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Erdozain AM, Brocos-Mosquera I, Gabilondo AM, Meana JJ, Callado LF. Differential α 2A- and α 2C-adrenoceptor protein expression in presynaptic and postsynaptic density fractions of postmortem human prefrontal cortex. J Psychopharmacol 2019; 33:244-249. [PMID: 30255728 DOI: 10.1177/0269881118798612] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Three different α2-adrenoceptor (α2-AR) subtypes have been described. The α2A-AR and α2C-AR subtypes are highly expressed in the human prefrontal cortex, where they modulate neurotransmission. However, due to the lack of subtype-selective ligands, the physiological relevance of both subtypes has not been fully resolved. AIMS In this context, the aim of the present study was to characterize the protein expression of both α2-AR subtypes, in different synaptic fractions of postmortem human prefrontal cortex. METHODS A subcellular fractionation of the samples was performed and the protein expression of α2A- and α2C-ARs was measured in presynaptic membranes and postsynaptic density fractions by Western blot. RESULTS The results revealed that the α2A-AR subtype is mainly located postsynaptically (95±3%) whereas the remaining 5±3% is in the presynapse. Conversely, the α2C-AR subtype showed a similar distribution between pre- and postsynaptic membranes, with a slightly higher percentage present in the presynapse (60±2% vs. 40±2%). CONCLUSIONS These findings could explain some contradictory effects reported for α2-AR agonists and antagonists in the human prefrontal cortex. Furthermore, the present data could contribute to elucidating the therapeutic potential of selectively targeting α2A- or α2C-AR subtypes.
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Affiliation(s)
- Amaia M Erdozain
- 1 Department of Pharmacology, University of the Basque Country, UPV/EHU, Leioa, Spain.,2 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain
| | - Iria Brocos-Mosquera
- 1 Department of Pharmacology, University of the Basque Country, UPV/EHU, Leioa, Spain
| | - Ane M Gabilondo
- 1 Department of Pharmacology, University of the Basque Country, UPV/EHU, Leioa, Spain.,2 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain.,3 Biocruces Health Research Institute, Barakaldo, Spain
| | - J Javier Meana
- 1 Department of Pharmacology, University of the Basque Country, UPV/EHU, Leioa, Spain.,2 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain.,3 Biocruces Health Research Institute, Barakaldo, Spain
| | - Luis F Callado
- 1 Department of Pharmacology, University of the Basque Country, UPV/EHU, Leioa, Spain.,2 Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain.,3 Biocruces Health Research Institute, Barakaldo, Spain
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Perez SD, Molinaro CA, Tan L, ThyagaRajan S, Lorton D, Bellinger DL. Sympathetic neurotransmission in spleens from aging Brown-Norway rats subjected to reduced sympathetic tone. J Neuroimmunol 2018; 324:1-15. [PMID: 30195094 DOI: 10.1016/j.jneuroim.2018.08.010] [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: 03/29/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 11/17/2022]
Abstract
Senescence of innate and adaptive responses and low-grade inflammation (inflammaging) hallmarks normal aging, which increases vulnerability to infectious diseases, autoimmunity and cancer. In normal aging, sympathetic dysregulation contributes to the dysregulation of innate and adaptive immunity and inflammaging. Sympathetic innervation of immune cells in secondary immune organs regulates immune responses. Previously in Fischer 344 (F344) rats, we reported an age-related increase in sympathetic tone and sympathetic dysfunction in beta-adrenergic receptor (AR) signaling of splenic lymphocytes that contributes to immune senescence, although the responsible mechanisms remains unexplored. In this study, we extend our previous findings using the much longer-lived Brown-Norway (BN) rats, whose behavior and immune response profile differ strikingly from F344 rats. Here, we investigated whether increased sympathetic nerve activity (SNA) in the aging spleen contributes to age-related sympathetic neuropathy and altered neurotransmission in splenic lymphocytes in BN rats. Fifteen-month male BN rats received 0, 0.5 or 1.5 μg/kg/day rilmenidine intraperitoneally for 90 days to lower sympathetic tone. Untreated young and age-matched rats controlled for effects of age. We found that elevated SNA in the aging BN rat spleen does not contribute significantly to sympathetic neuropathy or the aging-induced impairment of canonical β-AR signal transduction. Despite the rilmenidine-induced increase in β-AR expression, splenocyte c-AMP production was comparable with age-matched controls, thus dampening nerve activity had no effect on receptor coupling to adenylate cyclase. Understanding how aging affects neuroimmune regulation in healthy aging rodent models may eventually lead to strategies that improve health in aging populations vulnerable to immunosenescence and low-grade systemic inflammation.
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Affiliation(s)
- Samuel D Perez
- Department of Biology, Washington Adventist University, MD, Virginia 20912, USA.
| | - Christine A Molinaro
- Department of Human Anatomy and Pathology, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
| | - Laren Tan
- Department of Pulmonary and Critical Care, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
| | - Srinivasan ThyagaRajan
- Integrative Medicine Laboratory, Department of Biotechnology, SRM University, Kattankulathur 603203, India.
| | - Dianne Lorton
- College of Arts and Sciences, Kent State University, Summa Health System, Akron, OH 44304, USA..
| | - Denise L Bellinger
- Department of Human Anatomy and Pathology, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA.
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The α2C-adrenoceptor antagonist, ORM-10921, exerts antidepressant-like effects in the Flinders Sensitive Line rat. Behav Pharmacol 2018; 28:9-18. [PMID: 27749317 DOI: 10.1097/fbp.0000000000000261] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Depression involves deficits in monoaminergic neurotransmission. Differential roles for α2A, B and C subtypes of the α2-adrenoceptor (AR) are evident, with selective α2C-AR antagonists purported to have antidepressant and procognitive properties. However, this has not been demonstrated in a genetic animal model of depression. The role of the α2C-AR in modulating two key depression-related behaviours in the Flinders Sensitive Line (FSL) rat was studied using a dose-response analysis following subcutaneous administration with the selective α2C-AR antagonist ORM-10921 (0.03; 0.3 mg/kg), the nonselective α2-AR antagonist idazoxan (3 mg/kg), or vehicle once daily for 14 days. Behaviour in the novel object recognition test, forced swim test (FST) and locomotor activity test was assessed. To ratify the validity of the FSL model, the reference tricyclic antidepressant imipramine (15 mg/kg, intraperitoneally) was used as a comparator drug in the FST. FSL rats demonstrated significantly increased immobility and recognition memory deficits versus Flinders Resistant Line controls, with imipramine significantly reversing said immobility. Similarly, ORM-10921 at both doses but not idazoxan significantly reversed immobility in the FST as well as attenuated cognitive deficits in FSL animals. We conclude that selective α2C-AR antagonism has potential as a novel therapeutic strategy in the treatment of depression and cognitive dysfunction.
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Uys MM, Shahid M, Harvey BH. Therapeutic Potential of Selectively Targeting the α 2C-Adrenoceptor in Cognition, Depression, and Schizophrenia-New Developments and Future Perspective. Front Psychiatry 2017; 8:144. [PMID: 28855875 PMCID: PMC5558054 DOI: 10.3389/fpsyt.2017.00144] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 07/24/2017] [Indexed: 12/12/2022] Open
Abstract
α2A- and α2C-adrenoceptors (ARs) are the primary α2-AR subtypes involved in central nervous system (CNS) function. These receptors are implicated in the pathophysiology of psychiatric illness, particularly those associated with affective, psychotic, and cognitive symptoms. Indeed, non-selective α2-AR blockade is proposed to contribute toward antidepressant (e.g., mirtazapine) and atypical antipsychotic (e.g., clozapine) drug action. Both α2C- and α2A-AR share autoreceptor functions to exert negative feedback control on noradrenaline (NA) release, with α2C-AR heteroreceptors regulating non-noradrenergic transmission (e.g., serotonin, dopamine). While the α2A-AR is widely distributed throughout the CNS, α2C-AR expression is more restricted, suggesting the possibility of significant differences in how these two receptor subtypes modulate regional neurotransmission. However, the α2C-AR plays a more prominent role during states of low endogenous NA activity, while the α2A-AR is relatively more engaged during states of high noradrenergic tone. Although augmentation of conventional antidepressant and antipsychotic therapy with non-selective α2-AR antagonists may improve therapeutic outcome, animal studies report distinct yet often opposing roles for the α2A- and α2C-ARs on behavioral markers of mood and cognition, implying that non-selective α2-AR antagonism may compromise therapeutic utility both in terms of efficacy and side-effect liability. Recently, several highly selective α2C-AR antagonists have been identified that have allowed deeper investigation into the function and utility of the α2C-AR. ORM-13070 is a useful positron emission tomography ligand, ORM-10921 has demonstrated antipsychotic, antidepressant, and pro-cognitive actions in animals, while ORM-12741 is in clinical development for the treatment of cognitive dysfunction and neuropsychiatric symptoms in Alzheimer's disease. This review will emphasize the importance and relevance of the α2C-AR as a neuropsychiatric drug target in major depression, schizophrenia, and associated cognitive deficits. In addition, we will present new prospects and future directions of investigation.
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Affiliation(s)
- Madeleine Monique Uys
- Division of Pharmacology, Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
| | | | - Brian Herbert Harvey
- Division of Pharmacology, Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom, South Africa
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Moranta D, Esteban S, García-Sevilla JA. Chronic treatment and withdrawal of the cannabinoid agonist WIN 55,212-2 modulate the sensitivity of presynaptic receptors involved in the regulation of monoamine syntheses in rat brain. Naunyn Schmiedebergs Arch Pharmacol 2008; 379:61-72. [PMID: 18709357 DOI: 10.1007/s00210-008-0337-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Accepted: 07/07/2008] [Indexed: 10/21/2022]
Abstract
Brain monoamines are involved in many neurochemical and behavioral effects of cannabinoids, but little is known on the regulation of noradrenaline, dopamine, and serotonin (5-HT) synthesis in cannabinoid addiction. This study investigated in rat brain the chronic effects of the potent cannabinoid agonist WIN 55,212-2 and of rimonabant-precipitated withdrawal, as well as the sensitivity of synthesis-modulating inhibitory receptors, on the accumulation of L-3,4-dihydroxyphenylalanine (DOPA) and 5-HTP after decarboxylase inhibition. Acute WIN (8 mg/kg; 1 h) increased DOPA synthesis in cortex (52%), hippocampus (51%), and cerebellum (56%) and decreased DOPA accumulation in striatum (31%). Acute WIN also decreased the synthesis of 5-HTP in all brain regions (40-53%). Chronic WIN (2-8 mg/kg; 5 days) and/or antagonist-precipitated withdrawal induced tolerance to the acute effects of WIN on the accumulation of DOPA (cortex and striatum) and 5-HTP (all brain regions). The inhibitory effect of clonidine (alpha2-agonist; 1 mg/kg) on the accumulation of DOPA (15-41%) and 5-HTP (22-41%) was markedly decreased or abolished after chronic WIN and precipitated withdrawal, mainly in noradrenergic and serotonergic brain regions, which indicated desensitization of alpha2-autoreceptors and alpha2-heteroreceptors regulating the synthesis of noradrenaline and 5-HT. In WIN-dependent rats (chronic and withdrawal states), the effect of a low dose of (+/-)-8-hydroxy-2-(di-n-propylamino)-tetralin (5-HT1A agonist; 0.1 mg/kg) on the accumulation of precursor amino acids was markedly potentiated in cerebellum and striatum, indicating the induction of supersensitivity of 5-HT1A-autoreceptors and 5-HT1A-heteroreceptors that regulate the synthesis of 5-HT, noradrenaline, and dopamine in these brain regions. These chronic adaptations in presynaptic receptor function could play a relevant role in cannabinoid addiction.
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Affiliation(s)
- David Moranta
- Laboratori de Neurofarmacologia, Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), Universitat de les Illes Balears, Cra. Valldemossa km 7.5, 07122, Palma de Mallorca, Spain
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Ribas C, Miralles A, Busquets X, García-Sevilla JA. Brain alpha(2)-adrenoceptors in monoamine-depleted rats: increased receptor density, G coupling proteins, receptor turnover and receptor mRNA. Br J Pharmacol 2001; 132:1467-76. [PMID: 11264240 PMCID: PMC1572698 DOI: 10.1038/sj.bjp.0703963] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study was designed to assess the molecular and cellular events involved in the up-regulation (and receptor supersensitivity) of brain alpha(2)-adrenoceptors as a result of chronic depletion of noradrenaline (and other monoamines) by reserpine. 2. Chronic reserpine (0.25 mg kg(-1) s.c., every 48 h for 6 - 14 days) increased significantly the density (B(max) values) of cortical alpha(2)-adrenoceptor agonist sites (34 - 48% for [(3)H]-UK14304, 22 - 32% for [(3)H]-clonidine) but not that of antagonist sites (11 - 18% for [(3)H]-RX821002). Competition of [(3)H]-RX821002 binding by (-)-adrenaline further indicated that chronic reserpine was associated with up-regulation of the high-affinity state of alpha(2)-adrenoceptors. 3. In cortical membranes of reserpine-treated rats (0.25 mg kg(-1) s.c., every 48 h for 20 days), the immunoreactivities of various G proteins (Galphai(1/2), Galphai(3), Galphao and Galphas) were increased (25 - 34%). Because the high-affinity conformation of the alpha(2)-adrenoceptor is most probably related to the complex with Galphai(2) proteins, these results suggested an increase in signal transduction through alpha(2)-adrenoceptors (and other monoamine receptors) induced by chronic reserpine. 4. After alpha(2)-adrenoceptor alkylation, the analysis of receptor recovery (B(max) for [(3)H]-UK14304) indicated that the increased density of cortical alpha(2)-adrenoceptors in reserpine-treated rats was probably due to a higher appearance rate constant of the receptor ((Delta)r=57%) and not to a decreased disappearance rate constant ((Delta)k=7%). 5. Northern- and dot-blot analyses of RNA extracted from the cerebral cortex of saline- and reserpine-treated rats (0.25 mg kg(-1), s.c., every 48 h for 20 days) revealed that reserpine markedly increased the expression of alpha(2a)-adrenoceptor mRNA in the brain (125%). This transcriptional activation of the receptor gene expression appears to be the cellular mechanism by which reserpine induces up-regulation in the density of brain alpha(2)-adrenoceptors.
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MESH Headings
- Adrenergic Uptake Inhibitors/pharmacology
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Binding, Competitive/drug effects
- Brain/drug effects
- Brain/metabolism
- Brimonidine Tartrate
- Clonidine/metabolism
- Dose-Response Relationship, Drug
- Epinephrine/pharmacology
- GTP-Binding Proteins/metabolism
- Gene Expression Regulation/drug effects
- Idazoxan/analogs & derivatives
- Idazoxan/metabolism
- Male
- Membranes/metabolism
- Norepinephrine/metabolism
- Quinolines/pharmacology
- Quinoxalines/metabolism
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Reserpine/pharmacology
- Tritium
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Affiliation(s)
- C Ribas
- Laboratory of Neuropharmacology, Associate Unit of the Institute Cajal/CSIC, Department of Biology, University of the Balearic Islands, Cra. Valldemossa Km 7.5, E-07071 Palma de Mallorca, Spain
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