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Pissas KP, Schilling M, Korkmaz A, Tian Y, Gründer S. Melatonin alters the excitability of mouse cerebellar granule neurons by inhibiting voltage-gated sodium, potassium, and calcium channels. J Pineal Res 2024; 76:e12919. [PMID: 37794846 DOI: 10.1111/jpi.12919] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 09/01/2023] [Accepted: 09/19/2023] [Indexed: 10/06/2023]
Abstract
Besides its role in the circadian rhythm, the pineal gland hormone melatonin (MLT) also possesses antiepileptogenic, antineoplastic, and cardioprotective properties, among others. The dosages necessary to elicit beneficial effects in these diseases often far surpass physiological concentrations. Although even high doses of MLT are considered to be largely harmless to humans, the possible side effects of pharmacological concentrations are so far not well investigated. In the present study, we report that pharmacological doses of MLT (3 mM) strongly altered the electrophysiological characteristics of cultured primary mouse cerebellar granule cells (CGCs). Using whole-cell patch clamp and ratiometric Ca2+ imaging, we observed that pharmacological concentrations of MLT inhibited several types of voltage-gated Na+ , K+ , and Ca2+ channels in CGCs independently of known MLT-receptors, altering the character and pattern of elicited action potentials (APs) significantly, quickly and reversibly. Specifically, MLT reduced AP frequency, afterhyperpolarization, and rheobase, whereas AP amplitude and threshold potential remained unchanged. The altered biophysical profile of the cells could constitute a possible mechanism underlying the proposed beneficial effects of MLT in brain-related disorders, such as epilepsy. On the other hand, it suggests potential adverse effects of pharmacological MLT concentrations on neurons, which should be considered when using MLT as a pharmacological compound.
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Affiliation(s)
| | - Maria Schilling
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Ahmet Korkmaz
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Yuemin Tian
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
| | - Stefan Gründer
- Medical faculty, Institute of Physiology, RWTH Aachen University, Aachen, Germany
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2
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Maziar A, Critch TNRHY, Ghosh S, Rajani V, Flynn CM, Qin T, Reinhardt C, Man KNM, Lee A, Hell JW, Yuan Q. Aging differentially affects LTCC function in hippocampal CA1 and piriform cortex pyramidal neurons. Cereb Cortex 2023; 33:1489-1503. [PMID: 35437602 PMCID: PMC9930631 DOI: 10.1093/cercor/bhac152] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/25/2022] [Accepted: 03/27/2022] [Indexed: 11/14/2022] Open
Abstract
Aging is associated with cognitive decline and memory loss in humans. In rats, aging-associated neuronal excitability changes and impairments in learning have been extensively studied in the hippocampus. Here, we investigated the roles of L-type calcium channels (LTCCs) in the rat piriform cortex (PC), in comparison with those of the hippocampus. We employed spatial and olfactory tasks that involve the hippocampus and PC. LTCC blocker nimodipine administration impaired spontaneous location recognition in adult rats (6-9 months). However, the same blocker rescued the spatial learning deficiency in aged rats (19-23 months). In an odor-associative learning task, infusions of nimodipine into either the PC or dorsal CA1 impaired the ability of adult rats to learn a positive odor association. Again, in contrast, nimodipine rescued odor associative learning in aged rats. Aged CA1 neurons had higher somatic expression of LTCC Cav1.2 subunits, exhibited larger afterhyperpolarization (AHP) and lower excitability compared with adult neurons. In contrast, PC neurons from aged rats showed higher excitability and no difference in AHP. Cav1.2 expression was similar in adult and aged PC somata, but relatively higher in PSD95- puncta in aged dendrites. Our data suggest unique features of aging-associated changes in LTCCs in the PC and hippocampus.
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Affiliation(s)
- Aida Maziar
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Tristian N R H Y Critch
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Sourav Ghosh
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Vishaal Rajani
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Cassandra M Flynn
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Tian Qin
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Camila Reinhardt
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
| | - Kwun Nok Mimi Man
- Department of Pharmacology, School of Medicine, University of California-Davis, Sacramento, CA 95817, United States
| | - Amy Lee
- Department of Neuroscience, University of Texas-Austin, Austin, TX 78712, United States
| | - Johannes W Hell
- Department of Pharmacology, School of Medicine, University of California-Davis, Sacramento, CA 95817, United States
| | - Qi Yuan
- Division of Biomedical Sciences, Faculty of Medicine, Memorial University, St. John's, NL A1B 3V6, Canada
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3
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Levic S. SK Current, Expressed During the Development and Regeneration of Chick Hair Cells, Contributes to the Patterning of Spontaneous Action Potentials. Front Cell Neurosci 2022; 15:766264. [PMID: 35069114 PMCID: PMC8770932 DOI: 10.3389/fncel.2021.766264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 11/29/2021] [Indexed: 11/30/2022] Open
Abstract
Chick hair cells display calcium (Ca2+)-sensitive spontaneous action potentials during development and regeneration. The role of this activity is unclear but thought to be involved in establishing proper synaptic connections and tonotopic maps, both of which are instrumental to normal hearing. Using an electrophysiological approach, this work investigated the functional expression of Ca2+-sensitive potassium [IK(Ca)] currents and their role in spontaneous electrical activity in the developing and regenerating hair cells (HCs) in the chick basilar papilla. The main IK(Ca) in developing and regenerating chick HCs is an SK current, based on its sensitivity to apamin. Analysis of the functional expression of SK current showed that most dramatic changes occurred between E8 and E16. Specifically, there is a developmental downregulation of the SK current after E16. The SK current gating was very sensitive to the availability of intracellular Ca2+ but showed very little sensitivity to T-type voltage-gated Ca2+ channels, which are one of the hallmarks of developing and regenerating hair cells. Additionally, apamin reduced the frequency of spontaneous electrical activity in HCs, suggesting that SK current participates in patterning the spontaneous electrical activity of HCs.
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Affiliation(s)
- Snezana Levic
- Center for Neuroscience, University of California, Davis, Davis, CA, United States
- Sensory Neuroscience Research Group, School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
- Brighton and Sussex Medical School, University of Sussex, Brighton, United Kingdom
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4
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Hong J, Fu S, Gao L, Cai Y, Lazartigues E, Wang HJ. Voltage-gated potassium channel dysfunction in dorsal root ganglia contributes to the exaggerated exercise pressor reflex in rats with chronic heart failure. Am J Physiol Heart Circ Physiol 2021; 321:H461-H474. [PMID: 34270374 DOI: 10.1152/ajpheart.00256.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An exaggerated exercise pressor reflex (EPR) causes excessive sympathoexcitation and exercise intolerance during physical activity in the chronic heart failure (CHF) state. Muscle afferent sensitization contributes to the genesis of the exaggerated EPR in CHF. However, the cellular mechanisms underlying muscle afferent sensitization in CHF remain unclear. Considering that voltage-gated potassium (Kv) channels critically regulate afferent neuronal excitability, we examined the potential role of Kv channels in mediating the sensitized EPR in male rats with CHF. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting experiments demonstrate that both mRNA and protein expressions of multiple Kv channel isoforms (Kv1.4, Kv3.4, Kv4.2, and Kv4.3) were downregulated in lumbar dorsal root ganglions (DRGs) of CHF rats compared with sham rats. Immunofluorescence data demonstrate significant decreased Kv channel staining in both NF200-positive and IB4-positive lumbar DRG neurons in CHF rats compared with sham rats. Data from patch-clamp experiments demonstrate that the total Kv current, especially IA, was dramatically decreased in medium-sized IB4-negative muscle afferent neurons (a subpopulation containing mostly Aδ neurons) from CHF rats compared with sham rats, indicating a potential functional loss of Kv channels in muscle afferent Aδ neurons. In in vivo experiments, adenoviral overexpression of Kv4.3 in lumbar DRGs for 1 wk attenuated the exaggerated EPR induced by muscle static contraction and the mechanoreflex by passive stretch without affecting the blunted cardiovascular response to hindlimb arterial injection of capsaicin in CHF rats. These data suggest that Kv channel dysfunction in DRGs plays a critical role in mediating the exaggerated EPR and muscle afferent sensitization in CHF.NEW & NOTEWORTHY The primary finding of this manuscript is that voltage-gated potassium (Kv) channel dysfunction in DRGs plays a critical role in mediating the exaggerated EPR and muscle afferent sensitization in chronic heart failure (CHF). We propose that manipulation of Kv channels in DRG neurons could be considered as a potential new approach to reduce the exaggerated sympathoexcitation and to improve exercise intolerance in CHF, which can ultimately facilitate an improved quality of life and reduce mortality.
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Affiliation(s)
- Juan Hong
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Shubin Fu
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha, Nebraska.,College of Animal Science and Technology, Southwest University, Chongqing, People's Republic of China
| | - Lie Gao
- Department of Cellular and Integrative Physiology, University of Nebraska Medical Center, Omaha, Nebraska
| | - Yanhui Cai
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana
| | - Eric Lazartigues
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana
| | - Han-Jun Wang
- Department of Anesthesiology, University of Nebraska Medical Center, Omaha, Nebraska
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5
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Hopp SC. Targeting microglia L-type voltage-dependent calcium channels for the treatment of central nervous system disorders. J Neurosci Res 2020; 99:141-162. [PMID: 31997405 DOI: 10.1002/jnr.24585] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 01/03/2020] [Accepted: 01/08/2020] [Indexed: 12/14/2022]
Abstract
Calcium (Ca2+ ) is a ubiquitous mediator of a multitude of cellular functions in the central nervous system (CNS). Intracellular Ca2+ is tightly regulated by cells, including entry via plasma membrane Ca2+ permeable channels. Of specific interest for this review are L-type voltage-dependent Ca2+ channels (L-VDCCs), due to their pleiotropic role in several CNS disorders. Currently, there are numerous approved drugs that target L-VDCCs, including dihydropyridines. These drugs are safe and effective for the treatment of humans with cardiovascular disease and may also confer neuroprotection. Here, we review the potential of L-VDCCs as a target for the treatment of CNS disorders with a focus on microglia L-VDCCs. Microglia, the resident immune cells of the brain, have attracted recent attention for their emerging inflammatory role in several CNS diseases. Intracellular Ca2+ regulates microglia transition from a resting quiescent state to an "activated" immune-effector state and is thus a valuable target for manipulation of microglia phenotype. We will review the literature on L-VDCC expression and function in the CNS and on microglia in vitro and in vivo and explore the therapeutic landscape of L-VDCC-targeting agents at present and future challenges in the context of Alzheimer's disease, Parkinson's disease, Huntington's disease, neuropsychiatric diseases, and other CNS disorders.
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Affiliation(s)
- Sarah C Hopp
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA.,Department of Pharmacology, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
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6
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Bailey CS, Moldenhauer HJ, Park SM, Keros S, Meredith AL. KCNMA1-linked channelopathy. J Gen Physiol 2019; 151:1173-1189. [PMID: 31427379 PMCID: PMC6785733 DOI: 10.1085/jgp.201912457] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 08/13/2019] [Indexed: 12/20/2022] Open
Abstract
Bailey et al. review a new neurological channelopathy associated with KCNMA1, encoding the BK voltage- and Ca2+-activated K+ channel. KCNMA1 encodes the pore-forming α subunit of the “Big K+” (BK) large conductance calcium and voltage-activated K+ channel. BK channels are widely distributed across tissues, including both excitable and nonexcitable cells. Expression levels are highest in brain and muscle, where BK channels are critical regulators of neuronal excitability and muscle contractility. A global deletion in mouse (KCNMA1−/−) is viable but exhibits pathophysiology in many organ systems. Yet despite the important roles in animal models, the consequences of dysfunctional BK channels in humans are not well characterized. Here, we summarize 16 rare KCNMA1 mutations identified in 37 patients dating back to 2005, with an array of clinically defined pathological phenotypes collectively referred to as “KCNMA1-linked channelopathy.” These mutations encompass gain-of-function (GOF) and loss-of-function (LOF) alterations in BK channel activity, as well as several variants of unknown significance (VUS). Human KCNMA1 mutations are primarily associated with neurological conditions, including seizures, movement disorders, developmental delay, and intellectual disability. Due to the recent identification of additional patients, the spectrum of symptoms associated with KCNMA1 mutations has expanded but remains primarily defined by brain and muscle dysfunction. Emerging evidence suggests the functional BK channel alterations produced by different KCNMA1 alleles may associate with semi-distinct patient symptoms, such as paroxysmal nonkinesigenic dyskinesia (PNKD) with GOF and ataxia with LOF. However, due to the de novo origins for the majority of KCNMA1 mutations identified to date and the phenotypic variability exhibited by patients, additional evidence is required to establish causality in most cases. The symptomatic picture developing from patients with KCNMA1-linked channelopathy highlights the importance of better understanding the roles BK channels play in regulating cell excitability. Establishing causality between KCNMA1-linked BK channel dysfunction and specific patient symptoms may reveal new treatment approaches with the potential to increase therapeutic efficacy over current standard regimens.
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Affiliation(s)
- Cole S Bailey
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Hans J Moldenhauer
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Su Mi Park
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Sotirios Keros
- Department of Pediatrics, University of South Dakota Sanford School of Medicine, Sioux Falls, SD
| | - Andrea L Meredith
- Dept. of Physiology, University of Maryland School of Medicine, Baltimore, MD
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7
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Parisi C, Chandaria VV, Nowlan NC. Blocking mechanosensitive ion channels eliminates the effects of applied mechanical loading on chick joint morphogenesis. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2017.0317. [PMID: 30249769 PMCID: PMC6158207 DOI: 10.1098/rstb.2017.0317] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2018] [Indexed: 11/12/2022] Open
Abstract
Abnormalities in joint shape are increasingly considered a critical risk factor for developing osteoarthritis in life. It has been shown that mechanical forces during prenatal development, particularly those due to fetal movements, play a fundamental role in joint morphogenesis. However, how mechanical stimuli are sensed or transduced in developing joint tissues is unclear. Stretch-activated and voltage-gated calcium ion channels have been shown to be involved in the mechanoregulation of chondrocytes in vitro. In this study, we analyse, for the first time, how blocking these ion channels influences the effects of mechanical loading on chick joint morphogenesis. Using in vitro culture of embryonic chick hindlimb explants in a mechanostimulation bioreactor, we block stretch-activated and voltage-gated ion channels using, respectively, gadolinium chloride and nifedipine. We find that the administration of high doses of either drug largely removed the effects of mechanical stimulation on growth and shape development in vitro, while neither drug had any effect in static cultures. This study demonstrates that, during joint morphogenesis, mechanical cues are transduced—at least in part—through mechanosensitive calcium ion channels, advancing our understanding of cartilage development and mechanotransduction. This article is part of the Theo Murphy meeting issue ‘Mechanics of development’.
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Affiliation(s)
- Cristian Parisi
- Department of Bioengineering, Faculty of Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Vikesh V Chandaria
- Department of Bioengineering, Faculty of Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Niamh C Nowlan
- Department of Bioengineering, Faculty of Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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8
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Lv Y, Wang Y, Zhu X, Zhang H. Aldosterone downregulates delayed rectifier potassium currents through an angiotensin type 1 receptor-dependent mechanism. Am J Transl Res 2018; 10:1413-1421. [PMID: 29887955 PMCID: PMC5992560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 04/06/2018] [Indexed: 06/08/2023]
Abstract
We have previously shown that aldosterone downregulates delayed rectifier potassium currents (IKs) via activation of the mineralocorticoid receptor (MR) in adult guinea pig cardiomyocytes. Here, we investigate whether angiotensin II/angiotensin type 1 receptor (AngII/AT1R) and intracellular calcium also play a role in these effects. Ventricular cardiomyocytes were isolated from adult guinea pigs and incubated with aldosterone (1 μmol·L-1) either alone or in combination with enalapril (1 μmol·L-1), losartan (1 μmol·L-1), nimodipine (1 μmol·L-1), or BAPTA-AM (2.5 μmol·L-1) for 24 h. We used the conventional whole cell patch-clamp technique to record the IKs component. In addition, we evaluated expression of the IKs subunits KCNQ1 and KCNE1 using Western blotting. Our results showed that both enalapril and losartan, but not nimodipine or BAPTA-AM, completely reversed the aldosterone-induced inhibition of IKs and its effects on KCNQ1/KCNE1 protein levels. Furthermore, we found that AngII/AT1R mediates the inhibitory effects of aldosterone on IKs. Finally, the downregulation of IKs induced by aldosterone did not occur secondarily to a change in intracellular calcium concentrations. Taken together, our findings demonstrate that crosstalk between MR and AT1R underlies the effects of aldosterone, and provide new insights into the mechanism underlying potassium channels.
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Affiliation(s)
- Yankun Lv
- Heart Center, Hebei General HospitalShijiazhuang, China
| | - Yanjun Wang
- Department of Acupuncture and Moxibustion, Affiliated Hospital of Hebei University of Chinese MedicineShijiazhuang, China
| | - Xiaoran Zhu
- Heart Center, Hebei General HospitalShijiazhuang, China
| | - Hua Zhang
- Department of Pharmacology, Hebei Medical UniversityShijiazhuang, China
- The Key Laboratory of New Drug Pharmacology and ToxicologyShijiazhuang, China
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9
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von der Ahe D, Huehnchen P, Balkaya M, Peruzzaro S, Endres M, Boehmerle W. Suramin-Induced Neurotoxicity: Preclinical Models and Neuroprotective Strategies. Molecules 2018; 23:molecules23020346. [PMID: 29414872 PMCID: PMC6017835 DOI: 10.3390/molecules23020346] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 01/23/2018] [Accepted: 02/03/2018] [Indexed: 11/16/2022] Open
Abstract
Suramin is a trypan blue analogon originally developed to treat protozoan infections, which was found to have diverse antitumor effects. One of the most severe side effects in clinical trials was the development of a peripheral sensory-motor polyneuropathy. In this study, we aimed to investigate suramin-induced neuropathy with a focus on calcium (Ca2+) homeostasis as a potential pathomechanism. Adult C57Bl/6 mice treated with a single injection of 250 mg/kg bodyweight suramin developed locomotor and sensory deficits, which were confirmed by electrophysiological measurements showing a predominantly sensory axonal-demyelinating polyneuropathy. In a next step, we used cultured dorsal root ganglia neurons (DRGN) as an in vitro cell model to further investigate underlying pathomechanisms. Cell viability of DRGN was significantly decreased after 24-hour suramin treatment with a calculated IC50 of 283 µM. We detected a suramin-induced Ca2+ influx into DRGN from the extracellular space, which could be reduced with the voltage-gated calcium channel (VGCC) inhibitor nimodipine. Co-incubation of suramin and nimodipine partially improved cell viability of DRGN after suramin exposure. In summary, we describe suramin-induced neurotoxic effects on DRGN as well as potentially neuroprotective agents targeting intracellular Ca2+ dyshomeostasis.
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Affiliation(s)
- David von der Ahe
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Klinik und Hochschulambulanz für Neurologie, Chariteplatz 1, 10117 Berlin, Germany.
| | - Petra Huehnchen
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Klinik und Hochschulambulanz für Neurologie, Chariteplatz 1, 10117 Berlin, Germany.
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Cluster of Excellence NeuroCure, 10117 Berlin, Germany.
- Berlin Institute of Health, Anna-Louisa-Karsch 2, 10178 Berlin, Germany.
| | - Mustafa Balkaya
- Burke-Cornell Medical Research Institute, White Plains, NY 10605, USA.
| | - Sarah Peruzzaro
- Field Neurosciences Institute Laboratory for Restorative Neurology, Central Michigan University, Mt. Pleasant, MI 48859, USA.
| | - Matthias Endres
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Klinik und Hochschulambulanz für Neurologie, Chariteplatz 1, 10117 Berlin, Germany.
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Cluster of Excellence NeuroCure, 10117 Berlin, Germany.
- Berlin Institute of Health, Anna-Louisa-Karsch 2, 10178 Berlin, Germany.
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Center for Stroke Resarch Berlin, 10117 Berlin, Germany.
- German Center for Neurodegenerative Diseases (DZNE), 10117 Berlin, Germany.
- German Center for Cardiovascular Research (DZHK), Partner Site Berlin, 10117 Berlin, Germany.
| | - Wolfgang Boehmerle
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Klinik und Hochschulambulanz für Neurologie, Chariteplatz 1, 10117 Berlin, Germany.
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Cluster of Excellence NeuroCure, 10117 Berlin, Germany.
- Berlin Institute of Health, Anna-Louisa-Karsch 2, 10178 Berlin, Germany.
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10
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Goldspink DA, Lu VB, Billing LJ, Larraufie P, Tolhurst G, Gribble FM, Reimann F. Mechanistic insights into the detection of free fatty and bile acids by ileal glucagon-like peptide-1 secreting cells. Mol Metab 2017; 7:90-101. [PMID: 29167062 PMCID: PMC5784317 DOI: 10.1016/j.molmet.2017.11.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/04/2017] [Accepted: 11/06/2017] [Indexed: 02/07/2023] Open
Abstract
Objectives The aim of this study was to investigate the electrical properties of ileal Glucagon-like peptide 1 (GLP-1) secreting L-cells using murine organoid cultures and the electrophysiological and intracellular signaling pathways recruited following activation of the Gαq-coupled free fatty acid receptors FFA1 and Gαs-coupled bile acid receptors GPBAR1. Methods Experiments were performed using ileal organoids generated from mice transgenically expressing fluorescent reporters (Epac2-camps and GCaMP3) under control of the proglucagon promoter. Electrophysiology and single cell imaging were performed on identified L-cells in organoids, and GLP-1 secretion from cultured organoids was measured by immunoassay. Results The FFA1 ligand TAK-875 triggered L-cell electrical activity, increased intracellular calcium, and activated a depolarizing current that was blocked by the TRPC3 inhibitor Pyr3. TAK-875 triggered GLP-1 secretion was Pyr3 sensitive, suggesting that the TRPC3 channel links FFA1 activation to calcium elevation and GLP-1 release in L-cells. GPBAR1 agonist triggered PKA-dependent L-type Ca2+ current activation and action potential firing in L-cells. The combination of TAK-875 and a GPBAR1 agonist triggered synergistic calcium elevation and GLP-1 secretory responses. Conclusions FFA1 and GPBAR1 activation individually increased electrical activity in L-cells by recruiting pathways that include activation of TRPC3 and L-type voltage-gated Ca2+ channels. Synergy between the pathways activated downstream of these receptors was observed both at the level of Ca2+ elevation and GLP-1 secretion. Organoid-derived ileal L-cells recapitulate the properties of primary ileal L-cells. GPBAR1 agonism stimulates L-type Ca2+ current-dependent action potentials in L-cells. FFA1 agonists depolarize L-cells via TRPC3 activation. Synergy between GPBAR1/FFA1 occurs at the levels of Ca2+ responses and secretion.
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Affiliation(s)
- Deborah A Goldspink
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Van B Lu
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Lawrence J Billing
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Pierre Larraufie
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Gwen Tolhurst
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK
| | - Fiona M Gribble
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK.
| | - Frank Reimann
- Metabolic Research Laboratories and MRC Metabolic Diseases Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK.
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11
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Grimsley CA, Green DB, Sivaramakrishnan S. L-type calcium channels refine the neural population code of sound level. J Neurophysiol 2016; 116:2550-2563. [PMID: 27605536 DOI: 10.1152/jn.00657.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 09/07/2016] [Indexed: 11/22/2022] Open
Abstract
The coding of sound level by ensembles of neurons improves the accuracy with which listeners identify how loud a sound is. In the auditory system, the rate at which neurons fire in response to changes in sound level is shaped by local networks. Voltage-gated conductances alter local output by regulating neuronal firing, but their role in modulating responses to sound level is unclear. We tested the effects of L-type calcium channels (CaL: CaV1.1-1.4) on sound-level coding in the central nucleus of the inferior colliculus (ICC) in the auditory midbrain. We characterized the contribution of CaL to the total calcium current in brain slices and then examined its effects on rate-level functions (RLFs) in vivo using single-unit recordings in awake mice. CaL is a high-threshold current and comprises ∼50% of the total calcium current in ICC neurons. In vivo, CaL activates at sound levels that evoke high firing rates. In RLFs that increase monotonically with sound level, CaL boosts spike rates at high sound levels and increases the maximum firing rate achieved. In different populations of RLFs that change nonmonotonically with sound level, CaL either suppresses or enhances firing at sound levels that evoke maximum firing. CaL multiplies the gain of monotonic RLFs with dynamic range and divides the gain of nonmonotonic RLFs with the width of the RLF. These results suggest that a single broad class of calcium channels activates enhancing and suppressing local circuits to regulate the sensitivity of neuronal populations to sound level.
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Affiliation(s)
- Calum Alex Grimsley
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
| | - David Brian Green
- Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio
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The inhibitory effects of nifedipine on outward voltage-gated potassium currents in mouse neuroblastoma N2A cells. Pharmacol Rep 2016; 68:631-7. [DOI: 10.1016/j.pharep.2015.12.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/17/2015] [Accepted: 12/18/2015] [Indexed: 11/22/2022]
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Medrano-Martínez V, Pérez-Sempere A, Moltó-Jordá JM, Fernández-Izquierdo S, Francés-Pont I, Mallada-Frechin J, Piqueras-Rodríguez L. Eyelid myokymia in patients with migraine taking topiramate. Acta Neurol Scand 2015; 132:143-6. [PMID: 25828425 DOI: 10.1111/ane.12395] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2015] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Although ocular side effects of topiramate are common, neuroophthalmologic manifestations such as blepharospasm, myokymia and oculogyric crisis are scarcely reported. METHODS We present a serie of 8 patients with migraine who developed eyelid myokymia after treatment with topiramate. We reviewed all patients with migraine treated with topiramate attending the headache outpatient clinic of our hospital from January 2008 to December 2012. RESULTS During the study period, a total of 140 patients with migraine were treated with topiramate in our headache clinic. Eight presented eyelid myokymia after beginning treatment with topiramate (5,7%). Topiramate was stopped and myokymia disappeared in all patients, it was prescribed again and eyelid myokymia reappeared with their previous characteristics in all patients. CONCLUSIONS Eyelid myokymia is an underreported side-effect of topiramate in patients with migraine, of unknown cause, so that in future, further studies are need to examine whether patients with migraine are predisposed or not to this adverse effect.
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Affiliation(s)
- V. Medrano-Martínez
- Department of Neurology; Hospital General Universitario Virgen De La Salud; Elda Spain
| | - A. Pérez-Sempere
- Department of Neurology; Hospital General Universitario De Alicante; Alicante Spain
| | | | | | - I. Francés-Pont
- Department of Neurology; Hospital General Universitario Virgen De La Salud; Elda Spain
| | - J. Mallada-Frechin
- Department of Neurology; Hospital General Universitario Virgen De La Salud; Elda Spain
| | - L. Piqueras-Rodríguez
- Department of Neurology; Hospital General Universitario Virgen De La Salud; Elda Spain
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Li XT, Li XQ, Hu XM, Qiu XY. The Inhibitory Effects of Ca2+ Channel Blocker Nifedipine on Rat Kv2.1 Potassium Channels. PLoS One 2015; 10:e0124602. [PMID: 25893973 PMCID: PMC4404097 DOI: 10.1371/journal.pone.0124602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 03/04/2015] [Indexed: 11/26/2022] Open
Abstract
It is well documented that nifedipine, a commonly used dihydropyridine Ca2+ channel blocker, has also significant interactions with voltage-gated K+ (Kv) channels. But to date, little is known whether nifedipine exerted an action on Kv2.1 channels, a member of the Shab subfamily with slow inactivation. In the present study, we explored the effects of nifedipine on rat Kv2.1 channels expressed in HEK293 cells. Data from whole-cell recording showed that nifedipine substantially reduced Kv2.1 currents with the IC50 value of 37.5 ± 5.7 μM and delayed the time course of activation without effects on the activation curve. Moreover, this drug also significantly shortened the duration of inactivation and deactivation of Kv2.1 currents in a voltage-dependent manner. Interestingly, the half-maximum inactivation potential (V1/2) of Kv2.1 currents was -11.4 ± 0.9 mV in control and became -38.5 ± 0.4 mV after application of 50 μM nifedipine. The large hyperpolarizing shift (27 mV) of the inactivation curve has not been reported previously and may result in more inactivation for outward delayed rectifier K+ currents mediated by Kv2.1 channels at repolarization phases. The Y380R mutant significantly increased the binding affinity of nifedipine to Kv2.1 channels, suggesting an interaction of nifedipine with the outer mouth region of this channel. The data present here will be helpful to understand the diverse effects exerted by nifedipine on various Kv channels.
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Affiliation(s)
- Xian-Tao Li
- Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, China
- * E-mail:
| | - Xiao-Qing Li
- Department of Neuroscience, College of Life Sciences, South-Central University for Nationalities, Wuhan, China
| | - Xi-Mu Hu
- South-Central University for Nationalities, Wuhan, China
| | - Xiao-Yue Qiu
- South-Central University for Nationalities, Wuhan, China
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dos Santos-Nascimento T, Veras KM, Cruz JS, Leal-Cardoso JH. Inhibitory effect of terpinen-4-ol on voltage-dependent potassium currents in rat small sensory neurons. JOURNAL OF NATURAL PRODUCTS 2015; 78:173-180. [PMID: 25607610 DOI: 10.1021/np4009249] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The biological and pharmacological activities of the terpenoid terpinen-4-ol (1), which include depressant effects in the central nervous system, are of potential therapeutic interest. In the present study, the effects of 1 on neuronal excitability and voltage-dependent K(+) currents in the somatic sensory system were investigated. Intact and dissociated neurons of rat dorsal root ganglia (DRG) were used for intracellular and patch-clamp recordings, respectively. In neurons of intact DRG, 1 caused concentration-dependent depolarization of the resting membrane potential and increased input resistance. 1 also inhibited action potentials (AP) and decreased AP parameters, with the exception of AP duration, which was increased. In dissociated DRG neurons, 1 partially blocked the total K(+) current in a concentration-dependent manner. 1 inhibited I(A), I(D), and I(K) with IC50 values of 3.2 ± 03, 0.7 ± 0.1, and 1.6 ± 0.7 mM, respectively. 1 did not shift either the steady-state activation or inactivation curves of I(A), I(D), and I(K) but reduced the decay time course of I(A). The alterations in DRG reported here are consistent with the inhibition of K(+) currents and might partially explain the effect of 1 on excitable tissues.
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Affiliation(s)
- Tiago dos Santos-Nascimento
- Laboratory of Electrophysiology, Superior Institute of Biomedical Sciences, State University of Ceará , Campus of Itaperi, Fortaleza, CE, Brazil
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Park MH, Son YK, Hong DH, Choi IW, Kim DJ, Lee H, Bang H, Na SH, Li H, Jo SH, Park WS. The Ca2+ channel inhibitor efonidipine decreases voltage-dependent K+ channel activity in rabbit coronary arterial smooth muscle cells. Vascul Pharmacol 2013; 59:90-5. [DOI: 10.1016/j.vph.2013.07.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 07/12/2013] [Accepted: 07/12/2013] [Indexed: 12/22/2022]
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Posthearing Ca(2+) currents and their roles in shaping the different modes of firing of spiral ganglion neurons. J Neurosci 2013; 32:16314-30. [PMID: 23152615 DOI: 10.1523/jneurosci.2097-12.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Whereas prehearing spiral ganglion neurons (SGNs) rely faithfully on outputs from spontaneously active developing hair cells, the electrical phenotypes of posthearing neurons are shaped by distinct rapid and graded receptor potentials from hair cells. To date, technical difficulties in isolation of fragile posthearing neurons from the rigid bony labyrinth of the inner ear have hindered analyses of the electrical phenotype of SGNs. Therefore, we have recently developed new strategies to isolate posthearing mouse SGNs for functional analyses. Here, we describe the coarse and fine properties of Ca(2+) currents, which sculpt the firing properties of posthearing SGNs. Murine SGNs express multiple Ca(2+) channel currents to enable diverse functions. We have demonstrated that suppression of Ca(2+) currents results in significant hyperpolarization of the resting membrane potential (rmp) of basal SGNs, suggesting that Ca(2+) influx primes rmp for excitation. In contrast, removal of external Ca(2+) has modest effects on rmp of apical SGNs. The blockade of Ca(2+) currents with a mixture of specific blockers attenuates spontaneously active SGNs. Paradoxically, different subtypes of Ca(2+) currents, such as R-type currents, may activate resting outward conductances since blockage of the current results in depolarization of rmp. In keeping with whole-cell current data, single-channel records revealed multiple diverse Ca(2+) channels in SGNs. Additionally, there were differential expressions of distinct Ca(2+) current densities in the apicobasal contour of the adult cochlea. This report provides invaluable insights into Ca(2+)-dependent processes in adult SGNs.
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Luoma JI, Stern CM, Mermelstein PG. Progesterone inhibition of neuronal calcium signaling underlies aspects of progesterone-mediated neuroprotection. J Steroid Biochem Mol Biol 2012; 131:30-6. [PMID: 22101209 PMCID: PMC3303940 DOI: 10.1016/j.jsbmb.2011.11.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 10/31/2011] [Accepted: 11/02/2011] [Indexed: 01/02/2023]
Abstract
Progesterone is being utilized as a therapeutic means to ameliorate neuron loss and cognitive dysfunction following traumatic brain injury. Although there have been numerous attempts to determine the means by which progesterone exerts neuroprotective effects, studies describing the underlying molecular mechanisms are lacking. What has become clear, however, is the notion that progesterone can thwart several physiological processes that are detrimental to neuron function and survival, including inflammation, edema, demyelination and excitotoxicity. One clue regarding the means by which progesterone has restorative value comes from the notion that these aforementioned biological processes all share the common theme of eliciting pronounced increases in intracellular calcium. Thus, we propose the hypothesis that progesterone regulation of calcium signaling underlies its ability to mitigate these cellular insults, ultimately leading to neuroprotection. Further, we describe recent findings that indicate neuroprotection is achieved via progesterone block of voltage-gated calcium channels, although additional outcomes may arise from blockade of various other ion channels and neurotransmitter receptors. This article is part of a Special Issue entitled 'Neurosteroids'.
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Affiliation(s)
- Jessie I Luoma
- Graduate Program in Neuroscience and Department of Neuroscience, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA
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Adermark L. Modulation of endocannabinoid-mediated long-lasting disinhibition of striatal output by cholinergic interneurons. Neuropharmacology 2011; 61:1314-20. [PMID: 21839753 DOI: 10.1016/j.neuropharm.2011.07.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Revised: 07/22/2011] [Accepted: 07/25/2011] [Indexed: 12/22/2022]
Abstract
The frequency and duration of glutamatergic inputs to the striatum are strong determinants of the net effect of retrograde endocannabinoid (eCB) signaling, and key factors in determining if long-term depression (LTD) has a net disinhibitory or inhibitory action in striatum. Low to moderate frequency stimulation in the dorsolateral striatum elevates eCB levels to an extent that primarily depresses transmitter release at inhibitory synapses, leading to a long-lasting disinhibition (DLL) of synaptic output. The aim of this study was to further characterize the basic features of endocannabinoid-mediated DLL of striatal output induced by moderate frequency stimulation (5 Hz, 60 s). DLL was inhibited in slices treated with the group 1 metabotropic glutamate receptor (mGluR) antagonists MPEP (40 μM) and CPCCOEt (40 μM), the dopamine D2 receptor antagonist sulpiride (5 μM), the L-type calcium channel blocker nifedipine (20 μM), the nicotinic receptor antagonist mecamylamine (10 μM), the muscarinic agonist oxotremorine sesquifumarate (10 μM), and strychnine (0.1 μM). Strychnine did not block DLL induced by WIN55,212-2 (250 nM), showing that glycine receptor-mediated modulation of eCB signaling occurs upstream from CB(1)R activation. Scopolamine (10 μM) restored DLL in strychnine-treated slices, suggesting that inhibition of glycine receptors on cholinergic interneurons could modulate eCB signaling by enhancing muscarinic receptor activation and reducing the opening of L-type calcium channels in response to depolarization. These data suggests that similar activation points are required for stimulation-induced DLL as for LTD at excitatory striatal synapses, and that cholinergic interneurons are key modulators of stimulation-induced eCB signaling in the striatum.
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Affiliation(s)
- Louise Adermark
- Addiction Biology Unit, Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, University of Gothenburg, Box 410, 405 30 Gothenburg, Sweden.
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Progesterone blocks multiple routes of ion flux. Mol Cell Neurosci 2011; 48:137-41. [PMID: 21782024 DOI: 10.1016/j.mcn.2011.07.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/01/2011] [Accepted: 07/07/2011] [Indexed: 01/07/2023] Open
Abstract
The administration of progesterone as a neuroprotective agent following traumatic brain injury has recently entered phase III clinical trials. Previous work has demonstrated that therapeutic concentrations of progesterone decrease excitotoxicity through direct inhibition of voltage-gated calcium channels, an action independent of the nuclear progesterone receptor. Here we report using cultured rat striatal neurons that these same concentrations of progesterone also block voltage-gated potassium channels, sodium channels and GABA(A) currents. The actions of progesterone act at the surface membrane of neurons in a steroid specific, voltage-independent, concentration-dependent manner. Notably, these broad actions of progesterone on ion channel and neurotransmitter receptor function mirror those of dihydropyridines, and indicate potential shared mechanisms of action, the prospective of additional therapeutic applications, and possibly, untoward effects.
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Kizilay F, Ekmekci B, Gungor H, Uysal H, Oh SJ. Flunarizine-induced fasciculation-myokymia. J Clin Neuromuscul Dis 2011; 12:246-247. [PMID: 22361525 DOI: 10.1097/cnd.0b013e31821a2507] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Multiple targets of μ-opioid receptor-mediated presynaptic inhibition at primary afferent Aδ- and C-fibers. J Neurosci 2011; 31:1313-22. [PMID: 21273416 DOI: 10.1523/jneurosci.4060-10.2011] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Agonists at μ-opioid receptors (MORs) represent the gold standard for the treatment of severe pain. A key element of opioid analgesia is the depression of nociceptive information at the first synaptic relay in spinal pain pathways. The underlying mechanisms are, however, largely unknown. In spinal cord slices with dorsal roots attached prepared from young rats, we determined the inhibitory effect of the selective MOR agonist [d-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) on monosynaptic Aδ- and C-fiber-evoked EPSCs in lamina I neurons. DAMGO depressed presynaptically Aδ- and C-fiber-mediated responses, indicating that MORs are expressed on central terminals of both fiber types. We next addressed the mechanisms of presynaptic inhibition. The effect of DAMGO at both Aδ- and C-fiber terminals was mainly mediated by an inhibition of N-type voltage-dependent Ca(2+) channels (VDCCs), and to a lesser extent of P/Q-type VDCCs. Inhibition by DAMGO was not reduced by K(+) channel blockers. The rate of miniature EPSCs was reduced by DAMGO in a dose-dependent manner. The opioid also reduced Ca(2+)-dependent, ionomycin-induced EPSCs downstream of VDCCs. DAMGO had no effect on the kinetics of vesicle exocytosis in C-fiber terminals, but decreased the rate of unloading of Aδ-fiber boutons moderately, as revealed by two-photon imaging of styryl dye destaining. Together, these results suggest that binding of opioids to MORs reduces nociceptive signal transmission at central Aδ- and C-fiber synapses mainly by inhibition of presynaptic N-type VDCCs. P/Q-type VDCCs and the transmitter release machinery are targets of opioid action as well.
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Wang D, Grillner S, Wallén P. 5-HT and dopamine modulates CaV1.3 calcium channels involved in postinhibitory rebound in the spinal network for locomotion in lamprey. J Neurophysiol 2011; 105:1212-24. [PMID: 21228305 DOI: 10.1152/jn.00324.2009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Postinhibitory rebound (PIR) can play a significant role for producing stable rhythmic motor patterns, like locomotion, by contributing to burst initiation following the phase of inhibition, and PIR may also be a target for modulatory systems acting on the network. The current aim was to explore the PIR in one type of interneuron in the lamprey locomotor network and its dependence on low voltage-activated (LVA) calcium channels, as well as its modulation by 5-HT and dopamine. PIR responses in commissural interneurons, mediating reciprocal inhibition and left-right alternation in the network, were significantly larger than in motoneurons. The L-type calcium channel antagonist nimodipine reduced PIR amplitude by ∼ 50%, whereas the L-channel agonist BAY K 8644 enhanced PIR amplitude, suggesting that LVA calcium channels of the L-subtype (Ca(V)1.3) participate in the PIR response. The remainder of the response was blocked by nickel, indicating that T-type (Ca(V)3) LVA calcium channels also contribute. No evidence was obtained for the involvement of a hyperpolarization-activated current. Furthermore, 5-HT, acting via 5-HT(1A) receptors, reduced PIR, as did dopamine, acting via D(2) receptors. Coapplication of nimodipine caused no further PIR reduction, indicating that these modulators target Ca(V)1.3 channels specifically. These results suggest that PIR may play a prominent role in the generation of alternating network activity and that the Ca(V)1.3 and Ca(V)3 subtypes of LVA calcium channels together underlie the PIR response. 5-HT and dopamine both target PIR via Ca(V)1.3 channels, which may contribute significantly to their modulatory influence on locomotor network activity.
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Affiliation(s)
- Di Wang
- Nobel Institute for Neurophysiology, Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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