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Felsing DE, Anastasio NC, Miszkiel JM, Gilbertson SR, Allen JA, Cunningham KA. Biophysical validation of serotonin 5-HT2A and 5-HT2C receptor interaction. PLoS One 2018; 13:e0203137. [PMID: 30157263 PMCID: PMC6114921 DOI: 10.1371/journal.pone.0203137] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 08/15/2018] [Indexed: 01/02/2023] Open
Abstract
The serotonin (5-HT) 5-HT2A receptor (5-HT2AR) and 5-HT2C receptor (5-HT2CR) in the central nervous system are implicated in a range of normal behaviors (e.g., appetite, sleep) and physiological functions (e.g., endocrine secretion) while dysfunctional 5-HT2AR and/or 5-HT2CR are implicated in neuropsychiatric disorders (e.g., addiction, obesity, schizophrenia). Preclinical studies suggest that the 5-HT2AR and 5-HT2CR may act in concert to regulate the neural bases for behavior. Here, we utilize three distinct biophysical and immunocytochemistry-based approaches to identify and study this receptor complex in cultured cells. Employing a split luciferase complementation assay (LCA), we demonstrated that formation of the 5-HT2AR:5-HT2CR complex exists within 50 nm, increases proportionally to the 5-HT2CR:5-HT2AR protein expression ratio, and is specific to the receptor interaction and not due to random complementation of the luciferase fragments. Using a proximity ligation assay (PLA), we found that cells stably expressing both the 5-HT2AR and 5-HT2CR exhibit 5-HT2AR:5-HT2CR heteroreceptor complexes within 40 nm of each other. Lastly, bioluminescence resonance energy transfer (BRET) analyses indicates the formation of a specific and saturable 5-HT2AR:5-HT2CR interaction, suggesting that the 5-HT2AR and 5-HT2CR form a close interaction within 10 nm of each other in intact live cells. The bioengineered receptors generated for the LCA and the BRET exhibit 5-HT-mediated intracellular calcium signaling as seen for the native receptors. Taken together, this study validates a very close 5-HT2AR:5-HT2CR interaction in cultured cells.
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Affiliation(s)
- Daniel E. Felsing
- Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Noelle C. Anastasio
- Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Joanna M. Miszkiel
- Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Scott R. Gilbertson
- Department of Chemistry, University of Houston, Houston, Texas, United States of America
| | - John A. Allen
- Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Kathryn A. Cunningham
- Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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Wild CT, Miszkiel JM, Wold EA, Soto CA, Ding C, Hartley RM, White MA, Anastasio NC, Cunningham KA, Zhou J. Design, Synthesis, and Characterization of 4-Undecylpiperidine-2-carboxamides as Positive Allosteric Modulators of the Serotonin (5-HT) 5-HT 2C Receptor. J Med Chem 2018; 62:288-305. [PMID: 29620897 DOI: 10.1021/acs.jmedchem.8b00401] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
An impaired signaling capacity of the serotonin (5-HT) 5-HT2C receptor (5-HT2CR) has been implicated in the neurobehavioral processes that promote relapse vulnerability in cocaine use disorder (CUD). Restoration of the diminished 5-HT2CR signaling through positive allosteric modulation presents a novel therapeutic approach. Several new molecules with the 4-alkylpiperidine-2-carboxamide scaffold were designed, synthesized, and pharmacologically evaluated, leading to the discovery of selective 5-HT2CR positive allosteric modulators (PAMs). Compound 16 (CYD-1-79) potentiated 5-HT-evoked intracellular calcium release in cells stably expressing the human 5-HT2CR but not the 5-HT2AR cells. A topographically distinct allosteric site was identified based on the newly solved 5-HT2CR structure. Compound 16 modulated 5-HT2CR-mediated spontaneous ambulation, partially substituted for the training dose of the 5-HT2CR agonist WAY163909, synergized with a low dose of WAY163909 to substitute fully for the stimulus effects of WAY163909, and attenuated relapse vulnerability as assessed in a rodent self-administration model, indicating its therapeutic promise for CUD.
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Adams WK, Barkus C, Ferland JMN, Sharp T, Winstanley CA. Pharmacological evidence that 5-HT 2C receptor blockade selectively improves decision making when rewards are paired with audiovisual cues in a rat gambling task. Psychopharmacology (Berl) 2017; 234:3091-3104. [PMID: 28733811 DOI: 10.1007/s00213-017-4696-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 07/05/2017] [Indexed: 01/19/2023]
Abstract
RATIONALE Adding reward-concurrent cues to a rat gambling task (rGT) increases risky choice. This cued version of the task may reflect an "addiction-like" cognitive process, more similar to human gambling than the uncued task. Serotonergic drugs that target 5-HT2 receptors alter mechanisms linked to impulse control. However, relatively little is known regarding the impact of such agents on either risky decision making, or the ability of conditioned stimuli to bias the choice process, despite potential relevance to addiction development and treatment. OBJECTIVES The aim of this study was to determine the effects of SB 242,084 and M100907, selective antagonists at the 5-HT2C and 5-HT2A receptors respectively, as well as the selective 5-HT2C receptor agonist Ro-60-0175, on performance of both cued and uncued versions of the rGT. RESULTS SB 242,084 significantly and dose-dependently increased choice of the most optimal option in the cued rGT only, despite concurrently increasing impulsive responses made prematurely on both the cued and uncued rGT. M100907 and Ro-60-0175 did not alter risky decision making, but nevertheless produced the expected decrease in premature responses on both task variants. CONCLUSIONS These findings demonstrate that the 5-HT2 receptor-mediated regulation of risky decision making and motor impulsivity can be pharmacologically dissociated and further show that the presence of highly salient reward-paired cues critically alters the neurochemical regulation of the choice process. Importantly, these results suggest that 5-HT2C receptor antagonists may be of use in disrupting maladaptive patterns of decision making.
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Affiliation(s)
- Wendy K Adams
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Chris Barkus
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.,Department of Pharmacology, University of Oxford, Oxford, UK
| | - Jacqueline-Marie N Ferland
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Trevor Sharp
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Catharine A Winstanley
- Department of Psychology, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.
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Activation of 5-HT 2A receptor disrupts rat maternal behavior. Neuropharmacology 2017; 128:96-105. [PMID: 28965828 DOI: 10.1016/j.neuropharm.2017.09.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 08/26/2017] [Accepted: 09/26/2017] [Indexed: 11/21/2022]
Abstract
Serotonin 5-HT2A receptor is widely distributed in the central nervous system and plays an important role in sensorimotor function, emotion regulation, motivation, executive control, learning and memory. We investigated its role in rat maternal behavior, a naturalistic behavior encompassing many psychological functions that the 5-HT2A receptor is involved in. We first showed that activation of 5-HT2A receptor by TCB-2 (a highly selective 5-HT2A agonist, 1, 2.5 or 5.0 mg/kg) disrupted maternal behavior dose-dependently, and this effect was reduced by pretreatment with a 5-HT2A receptor antagonist MDL 100907, but exacerbated by pretreatment with a 5-HT2C receptor antagonist SB242084 and a 5-HT2C receptor agonist MK212, indicating that the maternal disruptive effect of 5-HT2A activation is receptor-specific and can be modulated by 5-HT2C receptor bidirectionally. We then microinjected TCB-2 into two brain regions important for the normal expression of maternal behavior: the medial prefrontal cortex (mPFC) and the medial preoptic area (mPOA) and found that only acute intra-mPFC infusion of TCB-2 suppressed pup retrieval, whereas intra-mPOA had no effect. Finally, using c-Fos immunohistochemistry, we identified that the ventral bed nucleus of stria terminalis (vBNST), the central amygdala (CeA), and the dorsal raphe (DR) were additionally involved in the maternal-disruptive effect of TCB-2. These findings suggest that the 5-HT2A receptor in the mPFC and other maternally related regions is required for the normal expression of maternal behavior through its intrinsic action or interactions with other receptors (e.g. 5-HT2C). Functional disruption of this neuroreceptor system might contribute to postpartum mental disorders (e.g. depression and psychosis) that impair the quality of maternal care.
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Abstract
Previous attempts to identify a unified theory of brain serotonin function have largely failed to achieve consensus. In this present synthesis, we integrate previous perspectives with new and older data to create a novel bipartite model centred on the view that serotonin neurotransmission enhances two distinct adaptive responses to adversity, mediated in large part by its two most prevalent and researched brain receptors: the 5-HT1A and 5-HT2A receptors. We propose that passive coping (i.e. tolerating a source of stress) is mediated by postsynaptic 5-HT1AR signalling and characterised by stress moderation. Conversely, we argue that active coping (i.e. actively addressing a source of stress) is mediated by 5-HT2AR signalling and characterised by enhanced plasticity (defined as capacity for change). We propose that 5-HT1AR-mediated stress moderation may be the brain's default response to adversity but that an improved ability to change one's situation and/or relationship to it via 5-HT2AR-mediated plasticity may also be important - and increasingly so as the level of adversity reaches a critical point. We propose that the 5-HT1AR pathway is enhanced by conventional 5-HT reuptake blocking antidepressants such as the selective serotonin reuptake inhibitors (SSRIs), whereas the 5-HT2AR pathway is enhanced by 5-HT2AR-agonist psychedelics. This bipartite model purports to explain how different drugs (SSRIs and psychedelics) that modulate the serotonergic system in different ways, can achieve complementary adaptive and potentially therapeutic outcomes.
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Affiliation(s)
- RL Carhart-Harris
- Psychedelic Research Group, Neuropsychopharmacology Unit, Centre for Psychiatry, Division of Brain Sciences, Department of Medicine, Imperial College London, London, UK
| | - DJ Nutt
- Psychedelic Research Group, Neuropsychopharmacology Unit, Centre for Psychiatry, Division of Brain Sciences, Department of Medicine, Imperial College London, London, UK
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Guo F, Xi YB, Gao M, Liu L, Fei NB, Qin W, Li C, Cui LB, Yan F, Yu L, Yuan JL, Yin H. Alterations in cortical thickness in nonmedicated premature ejaculation patients: A morphometric MRI study. J Magn Reson Imaging 2017; 47:656-662. [PMID: 28736888 DOI: 10.1002/jmri.25808] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 06/20/2017] [Indexed: 01/12/2023] Open
Affiliation(s)
- Fan Guo
- Department of Radiology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
- Key Laboratory of Molecular Imaging of the Chinese Academy of Sciences; Institute of Automation, Chinese Academy of Sciences; Beijing P.R. China
| | - Yi-Bin Xi
- Department of Radiology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Ming Gao
- Department of Urology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
- Assisted Reproduction Center; Northwest Women and Children Hospital/Maternity Hospital of Shaanxi Province; Xi'an Shaanxi P.R. China
| | - Lin Liu
- Life Sciences Research Center; School of Life Sciences and Technology, Xidian University; Xi'an Shaanxi P.R. China
| | - Ning-Bo Fei
- Life Sciences Research Center; School of Life Sciences and Technology, Xidian University; Xi'an Shaanxi P.R. China
| | - Wei Qin
- Life Sciences Research Center; School of Life Sciences and Technology, Xidian University; Xi'an Shaanxi P.R. China
| | - Chen Li
- Department of Radiology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Long-Biao Cui
- Department of Radiology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Fei Yan
- Department of Urology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Lei Yu
- Department of Urology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Jian-Lin Yuan
- Department of Urology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
| | - Hong Yin
- Department of Radiology; Xijing Hospital, The Fourth Military Medical University; Xi'an Shaanxi P.R. China
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Palacios JM, Pazos A, Hoyer D. A short history of the 5-HT 2C receptor: from the choroid plexus to depression, obesity and addiction treatment. Psychopharmacology (Berl) 2017; 234:1395-1418. [PMID: 28265714 DOI: 10.1007/s00213-017-4545-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Accepted: 01/23/2017] [Indexed: 12/20/2022]
Abstract
This paper is a personal account on the discovery and characterization of the 5-HT2C receptor (first known as the 5-HT1C receptor) over 30 years ago and how it translated into a number of unsuspected features for a G protein-coupled receptor (GPCR) and a diversity of clinical applications. The 5-HT2C receptor is one of the most intriguing members of the GPCR superfamily. Initially referred to as 5-HT1CR, the 5-HT2CR was discovered while studying the pharmacological features and the distribution of [3H]mesulergine-labelled sites, primarily in the brain using radioligand binding and slice autoradiography. Mesulergine (SDZ CU-085), was, at the time, best defined as a ligand with serotonergic and dopaminergic properties. Autoradiographic studies showed remarkably strong [3H]mesulergine-labelling to the rat choroid plexus. [3H]mesulergine-labelled sites had pharmacological properties different from, at the time, known or purported 5-HT receptors. In spite of similarities with 5-HT2 binding, the new binding site was called 5-HT1C because of its very high affinity for 5-HT itself. Within the following 10 years, the 5-HT1CR (later named 5-HT2C) was extensively characterised pharmacologically, anatomically and functionally: it was one of the first 5-HT receptors to be sequenced and cloned. The 5-HT2CR is a GPCR, with a very complex gene structure. It constitutes a rarity in the GPCR family: many 5-HT2CR variants exist, especially in humans, due to RNA editing, in addition to a few 5-HT2CR splice variants. Intense research led to therapeutically active 5-HT2C receptor ligands, both antagonists (or inverse agonists) and agonists: keeping in mind that a number of antidepressants and antipsychotics are 5-HT2CR antagonists/inverse agonists. Agomelatine, a 5-HT2CR antagonist is registered for the treatment of major depression. The agonist Lorcaserin is registered for the treatment of aspects of obesity and has further potential in addiction, especially nicotine/ smoking. There is good evidence that the 5-HT2CR is involved in spinal cord injury-induced spasms of the lower limbs, which can be treated with 5-HT2CR antagonists/inverse agonists such as cyproheptadine or SB206553. The 5-HT2CR may play a role in schizophrenia and epilepsy. Vabicaserin, a 5-HT2CR agonist has been in development for the treatment of schizophrenia and obesity, but was stopped. As is common, there is potential for further indications for 5-HT2CR ligands, as suggested by a number of preclinical and/or genome-wide association studies (GWAS) on depression, suicide, sexual dysfunction, addictions and obesity. The 5-HT2CR is clearly affected by a number of established antidepressants/antipsychotics and may be one of the culprits in antipsychotic-induced weight gain.
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Affiliation(s)
| | - Angel Pazos
- Instituto de Biomedicina y Biotecnología de Cantabria, IBBTEC, Universidad de Cantabria, CSIC, SODERCAN, Centro de Investigación Biomédica en Red de Salud Mental CIBERSAM, Santander, 39011, Spain
| | - Daniel Hoyer
- Department of Pharmacology and Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia. .,The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia. .,Department of Molecular Medicine, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA, 92037, USA.
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58
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Moutkine I, Quentin E, Guiard BP, Maroteaux L, Doly S. Heterodimers of serotonin receptor subtypes 2 are driven by 5-HT 2C protomers. J Biol Chem 2017; 292:6352-6368. [PMID: 28258217 DOI: 10.1074/jbc.m117.779041] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/02/2017] [Indexed: 11/06/2022] Open
Abstract
The serotonin receptor subtypes 2 comprise 5-HT2A, 5-HT2B, and 5-HT2C, which are Gαq-coupled receptors and display distinct pharmacological properties. Although co-expressed in some brain regions and involved in various neurological disorders, their functional interactions have not yet been studied. We report that 5-HT2 receptors can form homo- and heterodimers when expressed alone or co-expressed in transfected cells. Co-immunoprecipitation and bioluminescence resonance energy transfer studies confirmed that 5-HT2C receptors interact with either 5-HT2A or 5-HT2B receptors. Although heterodimerization with 5-HT2C receptors does not alter 5-HT2C Gαq-dependent inositol phosphate signaling, 5-HT2A or 5-HT2B receptor-mediated signaling was totally blunted. This feature can be explained by a dominance of 5-HT2C on 5-HT2A and 5-HT2B receptor binding; in 5-HT2C-containing heterodimers, ligands bind and activate the 5-HT2C protomer exclusively. This dominant effect on the associated protomer was also observed in neurons, supporting the physiological relevance of 5-HT2 receptor heterodimerization in vivo Accordingly, exogenous expression of an inactive form of the 5-HT2C receptor in the locus ceruleus is associated with decreased 5-HT2A-dependent noradrenergic transmission. These data demonstrate that 5-HT2 receptors can form functionally asymmetric heterodimers in vitro and in vivo that must be considered when analyzing the physiological or pathophysiological roles of serotonin in tissues where 5-HT2 receptors are co-expressed.
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Affiliation(s)
- Imane Moutkine
- From the INSERM UMR-S839, Paris 75005.,the Université Pierre et Marie Curie, Paris 75005.,the Institut du Fer à Moulin, Paris 75005
| | - Emily Quentin
- From the INSERM UMR-S839, Paris 75005.,the Université Pierre et Marie Curie, Paris 75005.,the Institut du Fer à Moulin, Paris 75005
| | - Bruno P Guiard
- the Research Center on Animal Cognition, Center for Integrative Biology, Université Paul Sabatier, UMR5169 CNRS, 118, Route de Narbonne, 31062, Toulouse Cedex 9, France
| | - Luc Maroteaux
- From the INSERM UMR-S839, Paris 75005, .,the Université Pierre et Marie Curie, Paris 75005.,the Institut du Fer à Moulin, Paris 75005
| | - Stephane Doly
- the Institut Cochin, INSERM U1016, CNRS UMR8104, Paris 75014, .,the Université Paris Descartes, Sorbonne Paris Cité, Paris 75014.,the Université Clermont Auvergne, INSERM, NEURO-DOL, F-63000 Clermont-Ferrand, and
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59
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60
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Schenk S, Aronsen D. Contribution of Impulsivity and Serotonin Receptor Neuroadaptations to the Development of an MDMA ('Ecstasy') Substance Use Disorder. Curr Top Behav Neurosci 2017; 34:17-32. [PMID: 26718587 DOI: 10.1007/7854_2015_421] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
As is the case with other drugs of abuse, a proportion of ecstasy users develop symptoms consistent with a substance use disorder (SUD). In this paper, we propose that the pharmacology of MDMA, the primary psychoactive component of ecstasy tablets, changes markedly with repeated exposure and that neuroadaptations in dopamine and serotonin brain systems underlie the shift from MDMA use to MDMA misuse in susceptible subjects. Data from both the human and laboratory animal literature are synthesized to support the idea that (1) MDMA becomes a less efficacious serotonin releaser and a more efficacious dopamine releaser with the development of behaviour consistent with an SUD and (2) that upregulated serotonin receptor mechanisms contribute to the development of the MDMA SUD via dysregulated inhibitory control associated with the trait of impulsivity.
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Affiliation(s)
- Susan Schenk
- School of Psychology, Victoria University of Wellington, Wellington, New Zealand.
| | - Dane Aronsen
- School of Psychology, Victoria University of Wellington, Wellington, New Zealand
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61
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5-HT 2C Receptor Knockdown in the Amygdala Inhibits Neuropathic-Pain-Related Plasticity and Behaviors. J Neurosci 2016; 37:1378-1393. [PMID: 28011743 DOI: 10.1523/jneurosci.2468-16.2016] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 11/28/2016] [Accepted: 12/20/2016] [Indexed: 12/31/2022] Open
Abstract
Neuroplasticity in the amygdala drives pain-related behaviors. The central nucleus (CeA) serves major amygdala output functions and can generate emotional-affective behaviors and modulate nocifensive responses. The CeA receives excitatory and inhibitory inputs from the basolateral nucleus (BLA) and serotonin receptor subtype 5-HT2CR in the BLA, but not CeA, has been implicated anxiogenic behaviors and anxiety disorders. Here, we tested the hypothesis that 5-HT2CR in the BLA plays a critical role in CeA plasticity and neuropathic pain behaviors in the rat spinal nerve ligation (SNL) model. Local 5-HT2CR knockdown in the BLA with stereotaxic injection of 5-HT2CR shRNA AAV vector decreased vocalizations and anxiety- and depression-like behaviors and increased sensory thresholds of SNL rats, but had no effect in sham controls. Extracellular single-unit recordings of CeA neurons in anesthetized rats showed that 5-HT2CR knockdown blocked the increase in neuronal activity (increased responsiveness, irregular spike firing, and increased burst activity) in SNL rats. At the synaptic level, 5-HT2CR knockdown blocked the increase in excitatory transmission from BLA to CeA recorded in brain slices from SNL rats using whole-cell patch-clamp conditions. Inhibitory transmission was decreased by 5-HT2CR knockdown in control and SNL conditions to a similar degree. The findings can be explained by immunohistochemical data showing increased expression of 5-HT2CR in non-GABAergic BLA cells in SNL rats. The results suggest that increased 5-HT2CR in the BLA contributes to neuropathic-pain-related amygdala plasticity by driving synaptic excitation of CeA neurons. As a rescue strategy, 5-HT2CR knockdown in the BLA inhibits neuropathic-pain-related behaviors.SIGNIFICANCE STATEMENT Neuroplasticity in the amygdala has emerged as an important pain mechanism. This study identifies a novel target and rescue strategy to control abnormally enhanced amygdala activity in an animal model of neuropathic pain. Specifically, an integrative approach of gene transfer, systems and brain slice electrophysiology, behavior, and immunohistochemistry was used to advance the novel concept that serotonin receptor subtype 5-HT2C contributes critically to the imbalance between excitatory and inhibitory drive of amygdala output neurons. Local viral vector-mediated 5-HT2CR knockdown in the amygdala normalizes the imbalance, decreases neuronal activity, and inhibits neuropathic-pain-related behaviors. The study provides valuable insight into serotonin receptor (dys)function in a limbic brain area.
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62
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Swinford-Jackson SE, Anastasio NC, Fox RG, Stutz SJ, Cunningham KA. Incubation of cocaine cue reactivity associates with neuroadaptations in the cortical serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system. Neuroscience 2016; 324:50-61. [PMID: 26926963 DOI: 10.1016/j.neuroscience.2016.02.052] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 02/15/2016] [Accepted: 02/23/2016] [Indexed: 11/28/2022]
Abstract
Intensification of craving elicited by drug-associated cues during abstinence occurs over time in human cocaine users while elevation of cue reactivity ("incubation") is observed in rats exposed to extended forced abstinence from cocaine self-administration. Incubation in rodents has been linked to time-dependent neuronal plasticity in the medial prefrontal cortex (mPFC). We tested the hypothesis that incubation of cue reactivity during abstinence from cocaine self-administration is accompanied by lower potency and/or efficacy of the selective serotonin (5-HT) 5-HT2C receptor (5-HT2CR) agonist WAY163909 to suppress cue reactivity and a shift in the subcellular localization profile of the mPFC 5-HT2CR protein. We observed incubation of cue reactivity (measured as lever presses reinforced by the discrete cue complex) between Day 1 and Day 30 of forced abstinence from cocaine relative to sucrose self-administration. Pharmacological and biochemical analyses revealed that the potency of the selective 5-HT2CR agonist WAY163909 to suppress cue reactivity, the expression of synaptosomal 5-HT2CR protein in the mPFC, and the membrane to cytoplasmic expression of the 5-HT2CR in mPFC were lower on Day 30 vs. Day 1 of forced abstinence from cocaine self-administration. Incubation of cue reactivity assessed during forced abstinence from sucrose self-administration did not associate with 5-HT2CR protein expression in the mPFC. Collectively, these outcomes are the first indication that neuroadaptations in the 5-HT2CR system may contribute to incubation of cocaine cue reactivity.
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Affiliation(s)
- S E Swinford-Jackson
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX, USA
| | - N C Anastasio
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX, USA; Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA
| | - R G Fox
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX, USA
| | - S J Stutz
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX, USA
| | - K A Cunningham
- Center for Addiction Research, University of Texas Medical Branch, Galveston, TX, USA; Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, USA.
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63
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Andrews AM. Prefrontal Cortex Vistas: A Serotonin Safari. ACS Chem Neurosci 2015; 6:936-7. [PMID: 26156792 DOI: 10.1021/acschemneuro.5b00187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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