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Uzungil V, Luza S, Opazo CM, Mees I, Li S, Ang CS, Williamson NA, Bush AI, Hannan AJ, Renoir T. Phosphoproteomics implicates glutamatergic and dopaminergic signalling in the antidepressant-like properties of the iron chelator deferiprone. Neuropharmacology 2024; 246:109837. [PMID: 38184274 DOI: 10.1016/j.neuropharm.2024.109837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 01/02/2024] [Accepted: 01/03/2024] [Indexed: 01/08/2024]
Abstract
BACKGROUND Current antidepressants have limitations due to insufficient efficacy and delay before improvement in symptoms. Polymorphisms of the serotonin transporter (5-HTT) gene have been linked to depression (when combined with stressful life events) and altered response to selective serotonergic reuptake inhibitors. We have previously revealed the antidepressant-like properties of the iron chelator deferiprone in the 5-HTT knock-out (KO) mouse model of depression. Furthermore, deferiprone was found to alter neural activity in the prefrontal cortex of both wild-type (WT) and 5-HTT KO mice. METHODS In the current study, we examined the molecular effects of acute deferiprone treatment in the prefrontal cortex of both genotypes via phosphoproteomics analysis. RESULTS In WT mice treated with deferiprone, there were 22 differentially expressed phosphosites, with gene ontology analysis implicating cytoskeletal proteins. In 5-HTT KO mice treated with deferiprone, we found 33 differentially expressed phosphosites. Gene ontology analyses revealed phosphoproteins that were predominantly involved in synaptic and glutamatergic signalling. In a drug-naïve cohort (without deferiprone administration), the analysis revealed 21 differentially expressed phosphosites in 5-HTT KO compared to WT mice. We confirmed the deferiprone-induced increase in tyrosine hydroxylase serine 40 residue phosphorylation (pTH-Ser40) (initially revealed in our phosphoproteomics study) by Western blot analysis, with deferiprone increasing pTH-Ser40 expression in WT and 5-HTT KO mice. CONCLUSION As glutamatergic and synaptic signalling are dysfunctional in 5-HTT KO mice (and are the target of fast-acting antidepressant drugs such as ketamine), these molecular effects may underpin deferiprone's antidepressant-like properties. Furthermore, dopaminergic signalling may also be involved in deferiprone's antidepressant-like properties.
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Affiliation(s)
- Volkan Uzungil
- Melbourne Brain Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Sandra Luza
- Melbourne Dementia Research Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia; Melbourne Neuropsychiatry Centre, Department of Psychiatry, The University of Melbourne & Melbourne Health, Carlton, VIC, Australia
| | - Carlos M Opazo
- Melbourne Dementia Research Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Isaline Mees
- Melbourne Brain Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Shanshan Li
- Melbourne Brain Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Ching-Seng Ang
- Bio21 Mass Spectrometry and Proteomics Facility, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Nicholas A Williamson
- Bio21 Mass Spectrometry and Proteomics Facility, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Ashley I Bush
- Melbourne Dementia Research Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia
| | - Anthony J Hannan
- Melbourne Brain Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia; Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Australia
| | - Thibault Renoir
- Melbourne Brain Centre, Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Australia; Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Australia.
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Abstract
Electrical synapses are an omnipresent feature of nervous systems, from the simple nerve nets of cnidarians to complex brains of mammals. Formed by gap junction channels between neurons, electrical synapses allow direct transmission of voltage signals between coupled cells. The relative simplicity of this arrangement belies the sophistication of these synapses. Coupling via electrical synapses can be regulated by a variety of mechanisms on times scales ranging from milliseconds to days, and active properties of the coupled neurons can impart emergent properties such as signal amplification, phase shifts and frequency-selective transmission. This article reviews the biophysical characteristics of electrical synapses and some of the core mechanisms that control their plasticity in the vertebrate central nervous system.
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Affiliation(s)
- Sebastian Curti
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
| | - John O'Brien
- Department of Ophthalmology & Visual Science, University of Texas Health Science Center, Houston, TX, USA.
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Moore KB, O'Brien J. Connexins in neurons and glia: targets for intervention in disease and injury. Neural Regen Res 2015; 10:1013-7. [PMID: 26330808 PMCID: PMC4541216 DOI: 10.4103/1673-5374.160092] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/14/2015] [Indexed: 01/13/2023] Open
Abstract
Both neurons and glia throughout the central nervous system are organized into networks by gap junctions. Among glia, gap junctions facilitate metabolic homeostasis and intercellular communication. Among neurons, gap junctions form electrical synapses that function primarily for communication. However, in neurodegenerative states due to disease or injury gap junctions may be detrimental to survival. Electrical synapses may facilitate hyperactivity and bystander killing among neurons, while gap junction hemichannels in glia may facilitate inflammatory signaling and scar formation. Advances in understanding mechanisms of plasticity of electrical synapses and development of molecular therapeutics to target glial gap junctions and hemichannels offer new hope to pharmacologically limit neuronal degeneration and enhance recovery.
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Affiliation(s)
- Keith B Moore
- Richard S. Ruiz, M.D. Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, TX, USA
| | - John O'Brien
- Richard S. Ruiz, M.D. Department of Ophthalmology & Visual Science, The University of Texas Health Science Center at Houston, TX, USA ; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, USA
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4
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Belousov AB, Fontes JD. Neuronal gap junctions: making and breaking connections during development and injury. Trends Neurosci 2013; 36:227-36. [PMID: 23237660 PMCID: PMC3609876 DOI: 10.1016/j.tins.2012.11.001] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 11/02/2012] [Accepted: 11/02/2012] [Indexed: 01/08/2023]
Abstract
In the mammalian central nervous system (CNS), coupling of neurons by gap junctions (i.e., electrical synapses) and the expression of the neuronal gap junction protein, connexin 36 (Cx36), transiently increase during early postnatal development. The levels of both subsequently decline and remain low in the adult, confined to specific subsets of neurons. However, following neuronal injury [such as ischemia, traumatic brain injury (TBI), and epilepsy], the coupling and expression of Cx36 rise. Here we summarize new findings on the mechanisms of regulation of Cx36-containing gap junctions in the developing and mature CNS and following injury. We also review recent studies suggesting various roles for neuronal gap junctions and in particular their role in glutamate-mediated neuronal death.
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Affiliation(s)
- Andrei B Belousov
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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5
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Lynn BD, Li X, Nagy JI. Under construction: building the macromolecular superstructure and signaling components of an electrical synapse. J Membr Biol 2012; 245:303-17. [PMID: 22722764 PMCID: PMC3506381 DOI: 10.1007/s00232-012-9451-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 06/01/2012] [Indexed: 10/28/2022]
Abstract
A great deal is now known about the protein components of tight junctions and adherens junctions, as well as how these are assembled. Less is known about the molecular framework of gap junctions, but these also have membrane specializations and are subject to regulation of their assembly and turnover. Thus, it is reasonable to consider that these three types of junctions may share macromolecular commonalities. Indeed, the tight junction scaffolding protein zonula occluden-1 (ZO-1) is also present at adherens and gap junctions, including neuronal gap junctions. On the basis of these earlier observations, we more recently found that two additional proteins, AF6 and MUPP1, known to be associated with ZO-1 at tight and adherens junctions, are also components of neuronal gap junctions in rodent brain and directly interact with connexin36 (Cx36) that forms these junctions. Here, we show by immunofluorescence labeling that the cytoskeletal-associated protein cingulin, commonly found at tight junctions, is also localized at neuronal gap junctions throughout the central nervous system. In consideration of known functions related to ZO-1, AF6, MUPP1, and cingulin, our results provide a context in which to examine functional relationships between these proteins at Cx36-containing electrical synapses in brain--specifically, how they may contribute to regulation of transmission at these synapses, and how they may govern gap junction channel assembly and/or disassembly.
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Affiliation(s)
- B. D. Lynn
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Xinbo Li
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - J. I. Nagy
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
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6
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Li X, Lynn BD, Nagy JI. The effector and scaffolding proteins AF6 and MUPP1 interact with connexin36 and localize at gap junctions that form electrical synapses in rodent brain. Eur J Neurosci 2012; 35:166-81. [PMID: 22211808 DOI: 10.1111/j.1460-9568.2011.07947.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Electrical synapses formed by neuronal gap junctions composed of connexin36 (Cx36) occur in most major structures in the mammalian central nervous system. These synapses link ensembles of neurons and influence their network properties. Little is known about the macromolecular constituents of neuronal gap junctions or how transmission through electrical synapses is regulated at the level of channel conductance or gap junction assembly/disassembly. Such knowledge is a prerequisite to understanding the roles of gap junctions in neuronal circuitry. Gap junctions share similarities with tight and adhesion junctions in that all three reside at close plasma membrane appositions, and therefore may associate with similar structural and regulatory proteins. Previously, we reported that the tight junction-associated protein zonula occludens-1 (ZO-1) interacts with Cx36 and is localized at gap junctions. Here, we demonstrate that two proteins known to be associated with tight and adherens junctions, namely AF6 and MUPP1, are components of neuronal gap junctions in rodent brain. By immunofluorescence, AF6 and MUPP1 were co-localized with Cx36 in many brain areas. Co-immunoprecipitation and pull-down approaches revealed an association of Cx36 with AF6 and MUPP1, which required the C-terminus PDZ domain interaction motif of Cx36 for interaction with the single PDZ domain of AF6 and with the 10th PDZ domain of MUPP1. As AF6 is a target of the cAMP/Epac/Rap1 signalling pathway and MUPP1 is a scaffolding protein that interacts with CaMKII, the present results suggest that AF6 may be a target for cAMP/Epac/Rap1 signalling at electrical synapses, and that MUPP1 may contribute to anchoring CaMKII at these synapses.
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Affiliation(s)
- X Li
- Department of Physiology, Faculty of Medicine, University of Manitoba, 745 Bannatyne Ave., Winnipeg, Manitoba, Canada
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Pandarinath C, Bomash I, Victor JD, Prusky GT, Tschetter WW, Nirenberg S. A novel mechanism for switching a neural system from one state to another. Front Comput Neurosci 2010; 4:2. [PMID: 20407612 PMCID: PMC2856633 DOI: 10.3389/fncom.2010.00002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2009] [Accepted: 02/27/2010] [Indexed: 11/30/2022] Open
Abstract
An animal's ability to rapidly adjust to new conditions is essential to its survival. The nervous system, then, must be built with the flexibility to adjust, or shift, its processing capabilities on the fly. To understand how this flexibility comes about, we tracked a well-known behavioral shift, a visual integration shift, down to its underlying circuitry, and found that it is produced by a novel mechanism – a change in gap junction coupling that can turn a cell class on and off. The results showed that the turning on and off of a cell class shifted the circuit's behavior from one state to another, and, likewise, the animal's behavior. The widespread presence of similar gap junction-coupled networks in the brain suggests that this mechanism may underlie other behavioral shifts as well.
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Affiliation(s)
- Chethan Pandarinath
- Department of Physiology and Biophysics, Weill Cornell Medical College, Cornell University New York, NY, USA
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Abstract
Histamine is a transmitter in the nervous system and a signaling molecule in the gut, the skin, and the immune system. Histaminergic neurons in mammalian brain are located exclusively in the tuberomamillary nucleus of the posterior hypothalamus and send their axons all over the central nervous system. Active solely during waking, they maintain wakefulness and attention. Three of the four known histamine receptors and binding to glutamate NMDA receptors serve multiple functions in the brain, particularly control of excitability and plasticity. H1 and H2 receptor-mediated actions are mostly excitatory; H3 receptors act as inhibitory auto- and heteroreceptors. Mutual interactions with other transmitter systems form a network that links basic homeostatic and higher brain functions, including sleep-wake regulation, circadian and feeding rhythms, immunity, learning, and memory in health and disease.
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Affiliation(s)
- Helmut L Haas
- Institute of Neurophysiology, Heinrich-Heine-University, Duesseldorf, Germany.
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9
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Poole SL, Lewis DI, Deuchars SA. Histamine depolarizes neurons in the dorsal vagal complex. Neurosci Lett 2007; 432:19-24. [PMID: 18162318 DOI: 10.1016/j.neulet.2007.11.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 11/20/2007] [Accepted: 11/29/2007] [Indexed: 11/17/2022]
Abstract
We sought to determine whether histamine has effects on single neurons in the dorsal vagal complex of the brainstem since previous studies have suggested a role for histamine receptors in this region. Using whole-cell patch clamp recordings from neurons within the nucleus of the tractus solitarius (NTS) and the dorsal vagal nucleus (DVN), histamine (20 microM) depolarized a small proportion of neurons in these regions accompanied by a decrease in input resistance. Although few neurons were depolarized (21% of NTS neurons and 15% of DVN neurons), those that were affected showed robust depolarizations of 13 mV. These depolarizations were antagonized by the histamine H1 receptor antagonist triprolidine (2 microM) and were subject to a level of desensitization. Neither histamine nor the H3 receptor agonist imetit caused any change in the amplitudes of excitatory or inhibitory postsynaptic potentials elicited in NTS neurons by stimulation of the solitary tract. These data indicate that histamine has a restricted but profound effect on neurons in the dorsal vagal complex.
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Affiliation(s)
- Sarah L Poole
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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10
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Whyment AD, Blanks AM, Lee K, Renaud LP, Spanswick D. Histamine Excites Neonatal Rat Sympathetic Preganglionic Neurons In Vitro Via Activation of H1 Receptors. J Neurophysiol 2006; 95:2492-500. [PMID: 16354729 DOI: 10.1152/jn.01135.2004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The role of histamine in regulating excitability of sympathetic preganglionic neurons (SPNs) and the expression of histamine receptor mRNA in SPNs was investigated using whole-cell patch-clamp electrophysiological recording techniques combined with single-cell reverse transcriptase polymerase chain reaction (RT-PCR) in transverse neonatal rat spinal cord slices. Bath application of histamine (100 μM) or the H1 receptor agonist histamine trifluoromethyl toluidide dimaleate (HTMT; 10 μM) induced membrane depolarization associated with a decrease in membrane conductance in the majority (70%) of SPNs tested, via activation of postsynaptic H1 receptors negatively coupled to one or more unidentified K+ conductances. Histamine and HTMT application also induced or increased the amplitude and/or frequency of membrane potential oscillations in electrotonically coupled SPNs. The H2 receptor agonist dimaprit (10 μM) or the H3 receptor agonist imetit (100 nM) were without significant effect on the membrane properties of SPNs. Histamine responses were sensitive to the H1 receptor antagonist triprolidine (10 μM) and the nonselective potassium channel blocker barium (1 mM) but were unaffected by the H2 receptor antagonist tiotidine (10 μM) and the H3 receptor antagonist, clobenpropit (5 μM). Single cell RT-PCR revealed mRNA expression for H1 receptors in 75% of SPNs tested, with no expression of mRNA for H2, H3, or H4 receptors. These data represent the first demonstration of H1 receptor expression in SPNs and suggest that histamine acts to regulate excitability of these neurons via a direct postsynaptic effect on H1 receptors.
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MESH Headings
- Action Potentials/drug effects
- Action Potentials/physiology
- Animals
- Animals, Newborn
- Autonomic Fibers, Preganglionic/chemistry
- Autonomic Fibers, Preganglionic/drug effects
- Autonomic Fibers, Preganglionic/physiology
- Barium/pharmacology
- Dimaprit/pharmacology
- Female
- Ganglia, Sympathetic/chemistry
- Ganglia, Sympathetic/drug effects
- Ganglia, Sympathetic/physiology
- Histamine/analogs & derivatives
- Histamine/pharmacology
- Histamine/physiology
- Histamine Agonists/pharmacology
- Histamine H1 Antagonists/pharmacology
- Imidazoles/pharmacology
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Neurons/chemistry
- Neurons/drug effects
- Neurons/physiology
- Patch-Clamp Techniques
- Potassium/physiology
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- Rats
- Rats, Inbred WKY
- Receptors, Histamine H1/genetics
- Receptors, Histamine H1/physiology
- Receptors, Histamine H2/physiology
- Receptors, Histamine H3/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Thiourea/analogs & derivatives
- Thiourea/pharmacology
- Triprolidine/pharmacology
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Affiliation(s)
- Andrew D Whyment
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, United Kingdom
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11
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Guix FX, Uribesalgo I, Coma M, Muñoz FJ. The physiology and pathophysiology of nitric oxide in the brain. Prog Neurobiol 2005; 76:126-52. [PMID: 16115721 DOI: 10.1016/j.pneurobio.2005.06.001] [Citation(s) in RCA: 480] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Revised: 06/10/2005] [Accepted: 06/14/2005] [Indexed: 12/11/2022]
Abstract
Nitric oxide (NO) is a molecule with pleiotropic effects in different tissues. NO is synthesized by NO synthases (NOS), a family with four major types: endothelial, neuronal, inducible and mitochondrial. They can be found in almost all the tissues and they can even co-exist in the same tissue. NO is a well-known vasorelaxant agent, but it works as a neurotransmitter when produced by neurons and is also involved in defense functions when it is produced by immune and glial cells. NO is thermodynamically unstable and tends to react with other molecules, resulting in the oxidation, nitrosylation or nitration of proteins, with the concomitant effects on many cellular mechanisms. NO intracellular signaling involves the activation of guanylate cyclase but it also interacts with MAPKs, apoptosis-related proteins, and mitochondrial respiratory chain or anti-proliferative molecules. It also plays a role in post-translational modification of proteins and protein degradation by the proteasome. However, under pathophysiological conditions NO has damaging effects. In disorders involving oxidative stress, such as Alzheimer's disease, stroke and Parkinson's disease, NO increases cell damage through the formation of highly reactive peroxynitrite. The paradox of beneficial and damaging effects of NO will be discussed in this review.
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Affiliation(s)
- F X Guix
- Laboratori de Fisiologia Molecular, Unitat de Senyalització Cellular, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Carrer Dr. Aiguader, 80, Barcelona 08003, Spain
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Abstract
Certain neurons in the mammalian brain have long been known to be joined by gap junctions, which are the most common type of electrical synapse. More recently, cloning of neuron-specific connexins, increased capability of visualizing cells within brain tissue, labeling of cell types by transgenic methods, and generation of connexin knockouts have spurred a rapid increase in our knowledge of the role of gap junctions in neural activity. This article reviews the many subtleties of transmission mediated by gap junctions and the mechanisms whereby these junctions contribute to synchronous firing.
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Affiliation(s)
- Michael V L Bennett
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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Belousov AB, Arumugam H, Denisova JV. Non-cholinergic excitation in neurons after a chronic glutamate receptor blockade. Neuroreport 2004; 15:113-7. [PMID: 15106842 DOI: 10.1097/00001756-200401190-00023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Previous experiments revealed a dramatic increase in excitatory acetylcholine transmission in hypothalamic cultures during a chronic decrease in glutamate activity. Data suggested that in the absence of glutamate excitation, acetylcholine becomes the major excitatory neurotransmitter. However, non-cholinergic excitatory activity was also detected in some neurons. Here, using calcium imaging in hypothalamic cultures chronically subjected to the glutamate receptor blockade, we demonstrate the contribution of metabotropic glutamate receptors, P2-purinoreceptors, histamine receptors, adrenoreceptors, and gap junctions, but not nitric oxide to this non-cholinergic excitation. We also show that the sensitivity of neurons to receptor agonists is increased following the blockade. Data suggest that multiple components contribute to the excitatory activity in hypothalamic neurons during a long-term decrease in glutamate activity.
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Affiliation(s)
- Andrei B Belousov
- Department of Cell and Molecular Biology, 2000 Percival Stern Hall, Tulane University, New Orleans, LA 70118, USA.
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Knigge U, Kjaer A, Kristoffersen U, Madsen K, Toftegaard C, Jørgensen H, Warberg J. Histamine and prostaglandin interaction in regulation of oxytocin and vasopressin secretion. J Neuroendocrinol 2003; 15:940-5. [PMID: 12969238 DOI: 10.1046/j.1365-2826.2003.01079.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prostaglandins and histamine in the hypothalamus are involved in the regulation of oxytocin and vasopressin secretion, and appear to be involved in the mediation of pituitary hormone responses to immunochallenges. Therefore, we investigated in conscious male rats: (i) whether blockade of H1 or H2 receptors affected the oxytocin and vasopressin responses to prostaglandins and (ii) whether blockade of prostaglandin synthesis affected the oxytocin and vasopressin responses to histamine or to Escherichia coli lipopolysaccharide (LPS), in order to determine any interaction between prostaglandins and histamine in the hypothalamus. Oxytocin secretion was dose-dependently stimulated by intracerebroventricular infusion of 1 or 5 microg of PGE1, PGE2 or PGF2alpha, with PGE2 being the most potent of the compounds used. Prior central infusion of the H1 receptor antagonist mepyramine or the H2 receptor antagonist cimetidine significantly inhibited the oxytocin response to all three prostaglandins by approximately 50%. Vasopressin secretion was increased by PGE1 but not by PGE2 or PGF2alpha. The stimulatory effect of PGE1 was almost annihilated by prior administration of mepyramine or cimetidine. Central infusion of histamine or immunochallenge with LPS administered intraperitoneally increased oxytocin and vasopressin secretion four- and two-fold, respectively. Pretreatment with systemic injection of the prostaglandin synthesis inhibitor indomethacin dose-dependently reduced the oxytocin response and prevented the vasopressin response to histamine or LPS. We conclude that histamine and PGE1, PGE2 or PGF2alpha interact in the regulation of oxytocin secretion, whereas histamine and only PGE1 interact in the regulation of vasopressin secretion. Furthermore, histamine as well as LPS may affect oxytocin and vasopressin neurones via activation of prostaglandins, probably in the hypothalamic supraoptic nucleus.
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Affiliation(s)
- U Knigge
- Department of Medical Physiology, Division of Endocrinology and Metabolism, The Panum Institute, University of Copenhagen, Denmark.
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