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Lozano Jiménez YY, Sánchez Mora RM. Canales de calcio como blanco de interés farmacológico. NOVA 2020. [DOI: 10.22490/24629448.3926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Los canales de calcio son proteínas de membrana que constituyen la vía más importante para el ingreso del ion calcio (Ca2+) a la célula. Al abrirse, permiten el ingreso selectivo del ion, iniciando una variedad de procesos como contracción muscular, secreción endocrina y liberación de neurotransmisores, entre otros. Estas proteínas se agrupan en tres categorías de acuerdo con sus propiedades estructurales y funcionales: (i) Canales de Ca2+ operados por interacción receptor-ligando (ROCC), (ii) Canales activados por parámetros físicos (Transient Receptor Potencial, TRP) y (iii) Canales de Calcio dependientes de voltaje (VDCCs), siendo estos últimos los más estudiados debido a su presencia en células excitables. Dada la importancia de Ca2+ en la fisiología celular, los canales de Ca2+ constituyen un punto de acción farmacológica importante para múltiples tratamientos y, por tanto, son objeto de estudio para el desarrollo de nuevos fármacos. El objetivo de esta revisión es explicar la importancia de los canales de Ca2+ desde una proyección farmacológica, a partir de la exploración documental de artículos publicados hasta la fecha teniendo en cuenta temas relacionados con la estructura de los canales Ca2+, sus propiedades biofísicas, localización celular, funcionamiento y su interacción farmacológica.
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Kumar A. Calcium Signaling During Brain Aging and Its Influence on the Hippocampal Synaptic Plasticity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:985-1012. [PMID: 31646542 DOI: 10.1007/978-3-030-12457-1_39] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Calcium (Ca2+) ions are highly versatile intracellular signaling molecules and are universal second messenger for regulating a variety of cellular and physiological functions including synaptic plasticity. Ca2+ homeostasis in the central nervous system endures subtle dysregulation with advancing age. Research has provided abundant evidence that brain aging is associated with altered neuronal Ca2+ regulation and synaptic plasticity mechanisms. Much of the work has focused on the hippocampus, a brain region critically involved in learning and memory, which is particularly susceptible to dysfunction during aging. The current chapter takes a specific perspective, assessing various Ca2+ sources and the influence of aging on Ca2+ sources and synaptic plasticity in the hippocampus. Integrating the knowledge of the complexity of age-related alterations in neuronal Ca2+ signaling and synaptic plasticity mechanisms will positively shape the development of highly effective therapeutics to treat brain disorders including cognitive impairment associated with aging and neurodegenerative disease.
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Affiliation(s)
- Ashok Kumar
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, USA.
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Shih CH, Chen CM, Ko WC. Mechanisms of butylidenephthalide for twitch facilitation in electrically stimulated mouse vas deferens. PHARMACEUTICAL BIOLOGY 2018; 56:378-384. [PMID: 30122096 PMCID: PMC6130712 DOI: 10.1080/13880209.2018.1495749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 06/27/2018] [Accepted: 06/28/2018] [Indexed: 06/08/2023]
Abstract
CONTEXT The rhizome of Ligusticum chuaxiong Hort. (Umbelliferae) has been used by Chinese for several thousand years. Its main constituent, butylidenephthalide (Bdph), was proved to be active in inhibiting rat uterine contractions induced by prostaglandin F2α and was reported to be a nonspecific antispamodic and a blocker of voltage-dependent Ca2+ channels (VDCCs). OBJECTIVES The present study investigates the mechanisms of Bdph for twitch facilitation in ICR mouse vas deferens (MVD). MATERIALS AND METHODS Electrical field stimulation (EFS, supramaximal voltage ranging from 60-90 V, 1 ms, 0.2 Hz) was applied to the isolated MVD in Krebs solution. Interactions between Bdph (50 µM) and calcium antagonist (verapamil, diltiazem or aspaminol) on the EFS-evoked twitch responses were determined. The number of experiments was 3-18. RESULTS Bdph (50 µM)-induced twitch facilitations from 100 to 391.9% were unrelated to activation of postjunctional cholinergic or adrenergic receptors. Verapamil and Bdph unabolished the twitch facilitation each other. Diltiazem unabolished the Bdph-induced twitch facilitation. In contrast, Bdph abolished those induced by diltiazem. Aspaminol at 20 μM abolished the Bdph-induced twitch facilitation. In contrast, Bdph abolished those induced by aspaminol. Tetraethylammonium and 4-aminopyridine, the K+ channel blockers, significantly augmented the Bdph-induced twitch facilitation. DISCUSSION AND CONCLUSIONS Bdph may bind to the different, more and same subtypes of VDCCs from verapamil, than diltiazem, and as aspaminol does on prejunctional membrane, respectively. Besides a blocker of VDCCs, Bdph may be a blocker of K+ channels on prejunctional membrane. Thus, Bdph depolarized the membrane and facilitated the cumulative Ca2+-induced twitch responses.
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Affiliation(s)
- Chung-Hung Shih
- Department of Internal Medicine, Division of Thoracic Medicine, Taipei Medical University Hospital, Taipei, Taiwan
- School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chi-Ming Chen
- Department of Medicinal Chemistry, School of Pharmacy, College of Pharmacy, Taipei Medical University, Taipei, Taiwan
| | - Wun-Chang Ko
- Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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eIF4B phosphorylation at Ser504 links synaptic activity with protein translation in physiology and pathology. Sci Rep 2017; 7:10563. [PMID: 28874824 PMCID: PMC5585320 DOI: 10.1038/s41598-017-11096-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/14/2017] [Indexed: 12/20/2022] Open
Abstract
Neuronal physiology requires activity-driven protein translation, a process in which translation initiation factors are key players. We focus on eukaryotic initiation factor 4B (eIF4B), a regulator of protein translation, whose function in neurons is undetermined. We show that neuronal activity affects eIF4B phosphorylation and identify Ser504 as a phosphorylation site regulated by casein kinases and sensitive to the activation of metabotropic glutamate receptors. Ser504 phosphorylation increases eIF4B recruitment to the pre-initiation complex and influences eIF4B localization at synapses. Moreover, Ser504 phosphorylation modulates the translation of protein kinase Mζ. Therefore, by sensing synaptic activity, eIF4B could adjust translation to neuronal needs, promoting adaptive changes in synaptic plasticity. We also show that Ser504 phosphorylation is increased in vivo in a rat model of epilepsy during epileptogenesis i.e. when translation drives maladaptive synaptic changes. We propose eIF4B as a mediator between neuronal activity and translation, with relevance in the control of synaptic plasticity.
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Lack of effect of Z-butylidenephthalide on presynaptic N-type Ca²⁺ channels in isolated guinea-pig ileum. Naunyn Schmiedebergs Arch Pharmacol 2016; 389:159-66. [PMID: 26497186 DOI: 10.1007/s00210-015-1183-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 10/07/2015] [Indexed: 01/23/2023]
Abstract
Z-Butylidenephthalide (Bdph) was reported to more potently inhibit electrically induced twitch responses than acetylcholine-induced tonic contraction in isolated guinea-pig ileum (GPI). The aim of the present study was to investigate the inhibitory effects of Z-Bdph on Ca2+ and K+ channels on GPI. In Locke-Ringer’s solution, both responses were isometrically recorded on a polygraph. Incubation of ω-conotoxin MVIIC, but not Z-Bdph, in the electrically stimulated GPI prior to adding ω-conotoxin GVIA, an irreversible blocker of N-type voltage-dependent Ca2+ channels (VDCCs), protected the binding sites and resulted in the twitch responses reversible by washing, suggesting that Z-Bdph did not bind to the N-type VDCCs. Interestingly, we found Z-Bdph concentration dependently delayed the onsets of K+-induced twitch responses, suggesting that Z-Bdph may be a blocker of K+ channels to interfere extracellular K+ across through the pre-junctional membrane of nerve ending in K+-free medium. Z-Bdph similar to nifedipine non-competitively inhibited cumulative ACh-induced phasic contractions, suggesting that Z-Bdph may bind to L-type of inositol-1,4,5-trisphosphate (IP3)-sensitive Ca2+ channels on the endoplasmic reticulum (ER) membrane. In the presence of verapamil, a L-type Ca2+ channel blocker or Z-Bdph, the twitch inhibitions by either were effectively reversed by exogenous Ca2+, suggesting that they may freely pass through pre-junctional N-type, but not L-type which was blocked at least a part by either, of VDDCs open when each electrical coaxial stimulation (ECS) into intracellular space of cholinergic nerve terminal and trigger release of transmitters. In conclusion, results confirm that Z-Bdph more potently inhibits ECS-induced twitch responses than ACh-induced PCs in GPI and suggest that this effect is not mediated by interaction with presynaptic N-type VDCCs.
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The Role of the Neuroprotective Factor Npas4 in Cerebral Ischemia. Int J Mol Sci 2015; 16:29011-28. [PMID: 26690124 PMCID: PMC4691091 DOI: 10.3390/ijms161226144] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Revised: 10/28/2015] [Accepted: 11/16/2015] [Indexed: 01/05/2023] Open
Abstract
Stroke is one of the leading causes of death and adult disability in the world. Although many molecules have been documented to have a neuroprotective effect, the majority of these molecules failed to improve the neurological outcomes for patients with brain ischemia. It has been proposed that neuroprotection alone may, in fact, not be adequate for improving the prognosis of ischemic stroke. Neuroprotectants that can regulate other processes which occur in the brain during ischemia could potentially be targets for the development of effective therapeutic interventions in stroke. Neuronal Per-Arnt-Sim domain protein 4 (Npas4) is an activity-dependent transcription factor whose expression is induced in various brain insults, including cerebral ischemia. It has been shown that Npas4 plays an important role in protecting neurons against many types of neurodegenerative insult. Recently, it was demonstrated that Npas4 indeed has a neuroprotective role in ischemic stroke and that Npas4 might be involved in modulating the cell death pathway and inflammatory response. In this review, we summarize the current knowledge of the roles that Npas4 may play in neuroinflammation and ischemia. Understanding how ischemic lesion size in stroke may be reduced through modulation of Npas4-dependent apoptotic and inflammatory pathways could lead to the development of new stroke therapies.
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Wallace MS. Ziconotide: a new nonopioid intrathecal analgesic for the treatment of chronic pain. Expert Rev Neurother 2014; 6:1423-8. [PMID: 17078783 DOI: 10.1586/14737175.6.10.1423] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ziconotide is a new nonopioid intrathecal agent recently approved for the treatment of chronic pain. Ziconotide is indicated for the management of severe chronic pain in patients for whom intrathecal therapy is warranted and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies or intrathecal morphine. Ziconotide blocks the N-type calcium channels located in the superficial dorsal horn of the spinal cord, resulting in potent analgesia. The efficacy of ziconotide has been demonstrated in three randomized, placebo-controlled trials in over 500 patients. In addition, its safety has been demonstrated in over 1200 subjects. Ziconotide is a potent analgesic with a narrow therapeutic window. The drug requires a slow titration in order to achieve analgesia while avoiding dose-limiting side effects. This review examines the currently available information on this new analgesic.
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Affiliation(s)
- Mark S Wallace
- Center for Pain Medicine, University of California, San Diego, 9500 Gilman Drive, 0924, San Diego, CA 92093, USA.
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Sendrowski K, Rusak M, Sobaniec P, Iłendo E, Dąbrowska M, Boćkowski L, Koput A, Sobaniec W. Study of the protective effect of calcium channel blockers against neuronal damage induced by glutamate in cultured hippocampal neurons. Pharmacol Rep 2013; 65:730-6. [DOI: 10.1016/s1734-1140(13)71052-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 12/13/2012] [Indexed: 11/28/2022]
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9
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Zhou YY, Li YX, Li YM, Yang XP, Mao MZ, Li ZM. Design, synthesis and structure-activity of N-glycosyl-1-pyridyl-1H-pyrazole-5-carboxamide as inhibitors of calcium channels. Chem Res Chin Univ 2013. [DOI: 10.1007/s40242-013-2263-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Over-expression of N-type calcium channels in cortical neurons from a mouse model of Amyotrophic Lateral Sclerosis. Exp Neurol 2012; 247:349-58. [PMID: 23142186 DOI: 10.1016/j.expneurol.2012.11.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 10/24/2012] [Accepted: 11/02/2012] [Indexed: 12/13/2022]
Abstract
Voltage-gated Ca(2+) channels (VGCCs) mediate calcium entry into neuronal cells in response to membrane depolarisation and play an essential role in a variety of physiological processes. In Amyotrophic Lateral Sclerosis (ALS), a fatal neurodegenerative disease caused by motor neuron degeneration in the brain and spinal cord, intracellular calcium dysregulation has been shown, while no studies have been carried out on VGCCs. Here we show that the subtype N-type Ca(2+) channels are over expressed in G93A cultured cortical neurons and in motor cortex of G93A mice compared to Controls. In fact, by western blotting, immunocytochemical and electrophysiological experiments, we observe higher membrane expression of N-type Ca(2+) channels in G93A neurons compared to Controls. G93A cortical neurons filled with calcium-sensitive dye Fura-2, show a net calcium entry during membrane depolarization that is significantly higher compared to Control. Analysis of neuronal vitality following the exposure of neurons to a high K(+) concentration (25 mM, 5h), shows a significant reduction of G93A cellular survival compared to Controls. N-type channels are involved in the G93A higher mortality because ω-conotoxin GVIA (1 μM), which selectively blocks these channels, is able to abolish the higher G93A mortality when added to the external medium. These data provide robust evidence for an excess of N-type Ca(2+) expression in G93A cortical neurons which induces a higher mortality following membrane depolarization. These results may be central to the understanding of pathogenic pathways in ALS and provide novel molecular targets for the design of rational therapies for the ALS disorder.
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NMDA receptor-mediated Ca2+ influx triggers nucleocytoplasmic translocation of diacylglycerol kinase ζ under oxygen–glucose deprivation conditions, an in vitro model of ischemia, in rat hippocampal slices. Histochem Cell Biol 2012; 137:499-511. [DOI: 10.1007/s00418-011-0907-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2011] [Indexed: 02/07/2023]
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12
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Bononi A, Missiroli S, Poletti F, Suski JM, Agnoletto C, Bonora M, De Marchi E, Giorgi C, Marchi S, Patergnani S, Rimessi A, Wieckowski MR, Pinton P. Mitochondria-Associated Membranes (MAMs) as Hotspot Ca2+ Signaling Units. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:411-37. [DOI: 10.1007/978-94-007-2888-2_17] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Calcium channel subtypes for cholinergic and nonadrenergic noncholinergic neurotransmission in isolated guinea pig trachea. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2010; 382:419-32. [PMID: 20820758 DOI: 10.1007/s00210-010-0556-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2010] [Accepted: 08/18/2010] [Indexed: 10/19/2022]
Abstract
The Ca(2+) channel subtypes in the neurotransmission of isolated guinea pig trachea were elucidated by monitoring the effects of specific Ca(2+) channel blockers on cholinergic contractions and nonadrenergic noncholinergic (NANC) relaxation elicited by electrical field stimulation (EFS). In isolated guinea pig trachea, cholinergic contractile responses to low- and high-frequency EFS were inhibited by the selective N-type calcium channel blocker, ω-conotoxin MVIIA. ω-Agatoxin IVA (a selective P-type blocker), ω-conotoxin MVIIC (a nonselective N-, Q-, and P-type blocker), and nifedipine (a selective L-type blocker) were ineffective, whereas Ni(2+) (a T- and R-type blocker) facilitated cholinergic contractions and produced a late contracture when its concentration exceeded 30 μM. The more the concentration of Ni(2+) increased, the greater the number of incidences and the late contracture areas which occurred. Late contracture did not seem to be due to the effects of acetylcholine, tachykinins, or other polypeptides, but disappeared in the absence of indomethacin. The NANC relaxant responses elicited by the low- and high-frequency EFS were inhibited by ω-conotoxin MVIIA or Ni(2+), but unaffected by ω-Agatoxin IVA, ω-conotoxin MVIIC, and nifedipine. In the absence of indomethacin, Ni(2+) did not alter the ω-conotoxin MVIIA (100 nM)-resistant component of cholinergic contraction, but significantly further inhibited that of NANC relaxation. These results suggest that in isolated guinea pig trachea, cholinergic contraction is regulated by N-type calcium channels which may mask T- and R-type calcium channels and may be co-modulated by both, while NANC relaxation is mainly and independently controlled by N-, T-, and R-type calcium channels.
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Pannexin channels in ATP release and beyond: an unexpected rendezvous at the endoplasmic reticulum. Cell Signal 2010; 23:305-16. [PMID: 20688156 DOI: 10.1016/j.cellsig.2010.07.018] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 07/22/2010] [Indexed: 01/13/2023]
Abstract
The pannexin (Panx) family of proteins, which is co-expressed with connexins (Cxs) in vertebrates, was found to be a new GJ-forming protein family related to invertebrate innexins. During the past ten years, different studies showed that Panxs mainly form hemichannels in the plasma membrane and mediate paracrine signalling by providing a flux pathway for ions such as Ca²(+), for ATP and perhaps for other compounds, in response to physiological and pathological stimuli. Although the physiological role of Panxs as a hemichannel was questioned, there is increasing evidence that Panx play a role in vasodilatation, initiation of inflammatory responses, ischemic death of neurons, epilepsy and in tumor suppression. Moreover, it is intriguing that Panxs may also function at the endoplasmic reticulum (ER) as intracellular Ca²(+)-leak channel and may be involved in ER-related functions. Although the physiological significance and meaning of such Panx-regulated intracellular Ca²(+) leak requires further exploration, this functional property places Panx at the centre of many physiological and pathophysiological processes, given the fundamental role of intracellular Ca²(+) homeostasis and dynamics in a plethora of physiological processes. In this review, we therefore want to focus on Panx as channels at the plasma membrane and at the ER membranes with a particular emphasis on the potential implications of the latter in intracellular Ca²(+) signalling.
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Kumar A, Bodhinathan K, Foster TC. Susceptibility to Calcium Dysregulation during Brain Aging. Front Aging Neurosci 2009; 1:2. [PMID: 20552053 PMCID: PMC2874411 DOI: 10.3389/neuro.24.002.2009] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 10/27/2009] [Indexed: 01/06/2023] Open
Abstract
Calcium (Ca(2+)) is a highly versatile intracellular signaling molecule that is essential for regulating a variety of cellular and physiological processes ranging from fertilization to programmed cell death. Research has provided ample evidence that brain aging is associated with altered Ca(2+) homeostasis. Much of the work has focused on the hippocampus, a brain region critically involved in learning and memory, which is particularly susceptible to dysfunction during senescence. The current review takes a broader perspective, assessing age-related changes in Ca(2+) sources, Ca(2+) sequestration, and Ca(2+) binding proteins throughout the nervous system. The nature of altered Ca(2+) homeostasis is cell specific and may represent a deficit or a compensatory mechanism, producing complex patterns of impaired cellular function. Incorporating the knowledge of the complexity of age-related alterations in Ca(2+) homeostasis will positively shape the development of highly effective therapeutics to treat brain disorders.
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Affiliation(s)
- Ashok Kumar
- Department of Neuroscience, McKnight Brain Institute, University of Florida Gainesville, FL, USA
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Rizzuto R, Marchi S, Bonora M, Aguiari P, Bononi A, De Stefani D, Giorgi C, Leo S, Rimessi A, Siviero R, Zecchini E, Pinton P. Ca(2+) transfer from the ER to mitochondria: when, how and why. BIOCHIMICA ET BIOPHYSICA ACTA 2009; 1787:1342-51. [PMID: 19341702 PMCID: PMC2730423 DOI: 10.1016/j.bbabio.2009.03.015] [Citation(s) in RCA: 340] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/21/2009] [Accepted: 03/24/2009] [Indexed: 10/25/2022]
Abstract
The heterogenous subcellular distribution of a wide array of channels, pumps and exchangers allows extracellular stimuli to induce increases in cytoplasmic Ca(2+) concentration ([Ca(2+)]c) with highly defined spatial and temporal patterns, that in turn induce specific cellular responses (e.g. contraction, secretion, proliferation or cell death). In this extreme complexity, the role of mitochondria was considered marginal, till the direct measurement with targeted indicators allowed to appreciate that rapid and large increases of the [Ca(2+)] in the mitochondrial matrix ([Ca(2+)]m) invariably follow the cytosolic rises. Given the low affinity of the mitochondrial Ca(2+) transporters, the close proximity to the endoplasmic reticulum (ER) Ca(2+)-releasing channels was shown to be responsible for the prompt responsiveness of mitochondria. In this review, we will summarize the current knowledge of: i) the mitochondrial and ER Ca(2+) channels mediating the ion transfer, ii) the structural and molecular foundations of the signaling contacts between the two organelles, iii) the functional consequences of the [Ca(2+)]m increases, and iv) the effects of oncogene-mediated signals on mitochondrial Ca(2+) homeostasis. Despite the rapid progress carried out in the latest years, a deeper molecular understanding is still needed to unlock the secrets of Ca(2+) signaling machinery.
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Affiliation(s)
- Rosario Rizzuto
- Dept. Biomedical Sciences, University of Padua, Via Colombo 3, Padua 35121, Italy.
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Wildburger NC, Lin-Ye A, Baird MA, Lei D, Bao J. Neuroprotective effects of blockers for T-type calcium channels. Mol Neurodegener 2009; 4:44. [PMID: 19863782 PMCID: PMC2774686 DOI: 10.1186/1750-1326-4-44] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 10/28/2009] [Indexed: 01/21/2023] Open
Abstract
Cognitive and functional decline with age is correlated with deregulation of intracellular calcium, which can lead to neuronal death in the brain. Previous studies have found protective effects of various calcium channel blockers in pathological conditions. However, little has been done to explore possible protective effects of blockers for T-type calcium channels, which forms a family of FDA approved anti-epileptic drugs. In this study, we found that neurons showed an increase in viability after treatment with either L-type or T-type calcium channel antagonists. The family of low-voltage activated, or T-type calcium channels, comprise of three members (Cav3.1, Cav3.2, and Cav3.3) based on their respective main pore-forming alpha subunits: α1G, α1H, and α1I. Among these three subunits, α1H is highly expressed in hippocampus and certain cortical regions. However, T-type calcium channel blockers can protect neurons derived from α1H-/- mice, suggesting that neuroprotection demonstrated by these drugs is not through the α1H subunit. In addition, blockers for T-type calcium channels were not able to confer any protection to neurons in long-term cultures, while blockers of L-type calcium channels could protect neurons. These data indicate a new function of blockers for T-type calcium channels, and also suggest different mechanisms to regulate neuronal survival by calcium signaling pathways. Thus, our findings have important implications in the development of new treatment for age-related neurodegenerative disorders.
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Affiliation(s)
- Norelle C Wildburger
- Department of Otolaryngology, Center for Aging, Washington University, 4560 Clayton Avenue, St Louis, MO 63110, USA.
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Puzianowska-Kuznicka M, Kuznicki J. The ER and ageing II: calcium homeostasis. Ageing Res Rev 2009; 8:160-72. [PMID: 19427411 DOI: 10.1016/j.arr.2009.05.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/30/2009] [Accepted: 05/01/2009] [Indexed: 11/29/2022]
Abstract
Increase in intracellular Ca(2+) concentration occurs by Ca(2+) influx through the plasma membrane and by Ca(2+) release from intracellular stores. The ER is the most important Ca(2+) store. Its stress, characterized by the impairment of Ca(2+) homeostasis and by the accumulation of misfolded proteins, can be induced by different factors. In turn, it induces defense mechanisms such as unfolded protein response, and when it is severe and prolonged, activation of the apoptotic pathway. Damage to the ER, impairment of its function, and a decreased level of its Ca(2+)-handling proteins might all play a role in physiological ageing by handicapping the ER stress response. Thus, healthy ageing is accompanied by subtle alterations of Ca(2+) homeostasis and signaling, including alterations in the ER Ca(2+) load and release. The expression and/or function of ryanodine receptors, IP3 receptors, and SERCA Ca(2+) pumps located in the ER membrane, and Ca(2+)-binding proteins within ER lumen all seem to be affected in aged cells. Data are presented on age-dependent, tissue-specific changes in ER-related Ca(2+) homeostasis in skeletal, cardiac and smooth muscles, as well as in the nervous and immune systems. Disturbances of Ca(2+) homeostasis and of signaling are potential targets for intervention in aged humans.
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Drugability of extracellular targets: discovery of small molecule drugs targeting allosteric, functional, and subunit-selective sites on GPCRs and ion channels. Neuropsychopharmacology 2009; 34:106-25. [PMID: 18800070 DOI: 10.1038/npp.2008.149] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Beginning with the discovery of the structure of deoxyribose nucleic acid in 1953, by James Watson and Francis Crick, the sequencing of the entire human genome some 50 years later, has begun to quantify the classes and types of proteins that may have relevance to human disease with the promise of rapidly identifying compounds that can modulate these proteins so as to have a beneficial and therapeutic outcome. This so called 'drugable space' involves a variety of membrane-bound proteins including the superfamily of G-protein-coupled receptors (GPCRs), ion channels, and transporters among others. The recent number of novel therapeutics targeting membrane-bound extracellular proteins that have reached the market in the past 20 years however pales in magnitude when compared, during the same timeframe, to the advancements made in the technologies available to aid in the discovery of these novel therapeutics. This review will consider select examples of extracellular drugable targets and focus on the GPCRs and ion channels highlighting the corticotropin releasing factor (CRF) type 1 and gamma-aminobutyric acid receptors, and the Ca(V)2.2 voltage-gated ion channel. These examples will elaborate current technological advancements in drug discovery and provide a prospective framework for future drug development.
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Marty V, El Hachmane M, Amédée T. Dual modulation of synaptic transmission in the nucleus tractus solitarius by prostaglandin E2 synthesized downstream of IL-1beta. Eur J Neurosci 2008; 27:3132-50. [PMID: 18598258 DOI: 10.1111/j.1460-9568.2008.06296.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The activation of the innate immune system induces the production of blood-borne proinflammatory cytokines like interleukin-1beta (IL-1beta), which in turn triggers brain-mediated adaptative responses referred to as sickness behaviour. These responses involve the modulation of neural networks in key regions of the brain. The nucleus tractus solitarius (NTS) of the brainstem is a key nucleus for immune-to-brain signalling. It is the main site of termination of vagal afferents and is adjacent to the area postrema, a circumventricular organ allowing blood-borne action of circulating IL-1beta. Although it is well described that IL-1beta activates cerebral endothelial and glial cells, it is still unknown if and how IL-1beta or downstream-synthesized molecules impact NTS synaptic function. In this study we report that IL-1beta did not modulate NTS synaptic transmission per se, whereas prostaglandin E(2) (PGE(2)), which is produced downstream of IL-1beta, produced opposite effects on spontaneous and evoked release. On the one hand, PGE(2) facilitated glutamatergic transmission between local NTS neurons by enhancing the frequency of spontaneous excitatory postsynaptic currents through a presynaptic receptor different from the classical EP1-4 subtypes. On the other hand, PGE(2) also depressed evoked excitatory input from vagal afferent terminals through presynaptic EP3 receptors coupled to G-proteins linked to adenylyl cyclase and protein kinase A activity. Our data show that IL-1beta-induced PGE(2) can modulate evoked and spontaneous release in the NTS differentially through different mechanisms. These data unravel some molecular mechanisms by which innate immune stimuli could signal to, and be integrated within, the brainstem to produce central adaptative responses.
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Affiliation(s)
- Vincent Marty
- Psychoneuroimmunology, Nutrition and Genetics (PsyNuGen), UMR 5226 CNRS-UB2/UMR 1286 INRA-UB2, Université Bordeaux 2, Institut François Magendie, 146 Rue Léo-Saignat, F-33077 Bordeaux, France
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21
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Morgado-Valle C, Beltran-Parrazal L, DiFranco M, Vergara JL, Feldman JL. Somatic Ca2+ transients do not contribute to inspiratory drive in preBötzinger Complex neurons. J Physiol 2008; 586:4531-40. [PMID: 18635649 DOI: 10.1113/jphysiol.2008.154765] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PreBötzinger Complex (preBötC) neurons are postulated to underlie respiratory rhythm generation. The inspiratory phase of the respiratory cycle in vitro results from preBötC neurons firing synchronous bursts of action potentials (APs) on top of 10-20 mV, 0.3-0.8 s inspiratory drive potentials. Is the inspiratory drive in individual neurons simply the result of the passive integration of inspiratory-modulated synaptic currents or do active processes modulate these currents? As somatic Ca(2+) is known to increase during inspiration, we hypothesized that it affects inspiratory drive. We combined whole cell recording in an in vitro slice preparation with Ca(2+) microfluorometry to detect single inspiratory neuron somatic Ca(2+) transients with high temporal resolution ( approximately mus). In neurons loaded with either Fluo-4 or Oregon Green BAPTA 5 N, we observed Ca(2+) transients associated with each AP. During inspiration, significant somatic Ca(2+) influx was a direct consequence of activation of voltage-gated Ca(2+) channels by APs. However, when we isolated the inspiratory drive potential in active preBötC neurons (by blocking APs with intracellular QX-314 or by hyperpolarization), we did not detect somatic Ca(2+) transients; yet, the parameters of inspiratory drive were the same with or without APs. We conclude that, in the absence of APs, somatic Ca(2+) transients do not shape the somatic inspiratory drive potential. This suggests that in preBötC neurons, substantial and widespread somatic Ca(2+) influx is a consequence of APs during the inspiratory phase and does not contribute substantively to the inspiratory drive potential. Given evidence that the Ca(2+) buffer BAPTA can significantly reduce inspiratory drive, we hypothesize that dendritic Ca(2+) transients amplify inspiratory-modulated synaptic currents.
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Affiliation(s)
- Consuelo Morgado-Valle
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Box 951763, Los Angeles, CA 90095-1763, USA.
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22
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Sonner PM, Filosa JA, Stern JE. Diminished A-type potassium current and altered firing properties in presympathetic PVN neurones in renovascular hypertensive rats. J Physiol 2008; 586:1605-22. [PMID: 18238809 DOI: 10.1113/jphysiol.2007.147413] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Accumulating evidence supports a contribution of the hypothalamic paraventricular nucleus (PVN) to sympathoexcitation and elevated blood pressure in renovascular hypertension. However, the underlying mechanisms resulting in altered neuronal function in hypertensive rats remain largely unknown. Here, we aimed to address whether the transient outward potassium current (I(A)) in identified rostral ventrolateral medulla (RVLM)-projecting PVN neurones is altered in hypertensive rats, and whether such changes affected single and repetitive action potential properties and associated changes in intracellular Ca(2+) levels. Patch-clamp recordings obtained from PVN-RVLM neurons showed a reduction in I(A) current magnitude and single channel conductance, and an enhanced steady-state current inactivation in hypertensive rats. Morphometric reconstructions of intracellularly labelled PVN-RVLM neurons showed a diminished dendritic surface area in hypertensive rats. Consistent with a diminished I(A) availability, action potentials in PVN-RVLM neurons in hypertensive rats were broader, decayed more slowly, and were less sensitive to the K(+) channel blocker 4-aminopyridine. Simultaneous patch clamp recordings and confocal Ca(2+) imaging demonstrated enhanced action potential-evoked intracellular Ca(2+) transients in hypertensive rats. Finally, spike broadening during repetitive firing discharge was enhanced in PVN-RVLM neurons from hypertensive rats. Altogether, our results indicate that diminished I(A) availability constitutes a contributing mechanism underlying aberrant central neuronal function in renovascular hypertension.
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Affiliation(s)
- Patrick M Sonner
- Department of Psychiatry, University of Cincinnati, Genome Research Institute, 2170 E. Galbraith Rd, Cincinnati, OH 45237, USA
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23
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Török TL. Electrogenic Na+/Ca2+-exchange of nerve and muscle cells. Prog Neurobiol 2007; 82:287-347. [PMID: 17673353 DOI: 10.1016/j.pneurobio.2007.06.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2006] [Revised: 04/12/2007] [Accepted: 06/12/2007] [Indexed: 12/19/2022]
Abstract
The plasma membrane Na(+)/Ca(2+)-exchanger is a bi-directional electrogenic (3Na(+):1Ca(2+)) and voltage-sensitive ion transport mechanism, which is mainly responsible for Ca(2+)-extrusion. The Na(+)-gradient, required for normal mode operation, is created by the Na(+)-pump, which is also electrogenic (3Na(+):2K(+)) and voltage-sensitive. The Na(+)/Ca(2+)-exchanger operational modes are very similar to those of the Na(+)-pump, except that the uncoupled flux (Na(+)-influx or -efflux?) is missing. The reversal potential of the exchanger is around -40 mV; therefore, during the upstroke of the AP it is probably transiently activated, leading to Ca(2+)-influx. The Na(+)/Ca(2+)-exchange is regulated by transported and non-transported external and internal cations, and shows ATP(i)-, pH- and temperature-dependence. The main problem in determining the role of Na(+)/Ca(2+)-exchange in excitation-secretion/contraction coupling is the lack of specific (mode-selective) blockers. During recent years, evidence has been accumulated for co-localisation of the Na(+)-pump, and the Na(+)/Ca(2+)-exchanger and their possible functional interaction in the "restricted" or "fuzzy space." In cardiac failure, the Na(+)-pump is down-regulated, while the exchanger is up-regulated. If the exchanger is working in normal mode (Ca(2+)-extrusion) during most of the cardiac cycle, upregulation of the exchanger may result in SR Ca(2+)-store depletion and further impairment in contractility. If so, a normal mode selective Na(+)/Ca(2+)-exchange inhibitor would be useful therapy for decompensation, and unlike CGs would not increase internal Na(+). In peripheral sympathetic nerves, pre-synaptic alpha(2)-receptors may regulate not only the VSCCs but possibly the reverse Na(+)/Ca(2+)-exchange as well.
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Affiliation(s)
- Tamás L Török
- Department of Pharmacodynamics, Semmelweis University, P.O. Box 370, VIII. Nagyvárad-tér 4, H-1445 Budapest, Hungary.
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25
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Shinn HK, Cha YD, Han JU, Yoon JW, Kim BS, Song JH. Antihyperalgesic Effects of Ethosuximide and Mibefradil, T-type Voltage Activated Calcium Channel Blockers, in a Rat Model of Postoperative Pain. Korean J Pain 2007. [DOI: 10.3344/kjp.2007.20.2.92] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Helen Ki Shinn
- Department of Anesthesiology and Pain Medicine, College of Medicine, Inha University, Incheon, Korea
| | - Young Deog Cha
- Department of Anesthesiology and Pain Medicine, College of Medicine, Inha University, Incheon, Korea
| | - Jeong Uk Han
- Department of Anesthesiology and Pain Medicine, College of Medicine, Inha University, Incheon, Korea
| | - Jeong Won Yoon
- Department of Anesthesiology and Pain Medicine, College of Medicine, Inha University, Incheon, Korea
| | | | - Jang Ho Song
- Department of Anesthesiology and Pain Medicine, College of Medicine, Inha University, Incheon, Korea
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26
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Abstract
UNLABELLED Injury to the nerve can produce changes in dorsal horn function and pain. This facilitated processing may be mediated in part by voltage-sensitive calcium channels. Activation of these channels increases intracellular calcium, thereby mediating transmitter release and activating cascades serving to alter membrane excitability and initiate protein transcription. Molecular techniques reveal the complexity and multiplicity of these channels. At the spinal level, blocking of several of these calcium channels, notably those of the N type, can prominently alter pain behavior. These effects are consistent with the high levels of expression on primary afferents and dorsal horn neurons of these channels. More recently, agents binding to auxiliary subunits such as the alpha2delta of these calcium channels diminish excitability of the membrane without completely blocking channel function. Drugs that bind to this site, highly expressed in the superficial dorsal horn, will diminish neuropathic pain states. Continuing developments in our understanding of these channel functions promises to advance the control of aberrant spinal functions initiated by nerve injury. PERSPECTIVE Pharmacologic studies showing the role of spinal voltage-sensitive calcium channels in neuropathic pain models provide evidence suggesting their applicability in human pain states.
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Affiliation(s)
- Tony L Yaksh
- Department of Anesthesiology, University of California, San Diego, La Jolla, California 92093-0818, USA.
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27
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Winquist RJ, Pan JQ, Gribkoff VK. Use-dependent blockade of Cav2.2 voltage-gated calcium channels for neuropathic pain. Biochem Pharmacol 2005; 70:489-99. [PMID: 15950195 DOI: 10.1016/j.bcp.2005.04.035] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 04/11/2005] [Accepted: 04/11/2005] [Indexed: 11/28/2022]
Abstract
The translocation of extracellular calcium (Ca(2+)) via voltage-gated Ca(2+) channels (VGCCs) in neurons is involved in triggering multiple physiological cell functions but also the abnormal, pathophysiological responses that develop as a consequence of injury. In conditions of neuropathic pain, VGCCs are involved in supplying the signal Ca(2+) important for the sustained neuronal firing and neurotransmitter release characteristic of these syndromes. Preclinical data have identified N-type VGCCs (Ca(v)2.2) as key participants in contributing to these Ca(2+) signaling events and clinical data with the peptide blocker Prialt have now validated Ca(v)2.2 as a bona fide target for future drug discovery efforts to identify new and novel therapeutics for neuropathic pain. Imperative for the success of such an endeavor will be the ability to identify compounds selective for Ca(v)2.2, versus other VGCCs, but also compounds which demonstrate effective blockade during the pathophysiological states of neuropathic pain without compromising channel activity associated with sustaining normal housekeeping cellular functions. An approach to obtain this research target profile is to identify compounds, which are more potent in blocking Ca(v)2.2 during higher frequencies of firing as compared to the slower more physiologically-relevant frequencies. This may be achieved by identifying compounds with enhanced potency for the inactivated state of Ca(v)2.2. This commentary explores the rationale and options for engineering a use-dependent blocker of Ca(v)2.2. It is anticipated that this use-dependent profile of channel blockade will result in new chemical entities with an improved therapeutic ratio for neuropathic pain.
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Affiliation(s)
- Raymond J Winquist
- Department of Pharmacology, Scion Pharmaceuticals Inc., 200 Boston Avenue, Suite 3600, Medford, MA 02155, USA.
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28
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Abstract
Although there are many analgesics on the market for the treatment of nociceptive pain, there are none with FDA approval for the treatment of neuropathic pain. With a better understanding of the anatomy and physiology of pain, there is a significant effort in developing new drugs that interact specifically with pain pathways. This higher drug specificity is likely to result in drugs that are more efficacious with fewer side effects. This has led to the development of many drugs for the treatment of neuropathic pain. These drugs are divided into the following therapeutic classes: 1) N-methyl-D-aspartate (NMDA) receptor antagonists, 2) ion channel antagonists, 3) alpha2-agonists, 4) nicotinic receptor agonists, 5) prostaglandin receptor antagonists, 6) adenosine agonists and adenosine kinase inhibitors, 7) neuropeptide antagonists, and 8) prosaposins. The results of preclinical and clinical trials are promising for these new agents. Whether these agents will be efficacious as single agents is yet to be determined; however, preliminary results show that combination therapy may be more beneficial with fewer side effects.
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Affiliation(s)
- M S Wallace
- University of California, San Diego, Center for Pain and Palliative Medicine, Department of Anesthesiology, 9500 Gilman Drive #0924, La Jolla, CA 92093-0924, USA.
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29
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Abstract
There are many different calcium channels expressed in the mammalian nervous system, but N-type and P/Q-type calcium channels appear to dominate the presynaptic terminals of central and peripheral neurons. The neurotransmitter-induced modulation of these channels can result in alteration of synaptic transmission. This review highlights the mechanisms by which neurotransmitters affect the activity of N-type and P/Q-type calcium channels. The inhibition of these channels by voltage-dependent and voltage-independent mechanisms is emphasized because of the wealth of information available on the intracellular mediators and on the effect of these pathways on the single-channel gating.
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Affiliation(s)
- Keith S Elmslie
- Department of Physiology, Tulane University Health Science Center, New Orleans, Louisiana 70112, USA.
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30
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Abstract
Over the last 20 years the combination of patch clamp and molecular biology techniques have resulted in an explosion in our knowledge of the different calcium channel types and their roles in physiology. A crucial component to this advance has been the discovery of specific blockers for different calcium channel types. These blockers have not only permitted researchers to assign specific functions to different channel types, but their specificity allowed them to be used to treat diseases that resulted from enhanced calcium channel function. In some cases, the enhanced calcium channel function is secondary to other problems leading to increased cellular excitability. The specificity of calcium channel blockers, however, has provided a means to treat symptoms of the pathophysiology until more effective treatments become available to address the underlying problems. The goal of this review is to introduce the various types of calcium channels, their primary physiologic roles, drugs that block these channels, and diseases that are currently being treated with these drugs.
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Affiliation(s)
- Keith S Elmslie
- Department of Physiology, Tulane University Health Science Center, New Orleans, Louisiana 70112, USA.
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31
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Dogrul A, Gardell LR, Ossipov MH, Tulunay FC, Lai J, Porreca F. Reversal of experimental neuropathic pain by T-type calcium channel blockers. Pain 2003; 105:159-68. [PMID: 14499432 DOI: 10.1016/s0304-3959(03)00177-5] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Experimental nerve injury results in exaggerated responses to tactile and thermal stimuli that resemble some aspects of human neuropathic pain. Neuronal hyperexcitability and neurotransmitter release have been suggested to promote such increased responses to sensory stimuli. Enhanced activity of Ca(2+) current is associated with increased neuronal activity and blockade of N- and P-types, but not L-type, calcium channels have been found to block experimental neuropathic pain. While T-type currents are believed to promote neuronal excitability and transmitter release, it is unclear whether these channels may also contribute to the neuropathic state. Rats were prepared with L(5)/L(6) spinal nerve ligation, and tactile and thermal hypersensitivities were established. Mibefradil or ethosuximide was administered either intraperitoneally, intrathecally (i.th.), or locally into the plantar aspect of the injured hindpaw. Systemic mibefradil or ethosuximide produced a dose-dependent blockade of both tactile and thermal hypersensitivities in nerve-injured rats; responses of sham-operated rats were unchanged. Local injection of mibefradil also blocked both end points. Ethosuximide, however, was inactive after local administration, perhaps reflecting its low potency when compared with mibefradil. Neither mibefradil nor ethosuximide given i.th. produced any blockade of neuropathic behaviors. The results presented here suggest that T-type calcium channels may play a role in the expression of the neuropathic state. The data support the view that selective T-type calcium channel blockers may have significant potential in the treatment of neuropathic pain states.
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Affiliation(s)
- Ahmet Dogrul
- Department of Pharmacology, Faculty of Medicine, Gulhane Medical Military Academy, Ankara, Turkey
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32
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Lasater EM, Solessio E. Regulation of voltage-sensitive Ca2+ channels in bipolar cells by divalent cations and polyamines. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 514:275-89. [PMID: 12596927 DOI: 10.1007/978-1-4615-0121-3_16] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Ca2+ plays a key role in intracellular signal transduction in neurons but in excess it can lead to cell death. Thus its entry into cells is highly regulated by both extrinsic and intrinsic mechanisms. Little is known of the regulation of Ca2+ entry into retinal neurons. Here we describe the role of divalent cations and polyamines as intrinsic modulators of Ca2+ entry into retinal bipolar cells. Cone-dominant (small) bipolar cells of the white bass retina were studied using whole cell patch clamp techniques. With biophysical and pharmacological tools it was determined that these cells expressed a Ca2+ current similar to an L-type current. This current was very susceptible to blockage by divalent cations including Ca2+. In addition, when tested with the polyamines, spermine, spermidine and putrescine, only spermine effectively inhibited the current. When the dose response curve was fit with the Hill function we found an EC50 of 28 microM and a Hill-coefficient of about 2. Our results indicate that divalent cations and the polyamine, spermine, are effective modulators of calcium entry into cone-dominated bipolar cells. The in vivo regulation of the concentrations of these molecules provides an exquisitely sensitive mechanism for regulating Ca2+ entry into bipolar cells under different conditions.
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Affiliation(s)
- Eric M Lasater
- Department of Ophthalmology and Visual Sciences, John Moran Eye Center, University of Utah, Salt Lake City, UT 84132, USA.
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Zhou Y, Zhao ZQ. Effects of neomycin on high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neuron. Eur J Pharmacol 2002; 450:29-35. [PMID: 12176105 DOI: 10.1016/s0014-2999(02)02050-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
High-threshold Ca(2+) channels and tetrodotoxin-resistant Na(+) channels are highly expressed in small dorsal root ganglion neurons. In acutely isolated rat dorsal root ganglion neurons, the effects of neomycin, one of the aminoglycoside antibiotics, on high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents were examined using whole-cell patch recording. We showed for the first time that neomycin dose-dependently inhibited peak high-threshold Ca(2+) currents and peak tetrodotoxin-resistant Na(+) currents with half-maximal inhibitory concentrations at 3.69 microM (n=20) and 1213.44 microM (n=25), respectively. Inactivation properties of high-threshold Ca(2+) currents and activation properties of tetrodotoxin-resistant Na(+) currents were also affected by neomycin with reduction of excitability of small dorsal root ganglion neurons. Half-maximal inactivation voltage of high-threshold Ca(2+) currents was -45.56 mV before and -50.46 mV after application of neomycin (n=10). Half-maximal activation voltage of tetrodotoxin-resistant Na(+) currents was -19.93 mV before and -11.19 mV after administration of neomycin (n=15). These results suggest that neomycin can inhibit high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents in small dorsal root ganglion neurons, which may contribute to neomycin-induced peripheral and central analgesia.
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Affiliation(s)
- Yu Zhou
- Institute of Neurobiology, Fu-Dan University, 220 Han-Dan Road, Shanghai 20043 PR China
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Dogrul A, Zagli U, Tulunay FC. The role of T-type calcium channels in morphine analgesia, development of antinociceptive tolerance and dependence to morphine, and morphine abstinence syndrome. Life Sci 2002; 71:725-34. [PMID: 12072160 DOI: 10.1016/s0024-3205(02)01736-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Involvement of T-type voltage dependent Ca2+ channels (VDCCs) on morphine antinociception, in the development of tolerance and dependence to morphine, and naloxone-precipitated abstinence syndrome in morphine dependent mice was examined by using mibefradil, a T-type VDCCs blocker. Mice were rendered tolerant and dependent on morphine by subcutaneous (s.c.) implantation of a morphine pellet containing 75 mg of morphine base for 72 hr. The tail-flick test was used to assess the nociceptive threshold. Coadministration of acute mibefradil (10 mg/kg, i.p.) with morphine enhanced the antinociceptive effects of acute morphine. Repeated mibefradil administration (10 mg/kg, i.p., just before, 24 and 48 hr after morphine pellet implantation) completely blocked the development of tolerance to the antinociceptive effect of morphine and even by this effect reached supersensitivity to morphine. However, repeated mibefradil treatment did not alter the development of dependence to morphine assessed by the A(50) values of naloxone (s.c.) required to precipitate withdrawal jumping 72 hr after morphine pellet. But, acute mibefradil (10, 30, and 50 mg/kg, i.p.) dose dependently decreased the expression of morphine abstinence syndrome when given directly 30 min prior to naloxone (0,05 mg/kg, s.c.) 72 hr after morphine pellet. These results indicate a critical role of T-type VDCCs in morphine antinociception, the development of tolerance to the antinociceptive effects of morphine and in morphine abstinence syndrome.
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Affiliation(s)
- Ahmet Dogrul
- Departments of Pharmacology, Faculties of Medicine, Gülhane Military Academy of Medicine, 06018, Etlik, Ankara, Turkey.
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Prado WA, Machado Filho EB. Antinociceptive potency of aminoglycoside antibiotics and magnesium chloride: a comparative study on models of phasic and incisional pain in rats. Braz J Med Biol Res 2002; 35:395-403. [PMID: 11887220 DOI: 10.1590/s0100-879x2002000300017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A close relationship exists between calcium concentration in the central nervous system and nociceptive processing. Aminoglycoside antibiotics and magnesium interact with N- and P/Q-type voltage-operated calcium channels. In the present study we compare the antinociceptive potency of intrathecal administration of aminoglycoside antibiotics and magnesium chloride in the tail-flick test and on incisional pain in rats, taken as models of phasic and persistent post-surgical pain, respectively. The order of potency in the tail-flick test was gentamicin (ED50 = 3.34 microg; confidence limits 2.65 and 4.2) > streptomycin (5.68 microg; 3.76 and 8.57) = neomycin (9.22 microg; 6.98 and 12.17) > magnesium (19.49 microg; 11.46 and 33.13). The order of potency to reduce incisional pain was gentamicin (ED50 = 2.06 microg; confidence limits 1.46 and 2.9) > streptomycin (47.86 microg; 26.3 and 87.1) = neomycin (83.17 microg; 51.6 and 133.9). The dose-response curves for each test did not deviate significantly from parallelism. We conclude that neomycin and streptomycin are more potent against phasic pain than against persistent pain, whereas gentamicin is equipotent against both types of pain. Magnesium was less potent than the antibiotics and effective in the tail-flick test only.
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Affiliation(s)
- W A Prado
- Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
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36
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Doğrul A, Yeşilyurt Ö, Işmer A, Güzeldemir EM. L-type and T-type calcium channel blockade potentiate the analgesic effects of morphine and selective mu opioid agonist, but not to selective delta and kappa agonist at the level of the spinal cord in mice. Pain 2001; 93:61-68. [PMID: 11406339 DOI: 10.1016/s0304-3959(01)00293-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We examined the effects of amlodipine, a selective L-type voltage dependent Ca(2+) channel (VDCC) blocker, and mibefradil, a selective T-type VDCC blocker on the antinociceptive effects of morphine, and mu, delta and kappa opioid receptor selective agonist-induced antinociception at the spinal level. Intrathecally administered amlodipine and mibefradil potentiated morphine and [D-Ala(2), N mePhe(4), Gly-ol(5)] enkephalin (DAMGO)-induced antinociception by shifting their dose response curves to the left. However, intrathecally administered amlodipine and mibefradil did not affect [D-Pen(2), D-Pen(5)]enkephalin (DPDPE) and [trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrolidinyl)cyclohexyl] benzene acetamide (U-50, 488H)-induced antinociception. These data indicate that L-type and T-type VDCC blockers synergistically potentiate the analgesic effects of mu opioid receptor agonists, but not delta and kappa opioid receptor agonists, at the spinal level. Additionally, these data suggest that there is an important functional interaction between L-type and/ or T-type VDCC and mu opioid receptors in the process of analgesia.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer/pharmacology
- Amlodipine/pharmacology
- Analgesics, Opioid/pharmacology
- Animals
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, T-Type/drug effects
- Drug Synergism
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, D-Penicillamine (2,5)-/pharmacology
- Male
- Mibefradil/pharmacology
- Mice
- Morphine/pharmacology
- Pain Measurement/drug effects
- Postural Balance/drug effects
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, kappa/agonists
- Receptors, Opioid, mu/agonists
- Spinal Cord/drug effects
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Affiliation(s)
- Ahmet Doğrul
- Department of Medical Pharmacology, Faculty of Medicine, Gülhane Military Academy of Medicine, Ankara, Turkey Department of Anesthesiology, Faculty of Medicine, Gülhane Military Academy of Medicine, Ankara, Turkey
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37
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Chung YH, Shin CM, Kim MJ, Shin DH, Yoo YB, Cha CI. Differential alterations in the distribution of voltage-gated calcium channels in aged rat cerebellum. Brain Res 2001; 903:247-52. [PMID: 11382411 DOI: 10.1016/s0006-8993(01)02392-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the present study, we used immunohistochemistry and Western blot analysis to determine region-specific changes in the distribution of voltage-gated calcium channels (VGCCs) in aged rat cerebellum. Age-dependent changes in the staining intensity of the alpha(1C) and alpha(1D) subunits were prominent in the Purkinje cells, whereas there was no change in the expression of the alpha(1A) and alpha(1B) subunits. In the aged rat, in particular, immunoreactivity for the alpha(1C) subunits were increased in the dendrites as well as in the cell bodies of Purkinje cells. On the other hand, decreases in immunoreactivity for alpha(1A) and alpha(1D) subunits were found in the molecular or granular layers. However, only alpha(1D) subunit immunoreactivity was decreased in the aged cerebellum membrane by Western blot analysis that, while not addressing regional specificity, further confirmed an age-related decrease in alpha(1D) subunit. These age-related changes in alpha(1D) subunit expression might reflect a gradual loss of regulation for L-type Ca(2+) channels in the senescent period. The first demonstration of age-related alterations in VGCC expression may provide useful data for future investigations on aging and neurodegenerative diseases.
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Affiliation(s)
- Y H Chung
- Department of Anatomy, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, South Korea.
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38
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Stewart AE, Foehring RC. Effects of spike parameters and neuromodulators on action potential waveform-induced calcium entry into pyramidal neurons. J Neurophysiol 2001; 85:1412-23. [PMID: 11287465 DOI: 10.1152/jn.2001.85.4.1412] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neocortical pyramidal neurons express several different calcium channel types. Previous studies with square voltage steps have found modest biophysical differences between these calcium channel types as well as differences in their modulation by transmitters. We used acutely dissociated neocortical pyramidal neurons to test whether this diversity extends to different activation by physiological stimuli. We conclude that 1) peak amplitude, latency to peak, and the total charge entry for the Ca(2+) channel current is dependent on the shape of the mock action potential waveforms (APWs). 2) The percent contribution of the five high-voltage-activated currents to the whole cell current was not altered by using an APW as opposed to a voltage step to elicit the current. 3) The identity of the charge carrier affects the amplitude and decay of the whole cell current. With Ca(2+), there was a greater contribution of T-type current to the whole cell current. 4) Total Ba(2+) charge entry is linearly dependent on the number of spikes in the stimulating waveform and relatively insensitive to spike frequency. 5) Current decay was greatest with Ca(2+) as the charge carrier and with minimal internal chelation. 6) Voltage-dependent neurotransmitter-mediated modulations can be reversed by multiple spikes. The extent of the reversal is dependent on the number of spikes in the stimulating waveform. Thus the neuronal activity pattern can determine the effectiveness of voltage-dependent and -independent modulatory pathways in neocortical pyramidal neurons.
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Affiliation(s)
- A E Stewart
- Department of Anatomy and Neurobiology, University of Tennessee, Memphis, Tennessee 38163, USA
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Schaible HG, Nebe J, Neugebauer V, Ebersberger A, Vanegas H. The role of high-threshold calcium channels in spinal neuron hyperexcitability induced by knee inflammation. PROGRESS IN BRAIN RESEARCH 2001; 129:173-90. [PMID: 11098689 DOI: 10.1016/s0079-6123(00)29013-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Affiliation(s)
- H G Schaible
- Institut für Physiologie, Friedrich-Schiller-Universität Jena, Germany
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40
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The Voltage-Gated Channels of Ca2+ Action Potentials: Generalization. Cell Mol Neurobiol 2001. [DOI: 10.1016/b978-0-12-311624-6.50010-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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41
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Bringmann A, Schopf S, Reichenbach A. Developmental regulation of calcium channel-mediated currents in retinal glial (Müller) cells. J Neurophysiol 2000; 84:2975-83. [PMID: 11110825 DOI: 10.1152/jn.2000.84.6.2975] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whole cell voltage-clamp recordings of freshly isolated cells were used to study changes in the currents through voltage-gated Ca(2+) channels during the postnatal development of immature radial glial cells into Müller cells of the rabbit retina. Using Ba(2+) or Ca(2+) ions as charge carriers, currents through transient low-voltage-activated (LVA) Ca(2+) channels were recorded in cells from early postnatal stages, with an activation threshold at -60 mV and a peak current at -25 mV. To increase the amplitude of currents through Ca(2+) channels, Na(+) ions were used as the main charge carriers, and currents were recorded in divalent cation-free bath solutions. Currents through transient LVA Ca(2+) channels were found in all radial glial cells from retinae between postnatal days 2 and 37. The currents activated at potentials positive to -80 mV and displayed a maximum at -40 mV. The amplitude of LVA currents increased during the first postnatal week; after postnatal day 6, the amplitude remained virtually constant. The density of LVA currents was highest at early postnatal days (days 2-5: 13 pA/pF) and decreased to a stable, moderate level within the first three postnatal weeks (3 pA/pF). A significant expression of currents through sustained, high-voltage-activated Ca(2+) channels was found after the third postnatal week in approximately 25% of the investigated cells. The early and sole expression of transient currents at high-density may suggest that LVA Ca(2+) channels are involved in early developmental processes of rabbit Müller cells.
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Affiliation(s)
- A Bringmann
- Department of Neurophysiology, Paul Flechsig Institute of Brain Research, University of Leipzig, D-04109 Leipzig, Germany.
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42
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Griffith WH, Jasek MC, Bain SH, Murchison D. Modification of ion channels and calcium homeostasis of basal forebrain neurons during aging. Behav Brain Res 2000; 115:219-33. [PMID: 11000422 DOI: 10.1016/s0166-4328(00)00260-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this paper we review the last several years of work from our lab with attention to changes in the properties of basal forebrain neurons during aging. These neurons play a central role in behavioral functions, such as: attention, arousal, cognition and autonomic activity, and these functions can be adversely affected during aging. Therefore, it is fundamental to define the cellular mechanisms of aging in order to understand the basal forebrain and to correct deficits associated with aging. We have examined changes in the physiological properties of basal forebrain neurons during aging with whole-cell and single-channel patch-clamp, as well as, microfluorimetric measurements of intracellular calcium concentrations. These studies contribute to the understanding of integration within the basal forebrain and to the identification of age-related changes within central mammalian neurons. Although extensive functional/behavioral decline is often assumed to occur during aging, our data support an interpretation of compensatory increases in function for excitatory amino acid receptors, GABA(A) receptors, voltage-gated calcium currents and calcium homeostatic mechanisms. We believe that these changes occur to compensate for decrements accruing with age, such as decreased synaptic contacts, ion imbalances or neuronal loss. The basal forebrain must retain functionality into late aging if senescence is to be productive. Thus, it is critical to recognize the potential cellular and subcellular targets for therapeutic interventions intended to correct age-related behavioral deficits.
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Affiliation(s)
- W H Griffith
- Department of Medical Pharmacology and Toxicology, College of Medicine, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA.
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43
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Abstract
During the 1950s to 70s most of the mechanisms that control transmitter release from presynaptic nerve terminals were described at the neuromuscular junction. It was not, however, until the 1990s that the multiplicity of protein-protein interactions that govern this process began to be identified. The sheer numbers of proteins and the complexity of their interactions at first appears excessive, even redundant. However, studies of identified central synapses indicate that this molecular diversity may underlie a important functional diversity. The task of the neuromuscular junction is to relay faithfully the rate and pattern code generated by the motoneurone. To demonstrate phenomena such as facilitation and augmentation that are apparent only when the probability of release is low, experimental manipulation is required. In the cortex, however, low probability synapses displaying facilitation can be recorded in parallel with high probability synapses displaying depression. The mechanisms are largely the same as those displayed by the neuromuscular junction, but some are differentially expressed and controlled. Central synapses demonstrate exquisitely fine tuned information transfer, each of the many types displaying its own repertoire of pattern- and frequency-dependent properties. These appear tuned to match both the discharge pattern in the presynaptic neurone and the integrative requirements of the postsynaptic cell. The molecular identification of these differentially expressed frequency filters is now just coming into sight. This review attempts to correlate these two aspects of synaptic physiology and to identify the components of the release process that are responsible for the diversity of function.
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Affiliation(s)
- A M Thomson
- Department of Physiology, Royal Free and University College Medical School, UCL, Rowland Hill Street, NW3 2PF, London, UK.
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Abstract
In the present study, we characterized the intrinsic electrophysiological properties and the membrane currents activated by dopamine (DA) D(2) and GABA(B) receptors in midbrain dopaminergic neurons, maintained in vitro in a slice preparation, from wild-type and homozygous weaver (wv/wv) mice. By using patch-clamp techniques, we found that membrane potential, apparent input resistance, and spontaneous firing of wv/wv dopaminergic neurons were similar to those of dopamine-containing cells recorded from nonaffected (+/+) animals. More interestingly, the wv/wv neurons were excited rather than inhibited by dopamine and the GABA(B) agonist baclofen. This neurotransmitter-mediated excitation was attributable to the activation of a G-protein-gated inward current that reversed polarity at a membrane potential of approximately -30 mV. We suggest that the altered behavior of the receptor-operated wv G-protein-gated inwardly rectifying K(+) channel 2 (GIRK2) might be related to the selective degeneration of the dopaminergic neurons. In addition, the wv GIRK2 would not only suppress the autoreceptor-mediated feedback inhibition of DA release but could also establish a feedforward mechanism of DA release in the terminal fields.
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Kukwa W, Macioch T, Rola R, Szulczyk P. Kinetic and pharmacological properties of Ca(2+) currents in postganglionic sympathetic neurones projecting to muscular and cutaneous effectors. Brain Res 2000; 873:173-80. [PMID: 10915828 DOI: 10.1016/s0006-8993(00)02552-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Voltage-gated Ca(2+) channels are expressed in neurones and greatly influence neuronal activity by activating Ca(2+)-dependent K(+) channels. The whole cell patch-clamp technique was used to compare the kinetic and pharmacological properties of voltage-dependent Ca(2+) currents in two groups of sympathetic neurones identified by the fluorescent tracer Fast Blue: putative muscular sympathetic neurones (MSN) and putative cutaneous sympathetic neurones (CSN). The tracer was injected into the muscular part of the diaphragm (to mark MSN) and into the skin of the ear (to mark CSN). The capacitance of MSN (23.0 pF) was larger than the capacitance of CSN (12.6 pF). The maximum current in MSN (1.3 nA) was also larger than in CSN (0.93 nA). However, the current density was larger in CSN (77. 3 pA/pF) than in MSN (57.7 pA/pF) and the current activation rate was faster in CSN (0.27 nA/ms) than in MSN (0.19 nA/ms). V(1/2) and slope factors of activation and inactivation were not significantly different for MSN and CSN. The majority of Ca(2+) current was available for activation in both categories of neurones at resting membrane potential. Ca(2+) currents in MSN and CSN were blocked by nifedipine (7.0 and 3.6%, respectively), omega-Agatoxin-IVA (23.0 and 25.6%, respectively) and omega-conotoxin-GVIA (67.0 and 65.1%, respectively). We found that CSN are twice as small, have higher Ca(2+) current density and their Ca(2+) activation rate is faster in comparison to MSN. Such properties may lead to faster rise of Ca(2+) concentration in the cytoplasm of the CSN comparing to MSN and more effectively dampen their activity due to more effective activation of Ca(2+)-dependent K(+) current. Both kinds of neurones express high proportion of N and P/Q Ca(2+) current.
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Affiliation(s)
- W Kukwa
- The Medical University of Warsaw, Department of Experimental and Clinical Physiology, Warsaw, Poland
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Blackburn-Munro G, Brown CH, Neumann ID, Landgraf R, Russell JA. Verapamil prevents withdrawal excitation of oxytocin neurones in morphine-dependent rats. Neuropharmacology 2000; 39:1596-607. [PMID: 10854904 DOI: 10.1016/s0028-3908(99)00232-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
We investigated whether the full expression of morphine withdrawal excitation by supraoptic nucleus (SON) oxytocin neurones is a property of the neurones themselves or a partial function of their afferent inputs, by interrupting synaptic input activity via central administration of the L-type Ca(2+) channel blocker verapamil. In morphine-dependent rats, withdrawal-induced release of oxytocin from the posterior pituitary was suppressed by prior administration of intracerebroventricular (i.c.v.) verapamil (160 microg), as was release of oxytocin within the SON measured by microdialysis. During morphine withdrawal the increased electrical activity of SON neurones was also reduced both by i.c.v. verapamil and microdialysis application of verapamil or nifedipine into the SON. Oxytocin secretion evoked by electrical stimulation of the pituitary stalk was unaffected by i.c.v. verapamil suggesting a central site of action. To determine whether the inhibitory actions of verapamil were specific to morphine withdrawal, we also investigated the effects of verapamil on other oxytocin-secreting stimuli. I.C.V. verapamil given to morphine-naïve rats abolished pituitary oxytocin release in response to activation of brainstem or rostral excitatory inputs by cholecystokinin (20 microg kg(-1), i.v.) and 1.5 M saline (4 ml kg(-1), i.p.) respectively, whilst in lactating rats, i.c.v. verapamil reduced suckling-induced release of oxytocin within the SON. These results suggest that verapamil has a central site of action on stimulated oxytocin release (including an action within the SON) and that both pre and post-synaptic L-type Ca(2+) channels are required for the full expression of morphine withdrawal in SON oxytocin neurones.
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Affiliation(s)
- G Blackburn-Munro
- Department of Biomedical Sciences, University Medical School, EH8 9XD, Edinburgh, United Kingdom.
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Schenberg LC, Marçal LP, Seeberger F, Barros MR, Sudré EC. L-type calcium channels selectively control the defensive behaviors induced by electrical stimulation of dorsal periaqueductal gray and overlying collicular layers. Behav Brain Res 2000; 111:175-85. [PMID: 10840143 DOI: 10.1016/s0166-4328(00)00154-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The present study reports the involvement of L-type calcium channels in the control of defensive behaviors produced by electrical stimulation of dorsal periaqueductal gray and overlying collicular layers. Rats that had chemitrodes in the dorsal midbrain and which stimulation produced freezing or flight behaviors with less than 55 microA were selected for drug experiments. Stimulation was repeated the day after the screening session 20 min following the microinjection into the dorsal periaqueductal gray of 15 nmol of either verapamil, a selective L-type calcium channel antagonist, or cobalt chloride (CoCl(2)), a calcium-specific channel modulator. Post-drug sessions were performed 48 h after. Threshold functions were obtained by logistic fitting of accumulated response frequencies. Verapamil and CoCl(2) significantly attenuated the output of immobility, exophthalmus, running and jumping. Although to a lesser degree, verapamil also attenuated defecation. Because CoCl(2) had no effect on defecation, the attenuation of this response by verapamil suggests a non-specific action of this drug. Neither verapamil nor CoCl(2) changed the output of micturition. Finally, whereas there was a complete recovery of defensive thresholds following the microinjection of verapamil, the attenuating effects of CoCl(2) were still present 48 h after. These results support an important role of L-type calcium channels in the neurogenesis of dorsal periaqueductal gray-evoked immobility, exophthalmus, running and jumping, but not defecation and micturition responses.
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Affiliation(s)
- L C Schenberg
- Department of Physiological Sciences, Biomedical Center, Laboratory of Neurobiology, Federal University of Espírito Santo, Av. Marechal Campos 1468 (Maruípe), 29040-090, ES, Vitória, Brazil.
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48
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Vanegas H, Schaible H. Effects of antagonists to high-threshold calcium channels upon spinal mechanisms of pain, hyperalgesia and allodynia. Pain 2000; 85:9-18. [PMID: 10692598 DOI: 10.1016/s0304-3959(99)00241-9] [Citation(s) in RCA: 193] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
High-threshold voltage-dependent calcium channels enable calcium ions to enter neurons upon depolarization and thereby influence synaptic mediator/receptor systems, membrane excitability levels, second and third messenger concentration, and gene expression. These phenomena underlie several processes including those of normal nociception and of hyperalgesia and allodynia. The present article deals with the role of spinal L-, N- and P/Q-type calcium channels in short-lasting nociception as well as in the hyperalgesia and allodynia elicited by chemical irritants of peripheral nociceptors, inflammatory and mechanical lesions of peripheral tissues, and lesions of peripheral nerves. The studies summarized herein are based on the spinal delivery of specific antagonists to high-threshold calcium channels, and reveal that blockade of L-type, P/Q-type and, particularly, N-type channels can prevent, attenuate, or both, subjective pain as well as primary and/or secondary hyperalgesia and allodynia in a variety of experimental and clinical conditions.
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Affiliation(s)
- H Vanegas
- Instituto Venezolano de Investigaciones Cientificas (IVIC), Apartado 21827, Caracas, Venezuela.
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49
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Grassi C, Martire M, Altobelli D, Azzena GB, Preziosi P. Characterization of Ca(2+)-channels responsible for K(+)-evoked [(3)H]noradrenaline release from rat brain cortex synaptosomes and their response to amyotrophic lateral sclerosis IgGs. Exp Neurol 1999; 159:520-7. [PMID: 10506523 DOI: 10.1006/exnr.1999.7164] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The contribution of the different Ca(2+)-channel subtypes to the K(+)-evoked [(3)H]noradrenaline release from rat cerebral cortex synaptosomes has been investigated. In the same experimental model, it was also verified whether the calcium-mediated neurotransmitter release is influenced by IgGs purified from sera of seven patients affected by sporadic amyotrophic lateral sclerosis. Synaptosome treatment with 3.0 microM nifedipine or 2.0 microM calciseptine, which block L-type channels, slightly decreased [(3)H]noradrenaline release, the reduction being 7 and 13% of the control values, respectively. The blockade of N-type Ca(2+)-channels with omega-conotoxin-GVIA (0.001-1.0 microM) induced a concentration-dependent reduction of the neurotransmitter release, with maximum effect of 34%. omega-Agatoxin-IVA failed to significantly affect the studied release, which was instead markedly reduced by omega-conotoxin-MVIIC. After the blockade of N-type channels with maximal concentrations of omega-conotoxin-GVIA, 3.0 microM omega-conotoxin-MVIIC reduced the release by 58%. Synaptosome treatment with amyotrophic lateral sclerosis IgGs enhanced the K(+)-evoked [(3)H]noradrenaline release, which was mostly mediated by P/Q- and N-type Ca(2+)-channels. The increase induced by pathologic IgGs (0.2 mg/ml) ranged from 11 to 62% for the different patients, and it was concentration-dependent. The basal release was instead unaffected by IgG treatment. The results of the present study suggest that the K(+)-evoked [(3)H]noradrenaline release from brain cortex synaptosomes is mainly mediated by activation of P/Q- and N-type Ca(2+)-channels. Autoantibodies present in the sera of patients affected by sporadic amyotrophic lateral sclerosis may interact with these channels by producing an increased calcium influx, with consequent enhancement of the neurotransmitter release. Preliminary results of the present study have been published in abstract form (Martire et al., 1997, Pharmacol. Res. 35:9).
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Affiliation(s)
- C Grassi
- Institute of Human Physiology, Institute of Pharmacology, Catholic University "S. Cuore", Largo F. Vito 1, Rome, 1-00168, Italy.
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Gustafsson H, Afrah A, Brodin E, Stiller CO. Pharmacological characterization of morphine-induced in vivo release of cholecystokinin in rat dorsal horn: effects of ion channel blockers. J Neurochem 1999; 73:1145-54. [PMID: 10461906 DOI: 10.1046/j.1471-4159.1999.0731145.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous studies indicate that an increased release of cholecystokinin (CCK) in response to morphine administration may counteract opioid-induced analgesia at the spinal level. In the present study we used in vivo microdialysis to demonstrate that systemic administration of antinociceptive doses of morphine (1-5 mg/kg, s.c.) induces a dose-dependent and naloxone-reversible release of CCK-like immunoreactivity (CCK-LI) in the dorsal horn of the spinal cord. A similar response could also be observed following perfusion of the dialysis probe for 60 min with 100 microM but not with 1 microM morphine. The CCK-LI release induced by morphine (5 mg/kg, s.c.) was found to be calcium-dependent and tetrodotoxin-sensitive (1 microM in the perfusion medium). Topical application of either the L-type calcium channel blocker verapamil (50 microg) or the N-type calcium channel blocker omega-conotoxin GVIA (0.4 microg) onto the dorsal spinal cord completely prevented the CCK-LI release induced by morphine (5 mg/kg, s.c.). Our data indicate that activation of L- and N-type calcium channels is of importance for morphine-induced CCK release, even though the precise site of action of morphine in the dorsal horn remains unclear. The present findings also suggest a mechanism for the potentiation of opioid analgesia by L- and N-type calcium channel blocking agents.
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Affiliation(s)
- H Gustafsson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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