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Allken V, Chepkoech JL, Einevoll GT, Halnes G. The subcellular distribution of T-type Ca2+ channels in interneurons of the lateral geniculate nucleus. PLoS One 2014; 9:e107780. [PMID: 25268996 PMCID: PMC4182431 DOI: 10.1371/journal.pone.0107780] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 07/17/2014] [Indexed: 12/31/2022] Open
Abstract
Inhibitory interneurons (INs) in the lateral geniculate nucleus (LGN) provide both axonal and dendritic GABA output to thalamocortical relay cells (TCs). Distal parts of the IN dendrites often enter into complex arrangements known as triadic synapses, where the IN dendrite plays a dual role as postsynaptic to retinal input and presynaptic to TC dendrites. Dendritic GABA release can be triggered by retinal input, in a highly localized process that is functionally isolated from the soma, but can also be triggered by somatically elicited Ca2+-spikes and possibly by backpropagating action potentials. Ca2+-spikes in INs are predominantly mediated by T-type Ca2+-channels (T-channels). Due to the complex nature of the dendritic signalling, the function of the IN is likely to depend critically on how T-channels are distributed over the somatodendritic membrane (T-distribution). To study the relationship between the T-distribution and several IN response properties, we here run a series of simulations where we vary the T-distribution in a multicompartmental IN model with a realistic morphology. We find that the somatic response to somatic current injection is facilitated by a high T-channel density in the soma-region. Conversely, a high T-channel density in the distal dendritic region is found to facilitate dendritic signalling in both the outward direction (increases the response in distal dendrites to somatic input) and the inward direction (the soma responds stronger to distal synaptic input). The real T-distribution is likely to reflect a compromise between several neural functions, involving somatic response patterns and dendritic signalling.
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Affiliation(s)
- Vaneeda Allken
- Dept. of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Joy-Loi Chepkoech
- Dept. of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway; Dept. of Psychology, University of Oslo, Oslo, Norway
| | - Gaute T Einevoll
- Dept. of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway; Dept. of Physics, University of Oslo, Oslo, Norway
| | - Geir Halnes
- Dept. of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
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Li Y, Wang F, Zhang X, Qi Z, Tang M, Szeto C, Li Y, Zhang H, Chen X. β-Adrenergic stimulation increases Cav3.1 activity in cardiac myocytes through protein kinase A. PLoS One 2012; 7:e39965. [PMID: 22808078 PMCID: PMC3396630 DOI: 10.1371/journal.pone.0039965] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 06/05/2012] [Indexed: 11/18/2022] Open
Abstract
The T-type Ca2+ channel (TTCC) plays important roles in cellular excitability and Ca2+ regulation. In the heart, TTCC is found in the sinoatrial nodal (SAN) and conduction cells. Cav3.1 encodes one of the three types of TTCCs. To date, there is no report regarding the regulation of Cav3.1 by β-adrenergic agonists, which is the topic of this study. Ventricular myocytes (VMs) from Cav3.1 double transgenic (TG) mice and SAN cells from wild type, Cav3.1 knockout, or Cav3.2 knockout mice were used to study β-adrenergic regulation of overexpressed or native Cav3.1-mediated T-type Ca2+ current (ICa-T(3.1)). ICa-T(3.1) was not found in control VMs but was robust in all examined TG-VMs. A β-adrenergic agonist (isoproterenol, ISO) and a cyclic AMP analog (dibutyryl-cAMP) significantly increased ICa-T(3.1) as well as ICa-L in TG-VMs at both physiological and room temperatures. The ISO effect on ICa-L and ICa-T in TG myocytes was blocked by H89, a PKA inhibitor. ICa-T was detected in control wildtype SAN cells but not in Cav3.1 knockout SAN cells, indicating the identity of ICa-T in normal SAN cells is mediated by Cav3.1. Real-time PCR confirmed the presence of Cav3.1 mRNA but not mRNAs of Cav3.2 and Cav3.3 in the SAN. ICa-T in SAN cells from wild type or Cav3.2 knockout mice was significantly increased by ISO, suggesting native Cav3.1 channels can be upregulated by the β-adrenergic (β-AR) system. In conclusion, β-adrenergic stimulation increases ICa-T(3.1) in cardiomyocytes, which is mediated by the cAMP/PKA pathway. The upregulation of ICa-T(3.1) by the β-adrenergic system could play important roles in cellular functions involving Cav3.1.
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Affiliation(s)
- Yingxin Li
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Fang Wang
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Xiaoying Zhang
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Zhao Qi
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Mingxin Tang
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Christopher Szeto
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Ying Li
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
- Institute of Burn Research, Southwest Hospital, State Key Laboratory of Trauma Burns and Combined Injury, Third Military Medical University, Chongqing, China
| | - Hongyu Zhang
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Xiongwen Chen
- Cardiovascular Research Center and Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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Shin MC, Wakita M, Xie DJ, Yamaga T, Iwata S, Torii Y, Harakawa T, Ginnaga A, Kozaki S, Akaike N. Inhibition of Membrane Na+ Channels by A Type Botulinum Toxin at Femtomolar Concentrations in Central and Peripheral Neurons. J Pharmacol Sci 2012; 118:33-42. [DOI: 10.1254/jphs.11060fp] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 11/06/2011] [Indexed: 10/14/2022] Open
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Himmel HM, Stengel W, Ravens U. Selectivity of blocking of low- versus high-voltage activated calcium currents by the dihydropyridine derivatives Bay E5759 and Bay A4339 in neuroblastoma--glioma NG 108-15 cells. Pharmacol Res 2001; 44:113-6. [PMID: 11516260 DOI: 10.1006/phrs.2001.0836] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Beneficial therapeutic effects of dihydropyridine derivatives in cardiovascular and neurological disorders are often associated with selective L-type Ca(2+)channel blockade. Here the new dihydropyridine derivatives Bay E5759 (1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid ethyl-1-methylethyl ester) and Bay A4339 (1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid dimethyl-ester) were tested for their potency and selectivity of blocking of Ba(2+)currents mediated by low-(LVACC)vs high-voltage activated Ca(2+)channels (HVACC) in neuroblastoma-glioma hybrid cells. Nisoldipine and mibefradil served as reference compounds. Bay E5759 and Bay A4339 blocked HVACC at low nanomolar concentrations, whereas LVACC was hardly reduced at up to 10 microM. The order of potency for blockade of HVACC was Bay E5759 (IC(50): 0.4 nM) > Bay A4339 (2.5 nM) approximately = nisoldipine (4 nM) >> mibefradil (3.8 microM). Thus Bay E5759 and Bay A4339 are highly potent and selective blockers of HVACC, presumably L-type Ca(2+)channels.
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Affiliation(s)
- H M Himmel
- Department of Pharmacology and Toxicology, Carl Gustav Carus Medical School, Dresden University of Technology, Dresden, Germany
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Randall A, Benham CD. Recent advances in the molecular understanding of voltage-gated Ca2+ channels. Mol Cell Neurosci 1999; 14:255-72. [PMID: 10588383 DOI: 10.1006/mcne.1999.0795] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- A Randall
- Department of Neuroscience Research, SmithKline Beecham Pharmaceuticals, New Frontiers Science Park, Harlow, Essex, United Kingdom.
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Churchill D, Macvicar BA. Biophysical and pharmacological characterization of voltage-dependent Ca2+ channels in neurons isolated from rat nucleus accumbens. J Neurophysiol 1998; 79:635-47. [PMID: 9463427 DOI: 10.1152/jn.1998.79.2.635] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The nucleus accumbens (NA) has an integrative role in behavior and may mediate addictive and psychotherapeutic drug action. Whole cell recording techniques were used to characterize electrophysiologically and pharmacologically high- and low-threshold voltage-dependent Ca2+ currents in isolated NA neurons. High-threshold Ca2+ currents, which were found in all neurons studied and include both sustained and inactivating components, activated at potentials greater than -50 mV and reached maximal activation at approximately 0 mV. In contrast, low-threshold Ca2+ currents activated at voltages greater than -64 mV with maximal activation occurring at -30 mV. These were observed in 42% of acutely isolated neurons. Further pharmacological characterization of high-threshold Ca2+ currents was attempted using nimodipine (Nim), omega-conotoxin-GVIA (omega-CgTx) and omega-agatoxin-IVA (omegaAga), which are thought to identify the L, N, and P/Q subtypes of Ca2+ currents, respectively. Nim (5-10 muM) blocked 18%, omegaCgTx (1-2 muM) blocked 25%, and omegaAga (200 nM) blocked 17% of total Ca2+ current. Nim primarily blocked a sustained high-threshold Ca2+ current in a partially reversible manner. In contrast, omegaCgTx irreversibly blocked both sustained and inactivating components. omegaAga irreversibly blocked only a sustained component. In all three of these Ca2+ channel blockers, plus 5 muM omega-conotoxin-MVIIC to eliminate a small unblocked Q-type Ca2+ current (7%), a toxin-resistant high-threshold Ca2+ current remained that was 32% of total Ca2+ current. This current inactivated much more rapidly than the other high-threshold Ca2+ currents, was depressed in 50 muM Ni2+ and reached maximal activation 5-10 mV negative to the toxin-sensitive high-threshold Ca2+ currents. Thus NA neurons have multiple types of high-threshold Ca2+ currents with a large component being the toxin-resistant "R" component.
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Affiliation(s)
- D Churchill
- Neuroscience Research Group, Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Alberta T2N 4N1, Canada
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Dzhura IO, Naidenov VG, Lyubanova OP, Kostyuk PG, Shuba YM. Characterization of hypothalamic low-voltage-activated Ca channels based on their functional expression in Xenopus oocytes. Neuroscience 1996; 70:729-38. [PMID: 9045084 DOI: 10.1016/s0306-4522(96)83010-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ca-channel currents expressed in Xenopus oocytes by means of messenger RNA extracted from rat thalamohypothalamic complex were studied using the double microelectrode technique. Currents were recorded in Cl(-)-free extracellular solutions with 40 mM Ba2+ as a charge carrier. In response to depolarizations from a very negative holding potential (Vh = -120 mV), inward Ba2+ current activated at around -80 mV, peaked at -30 to -20 mV and reversed at +50 mV indicating that it may be transferred through the low voltage-activated calcium channels. The time-dependent inactivation of the current during prolonged depolarization to -20 mV was quite slow and followed a single exponential decay with a time-constant of 1550 ms and a maintained component constituting 30% of the maximal amplitude. The current could not be completely inactivated at any holding potential. As expected for low voltage-activated current, steady-state inactivation curve shifted towards negative potentials. It could be described by the Boltzmann equation with half inactivation potential -78 mV, slope factor 15 mV and maintained level 0.3. Expressed Ba2+ current could be blocked by flunarizine with Kd = 0.42 microM, nifedipine, Kd = 10 microM, and amiloride at 500 microM concentration. Among inorganic Ca-channel blockers the most potent was La3+ (Kd = 0.48 microM) while Cd2+ and Ni2+ were not very discriminative and almost 1000-fold less effective than La3+ (Kd = 0.52 mM and Kd = 0.62 mM, respectively). Our data show that messenger RNA purified from thalamohypothalamic complex induces expression in the oocytes of almost exclusively low voltage-activated calcium channels with voltage-dependent and pharmacological properties very similar to those observed for T-type calcium current in native hypothalamic neurons, though kinetic properties of the expressed and natural currents are somewhat different.
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Affiliation(s)
- I O Dzhura
- A. A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kiev
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