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Geisler SM, Ottaviani MM, Jacobo-Piqueras N, Theiner T, Mastrolia V, Guarina L, Ebner K, Obermair GJ, Carbone E, Tuluc P. Deletion of the α 2δ-1 calcium channel subunit increases excitability of mouse chromaffin cells. J Physiol 2024; 602:3793-3814. [PMID: 39004870 DOI: 10.1113/jp285681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 06/26/2024] [Indexed: 07/16/2024] Open
Abstract
High voltage-gated Ca2+ channels (HVCCs) shape the electrical activity and control hormone release in most endocrine cells. HVCCs are multi-subunit protein complexes formed by the pore-forming α1 and the auxiliary β, α2δ and γ subunits. Four genes code for the α2δ isoforms. At the mRNA level, mouse chromaffin cells (MCCs) express predominantly the CACNA2D1 gene coding for the α2δ-1 isoform. Here we show that α2δ-1 deletion led to ∼60% reduced HVCC Ca2+ influx with slower inactivation kinetics. Pharmacological dissection showed that HVCC composition remained similar in α2δ-1-/- MCCs compared to wild-type (WT), demonstrating that α2δ-1 exerts similar functional effects on all HVCC isoforms. Consistent with reduced HVCC Ca2+ influx, α2δ-1-/- MCCs showed reduced spontaneous electrical activity with action potentials (APs) having a shorter half-maximal duration caused by faster rising and decay slopes. However, the induced electrical activity showed opposite effects with α2δ-1-/- MCCs displaying significantly higher AP frequency in the tonic firing mode as well as an increase in the number of cells firing AP bursts compared to WT. This gain-of-function phenotype was caused by reduced functional activation of Ca2+-dependent K+ currents. Additionally, despite the reduced HVCC Ca2+ influx, the intracellular Ca2+ transients and vesicle exocytosis or endocytosis were unaltered in α2δ-1-/- MCCs compared to WT during sustained stimulation. In conclusion, our study shows that α2δ-1 genetic deletion reduces Ca2+ influx in cultured MCCs but leads to a paradoxical increase in catecholamine secretion due to increased excitability. KEY POINTS: Deletion of the α2δ-1 high voltage-gated Ca2+ channel (HVCC) subunit reduces mouse chromaffin cell (MCC) Ca2+ influx by ∼60% but causes a paradoxical increase in induced excitability. MCC intracellular Ca2+ transients are unaffected by the reduced HVCC Ca2+ influx. Deletion of α2δ-1 reduces the immediately releasable pool vesicle exocytosis but has no effect on catecholamine (CA) release in response to sustained stimuli. The increased electrical activity and CA release from MCCs might contribute to the previously reported cardiovascular phenotype of patients carrying α2δ-1 loss-of-function mutations.
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Affiliation(s)
- Stefanie M Geisler
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Matteo M Ottaviani
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Noelia Jacobo-Piqueras
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Tamara Theiner
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Vincenzo Mastrolia
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Laura Guarina
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Karl Ebner
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Emilio Carbone
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
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Abstract
Because catecholamines secretion mainly relies on the excitable nature of adrenal chromaffin cells, monitoring their electrical activity is an essential step in assessing the adrenal medullary tissue function. The difficult access to the gland in vivo allows only population activity to be recorded in this condition. In vitro preparations allow recordings of spontaneous or evoked activity from single or multiple cells, depending on the biological samples used (dissociated chromaffin cells versus adrenal tissue preparations). In this chapter, I provide a detailed description of the techniques used for electrophysiological recordings in rodent chromaffin cells in acute adrenal slices, using the patch-clamp technique. This methodology allows preservation of the tissue integrity and detection of action potentials, synaptic activity, and secretory events; it is thus suitable for the study of adrenomedullary activity-secretion coupling.
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Affiliation(s)
- Nathalie C Guérineau
- Institute of Functional Genomics, University of Montpellier, CNRS, INSERM, Montpellier, France.
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Guérineau NC, Campos P, Le Tissier PR, Hodson DJ, Mollard P. Cell Networks in Endocrine/Neuroendocrine Gland Function. Compr Physiol 2022; 12:3371-3415. [PMID: 35578964 DOI: 10.1002/cphy.c210031] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Reproduction, growth, stress, and metabolism are determined by endocrine/neuroendocrine systems that regulate circulating hormone concentrations. All these systems generate rhythms and changes in hormone pulsatility observed in a variety of pathophysiological states. Thus, the output of endocrine/neuroendocrine systems must be regulated within a narrow window of effective hormone concentrations but must also maintain a capacity for plasticity to respond to changing physiological demands. Remarkably most endocrinologists still have a "textbook" view of endocrine gland organization which has emanated from 20th century histological studies on thin 2D tissue sections. However, 21st -century technological advances, including in-depth 3D imaging of specific cell types have vastly changed our knowledge. We now know that various levels of multicellular organization can be found across different glands, that organizational motifs can vary between species and can be modified to enhance or decrease hormonal release. This article focuses on how the organization of cells regulates hormone output using three endocrine/neuroendocrine glands that present different levels of organization and complexity: the adrenal medulla, with a single neuroendocrine cell type; the anterior pituitary, with multiple intermingled cell types; and the pancreas with multiple intermingled cell types organized into distinct functional units. We give an overview of recent methodologies that allow the study of the different components within endocrine systems, particularly their temporal and spatial relationships. We believe the emerging findings about network organization, and its impact on hormone secretion, are crucial to understanding how homeostatic regulation of endocrine axes is carried out within endocrine organs themselves. © 2022 American Physiological Society. Compr Physiol 12:3371-3415, 2022.
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Affiliation(s)
| | - Pauline Campos
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK
| | - Paul R Le Tissier
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, Scotland, UK
| | - David J Hodson
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Edgbaston, UK.,Centre for Endocrinology, Diabetes and Metabolism, Birmingham Health Partners, Birmingham, UK.,COMPARE University of Birmingham and University of Nottingham Midlands, UK.,Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), NIHR Oxford Biomedical Research Centre, Churchill Hospital, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Patrice Mollard
- IGF, University of Montpellier, CNRS, INSERM, Montpellier, France
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Milman A, Ventéo S, Bossu JL, Fontanaud P, Monteil A, Lory P, Guérineau NC. A sodium background conductance controls the spiking pattern of mouse adrenal chromaffin cells in situ. J Physiol 2021; 599:1855-1883. [PMID: 33450050 PMCID: PMC7986707 DOI: 10.1113/jp281044] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/04/2021] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS Mouse chromaffin cells in acute adrenal slices exhibit two distinct spiking patterns, a repetitive mode and a bursting mode. A sodium background conductance operates at rest as demonstrated by the membrane hyperpolarization evoked by a low Na+ -containing extracellular saline. This sodium background current is insensitive to TTX, is not blocked by Cs+ ions and displays a linear I-V relationship at potentials close to chromaffin cell resting potential. Its properties are reminiscent of those of the sodium leak channel NALCN. In the adrenal gland, Nalcn mRNA is selectively expressed in chromaffin cells. The study fosters our understanding of how the spiking pattern of chromaffin cells is regulated and adds a sodium background conductance to the list of players involved in the stimulus-secretion coupling of the adrenomedullary tissue. ABSTRACT Chromaffin cells (CCs) are the master neuroendocrine units for the secretory function of the adrenal medulla and a finely-tuned regulation of their electrical activity is required for appropriate catecholamine secretion in response to the organismal demand. Here, we aim at deciphering how the spiking pattern of mouse CCs is regulated by the ion conductances operating near the resting membrane potential (RMP). At RMP, mouse CCs display a composite firing pattern, alternating between active periods composed of action potentials spiking with a regular or a bursting mode, and silent periods. RMP is sensitive to changes in extracellular sodium concentration, and a low Na+ -containing saline hyperpolarizes the membrane, regardless of the discharge pattern. This RMP drive reflects the contribution of a depolarizing conductance, which is (i) not blocked by tetrodotoxin or caesium, (ii) displays a linear I-V relationship between -110 and -40 mV, and (iii) is carried by cations with a conductance sequence gNa > gK > gCs . These biophysical attributes, together with the expression of the sodium-leak channel Nalcn transcript in CCs, state credible the contribution of NALCN. This inaugural report opens new research routes in the field of CC stimulus-secretion coupling, and extends the inventory of tissues in which NALCN is expressed to neuroendocrine glands.
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Affiliation(s)
- Alexandre Milman
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | | | - Jean-Louis Bossu
- Institut des Neurosciences Cellulaires et Intégratives, CNRS UPR 3212, Strasbourg, France
| | - Pierre Fontanaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France
| | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | - Philippe Lory
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
| | - Nathalie C Guérineau
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France.,LabEx "Ion Channel Science and Therapeutics", Montpellier, France
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Baraibar AM, Hernández-Guijo JM. Micromolar concentrations of Zn 2+ depress cellular excitability through a blockade of calcium current in rat adrenal slices. Toxicology 2020; 444:152543. [PMID: 32858065 DOI: 10.1016/j.tox.2020.152543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/08/2020] [Accepted: 07/25/2020] [Indexed: 11/30/2022]
Abstract
The present work, using chromaffin cells in rat adrenal slices (RCCs), aims to describe what type of ionic current alterations induced by zinc underlies their effects reported on synaptic transmission. Thus, Zn2+ blocked calcium channels of RCCs in a time- and concentration-dependent manner with an IC50 of 391 μM. This blockade was partially reversed upon washout and was greater at more depolarizing holding potentials (i.e. 32 ± 5% at -110 mV, and 43 ± 6% at -50 mV, after 5 min perfusion). In ω-toxins-sensitive calcium channels (N-, P- and Q-types), Zn2+caused a lower blockade of ICa, 33.3%, than in ω-toxins-resistant ones (L-type, 55.3%; and R-type, 90%). This compound inhibited calcium current at all test potentials and shows a shift of the I-V curve to more depolarized values of about 10 mV. The sodium current was not blocked by acute application of high Zn2+concentrations. Voltage-dependent potassium current was marginally affected by high Zn2+ concentrations showing no concentration-dependence. Nevertheless, calcium- and voltage-dependent potassium current was drastically depressed in a dose-dependent manner, with an IC50 of 453 μM. This blockade was related to the prevention of Ca2+ influx through voltage-dependent calcium channels coupled to BK channels. Under current-clamp conditions, RCCs exhibit a resting potential of -50.7 mV, firing spontaneous APs (1-2 spikes/s) generated by the opening of Na+ and Ca2+-channels, and terminated by the activation of voltage and Ca2+-activated K+-channels (BK). We found that the blockade of these ionic currents by Zn2+ led to a drastic alteration of cellular excitability with a depolarization of the membrane potential, the slowdown and broadening of the APs and the severe reduction of the after hyperpolarization (AHP) which led to a decrease in the APs firing frequency. Taken together, these results point to a neurotoxic action evoked by zinc that is associated with changes to cellular excitability by blocking the ionic currents responsible for both the neurotransmitter release and the action potentials firing.
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Affiliation(s)
- Andrés M Baraibar
- Department of Neuroscience, University of Minnesota, 4-260 Wallin Medical Biosciences Building, 2101 6th Street SE, Minneapolis, MN, 55455, USA
| | - Jesús M Hernández-Guijo
- Department of Pharmacology and Therapeutic, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain; Instituto Teófilo Hernando, Facultad de Medicina, Univ. Autónoma de Madrid, Av. Arzobispo Morcillo 4, 28029, Madrid, Spain; Instituto Ramón y Cajal de Investigación Sanitaria, IRYCIS, Hospital Ramón y Cajal, Ctra. de Colmenar Viejo, Km. 9,100, 28029, Madrid, Spain.
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Guérineau NC. Cholinergic and peptidergic neurotransmission in the adrenal medulla: A dynamic control of stimulus‐secretion coupling. IUBMB Life 2019; 72:553-567. [DOI: 10.1002/iub.2117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 06/18/2019] [Indexed: 12/17/2022]
Affiliation(s)
- Nathalie C. Guérineau
- IGFUniv. Montpellier, CNRS, INSERM Montpellier France
- LabEx “Ion Channel Science and Therapeutics” Montpellier France
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Schwerdtfeger LA, Tobet SA. From organotypic culture to body-on-a-chip: A neuroendocrine perspective. J Neuroendocrinol 2019; 31:e12650. [PMID: 30307079 DOI: 10.1111/jne.12650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/02/2018] [Accepted: 10/07/2018] [Indexed: 12/22/2022]
Abstract
The methods used to study neuroendocrinology have been as diverse as the discoveries to come out of the field. Maintaining live neurones outside of a body in vitro was important from the beginning, building on methods that dated back to at least the first decade of the 20th Century. Neurosecretion defines an essential foundation of neuroendocrinology based on work that began in the 1920s and 1930s. Throughout the first half of the 20th Century, many paradigms arose for studying everything from single neurones to whole organs in vitro. Two of these survived as preeminent systems for use throughout the second half of the century: cell cultures and explant systems. Slice cultures and explants that emerged as organotypic technologies included such neuroendocrine organs such as the brain, pituitary, adrenals and intestine. The vast majority of these studies were carried out in static cultures for which media were changed over a time scale of days. Tissues were used for experimental techniques such as electrical recording of neuronal physiology in single cells and observation by live microscopy. When maintained in vitro, many of these systems only partially capture the in vivo physiology of the organ system of interest, often because of a lack of cellular diversity (eg, neuronal cultures lacking glia). Modern microfluidic methodologies show promise for organ systems, ranging from the reproductive to the gastrointestinal to the brain. Moving forward and striving to understand the mechanisms that drive neuroendocrine signalling centrally and peripherally, there will always be a need to consider the heterogeneous cellular compositions of organs in vivo.
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Affiliation(s)
- Luke A Schwerdtfeger
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
| | - Stuart A Tobet
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado
- School of Biomedical Engineering, Colorado State University, Fort Collins, Colorado
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9
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Alejandre-García T, Peña-del Castillo JG, Hernández-Cruz A. GABAA receptor: a unique modulator of excitability, Ca2+ signaling, and catecholamine release of rat chromaffin cells. Pflugers Arch 2017; 470:67-77. [DOI: 10.1007/s00424-017-2080-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/11/2017] [Accepted: 10/13/2017] [Indexed: 01/12/2023]
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10
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Roles of Na +, Ca 2+, and K + channels in the generation of repetitive firing and rhythmic bursting in adrenal chromaffin cells. Pflugers Arch 2017; 470:39-52. [PMID: 28776261 DOI: 10.1007/s00424-017-2048-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 07/23/2017] [Indexed: 12/30/2022]
Abstract
Adrenal chromaffin cells (CCs) are the main source of circulating catecholamines (CAs) that regulate the body response to stress. Release of CAs is controlled neurogenically by the activity of preganglionic sympathetic neurons through trains of action potentials (APs). APs in CCs are generated by robust depolarization following the activation of nicotinic and muscarinic receptors that are highly expressed in CCs. Bovine, rat, mouse, and human CCs also express a composite array of Na+, K+, and Ca2+ channels that regulate the resting potential, shape the APs, and set the frequency of AP trains. AP trains of increasing frequency induce enhanced release of CAs. If the primary role of CCs is simply to relay preganglionic nerve commands to CA secretion, why should they express such a diverse set of ion channels? An answer to this comes from recent observations that, like in neurons, CCs undergo complex firing patterns of APs suggesting the existence of an intrinsic CC excitability (non-neurogenically controlled). Recent work has shown that CCs undergo occasional or persistent burst firing elicited by altered physiological conditions or deletion of pore-regulating auxiliary subunits. In this review, we aim to give a rationale to the role of the many ion channel types regulating CC excitability. We will first describe their functional properties and then analyze how they contribute to pacemaking, AP shape, and burst waveforms. We will also furnish clear indications on missing ion conductances that may be involved in pacemaking and highlight the contribution of the crucial channels involved in burst firing.
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De Nardi F, Lefort C, Bréard D, Richomme P, Legros C, Guérineau NC. Monitoring the Secretory Behavior of the Rat Adrenal Medulla by High-Performance Liquid Chromatography-Based Catecholamine Assay from Slice Supernatants. Front Endocrinol (Lausanne) 2017; 8:248. [PMID: 28993760 PMCID: PMC5622411 DOI: 10.3389/fendo.2017.00248] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/11/2017] [Indexed: 12/21/2022] Open
Abstract
Catecholamine (CA) secretion from the adrenal medullary tissue is a key step of the adaptive response triggered by an organism to cope with stress. Whereas molecular and cellular secretory processes have been extensively studied at the single chromaffin cell level, data available for the whole gland level are much scarcer. We tackled this issue in rat by developing an easy to implement experimental strategy combining the adrenal acute slice supernatant collection with a high-performance liquid chromatography-based epinephrine and norepinephrine (NE) assay. This technique affords a convenient method for measuring basal and stimulated CA release from single acute slices, allowing thus to individually address the secretory function of the left and right glands. Our data point that the two glands are equally competent to secrete epinephrine and NE, exhibiting an equivalent epinephrine:NE ratio, both at rest and in response to a cholinergic stimulation. Nicotine is, however, more efficient than acetylcholine to evoke NE release. A pharmacological challenge with hexamethonium, an α3-containing nicotinic acetylcholine receptor antagonist, disclosed that epinephrine- and NE-secreting chromaffin cells distinctly expressed α3 nicotinic receptors, with a dominant contribution in NE cells. As such, beyond the novelty of CA assays from acute slice supernatants, our study contributes at refining the secretory behavior of the rat adrenal medullary tissue, and opens new perspectives for monitoring the release of other hormones and transmitters, especially those involved in the stress response.
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Affiliation(s)
- Frédéric De Nardi
- Mitochondrial and Cardiovascular Pathophysiology – MITOVASC, CNRS UMR6015, INSERM U1083, UBL/Angers University, Angers, France
| | - Claudie Lefort
- Mitochondrial and Cardiovascular Pathophysiology – MITOVASC, CNRS UMR6015, INSERM U1083, UBL/Angers University, Angers, France
| | - Dimitri Bréard
- EA921, SONAS, SFR QUASAV, UBL/Angers University, Angers, France
| | - Pascal Richomme
- EA921, SONAS, SFR QUASAV, UBL/Angers University, Angers, France
| | - Christian Legros
- Mitochondrial and Cardiovascular Pathophysiology – MITOVASC, CNRS UMR6015, INSERM U1083, UBL/Angers University, Angers, France
- *Correspondence: Christian Legros, ; Nathalie C. Guérineau,
| | - Nathalie C. Guérineau
- Mitochondrial and Cardiovascular Pathophysiology – MITOVASC, CNRS UMR6015, INSERM U1083, UBL/Angers University, Angers, France
- *Correspondence: Christian Legros, ; Nathalie C. Guérineau,
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Tzitzitlini AG, Pedro SC, Martha PAE, Rodolfo DL, Arturo HC. Modulation of spontaneous intracellular Ca²⁺ fluctuations and spontaneous cholinergic transmission in rat chromaffin cells in situ by endogenous GABA acting on GABAA receptors. Pflugers Arch 2015; 468:351-65. [PMID: 26490458 DOI: 10.1007/s00424-015-1744-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 09/21/2015] [Accepted: 10/04/2015] [Indexed: 12/30/2022]
Abstract
Using fluorescence [Ca(2+)]i imaging in rat adrenal slices, we characterized the effects of agonists and antagonists of the GABAA receptor (GABAA-R) on resting intracellular Ca(2+) ([Ca(2+)]i) and spontaneous [Ca(2+)]i fluctuations (SCFs) in hundreds of individual chromaffin cells (CCs) recorded simultaneously in situ. Muscimol, a GABAA-R agonist (20 μM; 25 s), induced an increase of resting [Ca(2+)]i in 43 ± 3 % of CCs, a decrease in 26 ± 2 %, and no response in 30 ± 5 %. In Ca(2+)-free external medium, SCFs ceased completely and muscimol failed to elicit [Ca(2+)]i rises. All muscimol-induced [Ca(2+)]i changes were blocked by the GABAA-R antagonist bicuculline, suggesting that they result from changes in membrane potential depending on the cell's Cl(-) equilibrium potential. Unexpectedly, bicuculline increased the amplitude and frequency of SCFs in 54 % of CCs, revealing a tonic inhibition of SCFs by ambient GABA acting through GABAA-R. Mecamylamine (a specific nicotinic cholinergic blocker) decreased basal SCF activity in 18 % of CCs and inhibited bicuculline-induced SCF intensification, suggesting that spontaneous acetylcholine (ACh) release from nerve endings contributes to SCF generation in CCs in situ and that blockade of presynaptic GABAA-Rs intensifies SCFs in part through the disinhibition of spontaneous cholinergic transmission. Electrophysiological experiments confirmed that spontaneous excitatory postsynaptic currents recorded from CCs in situ were enhanced by bicuculline. To our knowledge, this is the first description of a regulatory effect of endogenous GABA on synaptic currents and SCFs of adrenal CCs. These findings denote a novel GABA-mediated presynaptic and postsynaptic regulatory mechanism of CC activity which may participate in the control of catecholamine secretion.
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Affiliation(s)
- Alejandre-García Tzitzitlini
- Departamento Neurociencia Cognitiva, Instituto de Fisiología Celular, UNAM. Circuito de la Investigación Científica s/n, Ciudad Universitaria, México, D.F., C.P. 04510, México
| | - Segura-Chama Pedro
- Laboratorio Nacional de Canalopatías from Instituto de Fisiología Celular, México, México
- Unidad de Investigación en Medicina Experimental, México, México
| | - Pérez-Armendáriz E Martha
- Departamento de Biología Celular y Tisular, from Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, México, D.F., C.P. 04510, Mexico
| | - Delgado-Lezama Rodolfo
- Departamento de Fisiología Biofísica y Neurociencias, from Centro de Investigación y Estudios Avanzados del IPN, Ave. IPN 2508, México City, D.F., México
| | - Hernández-Cruz Arturo
- Departamento Neurociencia Cognitiva, Instituto de Fisiología Celular, UNAM. Circuito de la Investigación Científica s/n, Ciudad Universitaria, México, D.F., C.P. 04510, México.
- Laboratorio Nacional de Canalopatías from Instituto de Fisiología Celular, México, México.
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Albiñana E, Segura-Chama P, Baraibar AM, Hernández-Cruz A, Hernández-Guijo JM. Different contributions of calcium channel subtypes to electrical excitability of chromaffin cells in rat adrenal slices. J Neurochem 2015; 133:511-21. [DOI: 10.1111/jnc.13055] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 12/22/2014] [Accepted: 01/22/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Elisa Albiñana
- Departament of Pharmacology and Therapeutics; University Autónoma de Madrid; Madrid Spain
- Instituto Teófilo Hernando; University Autónoma de Madrid; Madrid Spain
- Facultad de Medicina; University Autónoma de Madrid; Madrid Spain
| | - Pedro Segura-Chama
- Unidad de Investigación de Medicina Experimental; Facultad de Medicina; Universidad Nacional Autónoma de México; Ciudad Universitaria; México City México
| | - Andres M. Baraibar
- Departament of Pharmacology and Therapeutics; University Autónoma de Madrid; Madrid Spain
- Instituto Teófilo Hernando; University Autónoma de Madrid; Madrid Spain
- Facultad de Medicina; University Autónoma de Madrid; Madrid Spain
| | - Arturo Hernández-Cruz
- Departamento de Neurociencia Cognitiva; Instituto de Fisiología Celular; Universidad Nacional Autónoma de México; Ciudad Universitaria; México City México
| | - Jesus M. Hernández-Guijo
- Departament of Pharmacology and Therapeutics; University Autónoma de Madrid; Madrid Spain
- Instituto Teófilo Hernando; University Autónoma de Madrid; Madrid Spain
- Facultad de Medicina; University Autónoma de Madrid; Madrid Spain
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Developmental Regulation of Glucosensing in Rat Adrenomedullary Chromaffin Cells: Potential Role of the KATP Channel. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 758:191-8. [DOI: 10.1007/978-94-007-4584-1_27] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
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Segura-Chama P, Rivera-Cerecedo CV, González-Ramírez R, Felix R, Hernández-Guijo JM, Hernández-Cruz A. Atypical Ca2+ currents in chromaffin cells from SHR and WKY rat strains result from the deficient expression of a splice variant of the α1D Ca2+ channel. Am J Physiol Heart Circ Physiol 2012; 302:H467-78. [DOI: 10.1152/ajpheart.00849.2011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ca2+ currents ( ICa) recorded from adrenal chromaffin cells (CCs) of spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats are similar to one another, but different from those recorded in other rodent species. ICa in WKY/SHR CCs comprises an early, transient ( ICae) and a late, sustained component ( ICas). In Wistar CCs, ICae is absent, and ICas is of greater amplitude. Activation and steady-state inactivation of ICae and ICas in WKY/SHR CCs suggest the recruitment of at least two populations of Ca2+ channels with different voltage dependence and kinetics. In WKY/SHR CCs, ICae is inhibited by nifedipine, enhanced by BAY K 8644, is not blocked by the mibefradil analog NNC 55–0396, and displays Ca2+-dependent inactivation and fast deactivation kinetics, suggesting that it results from the opening of L-type rather than T-type Ca2+ channels. ICae properties suggest that it originates from the opening of Ca2+ channels formed with the short splice variant (CaV1.342A). RT-PCR showed that expression of CaV1.342A mRNA is similar in both Wistar and WKY/SHR, but that the long variant (CaV1.342) is virtually absent in WKY/SHR. Thus ICae corresponds to the recruitment of CaV1.342A channels, unmasked by the absence of CaV1.342 channels. Studies in WKY CCs do not report major functional alterations, despite the unusual expression pattern of CaV1.3 splice variants. It remains to be established if more subtle functional alterations exist, and if the atypical splicing pattern of CaV1.3 could be related to the functional and behavioral alterations reported in WKY/SHR rats, including their susceptibility to develop hypertension.
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Affiliation(s)
| | - Claudia V. Rivera-Cerecedo
- Unidad Académica Bioterio, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, and
| | - Ricardo González-Ramírez
- Departamento de Biología Molecular e Histocompatibilidad, Hospital General “Dr. Manuel Gea González”, Secretaría de Salud, Mexico City; and
| | - Ricardo Felix
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico; and
| | - Jesús M. Hernández-Guijo
- Departamento de Farmacología y Terapéutica, Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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16
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Colomer C, Martin AO, Desarménien MG, Guérineau NC. Gap junction-mediated intercellular communication in the adrenal medulla: an additional ingredient of stimulus-secretion coupling regulation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:1937-51. [PMID: 21839720 DOI: 10.1016/j.bbamem.2011.07.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/20/2011] [Accepted: 07/25/2011] [Indexed: 01/28/2023]
Abstract
The traditional understanding of stimulus-secretion coupling in adrenal neuroendocrine chromaffin cells states that catecholamines are released upon trans-synaptic sympathetic stimulation mediated by acetylcholine released from the splanchnic nerve terminals. Although this statement remains largely true, it deserves to be tempered. In addition to its neurogenic control, catecholamine secretion also depends on a local gap junction-mediated communication between chromaffin cells. We review here the insights gained since the first description of gap junctions in the adrenal medullary tissue. Adrenal stimulus-secretion coupling now appears far more intricate than was previously envisioned and its deciphering represents a challenge for neurobiologists engaged in the study of the regulation of neuroendocrine secretion. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.
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Affiliation(s)
- Claude Colomer
- Institut de Génomique Fonctionnelle, F-34000 Montpellier, France
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17
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Han TH, Lim CJ, Choi JH, Lee SY, Ryu PD. Viability assessment of primo-node slices from organ surface primo-vascular tissues in rats. J Acupunct Meridian Stud 2011; 3:241-8. [PMID: 21185538 DOI: 10.1016/s2005-2901(10)60043-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 10/14/2010] [Indexed: 02/04/2023] Open
Abstract
The primo-vascular system is a novel thread-like structure which is recently rediscovered, but its cellular properties are largely unknown. In this study, a slice preparation for primo-nodes was developed to facilitate study of the cellular properties of primo-node cells in vitro. Slices (4-8 slices; 200 μm thick) were sectioned from single primo-nodes collected from the abdominal organ surface of rats and incubated in oxygenated Krebs solution at 25°C or 31°C for up to 7 hours. Trypan blue staining and whole-cell patch-clamp recordings were performed to estimate the viability of cells in the slices. Viability was largely maintained during the first 3 hours, but subsequently decreased (from 80% to 21%, p < 0.001). In addition, the viability of slices incubated at 31°C was higher than those incubated at 25°C (80%vs. 47%, p < 0.001). In whole-cell patch-clamp experiments, high resistance seals readily formed and primo-node cells showed a mean resting membrane potential (-38 mV) comparable to that recorded with sharp electrodes and outwardly-rectifying current-voltage relationships. The results show that the primo-node slices developed in this study maintained viability for up to 4 hours in vitro.
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Affiliation(s)
- Tae Hee Han
- Laboratory of Veterinary Pharmacology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, Korea
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18
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Hernández A, Segura-Chama P, Jiménez N, García AG, Hernández-Guijo JM, Hernández-Cruz A. Modulation by endogenously released ATP and opioids of chromaffin cell calcium channels in mouse adrenal slices. Am J Physiol Cell Physiol 2010; 300:C610-23. [PMID: 21160033 DOI: 10.1152/ajpcell.00380.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Modulation of high-threshold voltage-dependent calcium channels by neurotransmitters has been the subject of numerous studies in cultures of neurons and chromaffin cells. However, no studies on such modulation exist in chromaffin cells in their natural environment, the intact adrenal medullary tissue. Here we performed such a study in voltage-clamped chromaffin cells of freshly prepared mouse adrenal slices under the whole cell configuration of the patch-clamp technique. The subcomponents of the whole cell inward Ca(2+) current (I(Ca)) accounted for 49% for L-, 28% for N-, and 36% for P/Q-type channels. T-type Ca(2+) channels or residual R-type Ca(2+) currents were not seen. However, under the perforated-patch configuration, 20% of I(Ca) accounted for a toxin-resistant R-type Ca(2+) current. Exogenously applied ATP and methionine-enkephalin (Met-enk) inhibited I(Ca) by 33%. Stop-flow and Ca(2+) replacement by Ba(2+), which favored the release of endogenous ATP and opioids, also inhibited I(Ca), with no changes in activation or inactivation kinetics. This inhibition was partially voltage independent and insensitive to prepulse facilitation. Furthermore, in about half of the cells, suramin and naloxone augmented I(Ca) in the absence of exogenous application of ATP/Met-enk. No additional modulation of I(Ca) was obtained after bath application of exogenous ATP and opioids to these already inhibited cells. Augmentation of I(Ca) was also seen upon intracellular dialysis of guanosine 5'-[β-thio]diphosphate (GDPβS), indicating the existence in the intact slice of a tonic inhibition of I(Ca) in resting conditions. These results suggest that in the intact adrenal tissue a tonic inhibition of I(Ca) exists, mediated by purinergic and opiate receptors.
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Affiliation(s)
- A Hernández
- Instituto Teófilo Hernando, Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Av. Arzobispo Morcillo 4, E-28029 Madrid, Spain
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19
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Comparison of Ca2+ Currents of Chromaffin Cells from Normotensive Wistar Kyoto and Spontaneously Hypertensive Rats. Cell Mol Neurobiol 2010; 30:1243-50. [DOI: 10.1007/s10571-010-9566-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Accepted: 09/02/2010] [Indexed: 10/18/2022]
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20
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Walsh PL, Petrovic J, Wightman RM. Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry. Am J Physiol Cell Physiol 2010; 300:C49-57. [PMID: 21048165 DOI: 10.1152/ajpcell.00332.2010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Electrical stimulation is an indispensible tool in studying electrically excitable tissues in neurobiology and neuroendocrinology. In this work, the consequences of high-intensity electrical stimulation on the release of catecholamines from adrenal gland slices were examined with fast-scan cyclic voltammetry at carbon fiber microelectrodes. A biphasic signal, consisting of a fast and slow phase, was observed when electrical stimulations typically used in tissue slices (10 Hz, 350 μA biphasic, 2.0 ms/phase pulse width) were applied to bipolar tungsten-stimulating electrodes. This signal was found to be stimulation dependent, and the slow phase of the signal was abolished when smaller (≤250 μA) and shorter (1 ms/phase) stimulations were used. The slow phase of the biphasic signal was found to be tetrodotoxin and hexamethonium independent, while the fast phase was greatly reduced using these pharmacological agents. Two different types of calcium responses were observed, where the fast phase was abolished by perfusion with a low-calcium buffer while both the fast and slow phases could be modulated when Ca²(+) was completely excluded from the solution using EGTA. Perfusion with nifedipine resulted in the reduction of the slow catecholamine release to 29% of the original signal, while the fast phase was only decreased to 74% of predrug values. From these results, it was determined that high-intensity stimulations of the adrenal medulla result in depolarizing not only the splanchnic nerves, but also the chromaffin cells themselves resulting in a biphasic catecholamine release.
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Affiliation(s)
- Paul L Walsh
- Department of Chemistry, University of North Carolina, Chapel Hill, 27599-3290, USA
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21
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Petrovic J, Walsh PL, Thornley KT, Miller CE, Wightman RM. Real-time monitoring of chemical transmission in slices of the murine adrenal gland. Endocrinology 2010; 151:1773-83. [PMID: 20181796 PMCID: PMC2850225 DOI: 10.1210/en.2009-1324] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The real-time electrochemical detection of catecholamine secretion from murine adrenal slices using fast-scan cyclic voltammetry (FSCV) and amperometry at carbon fiber microelectrodes is described. Bright-field and immunofluorescent microscopy supported that chromaffin cells in the adrenal medulla are organized into clusters and positively stain for tyrosine hydroxylase confirming that they are catecholaminergic. Spontaneous exocytotic catecholamine events were observed inside chromaffin cell clusters with both FSCV and amperometry and were modulated by the nicotinic acetylcholine receptor antagonist hexamethonium and low extracellular calcium. Reintroduction of extracellular calcium and pressure ejection of acetylcholine caused the frequency of spikes to increase back to predrug levels. Electrical stimulation caused the synchronous secretion from multiple cells within the gland, which were modulated by nicotinic acetylcholine receptors but not muscarinic receptors or gap junctions. Furthermore, electrically stimulated release was abolished with perfusion of low extracellular calcium or tetrodotoxin, indicating that the release requires electrical excitability. An extended waveform was used to study the spontaneous and stimulated release events to determine their chemical content by FSCV. Consistent with total content analysis and immunohistochemical studies, about two thirds of the cells studied spontaneously secreted epinephrine, whereas one third secreted norepinephrine. Whereas adrenergic sites contained mostly epinephrine during electrical stimulation, noradrenergic sites contained a mixture of the catecholamines showing the heterogeneity of the adrenal medulla.
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Affiliation(s)
- Jelena Petrovic
- Neuroscience Center (R.M.W.), Caudill Laboratories, Venable Hall B-5, CB 3290, Chapel Hill, North Carolina 27599-3290, USA
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22
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de Diego AMG. Electrophysiological and morphological features underlying neurotransmission efficacy at the splanchnic nerve-chromaffin cell synapse of bovine adrenal medulla. Am J Physiol Cell Physiol 2009; 298:C397-405. [PMID: 19940070 DOI: 10.1152/ajpcell.00440.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The ability of adrenal chromaffin cells to fast-release catecholamines relies on their capacity to fire action potentials (APs). However, little attention has been paid to the requirements needed to evoke the controlled firing of APs. Few data are available in rodents and none on the bovine chromaffin cell, a model extensively used by researchers. The aim of this work was to clarify this issue. Short puffs of acetylcholine (ACh) were fast perifused to current-clamped chromaffin cells and produced the firing of single APs. Based on the currents generated by such ACh applications and previous literature, current waveforms that efficiently elicited APs at frequencies up to 20 Hz were generated. Complex waveforms were also generated by adding simple waveforms with different delays; these waveforms aimed at modeling the stimulation patterns that a chromaffin cell would conceivably undergo upon strong synaptic stimulation. Cholinergic innervation was assessed using the acetylcholinesterase staining technique on the supposition that the innervation pattern is a determinant of the kind of stimuli chromaffin cells can receive. It is concluded that 1) a reliable method to produce frequency-controlled APs by applying defined current injection waveforms is achieved; 2) the APs thus generated have essentially the same features as those spontaneously emitted by the cell and those elicited by fast-ACh perifusion; 3) the higher frequencies attainable peak at around 30 Hz; and 4) the bovine adrenal medulla shows abundant cholinergic innervation, and chromaffin cells show strong acetylcholinesterase staining, consistent with a tight cholinergic presynaptic control of firing frequency.
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Affiliation(s)
- Antonio M G de Diego
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Instituto Teófilo Hernando, Universidad Autónoma de Madrid, Arzobispo Morcillo, 4, 28029 Madrid, Spain.
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23
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Chen XW, Feng YQ, Hao CJ, Guo XL, He X, Zhou ZY, Guo N, Huang HP, Xiong W, Zheng H, Zuo PL, Zhang CX, Li W, Zhou Z. DTNBP1, a schizophrenia susceptibility gene, affects kinetics of transmitter release. ACTA ACUST UNITED AC 2008; 181:791-801. [PMID: 18504299 PMCID: PMC2396815 DOI: 10.1083/jcb.200711021] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Schizophrenia is one of the most debilitating neuropsychiatric disorders, affecting 0.5–1.0% of the population worldwide. Its pathology, attributed to defects in synaptic transmission, remains elusive. The dystrobrevin-binding protein 1 (DTNBP1) gene, which encodes a coiled-coil protein, dysbindin, is a major susceptibility gene for schizophrenia. Our previous results have demonstrated that the sandy (sdy) mouse harbors a spontaneously occurring deletion in the DTNBP1 gene and expresses no dysbindin protein (Li, W., Q. Zhang, N. Oiso, E.K. Novak, R. Gautam, E.P. O'Brien, C.L. Tinsley, D.J. Blake, R.A. Spritz, N.G. Copeland, et al. 2003. Nat. Genet. 35:84–89). Here, using amperometry, whole-cell patch clamping, and electron microscopy techniques, we discovered specific defects in neurosecretion and vesicular morphology in neuroendocrine cells and hippocampal synapses at the single vesicle level in sdy mice. These defects include larger vesicle size, slower quantal vesicle release, lower release probability, and smaller total population of the readily releasable vesicle pool. These findings suggest that dysbindin functions to regulate exocytosis and vesicle biogenesis in endocrine cells and neurons. Our work also suggests a possible mechanism in the pathogenesis of schizophrenia at the synaptic level.
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Affiliation(s)
- Xiao-Wei Chen
- Institute of Molecular Medicine and 2State Key Laboratory of Biomembrane Engineering, Peking University, Beijing 100871, China
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24
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Chen XW, Huang W, Yan JA, Fan HX, Guo N, Lü J, Xiu Y, Gu JL, Zhang CX, Ruan HZ, Hu ZA, Yu ZP, Zhou Z. Reinvestigation of the effect of orexin A on catecholamine release from adrenal chromaffin cells. Neurosci Lett 2008; 436:181-4. [DOI: 10.1016/j.neulet.2008.03.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 02/26/2008] [Accepted: 03/07/2008] [Indexed: 11/16/2022]
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25
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Abstract
Excitation-secretion coupling in adrenomedullary chromaffin cells physiologically commences when acetylcholine molecules released from splanchnic nerve terminals bind to cholinergic receptors located at the cell's plasma membrane. While nicotinic acetylcholine receptors ensure a rapid and efficacious transmission of preganglionic impulses, muscarinic acetylcholine receptors are considered to play a subsidiary role mostly by facilitating the nicotinic responses. Nevertheless, the variety of effects brought about by muscarinic stimulation in chromaffin cells (release of intracellular Ca2+, activation of Ca2+ entry through non-selective cation channels and voltage-dependent Ca2+ channels, impairment and/or enhancement of action potential firing, etc.) and the long-lasting nature of many of them suggests that muscarinic receptors might contribute to the fine tuning of the catecholamine secretory response upon graded preganglionic stimulation and prolonged periods of time. Such a variety of effects probably reflects not only the diversity of muscarinic receptors expressed in chromaffin cells but also the existence of differences among the animal species employed in the reported investigations. Accordingly, we first review on an animal species-based approach the most relevant features of the muscarinic response in chromaffin cells from a set of mammals, and finally present a unified picture of the mechanisms of muscarinic excitation-secretion coupling in chromaffin cells.
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Affiliation(s)
- L Olivos
- Department of Toxicology and Pharmacology, School of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain
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26
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García-Fernández M, Mejías R, López-Barneo J. Developmental changes of chromaffin cell secretory response to hypoxia studied in thin adrenal slices. Pflugers Arch 2006; 454:93-100. [PMID: 17165070 DOI: 10.1007/s00424-006-0186-y] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Revised: 10/16/2006] [Accepted: 11/30/2006] [Indexed: 11/30/2022]
Abstract
Adrenomedullary chromaffin (AMC) cells are sensitive to hypoxia in the newborn, but whether this property is lost during postnatal maturation is a matter of controversy. We have developed a rat adrenal slice preparation that allows the study of neonatal and adult AMC cell sensitivity to hypoxia in almost optimal physiological conditions. Responses to secretagogues can be quantitatively and noninvasively monitored in intact cells by amperometry. We have found hypoxia "responsive" (R) and "non-responsive" AMC cells in both neonatal (P0-P8) and juvenile/adult (P12-P60) adrenal glands. However, in the neonate, the proportion of R cells and the magnitude of the response to hypoxia were larger than in the adult. This developmental change of hypoxia responsiveness did not seem to depend on a decrease of the AMC cell's excitability. Spontaneous secretory activity in slices from adult rats was even increased with respect to neonatal animals. The analysis of the secretory events suggests that changes in spike frequency, rather than in vesicle size, account for the increased basal secretion rate in adult AMC cells. Thus, we report a major, but not complete, loss of direct hypoxia sensitivity in adult AMC cells. The adrenal slice appears to be a valuable technique to study acute O(2) sensing and its modifications in pathophysiological states.
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Affiliation(s)
- María García-Fernández
- Laboratorio de Investigaciones Biomédicas, Edificio de Laboratorios, Hospital Universitario Virgen del Rocío, Avenida Manuel Siurot s/n, 41013 Seville, Spain
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27
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Arroyo G, Fuentealba J, Sevane-Fernández N, Aldea M, García AG, Albillos A. Amperometric Study of the Kinetics of Exocytosis in Mouse Adrenal Slice Chromaffin Cells: Physiological and Methodological Insights. J Neurophysiol 2006; 96:1196-202. [PMID: 16723417 DOI: 10.1152/jn.00088.2006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was designed to examine the kinetics of neurotransmitter release using the carbon fiber amperometric technique on cells in slices of mouse adrenal glands superfused with bicarbonate phosphate buffer–based solutions. The exocytotic amperometric response evoked by electrical stimulation was significantly faster than that produced after exogenous application of ACh or K+. Splanchnic nerve–evoked neurotransmitter release was blocked by hexamethonium, indicating the involvement of ACh nicotinic receptors. We discuss the implications of our data for understanding the mechanisms underlying the vesicle fusion process.
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Affiliation(s)
- Gloria Arroyo
- Instituto Teófilo Hernando, Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
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28
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Gap junctions mediate electrical signaling and ensuing cytosolic Ca2+ increases between chromaffin cells in adrenal slices: A role in catecholamine release. J Neurosci 2001. [PMID: 11466411 DOI: 10.1523/jneurosci.21-15-05397.2001] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In adrenal chromaffin cells, a rise in cytosolic calcium concentration ([Ca(2+)]i) is a key event in the triggering of catecholamine exocytosis after splanchnic nerve activation. Action potential- or nicotine-induced [Ca(2+)]i transients are well described in individual chromaffin cells, but whether they remain spatially confined to the stimulated cell or propagate to adjacent cells is not yet known. To address this issue, the spatiotemporal organization of electrical and associated Ca(2+) events between chromaffin cells was investigated using the patch-clamp technique and real-time confocal imaging in rat acute adrenal slices. Spontaneous or electrically evoked action potential-driven [Ca(2+)]i transients were simultaneously detected in neighboring cells. This was likely attributable to gap junction-mediated electrotonic communication, as shown by (1) the bidirectional reflection of voltage changes monitored between cell pairs, (2) Lucifer yellow (LY) diffusion between cells exhibiting spontaneous synchronized [Ca(2+)]i transients, and (3) the reduction of LY diffusion using the uncoupling agent carbenoxolone. Furthermore, transcripts encoding two connexins (Cx36 and Cx43) were found in single chromaffin cells. This gap junctional coupling was activated after a synaptic-like application of nicotine that mediated synchronous multicellular [Ca(2+)]i increases. In addition, nicotinic stimulation of a single cell triggered catecholamine release in coupled cells, as shown by amperometric detection of secretory events. Functional coupling between chromaffin cells in situ may represent an efficient complement to synaptic transmission to amplify catecholamine release after synaptic stimulation of a single excited chromaffin cell.
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