-dependent manner, with an IC50 of 447 μM. This inhibition was related to the depression of calcium influx through voltage-dependent calcium channels subtypes coupled to BK channels. In summary, the blockade of these ionic conductance altered cellular excitability that reduced the action potentials firing and so, the neurotransmitter release and the synaptic transmission. These findings prove that aluminum has neurotoxic properties because it alters neuronal excitability by inhibiting the sodium currents responsible for the generation and propagation of impulse nerve, the potassium current responsible for the termination of action potentials, and the calcium current responsible for the neurotransmitters release.
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Affiliation(s)
- Andrés M Baraibar
- Department of Neurosciences, Universidad del País Vasco UPV/EHU, Leioa, Spain.,Achucarro Basque Center for Neuroscience, Leioa, Spain.,Biocruces Bizkaia Health Research Institute, Baracaldo, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | | | | | - Ninfa Liccardi
- Department of Pharmacology and Therapeutic, Madrid, Spain
| | | | - Jesús M Hernández-Guijo
- Department of Pharmacology and Therapeutic, Madrid, Spain.,Instituto Teófilo Hernando, Facultad de Medicina, Univ. Autónoma de Madrid, Madrid, Spain.,Instituto Ramón y Cajal de Investigación Sanitaria, IRYCIS, Hospital Ramón y Cajal, Madrid, Spain
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5
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Marosi EL, Arszovszki A, Brunner J, Szabadics J. Similar Presynaptic Action Potential-Calcium Influx Coupling in Two Types of Large Mossy Fiber Terminals Innervating CA3 Pyramidal Cells and Hilar Mossy Cells. eNeuro 2023; 10:ENEURO.0017-23.2023. [PMID: 36697256 PMCID: PMC9907395 DOI: 10.1523/eneuro.0017-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 01/16/2023] [Indexed: 01/26/2023] Open
Abstract
Morphologically similar axon boutons form synaptic contacts with diverse types of postsynaptic cells. However, it is less known to what extent the local axonal excitability, presynaptic action potentials (APs), and AP-evoked calcium influx contribute to the functional diversity of synapses and neuronal activity. This is particularly interesting in synapses that contact cell types that show only subtle cellular differences but fulfill completely different physiological functions. Here, we tested these questions in two synapses that are formed by rat hippocampal granule cells (GCs) onto hilar mossy cells (MCs) and CA3 pyramidal cells, which albeit share several morphologic and synaptic properties but contribute to distinct physiological functions. We were interested in the deterministic steps of the action potential-calcium ion influx coupling as these complex modules may underlie the functional segregation between and within the two cell types. Our systematic comparison using direct axonal recordings showed that AP shapes, Ca2+ currents and their plasticity are indistinguishable in synapses onto these two cell types. These suggest that the complete module that couples granule cell activity to synaptic release is shared by hilar mossy cells and CA3 pyramidal cells. Thus, our findings present an outstanding example for the modular composition of distinct cell types, by which cells employ different components only for those functions that are deterministic for their specialized functions, while many of their main properties are shared.
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Affiliation(s)
| | | | - János Brunner
- Institute of Experimental Medicine, Budapest, 1083, Hungary
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6
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Kadurin I, Dahimene S, Page KM, Ellaway JIJ, Chaggar K, Troeberg L, Nagase H, Dolphin AC. ADAM17 Mediates Proteolytic Maturation of Voltage-Gated Calcium Channel Auxiliary α 2δ Subunits, and Enables Calcium Current Enhancement. Function (Oxf) 2022; 3:zqac013. [PMID: 35462614 PMCID: PMC9016415 DOI: 10.1093/function/zqac013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 01/07/2023] Open
Abstract
The auxiliary α2δ subunits of voltage-gated calcium (CaV) channels are key to augmenting expression and function of CaV1 and CaV2 channels, and are also important drug targets in several therapeutic areas, including neuropathic pain. The α2δ proteins are translated as preproteins encoding both α2 and δ, and post-translationally proteolyzed into α2 and δ subunits, which remain associated as a complex. In this study, we have identified ADAM17 as a key protease involved in proteolytic processing of pro-α2δ-1 and α2δ-3 subunits. We provide three lines of evidence: First, proteolytic cleavage is inhibited by chemical inhibitors of particular metalloproteases, including ADAM17. Second, proteolytic cleavage of both α2δ-1 and α2δ-3 is markedly reduced in cell lines by knockout of ADAM17 but not ADAM10. Third, proteolytic cleavage is reduced by the N-terminal active domain of TIMP-3 (N-TIMP-3), which selectively inhibits ADAM17. We have found previously that proteolytic cleavage into mature α2δ is essential for the enhancement of CaV function, and in agreement, knockout of ADAM17 inhibited the ability of α2δ-1 to enhance both CaV2.2 and CaV1.2 calcium currents. Finally, our data also indicate that the main site of proteolytic cleavage of α2δ-1 is the Golgi apparatus, although cleavage may also occur at the plasma membrane. Thus, our study identifies ADAM17 as a key protease required for proteolytic maturation of α2δ-1 and α2δ-3, and thus a potential drug target in neuropathic pain.
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Affiliation(s)
- Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Karen M Page
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Joseph I J Ellaway
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Kanchan Chaggar
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Linda Troeberg
- Norwich Medical School, University of East Anglia, Norwich NR4 7UQ, UK
| | - Hideaki Nagase
- Kennedy Institute of Rheumatology, University of Oxford, Oxford OX3 7FY, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
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7
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Grijalva-Guiza RE, Jiménez-Garduño AM, Hernández LR. Potential Benefits of Flavonoids on the Progression of Atherosclerosis by Their Effect on Vascular Smooth Muscle Excitability. Molecules 2021; 26:3557. [PMID: 34200914 PMCID: PMC8230563 DOI: 10.3390/molecules26123557] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/05/2021] [Accepted: 06/06/2021] [Indexed: 12/26/2022] Open
Abstract
Flavonoids are a group of secondary metabolites derived from plant-based foods, and they offer many health benefits in different stages of several diseases. This review will focus on their effects on ion channels expressed in vascular smooth muscle during atherosclerosis. Since ion channels can be regulated by redox potential, it is expected that during the onset of oxidative stress-related diseases, ion channels present changes in their conductive activity, impacting the progression of the disease. A typical oxidative stress-related condition is atherosclerosis, which involves the dysfunction of vascular smooth muscle. We aim to present the state of the art on how redox potential affects vascular smooth muscle ion channel function and summarize if the benefits observed in this disease by using flavonoids involve restoring the ion channel activity.
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Affiliation(s)
- Rosa Edith Grijalva-Guiza
- Departamento de Ciencias Químico Biológicas, Universidad de las Américas Puebla, San Andrés Cholula 72810, Mexico;
| | | | - Luis Ricardo Hernández
- Departamento de Ciencias Químico Biológicas, Universidad de las Américas Puebla, San Andrés Cholula 72810, Mexico;
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8
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Meyer JO, Dahimene S, Page KM, Ferron L, Kadurin I, Ellaway JIJ, Zhao P, Patel T, Rothwell SW, Lin P, Pratt WS, Dolphin AC. Disruption of the Key Ca 2+ Binding Site in the Selectivity Filter of Neuronal Voltage-Gated Calcium Channels Inhibits Channel Trafficking. Cell Rep 2020; 29:22-33.e5. [PMID: 31577951 PMCID: PMC6899504 DOI: 10.1016/j.celrep.2019.08.079] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 06/20/2019] [Accepted: 08/22/2019] [Indexed: 12/05/2022] Open
Abstract
Voltage-gated calcium channels are exquisitely Ca2+ selective, conferred primarily by four conserved pore-loop glutamate residues contributing to the selectivity filter. There has been little previous work directly measuring whether the trafficking of calcium channels requires their ability to bind Ca2+ in the selectivity filter or to conduct Ca2+. Here, we examine trafficking of neuronal CaV2.1 and 2.2 channels with mutations in their selectivity filter and find reduced trafficking to the cell surface in cell lines. Furthermore, in hippocampal neurons, there is reduced trafficking to the somatic plasma membrane, into neurites, and to presynaptic terminals. However, the CaV2.2 selectivity filter mutants are still influenced by auxiliary α2δ subunits and, albeit to a reduced extent, by β subunits, indicating the channels are not grossly misfolded. Our results indicate that Ca2+ binding in the pore of CaV2 channels may promote their correct trafficking, in combination with auxiliary subunits. Furthermore, physiological studies utilizing selectivity filter mutant CaV channels should be interpreted with caution. Selectivity filter mutations in CaV2 channels block inward Ba2+ currents Surprisingly, these mutations severely reduce trafficking of the CaV2 channels Pore mutant N-type channels show reduced expression in presynaptic terminals Pore mutant channels still require β and α2δ and thus are not grossly misfolded
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Affiliation(s)
- James O Meyer
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Karen M Page
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Ivan Kadurin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Joseph I J Ellaway
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Pengxiang Zhao
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Tarun Patel
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Simon W Rothwell
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Peipeng Lin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
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9
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Su X, Wu B, Zhang W, Ji YH, Wang Q, Tan ZY. Inhibitory Effects of Columbianadin on Nociceptive Behaviors in a Neuropathic Pain Model, and on Voltage-Gated Calcium Currents in Dorsal Root Ganglion Neurons in Mice. Front Pharmacol 2020; 10:1522. [PMID: 31998126 PMCID: PMC6970200 DOI: 10.3389/fphar.2019.01522] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Accepted: 11/25/2019] [Indexed: 12/30/2022] Open
Abstract
Radix angelicae pubescentis (RAP) has been used in Chinese traditional medicine to treat painful diseases such as rheumatism and headache. A previous study has reported that columbianadin (CBN), a major coumarin in RAP inhibits acute and inflammatory pain behaviors. However, the effects of CBN on neuropathic pain behaviors, and the potential underlying mechanism have not been reported. In the present study, the effects of CBN, compared to another major coumarin of RAP osthole (OST), on oxaliplatin-induced neuropathic pain behaviors and on the voltage-gated calcium currents in small dorsal root ganglion (DRG) neurons were studied in mice. It was found that CBN and OST inhibited both mechanical and cold hypersensitivity induced by oxaliplatin. Moreover, CBN and OST might preferentially inhibit T- and L-type calcium currents (Ica). The inhibitory effects of CBN and OST on the oxaliplatin-induced mechanical allodynia were prevented by gabapentin. These results suggest that CBN, as well as OST might inhibit neuropathic pain behaviors through an inhibition of T- and L-type calcium currents in nociceptive DRG neurons.
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Affiliation(s)
- Xiaolin Su
- Key Laboratory of Chinese Materia Medica, Heilongjiang University of Chinese Medicine, Harbin, China.,Department of Pharmacology and Toxicology and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Bin Wu
- Department of Pharmacology and Toxicology and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States.,Institute of Special Environment Medicine, Nantong University, Nantong, China
| | - Wentong Zhang
- Department of Pharmacology and Toxicology and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Yong-Hua Ji
- Lab of Neuropharmacology and Neurotoxicology, Shanghai University, Shanghai, China
| | - Qiuhong Wang
- Key Laboratory of Chinese Materia Medica, Heilongjiang University of Chinese Medicine, Harbin, China.,School of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou, China
| | - Zhi-Yong Tan
- Department of Pharmacology and Toxicology and Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
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10
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Urbano FJ, Bisagno V, Garcia-Rill E. Gamma oscillations in the pedunculopontine nucleus are regulated by F-actin: neuroepigenetic implications. Am J Physiol Cell Physiol 2019; 318:C282-C288. [PMID: 31747316 DOI: 10.1152/ajpcell.00374.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pedunculopontine nucleus (PPN) is part of the reticular activating system (RAS) in charge of arousal and rapid eye movement sleep. The presence of high-frequency membrane oscillations in the gamma-band range in the PPN has been extensively demonstrated both in vivo and in vitro. Our group previously described histone deacetylation (HDAC) inhibition in vitro induced protein changes in F-actin cytoskeleton and intracellular Ca2+ concentration regulation proteins in the PPN. Here, we present evidence that supports the presence of a fine balance between HDAC function and calcium calmodulin kinase II-F-actin interactions in the PPN. We modified F-actin polymerization in vitro by using jasplakinolide (1 μM, a promoter of F-actin stabilization), or latrunculin-B (1 μM, an inhibitor of actin polymerization). Our results showed that shifting the balance in either direction significantly reduced PPN gamma oscillation as well as voltage-dependent calcium currents.
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Affiliation(s)
- Francisco J Urbano
- Instituto de Investigaciones Farmacológicas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Veronica Bisagno
- Instituto de Fisiología, Biología Molecular, y Neurociencias, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Edgar Garcia-Rill
- Center for Translational Neuroscience, University of Arkansas for Medical Sciences, Little Rock, Arakansas
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11
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Pilote S, Simard C, Drolet B. Fingolimod (Gilenya ® ) in multiple sclerosis: bradycardia, atrioventricular blocks, and mild effect on the QTc interval. Something to do with the L-type calcium channel? Fundam Clin Pharmacol 2017; 31:392-402. [PMID: 28299825 DOI: 10.1111/fcp.12284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/03/2017] [Accepted: 03/13/2017] [Indexed: 11/28/2022]
Abstract
Cardiac arrhythmias and ECG abnormalities including bradycardia, prolongation of the QT interval, and atrioventricular (AV) conduction blocks have been extensively observed with fingolimod, the first marketed oral drug for treating the relapsing-remitting form of multiple sclerosis. This study was aiming to further elucidate the effects of fingolimod on cardiac electrophysiology at three different levels: (i) in vitro, (ii) ex vivo, and (iii) in vivo. (i) Patch-clamp experiments in whole cell configuration were performed on Cav 1.2-transfected tsA201 cells exposed to fingolimod-phosphate 100 or 500 nmol/L (n = 27 cells, total) to measure drug effect on L-type calcium current (ICaL ). (ii) Langendorff perfusion experiments were undertaken on male Hartley guinea-pigs isolated hearts (n = 4) exposed to fingolimod 10 and 100 nmol/L to evaluate drug-induced effects on monophasic action potential duration measured at 90% repolarization (MAPD90 ). (iii) Implanted cardiac telemeters were used to record ECGs in guinea-pigs (n = 7) treated with a single dose of fingolimod 0.0625 mg/kg suspension, administered as an oral gavage. (i) In vitro cellular experiments showed that fingolimod-phosphate causes a concentration-dependent reduction in ICaL . (ii) Ex vivo Langendorff experiments revealed that fingolimod had no significant effect on MAPD90 . (iii) Fingolimod caused significant prolongations of the RR, PR, QT, and QTcF intervals in vivo. Reversible AV blocks were also observed in 7/7 animals. Fingolimod possesses ICaL -blocking properties, further contributing to its AV conduction-slowing effects. These properties are also consistent with its mitigated effect on the QT interval in humans, despite previously shown HERG-blocking effect.
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Affiliation(s)
- Sylvie Pilote
- Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec (CRIUCPQ), 2725, Chemin Sainte-Foy, Québec, QC, Canada, G1V 4G5
| | - Chantale Simard
- Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec (CRIUCPQ), 2725, Chemin Sainte-Foy, Québec, QC, Canada, G1V 4G5.,Faculté de Pharmacie, Université Laval, 1050 Avenue de la médecine, Québec, QC, Canada, G1V 0A6
| | - Benoit Drolet
- Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec (CRIUCPQ), 2725, Chemin Sainte-Foy, Québec, QC, Canada, G1V 4G5.,Faculté de Pharmacie, Université Laval, 1050 Avenue de la médecine, Québec, QC, Canada, G1V 0A6
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12
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Stagkourakis S, Kim H, Lyons DJ, Broberger C. Dopamine Autoreceptor Regulation of a Hypothalamic Dopaminergic Network. Cell Rep 2016; 15:735-747. [PMID: 27149844 PMCID: PMC4850423 DOI: 10.1016/j.celrep.2016.03.062] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Revised: 02/17/2016] [Accepted: 03/16/2016] [Indexed: 02/01/2023] Open
Abstract
How autoreceptors contribute to maintaining a stable output of rhythmically active neuronal circuits is poorly understood. Here, we examine this issue in a dopamine population, spontaneously oscillating hypothalamic rat (TIDA) neurons, that underlie neuroendocrine control of reproduction and neuroleptic side effects. Activation of dopamine receptors of the type 2 family (D2Rs) at the cell-body level slowed TIDA oscillations through two mechanisms. First, they prolonged the depolarizing phase through a combination of presynaptic increases in inhibition and postsynaptic hyperpolarization. Second, they extended the discharge phase through presynaptic attenuation of calcium currents and decreased synaptic inhibition. Dopamine reuptake blockade similarly reconfigured the oscillation, indicating that ambient somatodendritic transmitter concentration determines electrical behavior. In the absence of D2R feedback, however, discharge was abolished by depolarization block. These results indicate the existence of an ultra-short feedback loop whereby neuroendocrine dopamine neurons tune network behavior to echoes of their own activity, reflected in ambient somatodendritic dopamine, and also suggest a mechanism for antipsychotic side effects.
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Affiliation(s)
| | - Hoseok Kim
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - David J Lyons
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Christian Broberger
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
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13
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Jaafari N, Marret E, Canepari M. Using simultaneous voltage and calcium imaging to study fast Ca(2+) channels. Neurophotonics 2015; 2:021010. [PMID: 26158000 PMCID: PMC4479034 DOI: 10.1117/1.nph.2.2.021010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 01/06/2015] [Indexed: 05/27/2023]
Abstract
The combination of fluorescence measurements of membrane potential and intracellular [Formula: see text] concentration allows correlating the electrical and calcium activity of a cell with spatial precision. The technical advances allowing this type of measurement were achieved only recently and represent an important step in the progress of the voltage imaging approach pioneered over 40 years ago by Lawrence B. Cohen. Here, we show how this approach can be used to investigate the function of [Formula: see text] channels using the foreseen possibility to extract [Formula: see text] currents from imaging experiments. The kinetics of the [Formula: see text] current, mediated by voltage-gated [Formula: see text] channels, can be accurately derived from the [Formula: see text] fluorescence measurement using [Formula: see text] indicators with [Formula: see text] that equilibrate in [Formula: see text]. In this respect, the imaging apparatus dedicated to this application is described in detail. Next, we illustrate the mathematical procedure to extract the current from the [Formula: see text] fluorescence change, including a method to calibrate the signal to charge flux density. Finally, we show an example of simultaneous membrane potential and [Formula: see text] optical measurement associated with an action potential at a CA1 hippocampal pyramidal neuron from a mouse brain slice. The advantages and limitations of this approach are discussed.
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Affiliation(s)
- Nadia Jaafari
- Inserm U836, Grenoble Institute of Neuroscience, Team 3, Grenoble Cedex 09, France
- Université Joseph Fourier, Laboratoire Interdisciplinare de Physique (CNRS UMR 5588), F-38000 Grenoble, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Elodie Marret
- Inserm U836, Grenoble Institute of Neuroscience, Team 3, Grenoble Cedex 09, France
- Université Joseph Fourier, Laboratoire Interdisciplinare de Physique (CNRS UMR 5588), F-38000 Grenoble, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
| | - Marco Canepari
- Inserm U836, Grenoble Institute of Neuroscience, Team 3, Grenoble Cedex 09, France
- Université Joseph Fourier, Laboratoire Interdisciplinare de Physique (CNRS UMR 5588), F-38000 Grenoble, France
- Laboratories of Excellence, Ion Channel Science and Therapeutics, France
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14
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Unal CT, Golowasch JP, Zaborszky L. Adult mouse basal forebrain harbors two distinct cholinergic populations defined by their electrophysiology. Front Behav Neurosci 2012; 6:21. [PMID: 22586380 PMCID: PMC3346982 DOI: 10.3389/fnbeh.2012.00021] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 04/19/2012] [Indexed: 11/13/2022] Open
Abstract
We performed whole-cell recordings from basal forebrain (BF) cholinergic neurons in transgenic mice expressing enhanced green fluorescent protein (eGFP) under the control of the choline acetyltransferase promoter. BF cholinergic neurons can be differentiated into two electrophysiologically identifiable subtypes: early and late firing neurons. Early firing neurons (∼70%) are more excitable, show prominent spike frequency adaptation and are more susceptible to depolarization blockade, a phenomenon characterized by complete silencing of the neuron following initial action potentials. Late firing neurons (∼30%), albeit being less excitable, could maintain a tonic discharge at low frequencies. In voltage clamp analysis, we have shown that early firing neurons have a higher density of low voltage activated (LVA) calcium currents. These two cholinergic cell populations might be involved in distinct functions: the early firing group being more suitable for phasic changes in cortical acetylcholine release associated with attention while the late firing neurons could support general arousal by maintaining tonic acetylcholine levels.
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Affiliation(s)
- Cagri T Unal
- Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark NJ, USA
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15
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Verma S, Robertson A, Martin R. Effects of SDPNFLRF-amide (PF1) on voltage-activated currents in Ascaris suum muscle. Int J Parasitol 2009; 39:315-26. [PMID: 18760280 PMCID: PMC2632723 DOI: 10.1016/j.ijpara.2008.07.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2008] [Revised: 06/20/2008] [Accepted: 07/13/2008] [Indexed: 11/16/2022]
Abstract
Helminth infections are of significant concern in veterinary and human medicine. The drugs available for chemotherapy are limited in number and the extensive use of these drugs has led to the development of resistance in parasites of animals and humans (Geerts and Gryseels, 2000; Kaplan, 2004; Osei-Atweneboana et al., 2007). The cyclooctadepsipeptide, emodepside, belongs to a new class of anthelmintic that has been released for animal use in recent years. Emodepside has been proposed to mimic the effects of the neuropeptide PF1 on membrane hyperpolarization and membrane conductance (Willson et al., 2003). We investigated the effects of PF1 on voltage-activated currents in Ascaris suum muscle cells. The whole cell voltage-clamp technique was employed to study these currents. Here we report two types of voltage-activated inward calcium currents: transient peak (I(peak)) and a steady-state (I(ss)). We found that 1microM PF1 inhibited the two calcium currents. The I(peak) decreased from -146nA to -99nA (P=0.0007) and the I(ss) decreased from -45nA to -12nA (P=0.002). We also found that PF1 in the presence of calcium increased the voltage-activated outward potassium current (from 521nA to 628nA (P=0.004)). The effect on the potassium current was abolished when calcium was removed and replaced with cobalt; it was also reduced at a higher concentration of PF1 (10microM). These studies demonstrate a mechanism by which PF1 decreases the excitability of the neuromuscular system by modulating calcium currents in nematodes. PF1 inhibits voltage-activated calcium currents and potentiates the voltage-activated calcium-dependent potassium current. The effect on a calcium-activated-potassium channel appears to be common to both PF1 and emodepside (Guest et al., 2007). It will be of interest to investigate the actions of emodepside on calcium currents to further elucidate the mechanism of action.
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Affiliation(s)
- S. Verma
- Department of Biomedical Science, Iowa State University, Ames, IA 50011, USA
| | - A.P. Robertson
- Department of Biomedical Science, Iowa State University, Ames, IA 50011, USA
| | - R.J. Martin
- Department of Biomedical Science, Iowa State University, Ames, IA 50011, USA
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16
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Tamse CT, Yamoah EN. Elementary properties of axonal calcium currents in type B photoreceptors in Hermissenda crassicornis. J Neurosci 2002; 22:10533-8. [PMID: 12486145 PMCID: PMC6758458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
Axons of the type B photoreceptors form synapses with hair cells and interneurons that are involved in classical conditioning in Hermissenda. We examined the differences in the Ca2+ channels expressed in the soma and axons of the B photoreceptors by direct functional recordings of single-channel currents. Although the soma of the B cells express two Ca2+ current subtypes, a transient BayK 8644-insensitive (approximately 17 pS) current and a sustained BayK 8644-sensitive (approximately 10 pS) current, the axons expressed only the latter. The axonal Ca2+ current activated at potentials positive to -20 mV. Moreover, the Ca2+ channels are distributed heterogeneously along the length of the axon, with the higher channel density (approximately 10-15 channel microm(-2)) occurring at the distal one-third of the isolated axons, with respect to the soma. The regions of Ca2+ channel clusters may represent the presynaptic site of the photoreceptor-interneuron synapses. Furthermore, the high-density clusters of Ca2+ channels may augment postsynaptic responses. The results of the present study represent the first direct recordings of Ca2+ currents at presumed synaptic sites. Expression of different Ca2+ channel subtypes at distinct compartments of the type B photoreceptors may generate diverse Ca2+ domains that may be required for neuronal plasticity in Hermissenda.
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Affiliation(s)
- Catherine T Tamse
- Center for Neuroscience, Department of Otolaryngology, University of California, Davis, Davis, California 95616, USA
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17
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Smotherman MS, Narins PM. The electrical properties of auditory hair cells in the frog amphibian papilla. J Neurosci 1999; 19:5275-92. [PMID: 10377339 PMCID: PMC6782313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
The amphibian papilla (AP) is the principal auditory organ of the frog. Anatomical and neurophysiological evidence suggests that this hearing organ utilizes both mechanical and electrical (hair cell-based) frequency tuning mechanisms, yet relatively little is known about the electrophysiology of AP hair cells. Using the whole-cell patch-clamp technique, we have investigated the electrical properties and ionic currents of isolated hair cells along the rostrocaudal axis of the AP. Electrical resonances were observed in the voltage response of hair cells harvested from the rostral and medial, but not caudal, regions of the AP. Two ionic currents, ICa and IK(Ca), were observed in every hair cell; however, their amplitudes varied substantially along the epithelium. Only rostral hair cells exhibited an inactivating potassium current (IA), whereas an inwardly rectifying potassium current (IK1) was identified only in caudal AP hair cells. Electrically tuned hair cells exhibited resonant frequencies from 50 to 375 Hz, which correlated well with hair cell position and the tonotopic organization of the papilla. Variations in the kinetics of the outward current contribute substantially to the determination of resonant frequency. ICa and IK(Ca) amplitudes increased with resonant frequency, reducing the membrane time constant with increasing resonant frequency. We conclude that a tonotopically organized hair cell substrate exists to support electrical tuning in the rostromedial region of the frog amphibian papilla and that the cellular mechanisms for frequency determination are very similar to those reported for another electrically tuned auditory organ, the turtle basilar papilla.
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Affiliation(s)
- M S Smotherman
- Department of Physiological Science, The University of California, Los Angeles, California 90095-1527, USA
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18
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Yamoah EN, Matzel L, Crow T. Expression of different types of inward rectifier currents confers specificity of light and dark responses in type A and B photoreceptors of Hermissenda. J Neurosci 1998; 18:6501-11. [PMID: 9698338 PMCID: PMC6793191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Each eye of the mollusc Hermissenda consists of five photoreceptors, two type A and three type B cells. Type A cells are quiescent, whereas B cells are spontaneously active in the dark. Differences in the intrinsic membrane properties of type A and B photoreceptors were studied using voltage- and current-clamp techniques. The current density of a Ni2+-sensitive, low-voltage activated Ca2+ current was similar in the two cell types. However, type B cells express an inward rectifier current (Ih) that has different permeation and pharmacological properties from the inward rectifier current in type A cells. The current in the B cells was time-dependent and was blocked by Cs+. Na+ and K+ were the charge carriers for Ih. The inward rectifier current in A cells (IK1) was time-independent, was selectively permeable to K+, and was blocked by Ba2+. Ni2+ reduced the spontaneous spike activities of type A and B cells, whereas Cs+ produced membrane hyperpolarization and reduced the spike activities of dark-adapted B cells. The application of both Cs+ and Ni2+ completely blocked dark-adapted spontaneous activities of B cells. Moreover, Ba2+ increased the excitability of type A cells but not B cells. Hence, differential expression of the two distinct inward rectifiers found in type A and B cells contributes to differences in their intrinsic membrane properties. Because changes in the excitability of the two cell types are correlates of conditioning in Hermissenda, modulation of these underlying currents may play a major role during conditioning-induced plasticity.
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Affiliation(s)
- E N Yamoah
- Department of Cell Biology, Neurobiology, and Anatomy, University of Cincinnati School of Medicine, Cincinnati, Ohio 45267, USA
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19
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Filippov AK, Webb TE, Barnard EA, Brown DA. P2Y2 nucleotide receptors expressed heterologously in sympathetic neurons inhibit both N-type Ca2+ and M-type K+ currents. J Neurosci 1998; 18:5170-9. [PMID: 9651200 PMCID: PMC6793489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/1998] [Revised: 04/23/1998] [Accepted: 04/28/1998] [Indexed: 02/08/2023] Open
Abstract
The P2Y2 receptor is a uridine/adenosine triphosphate (UTP/ATP)-sensitive G-protein-linked nucleotide receptor that previously has been reported to stimulate the phosphoinositide signaling pathway. Messenger RNA for this receptor has been detected in brain tissue. We have investigated the coupling of the molecularly defined rat P2Y2 receptor to neuronal N-type Ca2+ channels and to M-type K+ channels by heterologous expression in rat superior cervical sympathetic (SCG) neurons. After the injection of P2Y2 cRNA, UTP inhibited the currents carried by both types of ion channel. As previously reported [Filippov AK, Webb TE, Barnard EA, Brown DA (1997) Inhibition by heterologously expressed P2Y2 nuerones. Br J Pharmacol 121:849-851], UTP inhibited the Ca2+ current (ICa(N)) by up to 64%, with an IC50 of approximately 0.5 microM. We now find that UTP also inhibited the K+M current (IK(M)) by up to 61%, with an IC50 of approximately 1.5 microM. UTP had no effect on either current in neurons not injected with P2Y2 cRNA. Structure-activity relations for the inhibition of ICa(N) and IK(M) in P2Y2 cRNA-injected neurons were similar, with UTP >/= ATP > ITP >> GTP,UDP. However, coupling to these two channels involved different G-proteins: pretreatment with Pertussis toxin (PTX) did not affect UTP-induced inhibition of IK(M) but reduced inhibition of ICa(N) by approximately 60% and abolished the voltage-dependent component of this inhibition. In unclamped neurons, UTP greatly facilitated depolarization-induced action potential discharges. Thus, the single P2Y2 receptor can couple to at least two G-proteins to inhibit both Ca2+N and K+M channels with near-equal facility. This implies that the P2Y2 receptor may induce a broad range of effector responses in the nervous system.
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Affiliation(s)
- A K Filippov
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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20
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Takahashi T, Kajikawa Y, Tsujimoto T. G-Protein-coupled modulation of presynaptic calcium currents and transmitter release by a GABAB receptor. J Neurosci 1998; 18:3138-46. [PMID: 9547222 PMCID: PMC6792650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Presynaptic GABAB receptors play a regulatory role in central synaptic transmission. To elucidate their underlying mechanism of action, we have made whole-cell recordings of calcium and potassium currents from a giant presynaptic terminal, the calyx of Held, and EPSCs from its postsynaptic target in the medial nucleus of the trapezoid body of rat brainstem slices. The GABAB receptor agonist baclofen suppressed EPSCs and presynaptic calcium currents but had no effect on voltage-dependent potassium currents. The calcium current-EPSC relationship measured during baclofen application was similar to that observed on reducing [Ca2+]o, suggesting that the presynaptic inhibition generated by baclofen is caused largely by the suppression of presynaptic calcium influx. Presynaptic loading of the GDP analog guanosine-5'-O-(2-thiodiphosphate) (GDPbetaS) abolished the effect of baclofen on both presynaptic calcium currents and EPSCs. The nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) suppressed presynaptic calcium currents and occluded the effect of baclofen on presynaptic calcium currents and EPSCs. Photoactivation of GTPgammaS induced an inward rectifying potassium current at the calyx of Held, whereas baclofen had no such effect. We conclude that presynaptic GABAB receptors suppress transmitter release through G-protein-coupled inhibition of calcium currents.
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Affiliation(s)
- T Takahashi
- Department of Neurophysiology, University of Tokyo Faculty of Medicine, Tokyo 113, Japan
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21
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Dong H, Earle ML, Jiang Y, Loutzenhiser KA, Triggle CR. Cardiovascular effects of CPU-23, a novel L-type calcium channel blocker with a unique molecular structure. Br J Pharmacol 1997; 122:1271-8. [PMID: 9421272 PMCID: PMC1565070 DOI: 10.1038/sj.bjp.0701508] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. The cardiovascular effects of CPU-23 (1-[1-[(6-methoxy)-naphth-2-yl]]-ethyl-2-(1-piperidinyl)-acetyl-6, 7-dimethoxy-1,2,3,4-tetrahydroisoquinoline), a cleavage product of tetrandrine, were investigated using the whole cell perforated patch-clamp technique, in vitro tension measurements and in vivo haemodynamic recordings. 2. CPU-23 (1 and 10 microM) dose-dependently reduced concentration-response curves for KCl and phenylephrine (PE) in the rat tail artery; inhibition of KCl-induced contraction was much more potent than for PE. At the same concentrations, CPU-23 inhibited the inward Ba2+ currents in single smooth muscle cells isolated from the rat tail artery, while CPU-23 (10 microM) produced 95% vasorelaxation of the rat middle cerebral artery preconstricted with BayK 8644. 3. CPU-23 (10 and 30 microM) inhibited the noradrenaline-induced phasic contraction of the rat tail artery in the absence of extracellular Ca2+ from 40% of control to 23% and 14%, respectively (P<0.01) and tonic contraction of the artery after addition of Ca2+ (2 mM) from 100% of control to 83% and 75%, respectively (P<0.01). In the presence of extracellular Ca2+ the PE-induced contraction was reduced by CPU-23 (30 and 100 microM) to 27% and 37%, respectively. 4. The haemodynamic profile of CPU-23 in the rat was very similar to diltiazem. At 5 mg kg(-1) CPU-23 induced a rapid onset and long-lasting decrease in left ventricular systolic pressure (LVSP), maximal velocity of pressure increase (dP/dt(max)), systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR). When haemodynamic actions of CPU-23, verapamil, diltiazem and nifedipine were compared at equidepressor doses, the order of potency for reducing LVSP and dP/dt(max) was verapamil > CPU-23 = diltiazem > nifedipine and the order of potency for decreasing HR was verapamil = CPU-23 = diltiazem > nifedipine. 5. These data indicate that CPU-23 is a novel calcium channel blocker with unique molecular structure, which exerts antihypertensive and cardiac depressant effects due primarily to its action on L-type voltage-gated calcium channels.
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Affiliation(s)
- H Dong
- Faculty of Medicine, University of Calgary, Alberta, Canada
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Williams S, Serafin M, Mühlethaler M, Bernheim L. Distinct contributions of high- and low-voltage-activated calcium currents to afterhyperpolarizations in cholinergic nucleus basalis neurons of the guinea pig. J Neurosci 1997; 17:7307-15. [PMID: 9295377 PMCID: PMC6573441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The contributions made by low- (LVA) and high-voltage-activated (HVA) calcium currents to afterhyperpolarizations (AHPs) of nucleus basalis (NB) cholinergic neurons were investigated in dissociated cells. Neurons with somata >25 microM were studied because 80% of them stained positively for choline acetyltransferase and had electrophysiological characteristics identical to those of cholinergic NB neurons previously recorded in basal forebrain slices. Calcium currents of cholinergic NB neurons first were dissected pharmacologically into an amiloride-sensitive LVA and at least five subtypes of HVA currents. Approximately 17% of the total HVA current was sensitive to nifedipine (3 microM), 35% to omega-conotoxin-GVIA (200-400 nM), 10% to omega-Agatoxin-IVA (100 nM), and 20% to omega-Agatoxin-IVA (300-500 nM), suggesting the presence of L-, N-, P-, and Q-type channels, respectively. A remaining current (R-type) resistant to these antagonists was blocked by cadmium (100-200 microM). We then assessed pharmacologically the role that LVA and HVA currents had in activating the apamin-insensitive AHP elicited by a long train of action potentials (sAHP) and the AHP evoked either by a short burst of action potentials or by a single action potential (mAHP) that is known to be apamin-sensitive. During sAHPs, approximately 60% of the hyperpolarization was activated by calcium flowing through N-type channels and approximately 20% through P-type channels, whereas T-, L-, and Q-type channels were not involved significantly. In contrast, during mAHPs, N- and T-type channels played key roles (approximately 60 and 30%, respectively), whereas L-, P-, and Q-type channels were not implicated significantly. It is concluded that in cholinergic NB neurons various subtypes of calcium channels can differentially activate the apamin-sensitive mAHP and the apamin-insensitive sAHP.
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Affiliation(s)
- S Williams
- Département de Physiologie, Centre Médical Universitaire, 1211 Genève 4, Switzerland
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Porter NM, Thibault O, Thibault V, Chen KC, Landfield PW. Calcium channel density and hippocampal cell death with age in long-term culture. J Neurosci 1997; 17:5629-39. [PMID: 9204944 PMCID: PMC6793822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/1997] [Revised: 05/02/1997] [Accepted: 05/07/1997] [Indexed: 02/04/2023] Open
Abstract
The expression of voltage-gated calcium (Ca2+) channel activity in brain cells is known to be important for several aspects of neuronal development. In addition, excessive Ca2+ influx has been linked clearly to neurotoxicity both in vivo and in vitro; however, the temporal relationship between the development of Ca2+ channel activity and neuronal survival is not understood. Over a period spanning 28 d in vitro, progressive increases in high voltage-activated whole-cell Ca2+ current and L-type Ca2+ channel activity were observed in cultured hippocampal neurons. On the basis of single-channel analyses, these increases seem to arise in part from a greater density of functionally available L-type Ca2+ channels. An increase in mRNA for the alpha1 subunit of L-type Ca2+ channels occurred over a similar time course, which suggests that a change in gene expression may underlie the increased channel density. Parallel studies showed that hippocampal neuronal survival over 28 d was inversely related to increasing Ca2+ current density. Chronic treatment of hippocampal neurons with the L-type Ca2+ channel antagonist nimodipine significantly enhanced survival. Together, these results suggest that age-dependent increases in the density of Ca2+ channels might contribute significantly to declining viability of hippocampal neurons. The results also are analogous to patterns seen in neurons of aged animals and therefore raise the possibility that long-term primary neuronal culture could serve as a model for some aspects of aging changes in hippocampal Ca2+ channel function.
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Affiliation(s)
- N M Porter
- University of Kentucky, Department of Pharmacology, College of Medicine, Lexington, Kentucky 40536, USA
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Filippov AK, Webb TE, Barnard EA, Brown DA. Inhibition by heterologously-expressed P2Y2 nucleotide receptors of N-type calcium currents in rat sympathetic neurones. Br J Pharmacol 1997; 121:849-51. [PMID: 9222539 PMCID: PMC1564782 DOI: 10.1038/sj.bjp.0701270] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The P2Y2 nucleotide receptor has previously been shown to stimulate phosphoinositide breakdown. We now show that, when P2Y2 receptors are heterologously expressed by cRNA injection into dissociated rat sympathetic neurones, activation of these receptors by uridine 5'-triphosphate (UTP) or adenosine 5'-triphosphate (ATP) inhibits the N-type voltage-gated calcium current by approximately 65%, with an IC50 of 0.5 microM. Thus, the same molecular species of nucleotide receptor can link to two different effector pathways.
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Affiliation(s)
- A K Filippov
- Department of Pharmacology, University College London
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25
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Pedroarena C, Llinás R. Dendritic calcium conductances generate high-frequency oscillation in thalamocortical neurons. Proc Natl Acad Sci U S A 1997; 94:724-8. [PMID: 9012852 PMCID: PMC19581 DOI: 10.1073/pnas.94.2.724] [Citation(s) in RCA: 157] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/1996] [Indexed: 02/03/2023] Open
Abstract
Cortical-projecting thalamic neurons, in guinea pig brain slices, display high-frequency membrane potential oscillations (20-80 Hz), when their somata are depolarized beyond -45 mV. These oscillations, preferentially located at dendritic sites, are supported by the activation of P/Q type calcium channels, as opposed to the expected persistent sodium conductance responsible for such rhythmic behavior in other central neurons. Short hyperpolarizing pulses reset the phase and transiently increase the amplitude of these oscillations. This intrinsic thalamic electroresponsiveness may serve as a cellular-based temporal binding mechanism that sharpens the temporal coincidence of cortical-feedback synaptic inputs, known to distribute at remote dendritic sites on thalamic neurons.
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Affiliation(s)
- C Pedroarena
- Department of Physiology and Neurosciences, New York University Medical Center, New York 10016, USA
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26
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Hesen W, Karst H, Meijer O, Cole TJ, Schmid W, de Kloet ER, Schütz G, Joëls M. Hippocampal cell responses in mice with a targeted glucocorticoid receptor gene disruption. J Neurosci 1996; 16:6766-74. [PMID: 8824317 PMCID: PMC6579238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Previous studies in rats have shown that cellular properties of hippocampal CA1 neurons are under coordinative control of mineralocorticoid and glucocorticoid receptors (MRs and GRs, respectively). In the present study, we examined electrical properties under conditions of exclusive MR occupation, by using mice with a genetic defect in GRs obtained by homologous recombination techniques. It appeared that in the animals homozygous for the genetic defect, the properties studied, i.e., the voltage-gated Ca currents and responses to serotonin and the cholinergic analog carbachol, resembled the effects observed in adrenalectomized mice, i.e., when no steroid receptors are activated. This may point to the necessity of functional GRs for the development of MR-induced actions. Ca current amplitude and transmitter responses in the heterozygous animals, which combine a reduced amount of GRs in the hippocampus with relatively high circulating levels of corticosterone, were large compared with those in the wild-type controls; this resembles the responses that were observed previously in rats subjected to a very high dose of corticosterone. These findings exemplify the use of GR knockout mice for the study of cellular properties in the brain. Further substantiation of the observations, however, awaits the development of site-specific, inducible GR knockouts.
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Affiliation(s)
- W Hesen
- Department of Experimental Zoology, University of Amsterdam, 1098 SM Amsterdam, The Netherlands
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27
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Campbell LW, Hao SY, Thibault O, Blalock EM, Landfield PW. Aging changes in voltage-gated calcium currents in hippocampal CA1 neurons. J Neurosci 1996; 16:6286-95. [PMID: 8815908 PMCID: PMC6579167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Previous current-clamp studies in rat hippocampal slice CA1 neurons have found aging-related increases in long-lasting calcium (Ca)-dependent and Ca-mediated potentials. These changes could reflect an increase in Ca influx through voltage-gated Ca channels but also could reflect a change in potassium currents. Moreover, if altered Ca influx is involved, it is nuclear whether it arises from generally increased Ca channel activity, lower threshold, or reduced inactivation. To analyze the basis for altered Ca potentials, whole-cell voltage-clamp studies of CA1 hippocampal neurons were performed in nondissociated hippocampal slices of adult (3- to 5-month-old) and aged (25- to 26-month-old) rats. An aging-related increase was found in high-threshold Ca and barium (Ba) currents, particularly in the less variable, slowly inactivating (late) current at the end of a depolarization step. Input resistance of neurons did not differ between age groups. In steady-state inactivation and repetitive-pulse protocols, inactivation of Ca and Ba currents was not reduced and, in some cases, was slightly greater in aged neurons, apparently because of larger inward current. The current blocked by nimodipine was greater in aged neurons, indicating that some of the aging increase was in L-type currents. These results indicate that whole-cell Ca currents are increased with aging in CA1 neurons, apparently attributable to greater channel activity rather than to reduced inactivation. The elevated Ca influx seems likely to play a role in impaired function and enhanced susceptibility to neurotoxic influences.
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Affiliation(s)
- L W Campbell
- Department of Pharmacology, College of Medicine, University of Kentucky, Lexington 40536, USA
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28
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de la Peña E, Geijo-Barrientos E. Laminar localization, morphology, and physiological properties of pyramidal neurons that have the low-threshold calcium current in the guinea-pig medial frontal cortex. J Neurosci 1996; 16:5301-11. [PMID: 8757243 PMCID: PMC6578882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
One of the several types of ionic currents present in central neurons is the low-threshold, or T-type calcium current (LTCC). This current is responsible for the firing of low-threshold calcium spikes (LTS) and participates in the generation of rhythmic activity and bursts of action potentials in several brain nuclei. We have studied the distribution and properties of pyramidal neurons recorded from the guinea-pig medial frontal cortex that have this calcium current. Pyramidal neurons were recorded in an in vitro slice preparation using either current clamp or single-electrode voltage-clamp recording. Pyramidal neurons that generated LTS or had the LTCC were found only between 500 mm from the pial surface and the white matter (approximately layers V/VI) and were absent in more superficial layers. All pyramidal neurons that fired LTS or had the LTCC were characterized as regular spiking and had some important morphological and physiological differences from the rest of the pyramidal neurons studied. This group of neurons had shorter and less complex apical dendritic arbors, fired action potentials of lower amplitude and longer duration, and were the only type of pyramidal neurons able to generate bursts of action potentials. In addition, the inhibitory synaptic potentials elicited by stimulation of layer I were more powerful in this group of neurons. This research provides new evidence for the presence of the LTCC in subsets of cortical pyramidal neurons, which have specific and well defined morphological and physiological properties.
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Affiliation(s)
- E de la Peña
- Departamento de Fisiologia, Universidad de Alicante, Spain
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29
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Olson EC. Onset of electrical excitability during a period of circus plasma membrane movements in differentiating Xenopus neurons. J Neurosci 1996; 16:5117-29. [PMID: 8756441 PMCID: PMC6579288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Living neurons are usually first identifiable in primary cultures at the time of neurite initiation, and studies of excitability have been restricted largely to the subsequent period. A morphological early marker is described that identifies neurons for whole-cell voltage-clamp recordings before neurite initiation. Video time-lapse recordings of cultured cells dissociated from neurectoderm of Xenopus neural plate stage embryos reveal cells demonstrating circus movements, in which blebs of plasma membrane propagate around the cell circumference within a period of several minutes. All neurons demonstrate circus movements before morphological differentiation; the fraction of cells exhibiting circus movements that differentiate morphologically depends on the substrate on which they are cultured. Blockade of circus activity with cytochalasin B does not prevent neuronal differentiation. Circus movements are not neurectoderm-specific because they similarly predict differentiation of myocytes developing in mesodermal cultures. Initially inexcitable, neurons develop voltage-dependent K+, Na+, and Ca2+ currents during the period of several hours in which they exhibit circus movements. The early development of depolarization-induced elevations of [Ca2+]i several hours before morphological differentiation corresponds to the previously described onset of functionally significant spontaneous elevations of [Ca2+]i in these neurons and demonstrates a role for early expression of voltage-dependent ion channels.
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Affiliation(s)
- E C Olson
- Department of Biology, University of California at San Diego, La Jolla 92093, USA
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30
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García KD, Beam KG. Reduction of calcium currents by Lambert-Eaton syndrome sera: motoneurons are preferentially affected, and L-type currents are spared. J Neurosci 1996; 16:4903-13. [PMID: 8756422 PMCID: PMC6579308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Previous work has demonstrated that Lambert-Eaton syndrome (LES) antibodies reduce calcium currents in nonneuronal cells and neurons and reduce the amplitude of extracellularly recorded currents at mouse motor nerve terminals. We compared effects of LES sera on whole-cell currents of cultured nerve and muscle. LES sera more strongly reduced calcium currents in motoneurons than in sensory neurons. Motoneuronal potassium currents were unaffected. The sera minimally affected calcium currents in skeletal and cardiac muscle. In motoneurons, both low voltage-activated (LVA) and high voltage-activated (HVA) components of calcium current were decreased, demonstrating that the sera targeted more than one calcium channel type. The HVA current remaining in LES-treated motoneurons was little affected by micromolar omega-conotoxin MVIIC but was reduced > 70% by micromolar nimodipine. This pharmacological profile contrasts with untreated cells and suggest that LES sera primarily spare L-type currents in motoneurons.
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Affiliation(s)
- K D García
- Department of Anatomy and Neurobiology, Colorado State University, Fort Collins 80523, USA
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