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Wang J, Wang Y, Du X, Zhang H. Potassium Channel Conductance Is Involved in Phenylephrine-Induced Spontaneous Firing of Serotonergic Neurons in the Dorsal Raphe Nucleus. Front Cell Neurosci 2022; 16:891912. [PMID: 35734219 PMCID: PMC9207280 DOI: 10.3389/fncel.2022.891912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 04/22/2022] [Indexed: 11/13/2022] Open
Abstract
The serotonergic (5-HT) network from the dorsal raphe nucleus (DRN) of the brain has been demonstrated to regulate cognition, emotion, and behaviors, including learning and the sleep-wake cycle. Dysregulation of the activity of 5-HT neurons in the DRN is thought to play an important role in emotional disorders. The activity of 5-HT neurons is regulated by norepinephrine (NE) released from the projection terminals of noradrenergic input from the locus coeruleus (LC) via activation of the α1-adrenoceptor. However, insight into the molecular mechanism underlying this NE-induced regulation of 5-HT neuron activity is not clear. In this study, using the agonist of α1-adrenoceptor phenylephrine (PE), brain slices, and patch clamp, we found that A-type, Kv7/KCNQ, and calcium-activated low-conductance K+ channels (SK) underlie PE-induced spontaneous firing in DRN 5-HT neurons. Using single-cell PCR and immunofluorescence, we also identified the isoforms of these K+ channel families that might contribute to the NE/PE-induced spontaneous firing of DRN 5-HT neurons.
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Affiliation(s)
- Jing Wang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, China
- Department of Pharmacochemistry, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Yingzi Wang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, China
| | - Xiaona Du
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, China
| | - Hailin Zhang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Medical University, Shijiazhuang, China
- *Correspondence: Hailin Zhang,
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2
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Neural serotonergic circuits for controlling long-term voluntary alcohol consumption in mice. Mol Psychiatry 2022; 27:4599-4610. [PMID: 36195637 PMCID: PMC9531213 DOI: 10.1038/s41380-022-01789-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 09/05/2022] [Accepted: 09/09/2022] [Indexed: 12/14/2022]
Abstract
Alcohol-use-disorders are chronic relapsing illnesses, often co-morbid with anxiety. We have previously shown using the "drinking-in-the-dark" model in mice that the stimulation of the serotonin receptor 1A (5-HT1A) reduces ethanol binge-drinking behaviour and withdrawal-induced anxiety. The 5-HT1A receptor is located either on Raphe neurons as autoreceptors, or on target neurons as heteroreceptors. By combining a pharmacological approach with biased agonists targeting the 5-HT1A auto- or heteroreceptor and a chemogenetic approach (DREADDs), here we identified that ethanol-binge drinking behaviour is dependent on 5-HT1A autoreceptors and 5-HT neuronal function, with a transition from DRN-dependent regulation of short-term (6 weeks) ethanol intake, to MRN-dependent regulation after longer ethanol exposure (12 weeks). We further identified a serotonergic microcircuit (5-HTMRN→DG) originating from the MRN and projecting to the dentate gyrus (DG) of the hippocampus, that is specifically affected by, and modulates long-term ethanol consumption. The present study indicates that targeting Raphe nuclei 5-HT1A autoreceptors with agonists might represent an innovative pharmacotherapeutic strategy to combat alcohol abuse.
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3
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Delcourte S, Etievant A, Haddjeri N. Role of central serotonin and noradrenaline interactions in the antidepressants' action: Electrophysiological and neurochemical evidence. PROGRESS IN BRAIN RESEARCH 2021; 259:7-81. [PMID: 33541681 DOI: 10.1016/bs.pbr.2021.01.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The development of antidepressant drugs, in the last 6 decades, has been associated with theories based on a deficiency of serotonin (5-HT) and/or noradrenaline (NA) systems. Although the pathophysiology of major depression (MD) is not fully understood, numerous investigations have suggested that treatments with various classes of antidepressant drugs may lead to an enhanced 5-HT and/or adapted NA neurotransmissions. In this review, particular morpho-physiological aspects of these systems are first considered. Second, principal features of central 5-HT/NA interactions are examined. In this regard, the effects of the acute and sustained antidepressant administrations on these systems are discussed. Finally, future directions including novel therapeutic strategies are proposed.
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Affiliation(s)
- Sarah Delcourte
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, Bron, France
| | - Adeline Etievant
- Integrative and Clinical Neurosciences EA481, University of Bourgogne Franche-Comté, Besançon, France
| | - Nasser Haddjeri
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, Bron, France.
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Tritschler L, Gaillard R, Gardier AM, David DJ, Guilloux JP. [Consequences of the monoaminergic systems cross-talk in the antidepressant activity]. Encephale 2018; 44:264-273. [PMID: 29801770 DOI: 10.1016/j.encep.2018.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 04/30/2018] [Indexed: 12/27/2022]
Abstract
Selective serotonin reuptake inhibitors (SSRIs) are the most prescribed antidepressant treatment for treat major depressive disorders. Despite their effectiveness, only 30% of SSRI-treated patients reach remission of depressive symptoms. SSRIs by inhibiting the serotonin transporter present some limits with residual symptoms. Increasing not only serotonin but also norepinephrine and dopamine levels in limbic areas seems to improve remission. Anatomical relationships across serotoninergic, dopaminergic and noradrenergic systems suggest tight reciprocal regulations among them. This review attempts to present, from acute to chronic administration the consequences of SSRI administration on monoaminergic neurotransmission. The serotonin neurons located in the raphe nucleus (RN) are connected to the locus coeruleus (locus coeruleus), the key structure of norepinephrine synthesis, through GABAergic-inhibiting interneurons. Activation of the 5-HT2A receptors expressed on GABAergic interneurons following SERT-inhibition induces an increase in serotonin leading to inhibitory effect on NE release. Similarly, the serotonin neurons exert negative regulation on dopaminergic neurons from the ventral tegmental area (VTA) through a GABAergic interneuron. These interneurons express the 5-HT2C and 5-HT3 receptors inducing an inhibitory effect of 5-HT on DA release. Positive reciprocal connections are also observed through direct projections from the locus coeruleus to the RN and from the VTA to the RN through α1 and D2 receptors respectively, both stimulating the serotoninergic activity. Acute SSRI treatment induces only a slight increase in 5-HT levels in limbic areas due to the activation of presynaptic 5-HT1A and 5-HT1B autoreceptors counteracting the effects of the transporter blockade. No change in NE levels and a small decrease in the dopaminergic neurotransmission is also observed. These weak changes in monoamine in the limbic areas after acute SSRI treatment seems to be one of key point involved in the onset of action. Following desensitization of the 5-HT1A and 5-HT1B autoreceptors, chronic SSRI treatment induces a large increase in the 5-HT neurotransmission. Changes in 5-HT levels at the limbic areas results in a decrease in NE transmission and an increase in DA transmission through an increase in the post-synaptic D2 receptors sensitivity and not from a change in DA levels, which is mainly due to a desensitization of the 5-HT2A receptor. The observed decrease of NE neurotransmission could explain some limits of the SSRI therapy and the interest to activate NE system for producing more robust effects. On the other hand, the D2 sensitization, especially in the nucleus accumbens, stimulates the motivation behavior as well as remission of anhedonia considering the major role of DA release in this structure. Finally, we need to take into account the key role of each monoaminergic neurotransmission to reach remission. Targeting only one system will limit the therapeutic effectiveness. Clinical evidences, including the STAR*D studies, confirmed this by an increase of the remission rate following the mobilization of several monoaminergic transmissions. However, these combinations cannot constitute first line of treatment considering the observed increase of side effects. Such an approach should be adapted to each patient in regard to its particular symptoms as well as clinical history. The next generation of antidepressant therapy will need to take into consideration the interconnections and the interrelation between the monoaminergic systems.
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Affiliation(s)
- L Tritschler
- CESP, Inserm UMRS1178, faculté de pharmacie, université Paris-Saclay, université Paris-Sud, 92296 Chatenay-Malabry, France
| | - R Gaillard
- Inserm UMR 894, centre de psychiatrie & neurosciences, CNRS GDR 3557, institut de psychiatrie, 75015 Paris, France; Université Paris Descartes, Sorbonne Paris Cité, 75015 Paris, France; Service hospitalo-universitaire, centre hospitalier Sainte-Anne, 75015 Paris, France
| | - A M Gardier
- CESP, Inserm UMRS1178, faculté de pharmacie, université Paris-Saclay, université Paris-Sud, 92296 Chatenay-Malabry, France
| | - D J David
- CESP, Inserm UMRS1178, faculté de pharmacie, université Paris-Saclay, université Paris-Sud, 92296 Chatenay-Malabry, France.
| | - J-P Guilloux
- CESP, Inserm UMRS1178, faculté de pharmacie, université Paris-Saclay, université Paris-Sud, 92296 Chatenay-Malabry, France.
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Joshi A, Youssofzadeh V, Vemana V, McGinnity TM, Prasad G, Wong-Lin K. An integrated modelling framework for neural circuits with multiple neuromodulators. J R Soc Interface 2017; 14:rsif.2016.0902. [PMID: 28100828 PMCID: PMC5310738 DOI: 10.1098/rsif.2016.0902] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 12/16/2016] [Indexed: 12/04/2022] Open
Abstract
Neuromodulators are endogenous neurochemicals that regulate biophysical and biochemical processes, which control brain function and behaviour, and are often the targets of neuropharmacological drugs. Neuromodulator effects are generally complex partly owing to the involvement of broad innervation, co-release of neuromodulators, complex intra- and extrasynaptic mechanism, existence of multiple receptor subtypes and high interconnectivity within the brain. In this work, we propose an efficient yet sufficiently realistic computational neural modelling framework to study some of these complex behaviours. Specifically, we propose a novel dynamical neural circuit model that integrates the effective neuromodulator-induced currents based on various experimental data (e.g. electrophysiology, neuropharmacology and voltammetry). The model can incorporate multiple interacting brain regions, including neuromodulator sources, simulate efficiently and easily extendable to large-scale brain models, e.g. for neuroimaging purposes. As an example, we model a network of mutually interacting neural populations in the lateral hypothalamus, dorsal raphe nucleus and locus coeruleus, which are major sources of neuromodulator orexin/hypocretin, serotonin and norepinephrine/noradrenaline, respectively, and which play significant roles in regulating many physiological functions. We demonstrate that such a model can provide predictions of systemic drug effects of the popular antidepressants (e.g. reuptake inhibitors), neuromodulator antagonists or their combinations. Finally, we developed user-friendly graphical user interface software for model simulation and visualization for both fundamental sciences and pharmacological studies.
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Affiliation(s)
- Alok Joshi
- School of Computer Science, University of Manchester, Manchester, UK
| | - Vahab Youssofzadeh
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Vinith Vemana
- Computer Science and Engineering, Indian Institute of Technology (IIT) Jodhpur, Jodhpur, India
| | - T M McGinnity
- Intelligent Systems Research Centre (ISRC), University of Ulster, Derry-Londonderry, UK.,College of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Girijesh Prasad
- Intelligent Systems Research Centre (ISRC), University of Ulster, Derry-Londonderry, UK
| | - KongFatt Wong-Lin
- Intelligent Systems Research Centre (ISRC), University of Ulster, Derry-Londonderry, UK
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6
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Galanin subtype 1 and subtype 2 receptors mediate opposite anxiety-like effects in the rat dorsal raphe nucleus. Behav Brain Res 2016; 314:125-33. [DOI: 10.1016/j.bbr.2016.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/01/2016] [Accepted: 08/03/2016] [Indexed: 01/09/2023]
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7
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Affiliation(s)
- Hailan Hu
- Interdisciplinary Institute of Neuroscience and Technology, Qiushi Academy for Advanced Studies, Zhejiang University, Hangzhou 310012, People's Republic of China;
- Center for Neuroscience, School of Medicine, Zhejiang University, Hangzhou 310058, People's Republic of China
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8
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Ye R, Quinlan MA, Iwamoto H, Wu HH, Green NH, Jetter CS, McMahon DG, Veestra-VanderWeele J, Levitt P, Blakely RD. Physical Interactions and Functional Relationships of Neuroligin 2 and Midbrain Serotonin Transporters. Front Synaptic Neurosci 2016; 7:20. [PMID: 26793096 PMCID: PMC4707279 DOI: 10.3389/fnsyn.2015.00020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 12/14/2015] [Indexed: 12/31/2022] Open
Abstract
The neurotransmitter serotonin [5-hydroxytryptamine (5-HT)] modulates many key brain functions including those subserving sensation, emotion, reward, and cognition. Efficient clearance of 5-HT after release is achieved by the antidepressant-sensitive 5-HT transporter (SERT, SLC6A4). To identify novel SERT regulators, we pursued a proteomic analysis of mouse midbrain SERT complexes, evaluating findings in the context of prior studies that established a SERT-linked transcriptome. Remarkably, both efforts converged on a relationship of SERT with the synaptic adhesion protein neuroligin 2 (NLGN2), a post-synaptic partner for presynaptic neurexins, and a protein well-known to organize inhibitory GABAergic synapses. Western blots of midbrain reciprocal immunoprecipitations confirmed SERT/NLGN2 associations, and also extended to other NLGN2 associated proteins [e.g., α-neurexin (NRXN), gephyrin]. Midbrain SERT/NLGN2 interactions were found to be Ca(2+)-independent, supporting cis vs. trans-synaptic interactions, and were absent in hippocampal preparations, consistent with interactions arising in somatodendritic compartments. Dual color in situ hybridization confirmed co-expression of Tph2 and Nlgn2 mRNA in the dorsal raphe, with immunocytochemical studies confirming SERT:NLGN2 co-localization in raphe cell bodies but not axons. Consistent with correlative mRNA expression studies, loss of NLGN2 expression in Nlgn2 null mice produced significant reductions in midbrain and hippocampal SERT expression and function. Additionally, dorsal raphe 5-HT neurons from Nlgn2 null mice exhibit reduced excitability, a loss of GABAA receptor-mediated IPSCs, and increased 5-HT1A autoreceptor sensitivity. Finally, Nlgn2 null mice display significant changes in behaviors known to be responsive to SERT and/or 5-HT receptor manipulations. We discuss our findings in relation to the possible coordination of intrinsic and extrinsic regulation afforded by somatodendritic SERT:NLGN2 complexes.
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Affiliation(s)
- Ran Ye
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Meagan A Quinlan
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Hideki Iwamoto
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Hsiao-Huei Wu
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Noah H Green
- Department of Biological Sciences, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Christopher S Jetter
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Douglas G McMahon
- Department of Pharmacology, Vanderbilt University School of Medicine, NashvilleTN, USA; Department of Biological Sciences, Vanderbilt University School of Medicine, NashvilleTN, USA
| | - Jeremy Veestra-VanderWeele
- Department of Psychiatry, NYS Psychiatric Institute, Columbia University Medical Center, New York NY, USA
| | - Pat Levitt
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville TN, USA
| | - Randy D Blakely
- Department of Pharmacology, Vanderbilt University School of Medicine, NashvilleTN, USA; Department of Psychiatry, Vanderbilt University School of Medicine, NashvilleTN, USA
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9
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Judge SJ, Savy CY, Campbell M, Dodds R, Gomes LK, Laws G, Watson A, Blain PG, Morris CM, Gartside SE. Mechanism for the acute effects of organophosphate pesticides on the adult 5-HT system. Chem Biol Interact 2015; 245:82-9. [PMID: 26721196 PMCID: PMC4732990 DOI: 10.1016/j.cbi.2015.12.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 12/03/2015] [Accepted: 12/18/2015] [Indexed: 11/07/2022]
Abstract
The neurotransmitter serotonin (5-HT) is involved in mood disorder aetiology and it has been reported that (organophosphate) OP exposure affects 5-HT turnover. The aim of this study was to elucidate the mechanism underlying OP effects on the adult 5-HT system. First, acute in vivo administration of the OP diazinon (0, 1.3, 13 or 39 mg/kg i.p.) to male Hooded Lister rats inhibited the activity of the cholinergic enzyme acetylcholinesterase in blood and in the hippocampus, dorsal raphe nucleus (DRN), striatum and prefrontal cortex. Diazinon-induced cholinesterase inhibition was greatest in the DRN, the brain's major source of 5-HT neurones. Second, acute in vivo diazinon exposure (0 or 39 mg/kg i.p.) increased the basal firing rate of DRN neurones measured ex vivo in brain slices. The excitatory responses of DRN neurones to α1-adrenoceptor or AMPA/kainate receptor activation were not affected by in vivo diazinon exposure but the inhibitory response to 5-HT was attenuated, indicating 5-HT1A autoreceptor down-regulation. Finally, direct application of the diazinon metabolite diazinon oxon to naive rat brain slices increased the firing rate of DRN 5-HT neurones, as did chlorpyrifos-oxon, indicating the effect was not unique to diazinon. The oxon-induced augmentation of firing was blocked by the nicotinic acetylcholine receptor antagonist mecamylamine and the AMPA/kainate glutamate receptor antagonist DNQX. Together these data indicate that 1) acute OP exposure inhibits DRN cholinesterase, leading to acetylcholine accumulation, 2) the acetylcholine activates nicotinic receptors on 5-HT neurones and also on glutamatergic neurones, thus releasing glutamate and activating 5-HT neuronal AMPA/kainate receptors 3) the increase in 5-HT neuronal activity, and resulting 5-HT release, may lead to 5-HT1A autoreceptor down-regulation. This mechanism may be involved in the reported increase in risk of developing anxiety and depression following occupational OP exposure. Organophosphate exposure inhibits dorsal raphe nucleus cholinesterase activity. Organophosphate oxon exposure activates 5-HT neurones in the dorsal raphe nucleus. Nicotinic and AMPA receptors mediate the oxon-induced activation of 5-HT neurones. Organophosphate exposure attenuates the response to 5-HT1A autoreceptor activation.
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Affiliation(s)
- Sarah J Judge
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
| | - Claire Y Savy
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Matthew Campbell
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Rebecca Dodds
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Larissa Kruger Gomes
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Grace Laws
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Anna Watson
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Peter G Blain
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Christopher M Morris
- Medical Toxicology Centre, Newcastle University, Newcastle upon Tyne, NE2 4AA, UK; Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Sarah E Gartside
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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da Silva ES, Flores RA, Cella EC, Levone BR, Taschetto AP, Kochenborger L, Terenzi MG, Faria MS, Paschoalini MA. Blockade of median raphe nucleus α1-adrenoceptor subtypes increases food intake in rats. Pharmacol Biochem Behav 2014; 124:350-5. [DOI: 10.1016/j.pbb.2014.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Revised: 06/11/2014] [Accepted: 06/15/2014] [Indexed: 10/25/2022]
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Tuckwell HC, Penington NJ. Computational modeling of spike generation in serotonergic neurons of the dorsal raphe nucleus. Prog Neurobiol 2014; 118:59-101. [PMID: 24784445 DOI: 10.1016/j.pneurobio.2014.04.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 04/14/2014] [Accepted: 04/21/2014] [Indexed: 01/14/2023]
Abstract
Serotonergic neurons of the dorsal raphe nucleus, with their extensive innervation of limbic and higher brain regions and interactions with the endocrine system have important modulatory or regulatory effects on many cognitive, emotional and physiological processes. They have been strongly implicated in responses to stress and in the occurrence of major depressive disorder and other psychiatric disorders. In order to quantify some of these effects, detailed mathematical models of the activity of such cells are required which describe their complex neurochemistry and neurophysiology. We consider here a single-compartment model of these neurons which is capable of describing many of the known features of spike generation, particularly the slow rhythmic pacemaking activity often observed in these cells in a variety of species. Included in the model are 11 kinds of ion channels: a fast sodium current INa, a delayed rectifier potassium current IKDR, a transient potassium current IA, a slow non-inactivating potassium current IM, a low-threshold calcium current IT, two high threshold calcium currents IL and IN, small and large conductance potassium currents ISK and IBK, a hyperpolarization-activated cation current IH and a leak current ILeak. In Sections 3-8, each current type is considered in detail and parameters estimated from voltage clamp data where possible. Three kinds of model are considered for the BK current and two for the leak current. Intracellular calcium ion concentration Cai is an additional component and calcium dynamics along with buffering and pumping is discussed in Section 9. The remainder of the article contains descriptions of computed solutions which reveal both spontaneous and driven spiking with several parameter sets. Attention is focused on the properties usually associated with these neurons, particularly long duration of action potential, steep upslope on the leading edge of spikes, pacemaker-like spiking, long-lasting afterhyperpolarization and the ramp-like return to threshold after a spike. In some cases the membrane potential trajectories display doublets or have humps or notches as have been reported in some experimental studies. The computed time courses of IA and IT during the interspike interval support the generally held view of a competition between them in influencing the frequency of spiking. Spontaneous activity was facilitated by the presence of IH which has been found in these neurons by some investigators. For reasonable sets of parameters spike frequencies between about 0.6Hz and 1.2Hz are obtained, but frequencies as high as 6Hz could be obtained with special parameter choices. Topics investigated and compared with experiment include shoulders, notches, anodal break phenomena, the effects of noradrenergic input, frequency versus current curves, depolarization block, effects of cell size and the effects of IM. The inhibitory effects of activating 5-HT1A autoreceptors are also investigated. There is a considerable discussion of in vitro versus in vivo firing behavior, with focus on the roles of noradrenergic input, corticotropin-releasing factor and orexinergic inputs. Location of cells within the nucleus is probably a major factor, along with the state of the animal.
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Affiliation(s)
- Henry C Tuckwell
- Max Planck Institute for Mathematics in the Sciences, Inselstr. 22, 04103 Leipzig, Germany; School of Electrical and Electronic Engineering, University of Adelaide, Adelaide, South Australia 5005, Australia.
| | - Nicholas J Penington
- Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, Box 29, 450 Clarkson Avenue, Brooklyn, NY 11203-2098, USA; Program in Neural and Behavioral Science and Robert F. Furchgott Center for Neural and Behavioral Science, State University of New York, Downstate Medical Center, Box 29, 450 Clarkson Avenue, Brooklyn, NY 11203-2098, USA
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12
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Wallace J, Jackson RK, Shotton TL, Munjal I, McQuade R, Gartside SE. Characterization of electrically evoked field potentials in the medial prefrontal cortex and orbitofrontal cortex of the rat: modulation by monoamines. Eur Neuropsychopharmacol 2014; 24:321-32. [PMID: 23932190 PMCID: PMC4623163 DOI: 10.1016/j.euroneuro.2013.07.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 05/31/2013] [Accepted: 07/05/2013] [Indexed: 10/26/2022]
Abstract
Medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) play critical roles in cognition and behavioural control. Glutamatergic, GABAergic, and monoaminergic dysfunction in the prefrontal cortex has been hypothesised to underlie symptoms in neuropsychiatric disorders. Here we characterised electrically-evoked field potentials in the mPFC and OFC. Electrical stimulation evoked field potentials in layer V/VI of the mPFC and layer V of the OFC. The earliest component (approximately 2 ms latency) was insensitive to glutamate receptor blockade and was presumed to be presynaptic. Later components were blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX (20 µM)) and were assumed to reflect monosynaptic (latency 4-6 ms) and polysynaptic activity (latency 6-40 ms) mediated by glutamate via AMPA/kainate receptor. In the mPFC, but not the OFC, the monosynaptic component was also partly blocked by 2-amino-5-phosphonopentanoic acid (AP-5 (50-100µM)) indicating the involvement of NMDA receptors. Bicuculline (3-10 µM) enhanced the monosynaptic component suggesting electrically-evoked and/or glutamate induced GABA release inhibits the monosynaptic component via GABAA receptor activation. There were complex effects of bicuculline on polysynaptic components. In the mPFC both the mono- and polysynaptic components were attenuated by 5-HT (10-100 µM) and NA (30 and 60 µM) and the monosynaptic component was attenuated by DA (100 µM). In the OFC the mono- and polysynaptic components were also attenuated by 5-HT (100 µM), NA (10-100 µM) but DA (10-100 µM) had no effect. We propose that these pharmacologically characterised electrically-evoked field potentials in the mPFC and OFC are useful models for the study of prefrontal cortical physiology and pathophysiology.
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Affiliation(s)
- Joanne Wallace
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Rosanna K Jackson
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Tanya L Shotton
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Ishaana Munjal
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Richard McQuade
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Sarah E Gartside
- Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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Dankoski EC, Wightman RM. Monitoring serotonin signaling on a subsecond time scale. Front Integr Neurosci 2013; 7:44. [PMID: 23760548 PMCID: PMC3672682 DOI: 10.3389/fnint.2013.00044] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 05/16/2013] [Indexed: 12/17/2022] Open
Abstract
Serotonin modulates a variety of processes throughout the brain, but it is perhaps best known for its involvement in the etiology and treatment of depressive disorders. Microdialysis studies have provided a clear picture of how ambient serotonin levels fluctuate with regard to behavioral states and pharmacological manipulation, and anatomical and electrophysiological studies describe the location and activity of serotonin and its targets. However, few techniques combine the temporal resolution, spatial precision, and chemical selectivity to directly evaluate serotonin release and uptake. Fast-scan cyclic voltammetry (FSCV) is an electrochemical method that can detect minute changes in neurotransmitter concentration on the same temporal and spatial dimensions as extrasynaptic neurotransmission. Subsecond measurements both in vivo and in brain slice preparations enable us to tease apart the processes of release and uptake. These studies have particularly highlighted the significance of regulatory mechanisms to proper functioning of the serotonin system. This article will review the findings of FSCV investigations of serotonergic neurotransmission and discuss this technique's potential in future studies of the serotonin system.
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Affiliation(s)
- Elyse C Dankoski
- Curriculum in Neurobiology, University of North Carolina Chapel Hill, NC, USA
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Tuckwell HC. Biophysical properties and computational modeling of calcium spikes in serotonergic neurons of the dorsal raphe nucleus. Biosystems 2013; 112:204-13. [PMID: 23391700 DOI: 10.1016/j.biosystems.2013.01.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 01/18/2013] [Accepted: 01/18/2013] [Indexed: 11/17/2022]
Abstract
Serotonergic neurons of the dorsal raphe nuclei, with their extensive innervation of nearly the whole brain have important modulatory effects on many cognitive and physiological processes. They play important roles in clinical depression and other psychiatric disorders. In order to quantify the effects of serotonergic transmission on target cells it is desirable to construct computational models and to this end these it is necessary to have details of the biophysical and spike properties of the serotonergic neurons. Here several basic properties are reviewed with data from several studies since the 1960s to the present. The quantities included are input resistance, resting membrane potential, membrane time constant, firing rate, spike duration, spike and afterhyperpolarization (AHP) amplitude, spike threshold, cell capacitance, soma and somadendritic areas. The action potentials of these cells are normally triggered by a combination of sodium and calcium currents which may result in autonomous pacemaker activity. We here analyse the mechanisms of high-threshold calcium spikes which have been demonstrated in these cells the presence of TTX (tetrodotoxin). The parameters for calcium dynamics required to give calcium spikes are quite different from those for regular spiking which suggests the involvement of restricted parts of the soma-dendritic surface as has been found, for example, in hippocampal neurons.
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Affiliation(s)
- Henry C Tuckwell
- Max Planck Institute for Mathematics in the Sciences, Inselstr. 22, 04103 Leipzig, Germany.
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Ayissi Mbomo R, Gartside S, Ngo Bum E, Njikam N, Okello E, McQuade R. Effect of Mimosa pudica (Linn.) extract on anxiety behaviour and GABAergic regulation of 5-HT neuronal activity in the mouse. J Psychopharmacol 2012; 26:575-83. [PMID: 21427203 DOI: 10.1177/0269881111398686] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Mimosa pudica (Linn.) (M. pudica L.) is a plant used in some countries to treat anxiety and depression. In the present study we investigated the effects of an aqueous extract of M. pudica L. on mouse anxiety-like behaviour using the elevated T maze, and on regulation of dorsal raphe nucleus (DRN) 5-hydroxytryptamine (5-HT) neuronal activity using an in-vitro mouse brain slice preparation. Acute treatment with M. pudica L. extract had an anxiolytic effect on behaviour in the elevated T maze, specifically on inhibitory avoidance behaviour. Acute application of the extract alone had no effect on the activity of DRN 5-HT neurones. However, when co-applied with the GABA(A) receptor agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), the extract enhanced the inhibitory effect of the THIP on DRN 5-HT neurones. These observed effects of M. pudica L. on both behaviour and GABA modulation of 5-HT neuronal activity are similar to the effects of diazepam, the established anxiolytic and positive modulator of the GABA(A) receptor. This study suggests that the aqueous extract of M. pudica L. contains a positive modulator of GABA(A) receptor function and provides impetus for further investigation of the neuropharmacologically active constituents of the extract.
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Affiliation(s)
- Rigobert Ayissi Mbomo
- Department of Animal Biology and Physiology, University of Yaounde 1, Yaounde, Cameroon
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16
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Effects of general anaesthetics on 5-HT neuronal activity in the dorsal raphe nucleus. Neuropharmacology 2011; 62:1787-96. [PMID: 22197516 DOI: 10.1016/j.neuropharm.2011.12.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 11/04/2011] [Accepted: 12/02/2011] [Indexed: 11/22/2022]
Abstract
The ascending 5-HT system has been and continues to be the subject of much research. The majority of in vivo electrophysiological and neurochemical studies of 5-HT function in rodents have been conducted in animals under anaesthesia - usually chloral hydrate or urethane. However, the effects of anaesthetics, on 5-HT function have not been systematically investigated. Here we used in vitro electrophysiology in dorsal raphe slices, to determine the effects of anaesthetically relevant concentrations of chloral hydrate (100 μM and 1 mM), urethane (10 and 30 mM), pentobarbitone (10 and 100 μM) and ketamine (10, 100 and 300 μM) on regulators of 5-HT firing activity. We examined i) basal firing (driven by α(1) adrenoceptors), ii) the excitatory response to N-methyl-d-aspartate (NMDA), iii) the 5-HT(1A) autoreceptor-mediated inhibitory response to 5-HT and iv) the GABA(A) receptor-mediated inhibitory response to 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridinyl-3-ol (THIP, gaboxadol). Pentobarbitone selectively enhanced the response to THIP. Ketamine decreased basal firing, attenuated the response to NMDA, and enhanced responses to both 5-HT and THIP. Chloral hydrate had marginal effects on basal firing, slightly attenuated the NMDA response, and enhanced both the 5-HT and THIP responses. Urethane increased basal firing, decreased the NMDA response, increased the response to THIP, but had no effect on the 5-HT response. Our data indicate that all anaesthetics tested significantly affect the regulators of 5-HT neuronal function. These findings will aid in the interpretation of previous reports of in vivo studies of the 5-HT system and will allow researchers to make a rational selection of anaesthetic for future studies.
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17
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Mansur SS, Terenzi MG, Neto JM, Faria MS, Paschoalini MA. Changes in food intake and anxiety-like behaviors after clonidine injected into the median raphe nucleus. Behav Brain Res 2010; 212:71-7. [DOI: 10.1016/j.bbr.2010.03.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Revised: 03/19/2010] [Accepted: 03/23/2010] [Indexed: 10/19/2022]
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18
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Harsing LG. The pharmacology of the neurochemical transmission in the midbrain raphe nuclei of the rat. Curr Neuropharmacol 2010; 4:313-39. [PMID: 18654635 DOI: 10.2174/157015906778520764] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2005] [Revised: 08/04/2006] [Accepted: 08/16/2006] [Indexed: 01/24/2023] Open
Abstract
Midbrain slices containing the dorsal and medial raphe nuclei were prepared from rat brain, loaded with [(3)H]serotonin ([(3)H]5-HT), superfused and the release of [(3)H]5-HT was determined at rest and in response to electrical stimulation. Compartmental analysis of [(3)H]5-HT taken up by raphe tissue indicated various pools where the neurotransmitter release may originate from these stores differed both in size and rate constant. 5-HT release originates not only from vesicles but also from cytoplasmic stores via a transporter-dependent exchange process establishing synaptic and non-synaptic neurochemical transmission in the serotonergic somatodendritic area. Manipulation of 5-HT transporter function modulates extracellular 5-HT concentrations in the raphe nuclei: of the SSRIs, fluoxetine was found 5-HT releaser, whereas citalopram did not exhibit this effect. Serotonergic projection neurons in the raphe nuclei possess inhibitory 5-HT(1A) and 5-HT(1B/1D) receptors and facilitatory 5-HT(3) receptors, which regulate 5-HT release in an opposing fashion. This observation indicates that somatodendritic 5-HT release in the raphe nuclei is under the control of several 5-HT homoreceptors. 5-HT(7) receptors located on glutamatergic axon terminals indirectly inhibit 5-HT release by reducing glutamatergic facilitation of serotonergic projection neurons. An opposite regulation of glutamatergic axon terminals was also found by involvement of the inhibitory 5-HT(7) and the stimulatory 5-HT(2) receptors as these receptors inhibit and stimulate glutamate release in raphe slice preparation, respectively, Furthermore, postsynaptic 5-HT(1B/1D) heteroreceptors interact with release of GABA in inhibitory fashion in raphe GABAergic interneurons. Serotonergic projection neurons also possess glutamate and GABA heteroreceptors; NMDA and AMPA receptors release 5-HT, whereas both GABAA and GABAB receptors inhibit somatodendritic 5-HT release. Evidence was found for reciprocal interactions between serotonergic and glutamatergic as well as serotonergic and GABAergic innervations in the raphe nuclei. Serotonergic neurons in the raphe nuclei also receive noradrenergic innervation arising from the locus coeruleus and alpha-1 and alpha-2 adrenoceptors inhibited [(3)H]5-HT release in our experimental conditions. The close relation between 5-HT transporter and release-mediating 5-HT autoreceptors was also shown by addition of L-deprenyl, a drug possessing inhibition of type B monoamine oxidase and 5-HT reuptake. L-Deprenyl selectively desensitizes 5-HT(1B) but not 5-HT(1A) receptors and these effects are not related to inhibition of 5-HT metabolism but rather to inhibition of 5-HT transporter.
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Affiliation(s)
- L G Harsing
- Division of Preclinical REsearch, EGIS Pharmaceuticals, Plc., Bokenyfoldi ut 116, 1165 Budapest, Hungary.
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Bartoszewicz R, Barbacka-Surowiak G. Phase response curve of mouse locomotor activity rhythm under constant light after 8-OH-DPAT and dark pulses. BIOL RHYTHM RES 2010. [DOI: 10.1080/09291010903557203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Renata Bartoszewicz
- a Department of Neurophysiology and Chronobiology , Institute of Zoology, Jagiellonian University , Krakow
| | - Grażyna Barbacka-Surowiak
- a Department of Neurophysiology and Chronobiology , Institute of Zoology, Jagiellonian University , Krakow
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20
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Affiliation(s)
- Peter Dayan
- Gatsby Computational Neuroscience Unit, University College London, London, WC1N 3AR, UK;
| | - Quentin J.M. Huys
- Gatsby Computational Neuroscience Unit, University College London, London, WC1N 3AR, UK;
- Center for Theoretical Neuroscience, Columbia University, New York, NY 10025;
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Involvement of median raphe nucleus 5-HT1A receptors in the regulation of generalized anxiety-related defensive behaviours in rats. Neurosci Lett 2008; 445:204-8. [DOI: 10.1016/j.neulet.2008.09.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 08/13/2008] [Accepted: 09/01/2008] [Indexed: 11/23/2022]
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22
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Sato H, Skelin I, Debonnel G, Diksic M. Chronic buspirone treatment normalizes open field behavior in olfactory bulbectomized rats: Assessment with a quantitative autoradiographic evaluation of the 5-HT1A binding sites. Brain Res Bull 2008; 75:545-55. [DOI: 10.1016/j.brainresbull.2007.09.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2007] [Accepted: 09/18/2007] [Indexed: 10/22/2022]
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23
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Perspectives on genetic animal models of serotonin toxicity. Neurochem Int 2008; 52:649-58. [DOI: 10.1016/j.neuint.2007.08.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Revised: 08/23/2007] [Accepted: 08/29/2007] [Indexed: 12/28/2022]
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24
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Effects of disulfiram and dopamine beta-hydroxylase knockout on cocaine-induced seizures. Pharmacol Biochem Behav 2008; 89:556-62. [PMID: 18329701 DOI: 10.1016/j.pbb.2008.02.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 01/30/2008] [Accepted: 02/06/2008] [Indexed: 11/23/2022]
Abstract
The antialcoholism drug disulfiram has shown recent promise as a pharmacotherapy for treating cocaine dependence, probably via inhibition of dopamine beta-hydroxylase (DBH), the enzyme that catalyzes the conversion of dopamine (DA) to norepinephrine (NE). We previously showed that DBH knockout (Dbh -/-) mice, which lack NE, are susceptible to seizures and are hypersensitive to the psychomotor, rewarding, and aversive effects of cocaine, suggesting that disulfiram might exacerbate cocaine-induced seizures (CIS) by inhibiting DBH. To test this, we examined CIS in wild-type and Dbh -/- mice following administration of disulfiram or the selective DBH inhibitor nepicastat. We found that Dbh genotype had no effect on CIS probability or frequency, whereas disulfiram, but not nepicastat, increased the probability of having CIS in both wild-type and Dbh -/- mice. Both disulfiram and nepicastat increased CIS frequency in wild-type but not Dbh -/- mice. There were no genotype or treatment effects on serum cocaine levels, except for an increase in disulfiram-treated Dbh -/- mice at the highest dose of cocaine. These results suggest that disulfiram enhances CIS via two distinct mechanisms: it both increases CIS frequency by inhibiting DBH and increases CIS frequency in a DBH-independent manner.
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Cedraz-Mercez PL, Mecawi AS, Lepletier A, Araújo IG, Costa-e-Sousa RH, Rocha FF, Olivares EL, Medeiros MA, Reis LC. Noradrenergic stimulation within midbrain raphe increases electrolyte excretion in rats. Exp Physiol 2007; 92:923-31. [PMID: 17591682 DOI: 10.1113/expphysiol.2007.037317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The present study was carried out to assess the influence of noradrenergic stimulation of the midbrain dorsal (DRN) and median raphe nuclei (MRN) on urinary volume and electrolyte excretion in hydrated rats. Wistar rats were implanted with a guide cannula into the MRN or DRN and then submitted to two intragastric administrations of water in order to attain an increased diuresis. The following treatments were performed. (1) Intra-DRN microinjections of saline (0.2 microl), alpha(1)-adrenergic agonist phenylephrine (PHE, 0.49 and 4.9 nmol in 0.2 microl), alpha(2)-adrenergic antagonist idazoxan (IDZ, 0.42 and 4.2 nmol in 0.2 microl) or the alpha(1)-adrenergic antagonist prazosin (PRZ, 0.24 and 2.4 nmol in 0.2 microl). (2) Intra-MRN microinjections of saline, IDZ (4.2 nmol in 0.2 microl), PHE (4.9 nmol in 0.2 microl) or PRZ (2.4 nmol in 0.2 microl). Urine samples were subsequently collected over 120 min at 20 min intervals for photometric measurement of sodium and potassium. Intra-DRN administration of PHE and IDZ significantly increased the urinary volume, natriuresis and kaliuresis. Intra-DRN microinjection of a higher dose of PRZ reduced the urinary volume and both sodium and potassium excretion. Intra-MRN microinjections of PHE, IDZ or PRZ did not induce any significant effect on urinary volume or electrolyte excretion. These data suggest that the increase of tonic excitatory noradrenergic input conveyed to DRN influences the hydroelectrolyte homeostasis, possibly through 5-HTergic circuitry.
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Affiliation(s)
- P L Cedraz-Mercez
- Department of Physiological Sciences, Biology Institute, Federal Rural University of Rio de Janeiro, BR465, Km 7, 23890-000, Seropédica, RJ, Brazil
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Judge SJ, Young RL, Gartside SE. GABA(A) receptor modulation of 5-HT neuronal firing in the median raphe nucleus: implications for the action of anxiolytics. Eur Neuropsychopharmacol 2006; 16:612-9. [PMID: 16531019 DOI: 10.1016/j.euroneuro.2006.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 01/13/2006] [Accepted: 01/24/2006] [Indexed: 10/24/2022]
Abstract
5-HT neurones in the median raphe nucleus (MRN) are involved in anxiety and the sleep/wake cycle. Here, using in vitro electrophysiology, we examined if the firing of MRN 5-HT neurones is regulated by GABA(A) receptors. The GABA(A) receptor agonists THIP and muscimol caused concentration dependent inhibition of MRN 5-HT neurones. The GABA(A) receptor antagonist bicuculline blocked the responses to THIP and muscimol. Bicuculline alone increased the basal firing activity. Responses to THIP were enhanced by the Z hypnotic zolpidem at concentrations selective for the alpha(2)/alpha(3) subunits of the GABA(A) receptor (0.2 and 1microM) but not at a concentration selective for the alpha(1) subunit (0.02microM). Consistent with these functional data, 5-HT neurones have been shown to express the alpha(3) (but not alpha(2)) subunit. The anxiolytic effects of GABA(A) receptor modulators are reportedly mediated by alpha(3)-containing receptors. Hence the MRN 5-HT system may be a target for anxiolytic drugs.
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Affiliation(s)
- Sarah J Judge
- Psychobiology Research Group, School of Neurology, Neurobiology and Psychiatry, The Medical School, University of Newcastle upon Tyne, NE2 4HH, UK.
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Thiagaraj HV, Ortiz TC, Devereaux MC, Seaver B, Hall B, Parker KK. Regulation of G proteins by human 5-HT1a receptor TM3/i2 and TM5/i3 loop peptides. Neurochem Int 2006; 50:109-18. [PMID: 16973243 DOI: 10.1016/j.neuint.2006.07.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 07/11/2006] [Indexed: 12/15/2022]
Abstract
A bioactive synthetic 11 amino acid peptide probe (P11) was constructed according to the published sequence of the human 5HT1a receptor. The probe was used to enhance understanding of cytoplasmic loop 2/G protein coupling and activation. Additionally, two peptides (P8, P9) from the cytoplasmic loop 3 region were synthesized and studied. These probes were tested in a model system of human 5HT1a receptor stably expressed in Chinese Hamster Ovary cells. In agonist inhibition studies, P11 was active in all three receptor preparations tested: whole cells, membrane bound, and solubilized. In analyses of the membrane bound receptor system, P11 demonstrated uncompetitive inhibition characteristics. When forskolin-stimulated cAMP levels were measured, P11 was inactive in this negatively coupled system. Utilizing a [35S]gamma-S-GTP incorporation assay, P11 was unable to stimulate G protein incorporation of GTP. While P8 and P9 were also broadly active as non-competitive agonist inhibitors, their characteristics differed in the signal transduction system. P8 and P9 did not significantly change forskolin-stimulated cAMP levels. However, P8 increased [35S]gamma-S-GTP incorporation, while P9 decreased incorporation. Thus, P11, a synthetic peptide from the TM3/i2 region of the receptor, provides suggestive evidence that this receptor region is involved in G protein coupling but not activation. On the other hand, P8 and P9 activities suggest that the TM5/i3 region is involved in both coupling to and regulation of G protein activity. The current evidence from these cytoplasmic loop regions is discussed in the overall context of an emerging model for human 5HT1a receptor-G protein interactions.
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Affiliation(s)
- Harish V Thiagaraj
- Department of Biomedical and Pharmaceutical Sciences (MPH I02), Skaggs School of Pharmacy, The University of Montana, 32 Campus Drive #1552, Missoula, MT 59812-1552, United States
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