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Boillot M, ter Horst J, López JR, Di Fazio I, Steens ILM, Cohen MX, Homberg JR. Serotonin transporter knockout in rats reduces beta- and gamma-band functional connectivity between the orbitofrontal cortex and amygdala during auditory discrimination. Cereb Cortex 2024; 34:bhae334. [PMID: 39128940 PMCID: PMC11317204 DOI: 10.1093/cercor/bhae334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 06/27/2024] [Indexed: 08/13/2024] Open
Abstract
The orbitofrontal cortex and amygdala collaborate in outcome-guided decision-making through reciprocal projections. While serotonin transporter knockout (SERT-/-) rodents show changes in outcome-guided decision-making, and in orbitofrontal cortex and amygdala neuronal activity, it remains unclear whether SERT genotype modulates orbitofrontal cortex-amygdala synchronization. We trained SERT-/- and SERT+/+ male rats to execute a task requiring to discriminate between two auditory stimuli, one predictive of a reward (CS+) and the other not (CS-), by responding through nose pokes in opposite-side ports. Overall, task acquisition was not influenced by genotype. Next, we simultaneously recorded local field potentials in the orbitofrontal cortex and amygdala of both hemispheres while the rats performed the task. Behaviorally, SERT-/- rats showed a nonsignificant trend for more accurate responses to the CS-. Electrophysiologically, orbitofrontal cortex-amygdala synchronization in the beta and gamma frequency bands during response selection was significantly reduced and associated with decreased hubness and clustering coefficient in both regions in SERT-/- rats compared to SERT+/+ rats. Conversely, theta synchronization at the time of behavioral response in the port associated with reward was similar in both genotypes. Together, our findings reveal the modulation by SERT genotype of the orbitofrontal cortex-amygdala functional connectivity during an auditory discrimination task.
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Affiliation(s)
- Morgane Boillot
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - Jordi ter Horst
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - José Rey López
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - Ilaria Di Fazio
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - Indra L M Steens
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - Michael X Cohen
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
| | - Judith R Homberg
- Department of Cognitive Neuroscience, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Kapittelweg 29, 6525 EN, Nijmegen, Netherlands
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Lee A, Thuras P, Baller J, Jiao C, Guo B, Erbes CR, Polusny MA, Liu C, Wu B, Lim KO, Bishop JR. Serotonin Transporter (SLC6A4) and FK506-Binding Protein 5 (FKBP5) Genotype and Methylation Relationships with Response to Meditation in Veterans with PTSD. Mol Neurobiol 2024:10.1007/s12035-024-04096-6. [PMID: 38671329 DOI: 10.1007/s12035-024-04096-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Accepted: 03/04/2024] [Indexed: 04/28/2024]
Abstract
Meditation-based interventions are novel and effective non-pharmacologic treatments for veterans with PTSD. We examined relationships between treatment response, early life trauma exposure, DNA polymorphisms, and methylation in the serotonin transporter (SLC6A4) and FK506-binding protein 5 (FKBP5) genes. DNA samples and clinical outcomes were examined in 72 veterans with PTSD who received meditation-based therapy in two separate studies of mindfulness-based stress reduction (MBSR) and Transcendental Meditation (TM). The PTSD Checklist was administered to assess symptoms at baseline and after 9 weeks of meditation intervention. We examined the SLC6A4 promoter (5HTTLPR_L/S insertion/deletion + rs25531_A/G) polymorphisms according to previously defined gene expression groups, and the FKBP5 variant rs1360780 previously associated with PTSD disease risk. Methylation for CpG sites of SLC6A4 (28 sites) and FKBP5 (45 sites) genes was quantified in DNA samples collected before and after treatment. The 5HTTLPR LALA high expression genotype was associated with greater symptom improvement in participants exposed to early life trauma (p = 0.015). Separately, pre to post-treatment change of DNA methylation in a group of nine FKBP5 CpG sites was associated with greater symptom improvement (OR = 2.8, 95% CI 1.1-7.1, p = 0.027). These findings build on a wealth of existing knowledge regarding epigenetic and genetic relationships with PTSD disease risk to highlight the potential importance of SLC6A4 and FKBP5 for treatment mechanisms and as biomarkers of symptom improvement.
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Affiliation(s)
- Adam Lee
- Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Room 7-115 Weaver-Densford Hall, 308 Harvard St SE, Minneapolis, MN, 55455, USA
| | - Paul Thuras
- Department of Psychiatry and Behavioral Sciences, University of Minnesota Medical School, Minneapolis, MN, USA
- Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
| | - Joshua Baller
- Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, MN, USA
| | - Chuan Jiao
- Department of Psychiatry, State University of New York Upstate Medical University, Syracuse, NY, USA
- Institute of Psychiatry and Neuroscience of Paris (IPNP), INSERM U1266, Team Krebs, Université Paris Cité, 75014, Paris, France
| | - Bin Guo
- Division of Biostatistics, University of Minnesota, Minneapolis, MN, USA
| | - Christopher R Erbes
- Department of Psychiatry and Behavioral Sciences, University of Minnesota Medical School, Minneapolis, MN, USA
- Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
- Center for Care Delivery and Outcomes Research, Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
| | - Melissa A Polusny
- Department of Psychiatry and Behavioral Sciences, University of Minnesota Medical School, Minneapolis, MN, USA
- Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
- Center for Care Delivery and Outcomes Research, Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
| | - Chunyu Liu
- Department of Psychiatry, State University of New York Upstate Medical University, Syracuse, NY, USA
| | - Baolin Wu
- Department of Epidemiology and Biostatistics, Program in Public Health, University of California-Irvine, Irvine, CA, USA
| | - Kelvin O Lim
- Department of Psychiatry and Behavioral Sciences, University of Minnesota Medical School, Minneapolis, MN, USA
- Minneapolis Veterans Affairs Health Care System, Minneapolis, MN, USA
- Geriatric Research, Education, and Clinical Center, Minneapolis VA Health Care System, Minneapolis, MN, USA
| | - Jeffrey R Bishop
- Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Room 7-115 Weaver-Densford Hall, 308 Harvard St SE, Minneapolis, MN, 55455, USA.
- Department of Psychiatry and Behavioral Sciences, University of Minnesota Medical School, Minneapolis, MN, USA.
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Sharp T, Collins H. Mechanisms of SSRI Therapy and Discontinuation. Curr Top Behav Neurosci 2024; 66:21-47. [PMID: 37955823 DOI: 10.1007/7854_2023_452] [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] [Indexed: 11/14/2023]
Abstract
SSRIs are one of the most widely used drug therapies in primary care and psychiatry, and central to the management of the most common mental health problems in today's society. Despite this, SSRIs suffer from a slow onset of therapeutic effect and relatively poor efficacy as well as adverse effects, with recent concerns being focused on a disabling SSRI discontinuation syndrome. The mechanism underpinning their therapeutic effect has long shifted away from thinking that SSRIs act simply by increasing 5-HT in the synapse. Rather, a current popular view is that increased 5-HT is just the beginning of a series of complex downstream signalling events, which trigger changes in neural plasticity at the functional and structural level. These changes in plasticity are then thought to interact with neuropsychological processes to enhance re-learning of emotional experiences that ultimately brings about changes in mood. This compelling view of SSRI action is underpinning attempts to understand fast-acting antidepressants, such as ketamine and psychedelic drugs, and aid the development of future therapies. An important gap in the theory is evidence that changes in plasticity are causally linked to relevant behavioural effects. Also, predictions that the SSRI-induced neural plasticity might have applicability in other areas of medicine have not yet been borne out. In contrast to the sophisticated view of the antidepressant action of SSRIs, the mechanism underpinning SSRI discontinuation is little explored. Nevertheless, evidence of rebound increases in 5-HT neuron excitability immediately on cessation of SSRI treatment provide a starting point for future investigation. Indeed, this evidence allows formulation of a mechanistic explanation of SSRI discontinuation which draws on parallels with the withdrawal states of other psychotropic drugs.
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Affiliation(s)
- Trevor Sharp
- Department of Pharmacology, University of Oxford, Oxford, UK.
| | - Helen Collins
- Department of Pharmacology, University of Oxford, Oxford, UK
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Zhao R, Liu P, Song A, Liu J, Chu Q, Liu Y, Jiang Y, Dong C, Shi H, Yan Z. Network pharmacology study on the mechanism of Qiangzhifang in the treatment of panic disorder. ANNALS OF TRANSLATIONAL MEDICINE 2021; 9:1350. [PMID: 34532487 PMCID: PMC8422112 DOI: 10.21037/atm-21-4090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 08/16/2021] [Indexed: 12/24/2022]
Abstract
Background Panic disorder (PD) is a kind of mental illness characterized by the symptom of recurring panic attacks. Qiangzhifang (QZF) is a novel decoction developed by Professor Zhaojun Yan based on a unique system of syndrome differentiation and clinical experience. It has achieved remarkable results after long-term clinical practice, but its mechanism of action is still unclear. This study aims to use network pharmacology and molecular docking to explore the mechanism of QZF in the treatment of PD. Methods We used the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), a literature search, and Encyclopedia of Traditional Chinese Medicine (ETCM) to find active ingredients and targets of QZF. We searched for PD targets in GeneCards, Online Mendelian Inheritance in Man (OMIM), the Comparative Toxicogenomics Database (CTD), and DrugBank. We established a PD target database, constructed a protein-protein interaction (PPI) network, and performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis in order to screen possible pathways of action and analyze the mechanism. Results This study identified 84 effective components of QZF, 691 potential targets, 357 PD targets, and 97 intersectional targets. Enrichment analysis using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) showed that QZF was associated with 118 biological processes (BPs), 18 cellular components (CCs), 35 molecular functions (MFs) [false discovery rate (FDR) <0.01], and 62 pathways (FDR <0.01). QZF mainly acts on its targets AKT1, FOS, and APP through active ingredients such as quercetin, β-sitosterol, 4-(4'-hydroxybenzyloxy)benzyl methyl ether, harmine, 1,7-dimethoxyxanthone, and 1-hydroxy-3,7-dimethoxyxanthone to regulate serotonin, gamma-aminobutyric acid (GABA), cyclic adenosine monophosphate (cAMP), and other signal pathways to treat PD. Conclusions Through network pharmacology and molecular docking technology, we predicted the possible mechanism of QZF in the treatment of PD, revealed the interaction targets and potential value of QZF, and provided a basis for its clinical application.
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Affiliation(s)
- Run Zhao
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Pulin Liu
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Anran Song
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Jianmin Liu
- Department of Psychosomatic Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Qian Chu
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yingnan Liu
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Yunyun Jiang
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Chengda Dong
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Huishan Shi
- First Clinical Medical College, Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Zhaojun Yan
- Department of Psychosomatic Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
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Ozawa A, Arakawa H. Chemogenetics drives paradigm change in the investigation of behavioral circuits and neural mechanisms underlying drug action. Behav Brain Res 2021; 406:113234. [PMID: 33741409 PMCID: PMC8110310 DOI: 10.1016/j.bbr.2021.113234] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 03/06/2021] [Accepted: 03/08/2021] [Indexed: 12/12/2022]
Abstract
Recent developments in chemogenetic approaches to the investigation of brain function have ushered in a paradigm change in the strategy for drug and behavior research and clinical drug-based medications. As the nature of the drug action is based on humoral regulation, it is a challenge to identify the neuronal mechanisms responsible for the expression of certain targeted behavior induced by drug application. The development of chemogenetic approaches has allowed researchers to control neural activities in targeted neurons through a toolbox, including engineered G protein-coupled receptors or ligand-gated ion channels together with exogenously inert synthetic ligands. This review provides a brief overview of the chemogenetics toolbox with an emphasis on the DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) technique used in rodent models, which is applicable to the investigation of how specific neural circuits regulate behavioral processes. The use of chemogenetics has had a significant impact on basic neuroscience for a better understanding of the relationships between brain activity and the expression of behaviors with cell- and circuit-specific orders. Furthermore, chemogenetics is potentially a useful tool to deconstruct the neuropathological mechanisms of mental diseases and its regulation by drug, and provide us with transformative therapeutics with medication. We also review recent findings in the use of chemogenetic techniques to uncover functional circuit connections of serotonergic neurons in rodent models.
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Affiliation(s)
- Akihiko Ozawa
- Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL, USA
| | - Hiroyuki Arakawa
- Department of Psychology, Tokiwa University, Mito, Ibaraki, Japan; Department of Systems Physiology, University of Ryukyus, Faculty of Medicine, Nakagami District, Okinawa, Japan.
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de Assis Brasil ES, Guerino Furini CR, da Silva Rodrigues F, Nachtigall EG, Kielbovicz Behling JA, Saenger BF, Farias CP, de Carvalho Myskiw J, Izquierdo I. The blockade of the serotoninergic receptors 5-HT5A, 5-HT6 and 5-HT7 in the basolateral amygdala, but not in the hippocampus facilitate the extinction of fear memory. Behav Brain Res 2019; 372:112055. [DOI: 10.1016/j.bbr.2019.112055] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/27/2019] [Accepted: 06/20/2019] [Indexed: 01/20/2023]
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Enhanced discriminative aversive learning and amygdala responsivity in 5-HT transporter mutant mice. Transl Psychiatry 2019; 9:139. [PMID: 30996249 PMCID: PMC6470159 DOI: 10.1038/s41398-019-0476-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 02/07/2019] [Accepted: 02/12/2019] [Indexed: 12/31/2022] Open
Abstract
Genetic variation in the human serotonin transporter (5-HTT) has been linked to altered fear learning but the data are inconsistent and the mechanism is unclear. The present study investigated conditioned aversive learning in 5-HTT knockout (KO) mice while simultaneously recording neural network activity (theta oscillations) and hemodynamic responses (tissue oxygen delivery) from the amygdala, a brain region necessary for forming fearful memories. Conditioned aversive learning was measured using a discrimination learning task in which one auditory cue was paired with foot-shock, whereas a second auditory cue was not. Compared with wild-type mice, 5-HTTKO mice exhibited faster discrimination learning. This effect was associated with stronger theta frequency oscillations and greater hemodynamic changes in the amygdala in response to both the emotionally relevant cues and the unconditioned foot-shock stimulus. Furthermore, hemodynamic responses to the unconditioned stimulus predicted behavioral discrimination performance the following day. Acute pharmacological 5-HTT blockade in wild-type mice produced a similar effect, to the extent that administration of citalopram during the fear conditioning sessions enhanced fear memory recall. Collectively, our data argue that loss of 5-HTT function enhances amygdala responsivity to aversive events and facilitates learning for emotionally relevant cues.
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Quentin E, Belmer A, Maroteaux L. Somato-Dendritic Regulation of Raphe Serotonin Neurons; A Key to Antidepressant Action. Front Neurosci 2018; 12:982. [PMID: 30618598 PMCID: PMC6307465 DOI: 10.3389/fnins.2018.00982] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/07/2018] [Indexed: 11/22/2022] Open
Abstract
Several lines of evidence implicate serotonin (5-hydroxytryptamine, 5-HT)in regulating personality traits and mood control. Serotonergic neurons are classically thought to be tonic regular-firing, “clock-like” neurons. Neurotransmission by serotonin is tightly regulated by the serotonin transporter (SERT) and by autoreceptors (serotonin receptors expressed by serotonin neurons) through negative feedback inhibition at the cell bodies and dendrites (5-HT1A receptors) of the dorsal raphe nuclei or at the axon terminals (5-HT1B receptors). In dorsal raphe neurons, the release of serotonin from vesicles in the soma, dendrites, and/or axonal varicosities is independent of classical synapses and can be induced by neuron depolarization, by the stimulation of L-type calcium channels, by activation of glutamatergic receptors, and/or by activation of 5-HT2 receptors. The resulting serotonin release displays a slow kinetic and a large diffusion. This process called volume transmission may ultimately affect the rate of discharge of serotonergic neurons, and their tonic activity. The therapeutic effects induced by serotonin-selective reuptake inhibitor (SSRI) antidepressants are initially triggered by blocking SERT but rely on consequences of chronic exposure, i.e., a selective desensitization of somatodendritic 5-HT1A autoreceptors. Agonist stimulation of 5-HT2B receptors mimicked behavioral and neurogenic SSRI actions, and increased extracellular serotonin in dorsal raphe. By contrast, a lack of effects of SSRIs was observed in the absence of 5-HT2B receptors (knockout-KO), even restricted to serotonergic neurons (Htr2b5-HTKO mice). The absence of 5-HT2B receptors in serotonergic neurons is associated with a higher 5-HT1A-autoreceptor reactivity and thus a lower firing activity of these neurons. In agreement, mice with overexpression of 5-HT1A autoreceptor show decreased neuronal activity and increased depression-like behavior that is resistant to SSRI treatment. We propose thus that the serotonergic tone results from the opposite control exerted by somatodendritic (Gi-coupled) 5-HT1A and (Gq-coupled) 5-HT2B receptors on dorsal raphe neurons. Therefore, 5-HT2B receptors may contribute to SSRI therapeutic effects by their positive regulation of adult raphe serotonergic neurons. Deciphering the molecular mechanism controlling extrasynaptic release of serotonin, and how autoreceptors interact in regulating the tonic activity of serotonergic neurons, is critical to fully understand the therapeutic effect of SSRIs.
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Affiliation(s)
- Emily Quentin
- INSERM UMR-S 839, Institut du Fer à Moulin, Paris, France.,Sorbonne Universités, UPMC University Paris 6, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Arnauld Belmer
- INSERM UMR-S 839, Institut du Fer à Moulin, Paris, France.,Sorbonne Universités, UPMC University Paris 6, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Luc Maroteaux
- INSERM UMR-S 839, Institut du Fer à Moulin, Paris, France.,Sorbonne Universités, UPMC University Paris 6, Paris, France.,Institut du Fer à Moulin, Paris, France
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Tyrer AE, Levitan RD, Houle S, Wilson AA, Nobrega JN, Meyer JH. Increased Seasonal Variation in Serotonin Transporter Binding in Seasonal Affective Disorder. Neuropsychopharmacology 2016; 41:2447-54. [PMID: 27087270 PMCID: PMC4987850 DOI: 10.1038/npp.2016.54] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/21/2016] [Accepted: 03/25/2016] [Indexed: 11/09/2022]
Abstract
Seasonal affective disorder (SAD) is highly prevalent with rates of 1-6% and greater prevalence at more extreme latitudes; however, there are almost no direct brain investigations of this disorder. In health, serotonin transporter binding potential (5-HTT BPND), an index of 5-HTT levels, is greater throughout the brain in fall-winter compared with spring-summer. We hypothesized that in SAD, this seasonal variation would be greater in brain regions containing structures that regulate affect such as the prefrontal and anterior cingulate cortices (PFC and ACC). Furthermore, given the dimensional nature of SAD symptoms, it was hypothesized that seasonal fluctuation of 5-HTT BPND in the PFC and ACC would be greatest in severe SAD. Twenty SAD and twenty healthy participants underwent [(11)C]DASB positron emission tomography scans in summer and winter to measure seasonal variation in [(11)C]DASB 5-HTT BPND. Seasonal increases in [(11)C]DASB 5-HTT BPND were greater in SAD compared with healthy in the PFC and ACC, primarily due to differences between severe SAD and healthy (severe SAD vs healthy; Mann-Whitney U, U=42.5 and 37.0, p=0.005 and 0.003, respectively; greater magnitude in severe SAD of 35.10 and 14.23%, respectively), with similar findings observed in other regions (U=40.0-62.0, p=0.004-0.048; greater magnitude in severe SAD of 13.16-17.49%). To our knowledge, this is the first brain biomarker identified in SAD. This creates a new opportunity for phase 0 studies to target this phenotype and optimize novel prevention/treatment strategies for SAD.
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Affiliation(s)
- Andrea E Tyrer
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Robert D Levitan
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Sylvain Houle
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Alan A Wilson
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - José N Nobrega
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada,Behavioural Neurobiology Laboratory, Departments of Psychiatry, Pharmacology and Toxicology, and Psychology, Campbell Family Mental Health Research Institute, University of Toronto, Toronto, ON, Canada
| | - Jeffrey H Meyer
- Departments of Psychiatry, Pharmacology and Toxicology, CAMH Research Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, and Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada,CAMH Research Imaging Centre, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T1R8, Canada, Tel: +1 416 535 8501 x 34007, Fax: +1 416 979 4656, E-mail:
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10
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Harro J, Oreland L. The role of MAO in personality and drug use. Prog Neuropsychopharmacol Biol Psychiatry 2016; 69:101-11. [PMID: 26964906 DOI: 10.1016/j.pnpbp.2016.02.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 02/16/2016] [Accepted: 02/17/2016] [Indexed: 02/04/2023]
Abstract
Monoamine oxidases, both MAO-A and MAO-B, have been implicated in personality traits and complex behaviour, including drug use. Findings supporting the involvement of MAO-A and MAO-B in shaping personality and in the development of strategies of making behavioural choices come from a variety of studies that have examined either prevalence of gene variants in clinical groups or population-derived samples, estimates of enzyme activity in blood or, by positron emission tomography, in the brain and, most recently, measurement of methylation of the gene. Most of the studies converge in associating MAO-A and MAO-B with impulsive, aggressive or antisocial personality traits or behaviours, including alcohol-related problems, and for MAO-A available evidence strongly supports interaction with adverse environmental exposures in childhood. What is known about genotype effects, and on expression and activity of the enzyme in the brain and in blood has not yet been possible to unite into a mechanistic model of the role of monoamine systems, but the reason for this low degree of generalization is likely caused by the cross-sectional nature of investigation that has not incorporated the developmental effects of MAO-s in critical time windows, including the foetal period. The "risk variants" of both MAO-s appear to increase behavioural plasticity, as supportive environments may particularly well enhance the hidden potential of their carriers. Importantly, male and female brain and behaviours have been found very different with regard to MAO×life events interaction. Future studies need to take into consideration these developmental aspects and sex/gender, as well as to specify the role of different types of environmental factors.
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Affiliation(s)
- Jaanus Harro
- Division of Neuropsychopharmacology, Department of Psychology, Estonian Centre of Behavioural and Health Sciences, University of Tartu, Estonia; Psychiatry Clinic, North Estonia Medical Centre, Tallinn, Estonia.
| | - Lars Oreland
- Department of Neuroscience, Pharmacology, University of Uppsala, Biomedical Centre, Uppsala, Sweden
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11
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Beart PM. Synaptic signalling and its interface with neuropathologies: snapshots from the past, present and future. J Neurochem 2016; 139 Suppl 2:76-90. [PMID: 27144305 DOI: 10.1111/jnc.13598] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 02/09/2016] [Accepted: 02/26/2016] [Indexed: 11/30/2022]
Abstract
This 'Past to Future' Review as part of the 60th anniversary year of the Journal of Neurochemistry focuses on synaptic transmission and associated signalling, and seeks to identify seminal progress in neurochemistry over the last 10 years which has advanced our understanding of neuronal communication in brain. The approach adopted analyses neurotransmitters on a case by case basis (i.e. amino acids, monoamines, acetylcholine, neuropeptides, ATP/purines and gasotransmitters) to highlight novel findings that have changed the way we view each type of transmitter, to explore commonalities and interactions, and to note how new insights have changed the way we view the biology of degenerative, psychiatric and behavioural conditions. Across all transmitter systems there was remarkable growth in the identification of targets likely to provide therapeutic benefit and which undoubtedly was driven by the elucidation of circuit function and new vistas of synaptic signalling. There has been an increasing trend to relate signalling to disease, notably for Alzheimer's and Parkinson's disease and related conditions, and which has occurred for each transmitter family. Forebrain circuitry and tonic excitatory control have been the centre of great attention yielding novel findings that will impact upon cognitive, emotional and addictive behaviours. Other impressive insights focus on gasotransmitters integrating activity as volume transmitters. Exciting developments in how serotonin, cholinergic, l-glutamate, galanin and adenosine receptors and their associated signalling can be beneficially targeted should underpin the development of new therapies. Clearly integrated, multifaceted neurochemistry has changed the way we view synaptic signalling and its relevance to pathobiology. Highlighted are important advances in synaptic signalling over the last decade in the Journal of Neurochemistry. Across all transmitter systems elucidation of circuit function, and notably molecular insights, have underpinned remarkable growth in the identification of targets likely to provide therapeutic benefit in neuropathologies. Another commonality was wide interest in forebrain circuitry and its tonic excitatory control. Increasingly observations relate to signalling in disease and behavioural conditions. This article is part of the 60th Anniversary special issue.
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Affiliation(s)
- Philip M Beart
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.
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Bocchio M, McHugh SB, Bannerman DM, Sharp T, Capogna M. Serotonin, Amygdala and Fear: Assembling the Puzzle. Front Neural Circuits 2016; 10:24. [PMID: 27092057 PMCID: PMC4820447 DOI: 10.3389/fncir.2016.00024] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 03/21/2016] [Indexed: 11/13/2022] Open
Abstract
The fear circuitry orchestrates defense mechanisms in response to environmental threats. This circuitry is evolutionarily crucial for survival, but its dysregulation is thought to play a major role in the pathophysiology of psychiatric conditions in humans. The amygdala is a key player in the processing of fear. This brain area is prominently modulated by the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT). The 5-HT input to the amygdala has drawn particular interest because genetic and pharmacological alterations of the 5-HT transporter (5-HTT) affect amygdala activation in response to emotional stimuli. Nonetheless, the impact of 5-HT on fear processing remains poorly understood.The aim of this review is to elucidate the physiological role of 5-HT in fear learning via its action on the neuronal circuits of the amygdala. Since 5-HT release increases in the basolateral amygdala (BLA) during both fear memory acquisition and expression, we examine whether and how 5-HT neurons encode aversive stimuli and aversive cues. Next, we describe pharmacological and genetic alterations of 5-HT neurotransmission that, in both rodents and humans, lead to altered fear learning. To explore the mechanisms through which 5-HT could modulate conditioned fear, we focus on the rodent BLA. We propose that a circuit-based approach taking into account the localization of specific 5-HT receptors on neurochemically-defined neurons in the BLA may be essential to decipher the role of 5-HT in emotional behavior. In keeping with a 5-HT control of fear learning, we review electrophysiological data suggesting that 5-HT regulates synaptic plasticity, spike synchrony and theta oscillations in the BLA via actions on different subcellular compartments of principal neurons and distinct GABAergic interneuron populations. Finally, we discuss how recently developed optogenetic tools combined with electrophysiological recordings and behavior could progress the knowledge of the mechanisms underlying 5-HT modulation of fear learning via action on amygdala circuits. Such advancement could pave the way for a deeper understanding of 5-HT in emotional behavior in both health and disease.
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Affiliation(s)
- Marco Bocchio
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford Oxford, UK
| | - Stephen B McHugh
- Department of Experimental Psychology, University of Oxford Oxford, UK
| | - David M Bannerman
- Department of Experimental Psychology, University of Oxford Oxford, UK
| | - Trevor Sharp
- Department of Pharmacology, University of Oxford Oxford, UK
| | - Marco Capogna
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford Oxford, UK
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13
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Dankoski EC, Carroll S, Wightman RM. Acute selective serotonin reuptake inhibitors regulate the dorsal raphe nucleus causing amplification of terminal serotonin release. J Neurochem 2016; 136:1131-1141. [PMID: 26749030 PMCID: PMC4939133 DOI: 10.1111/jnc.13528] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 12/31/2015] [Accepted: 01/05/2016] [Indexed: 01/19/2023]
Abstract
Selective serotonin reuptake inhibitors (SSRIs) were designed to treat depression by increasing serotonin levels throughout the brain via inhibition of clearance from the extracellular space. Although increases in serotonin levels are observed after acute SSRI exposure, 3–6 weeks of continuous use is required for relief from the symptoms of depression. Thus, it is now believed that plasticity in multiple brain systems that are downstream of serotonergic inputs contributes to the therapeutic efficacy of SSRIs. The onset of antidepressant effects also coincides with desensitization of somatodendritic serotonin autoreceptors in the dorsal raphe nucleus (DRN), suggesting that disrupting inhibitory feedback within the serotonin system may contribute to the therapeutic effects of SSRIs. Previously, we showed that chronic SSRI treatment caused a frequency‐dependent facilitation of serotonin signaling that persisted in the absence of uptake inhibition. In this work, we use in vivo fast‐scan cyclic voltammetry in mice to investigate a similar facilitation after a single treatment of the SSRI citalopram hydrobromide. Acute citalopram hydrobromide treatment resulted in frequency‐dependent increases of evoked serotonin release in the substantia nigra pars reticulata. These increases were independent of changes in uptake velocity, but required SERT expression. Using microinjections, we show that the frequency‐dependent enhancement in release is because of SERT inhibition in the DRN, demonstrating that SSRIs can enhance serotonin release by inhibiting uptake in a location distal to the terminal release site. The novel finding that SERT inhibition can disrupt modulatory mechanisms at the level of the DRN to facilitate serotonin release will help future studies investigate serotonin's role in depression and motivated behavior.
In this work, stimulations of the dorsal raphe nucleus (DRN) evoke serotonin release that is recorded in the substantia nigra pars reticulata (SNpr) using in vivo fast‐scan cyclic voltammetry. Systemic administration of a selective serotonin reuptake inhibitor (SSRI) causes both an increase in t1/2 and an increase in [5‐HT]max in the SNpr. Local application of SSRI to the DRN recapitulates the increase in [5‐HT]max observed in the SNpr without affecting uptake. Thus, SSRIs increase serotonin signaling via two distinct SERT‐mediated mechanisms.
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Affiliation(s)
- Elyse C Dankoski
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Susan Carroll
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Robert Mark Wightman
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.,Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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14
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Yang H, Sampson MM, Senturk D, Andrews AM. Sex- and SERT-mediated differences in stimulated serotonin revealed by fast microdialysis. ACS Chem Neurosci 2015; 6:1487-501. [PMID: 26167657 DOI: 10.1021/acschemneuro.5b00132] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In vivo microdialysis is widely used to investigate how neurotransmitter levels in the brain respond to biologically relevant challenges. Here, we combined recent improvements in the temporal resolution of online sampling and analysis for serotonin with a brief high-K(+) stimulus paradigm to study the dynamics of evoked release. We observed stimulated serotonin overflow with high-K(+) pulses as short as 1 min when determined with 2-min dialysate sampling in ventral striatum. Stimulated serotonin levels in female mice during the high estrogen period of the estrous cycle were similar to serotonin levels in male mice. By contrast, stimulated serotonin overflow during the low estrogen period in female mice was increased to levels similar to those in male mice with local serotonin transporter (SERT) inhibition. Stimulated serotonin levels in mice with constitutive loss of SERT were considerably higher yet, pointing to neuroadaptive potentiation of serotonin release. When combined with brief K(+) stimulation, fast microdialysis reveals dynamic changes in extracellular serotonin levels associated with normal hormonal cycles and pharmacologic vs genetic loss of SERT function.
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Affiliation(s)
- Hongyan Yang
- Department of Psychiatry & Biobehavioral Sciences, Hatos Center for Neuropharmacology, Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, ‡Molecular Toxicology Interdepartmental Program, §Department of Chemistry & Biochemistry, and ∥Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Maureen M. Sampson
- Department of Psychiatry & Biobehavioral Sciences, Hatos Center for Neuropharmacology, Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, ‡Molecular Toxicology Interdepartmental Program, §Department of Chemistry & Biochemistry, and ∥Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Damla Senturk
- Department of Psychiatry & Biobehavioral Sciences, Hatos Center for Neuropharmacology, Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, ‡Molecular Toxicology Interdepartmental Program, §Department of Chemistry & Biochemistry, and ∥Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California 90095, United States
| | - Anne M. Andrews
- Department of Psychiatry & Biobehavioral Sciences, Hatos Center for Neuropharmacology, Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine, ‡Molecular Toxicology Interdepartmental Program, §Department of Chemistry & Biochemistry, and ∥Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, California 90095, United States
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15
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McHugh SB, Barkus C, Lima J, Glover LR, Sharp T, Bannerman DM. SERT and uncertainty: serotonin transporter expression influences information processing biases for ambiguous aversive cues in mice. GENES BRAIN AND BEHAVIOR 2015; 14:330-6. [PMID: 25824641 PMCID: PMC4440341 DOI: 10.1111/gbb.12215] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 03/26/2015] [Accepted: 03/26/2015] [Indexed: 12/18/2022]
Abstract
The long allele variant of the serotonin transporter (SERT, 5-HTT) gene-linked polymorphic region (5-HTTLPR) is associated with higher levels of 5-HTT expression and reduced risk of developing affective disorders. However, little is known about the mechanisms underlying this protective effect. One hypothesis is that 5-HTT expression influences aversive information processing, with reduced negative cognitive bias present in those with higher 5-HTT expression. Here we investigated this hypothesis using genetically-modified mice and a novel aversive learning paradigm. Mice with high levels of 5-HTT expression (5-HTT over-expressing, 5-HTTOE mice) and wild-type mice were trained to discriminate between three distinct auditory cues: one cue predicted footshock on all trials (CS+); a second cue predicted the absence of footshock (CS−); and a third cue predicted footshock on 20% of trials (CS20%), and was therefore ambiguous. Wild-type mice exhibited equivalently high levels of fear to the CS+ and CS20% and minimal fear to the CS−. In contrast, 5-HTTOE mice exhibited high levels of fear to the CS+ but minimal fear to the CS− and the CS20%. This selective reduction in fear to ambiguous aversive cues suggests that increased 5-HTT expression reduces negative cognitive bias for stimuli with uncertain outcomes.
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Affiliation(s)
- S B McHugh
- Department of Experimental Psychology, University of Oxford, Oxford, UK
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16
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Line SJ, Barkus C, Rawlings N, Jennings K, McHugh S, Sharp T, Bannerman DM. Reduced sensitivity to both positive and negative reinforcement in mice over-expressing the 5-hydroxytryptamine transporter. Eur J Neurosci 2014; 40:3735-45. [PMID: 25283165 PMCID: PMC4737229 DOI: 10.1111/ejn.12744] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Revised: 08/30/2014] [Accepted: 09/02/2014] [Indexed: 11/30/2022]
Abstract
The 5‐hydroxytryptamine (5‐HT) transporter (5‐HTT) is believed to play a key role in both normal and pathological psychological states. Much previous data suggest that the s allele of the polymorphic regulatory region of the 5‐HTT gene promoter is associated with reduced 5‐HTT expression and vulnerability to psychiatric disorders, including anxiety and depression. In comparison, the l allele, which increases 5‐HTT expression, is generally considered protective. However, recent data link this allele to both abnormal 5‐HT signalling and psychopathic traits. Here, we studied the processing of aversive and rewarding cues in transgenic mice that over‐express the 5‐HTT (5‐HTTOE mice). Compared with wild‐type mice, 5‐HTTOE mice froze less in response to both a tone that had previously been paired with footshock, and the conditioning context. In addition, on a decision‐making T‐maze task, 5‐HTTOE mice displayed reduced preference for a larger, delayed reward and increased preference for a smaller, immediate reward, suggesting increased impulsiveness compared with wild‐type mice. However, further inspection of the data revealed that 5‐HTTOE mice displayed a relative insensitivity to reward magnitude, irrespective of delay. In contrast, 5‐HTTOE mice appeared normal on tests of spatial working and reference memory, which required an absolute choice between options associated with either reward or no reward. Overall, the present findings suggest that 5‐HTT over‐expression results in a reduced sensitivity to both positive and negative reinforcers. Thus, these data show that increased 5‐HTT expression has some maladaptive effects, supporting recent suggestions that l allele homozygosity may be a potential risk factor for disabling psychiatric traits.
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Affiliation(s)
- Samantha J Line
- Department of Experimental Psychology, The University of Oxford, South Parks Road, Oxford, OX1 3UD, UK
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17
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Xiao N, Privman E, Venton BJ. Optogenetic control of serotonin and dopamine release in Drosophila larvae. ACS Chem Neurosci 2014; 5:666-73. [PMID: 24849718 DOI: 10.1021/cn500044b] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Optogenetic control of neurotransmitter release is an elegant method to investigate neurobiological mechanisms with millisecond precision and cell type-specific resolution. Channelrhodopsin-2 (ChR2) can be expressed in specific neurons, and blue light used to activate those neurons. Previously, in Drosophila, neurotransmitter release and uptake have been studied after continuous optical illumination. In this study, we investigated the effects of pulsed optical stimulation trains on serotonin or dopamine release in larval ventral nerve cords. In larvae with ChR2 expressed in serotonergic neurons, low-frequency stimulations produced a distinct, steady-state response while high-frequency patterns were peak shaped. Evoked serotonin release increased with increasing stimulation frequency and then plateaued. The steady-state response and the frequency dependence disappeared after administering the uptake inhibitor fluoxetine, indicating that uptake plays a significant role in regulating the extracellular serotonin concentration. Pulsed stimulations were also used to evoke dopamine release in flies expressing ChR2 in dopaminergic neurons and similar frequency dependence was observed. Release due to pulsed optical stimulations was modeled to determine the uptake kinetics. For serotonin, Vmax was 0.54 ± 0.07 μM/s and Km was 0.61 ± 0.04 μM; and for dopamine, Vmax was 0.12 ± 0.03 μM/s and Km was 0.45 ± 0.13 μM. The amount of serotonin released per stimulation pulse was 4.4 ± 1.0 nM, and the amount of dopamine was 1.6 ± 0.3 nM. Thus, pulsed optical stimulations can be used to mimic neuronal firing patterns and will allow Drosophila to be used as a model system for studying mechanisms underlying neurotransmission.
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Affiliation(s)
- Ning Xiao
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - Eve Privman
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904, United States
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, P.O. Box 400319, Charlottesville, Virginia 22904, United States
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18
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Barkus C, Line SJ, Huber A, Capitao L, Lima J, Jennings K, Lowry J, Sharp T, Bannerman DM, McHugh SB. Variation in serotonin transporter expression modulates fear-evoked hemodynamic responses and theta-frequency neuronal oscillations in the amygdala. Biol Psychiatry 2014; 75:901-8. [PMID: 24120093 PMCID: PMC4032572 DOI: 10.1016/j.biopsych.2013.09.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 09/04/2013] [Accepted: 09/04/2013] [Indexed: 01/16/2023]
Abstract
BACKGROUND Gene association studies detect an influence of natural variation in the 5-hydroxytryptamine transporter (5-HTT) gene on multiple aspects of individuality in brain function, ranging from personality traits through to susceptibility to psychiatric disorders such as anxiety and depression. The neural substrates of these associations are unknown. Human neuroimaging studies suggest modulation of the amygdala by 5-HTT variation, but this hypothesis is controversial and unresolved, and difficult to investigate further in humans. METHODS We used a mouse model in which the 5-HTT is overexpressed throughout the brain and recorded hemodynamic responses (using a novel in vivo voltammetric monitoring method, analogous to blood oxygen level-dependent functional magnetic resonance imaging) and local field potentials during Pavlovian fear conditioning. RESULTS Increased 5-HTT expression impaired, but did not prevent, fear learning and significantly reduced amygdala hemodynamic responses to aversive cues. Increased 5-HTT expression was also associated with reduced theta oscillations, which were a feature of aversive cue presentation in controls. Moreover, in control mice, but not those with high 5-HTT expression, there was a strong correlation between theta power and the amplitude of the hemodynamic response. CONCLUSIONS Direct experimental manipulation of 5-HTT expression levels throughout the brain markedly altered fear learning, amygdala hemodynamic responses, and neuronal oscillations.
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Affiliation(s)
- Christopher Barkus
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Samantha J Line
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Anna Huber
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Liliana Capitao
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Joao Lima
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Katie Jennings
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom
| | - John Lowry
- Department of Chemistry, National University of Ireland, Maynooth, Ireland
| | - Trevor Sharp
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - David M Bannerman
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom
| | - Stephen B McHugh
- Department of Experimental Psychology, University of Oxford, Oxford, United Kingdom.
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19
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Kerr TM, Muller CL, Miah M, Jetter CS, Pfeiffer R, Shah C, Baganz N, Anderson GM, Crawley JN, Sutcliffe JS, Blakely RD, Veenstra-Vanderweele J. Genetic background modulates phenotypes of serotonin transporter Ala56 knock-in mice. Mol Autism 2013; 4:35. [PMID: 24083388 PMCID: PMC3851031 DOI: 10.1186/2040-2392-4-35] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 08/27/2013] [Indexed: 12/25/2022] Open
Abstract
Background Previously, we identified multiple, rare serotonin (5-HT) transporter (SERT) variants in children with autism spectrum disorder (ASD). Although in our study the SERT Ala56 variant was over-transmitted to ASD probands, it was also seen in some unaffected individuals, suggesting that associated ASD risk is influenced by the epistatic effects of other genetic variation. Subsequently, we established that mice expressing the SERT Ala56 variant on a 129S6/S4 genetic background display multiple biochemical, physiological and behavioral changes, including hyperserotonemia, altered 5-HT receptor sensitivity, and altered social, communication, and repetitive behavior. Here we explore the effects of genetic background on SERT Ala56 knock-in phenotypes. Methods To explore the effects of genetic background, we backcrossed SERT Ala56 mice on the 129 background into a C57BL/6 (B6) background to achieve congenic B6 SERT Ala56 mice, and assessed autism-relevant behavior, including sociability, ultrasonic vocalizations, and repetitive behavior in the home cage, as well as serotonergic phenotypes, including whole blood serotonin levels and serotonin receptor sensitivity. Results One consistent phenotype between the two strains was performance in the tube test for dominance, where mutant mice displayed a greater tendency to withdraw from a social encounter in a narrow tube as compared to wildtype littermate controls. On the B6 background, mutant pup ultrasonic vocalizations were significantly increased, in contrast to decreased vocalizations seen previously on the 129 background. Several phenotypes seen on the 129 background were reduced or absent when the mutation was placed on the B6 background, including hyperserotonemia, 5-HT receptor hypersensivity, and repetitive behavior. Conclusions Our findings provide a cogent example of how epistatic interactions can modulate the impact of functional genetic variation and suggest that some aspects of social behavior may be especially sensitive to changes in SERT function. Finally, these results provide a platform for the identification of genes that may modulate the risk of ASD in humans.
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Affiliation(s)
- Travis M Kerr
- Department of Psychiatry, Vanderbilt University, 465 21st Ave S, Nashville, TN 37232, USA.
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20
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Deficits in dopaminergic transmission precede neuron loss and dysfunction in a new Parkinson model. Proc Natl Acad Sci U S A 2013; 110:E4016-25. [PMID: 24082145 DOI: 10.1073/pnas.1309143110] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The pathological end-state of Parkinson disease is well described from postmortem tissue, but there remains a pressing need to define early functional changes to susceptible neurons and circuits. In particular, mechanisms underlying the vulnerability of the dopamine neurons of the substantia nigra pars compacta (SNc) and the importance of protein aggregation in driving the disease process remain to be determined. To better understand the sequence of events occurring in familial and sporadic Parkinson disease, we generated bacterial artificial chromosome transgenic mice (SNCA-OVX) that express wild-type α-synuclein from the complete human SNCA locus at disease-relevant levels and display a transgene expression profile that recapitulates that of endogenous α-synuclein. SNCA-OVX mice display age-dependent loss of nigrostriatal dopamine neurons and motor impairments characteristic of Parkinson disease. This phenotype is preceded by early deficits in dopamine release from terminals in the dorsal, but not ventral, striatum. Such neurotransmission deficits are not seen at either noradrenergic or serotoninergic terminals. Dopamine release deficits are associated with an altered distribution of vesicles in dopaminergic axons in the dorsal striatum. Aged SNCA-OVX mice exhibit reduced firing of SNc dopamine neurons in vivo measured by juxtacellular recording of neurochemically identified neurons. These progressive changes in vulnerable SNc neurons were observed independently of overt protein aggregation, suggesting neurophysiological changes precede, and are not driven by, aggregate formation. This longitudinal phenotyping strategy in SNCA-OVX mice thus provides insights into the region-specific neuronal disturbances preceding and accompanying Parkinson disease.
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21
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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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22
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Yang H, Thompson A, McIntosh BJ, Altieri SC, Andrews AM. Physiologically relevant changes in serotonin resolved by fast microdialysis. ACS Chem Neurosci 2013; 4:790-8. [PMID: 23614776 PMCID: PMC3656759 DOI: 10.1021/cn400072f] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 04/03/2013] [Indexed: 01/17/2023] Open
Abstract
Online microdialysis is a sampling and detection method that enables continuous interrogation of extracellular molecules in freely moving subjects under behaviorally relevant conditions. A majority of recent publications using brain microdialysis in rodents report sample collection times of 20-30 min. These long sampling times are due, in part, to limitations in the detection sensitivity of high performance liquid chromatography (HPLC). By optimizing separation and detection conditions, we decreased the retention time of serotonin to 2.5 min and the detection threshold to 0.8 fmol. Sampling times were consequently reduced from 20 to 3 min per sample for online detection of serotonin (and dopamine) in brain dialysates using a commercial HPLC system. We developed a strategy to collect and to analyze dialysate samples continuously from two animals in tandem using the same instrument. Improvements in temporal resolution enabled elucidation of rapid changes in extracellular serotonin levels associated with mild stress and circadian rhythms. These dynamics would be difficult or impossible to differentiate using conventional microdialysis sampling rates.
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Affiliation(s)
- Hongyan Yang
- Semel Institute for Neuroscience & Human
Behavior and Hatos Center for Neuropharmacology, David Geffen School
of Medicine, Department of Chemistry and Biochemistry, and California NanoSystems Institute, University of California, Los Angeles,
California, United States
| | - Andrew
B. Thompson
- Semel Institute for Neuroscience & Human
Behavior and Hatos Center for Neuropharmacology, David Geffen School
of Medicine, Department of Chemistry and Biochemistry, and California NanoSystems Institute, University of California, Los Angeles,
California, United States
| | | | - Stefanie C. Altieri
- Semel Institute for Neuroscience & Human
Behavior and Hatos Center for Neuropharmacology, David Geffen School
of Medicine, Department of Chemistry and Biochemistry, and California NanoSystems Institute, University of California, Los Angeles,
California, United States
| | - Anne M. Andrews
- Semel Institute for Neuroscience & Human
Behavior and Hatos Center for Neuropharmacology, David Geffen School
of Medicine, Department of Chemistry and Biochemistry, and California NanoSystems Institute, University of California, Los Angeles,
California, United States
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23
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Jennings KA. A comparison of the subsecond dynamics of neurotransmission of dopamine and serotonin. ACS Chem Neurosci 2013; 4:704-14. [PMID: 23627553 DOI: 10.1021/cn4000605] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The neuromodulators dopamine (DA) and serotonin (5-hydroxytryptamine; 5-HT) are similar in a number of ways. Both monoamines can act by volume transmission at metabotropic receptors to modulate synaptic transmission in brain circuits. Presynaptic regulation of 5-HT and DA is governed by parallel processes, and behaviorally, both exert control over emotional processing. However, differences are also apparent: more than twice as many 5-HT receptor subtypes mediate postsynaptic effects than DA receptors and different presynaptic regulation is also emerging. Monoamines are amenable to real-time electrochemical detection using fast scan cyclic voltammetry (FSCV), which allows resolution of the subsecond dynamics of release and reuptake in response to a single action potential. This approach has greatly enriched understanding of DA transmission and has facilitated an integrated view of how DA mediates behavioral control. However, technical challenges are associated with FSCV measurement of 5-HT and understanding of 5-HT transmission at subsecond resolution has not advanced at the same rate. As a result, how the actions of 5-HT at the level of the synapse translate into behavior is poorly understood. Recent technical advances may aid the study of 5-HT in real-time. It is timely, therefore, to compare and contrast what is currently understood of the subsecond characteristics of transmission for DA and 5-HT. In doing so, a number of areas are highlighted as being worthy of exploration for 5-HT.
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Affiliation(s)
- Katie A. Jennings
- Department of Physiology, Anatomy and Genetics, Oxford University, South Parks Road, Oxford, U.K. OX1
3PT
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24
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Pryce CR, Klaus F. Translating the evidence for gene association with depression into mouse models of depression-relevant behaviour: current limitations and future potential. Neurosci Biobehav Rev 2013; 37:1380-402. [PMID: 23680698 DOI: 10.1016/j.neubiorev.2013.05.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 04/15/2013] [Accepted: 05/03/2013] [Indexed: 12/11/2022]
Abstract
Depression is characterised by high prevalence and complex, heterogeneous psychopathology. At the level of aetio-pathology, considerable research effort has been invested to identify specific gene polymorphisms associated with increased depression prevalence. Genome-wide association studies have not identified any risk polymorphisms, and candidate gene case-control studies have identified a small number of risk polymorphisms. It is increasingly recognised that interaction between genotype and environmental factors (G×E), notably stressful life events, is the more realistic unit of depression aetio-pathology, with G×E evidence described for a small number of risk polymorphisms. An important complementary approach has been to describe genes exhibiting brain region-specific expression changes in depression. Mouse models of depression informed by the human evidence allow for the study of causality, but to-date have also yielded limited insights into depression aetio-pathology. This review of the translational evidence integrates human and mouse research approaches and evidence. It also makes specific recommendations in terms of how future research in human and mouse should be designed in order to deliver evidence for depression aetio-pathology and thereby to inform the development of novel and improved antidepressant treatments.
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Affiliation(s)
- Christopher R Pryce
- Preclinical Laboratory for Translational Research into Affective Disorders (PLaTRAD), Department of Psychiatry, Psychotherapy & Psychosomatics, Zurich University Hospital for Psychiatry, August Forel-Strasse 7, CH-8008 Zurich, Switzerland; Neuroscience Center Zurich, University of Zurich and ETH Zurich, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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Beikmann BS, Tomlinson ID, Rosenthal SJ, Andrews AM. Serotonin uptake is largely mediated by platelets versus lymphocytes in peripheral blood cells. ACS Chem Neurosci 2013; 4:161-70. [PMID: 23336055 DOI: 10.1021/cn300146w] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 10/22/2012] [Indexed: 12/12/2022] Open
Abstract
The serotonin transporter (SERT), a primary target for many antidepressants, is expressed in the brain and also in peripheral blood cells. Although platelet SERT function is well accepted, lymphocyte SERT function has not been definitively characterized. Due to their small size, platelets often are found in peripheral blood mononuclear cell preparations aimed at isolating lymphocytes, monocytes, and macrophages. The presence of different cells makes it difficult to assign SERT expression and function to specific cell types. Here, we use flow cytometry and IDT307, a monoamine transporter substrate that fluoresces after uptake into cells, to investigate SERT function in lymphocyte and platelet populations independently, as well as simultaneously without prior isolation. We find that murine lymphocytes exhibit temperature-dependent IDT307 transport but uptake is independent of SERT. Lack of measurable SERT function in lymphocytes was corroborated by chronoamperometry using serotonin as a substrate. When we examined rhesus and human mixed blood cell populations, we found that platelets, and not lymphocytes, were primary contributors to SERT function. Overall, these findings indicate that lymphocyte SERT function is minimal. Moreover, flow cytometry, in conjunction with the fluorescent transporter substrate IDT307, can be widely applied to investigate SERT in platelets from populations of clinical significance.
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Affiliation(s)
- Brendan S. Beikmann
- Semel Institute for Neuroscience & Human Behavior and Hatos Center for Neuropharmacology, David Geffen School of Medicine, University of California, Los Angeles, California, United States
| | | | | | - Anne Milasincic Andrews
- Semel Institute for Neuroscience & Human Behavior and Hatos Center for Neuropharmacology, David Geffen School of Medicine, University of California, Los Angeles, California, United States
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Genetic variation in 5-hydroxytryptamine transporter expression causes adaptive changes in 5-HT₄ receptor levels. Int J Neuropsychopharmacol 2012; 15:1099-107. [PMID: 21846421 DOI: 10.1017/s1461145711001258] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Genetic variation in 5-HT transporter (5-HTT) expression is a key risk factor for psychiatric disorder and has been linked to changes in the expression of certain 5-HT receptor subtypes. This study investigated the effect of variation in 5-HTT expression on 5-HT₄ receptor levels in both 5-HTT knockout (KO) and overexpressing (OE) mice using autoradiography with the selective 5-HT₄ receptor radioligand, [³H]SB207145. Compared to wild-type (5-HTT⁺/⁺) controls, homozygous 5-HTT KO mice (5-HTT⁻/⁻) had reduced 5-HT₄ receptor binding site density in all brain regions examined (35-65% of 5-HTT⁺/⁺). In contrast, the density of 5-HT₄ receptor binding sites was not significantly different between heterozygous 5-HTT KO mice (5-HTT⁻/⁺) and 5-HTT⁺/⁺ mice. The 5-HT synthesis inhibitor p-chlorophenylalanine (250 mg/kg twice daily for 3 d) abolished the difference in 5-HT₄ binding between 5-HTT⁻/⁻ and 5-HTT⁺/⁺ mice in all brain regions. Compared to wild-type (WT) littermate controls, 5-HTT OE mice had increased 5-HT₄ binding density across all brain regions, except amygdala (118-164% of WT) and this difference between genotypes was reduced by the 5-HTT inhibitor, fluoxetine (20 mg/kg twice daily, 3 d). Together, these findings suggest that variation in 5-HTT expression causes adaptive changes in 5-HT₄ receptor levels which are directly linked to alterations in 5-HT availability.
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Ineichen C, Sigrist H, Spinelli S, Lesch KP, Sautter E, Seifritz E, Pryce CR. Establishing a probabilistic reversal learning test in mice: evidence for the processes mediating reward-stay and punishment-shift behaviour and for their modulation by serotonin. Neuropharmacology 2012; 63:1012-21. [PMID: 22824190 DOI: 10.1016/j.neuropharm.2012.07.025] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 07/12/2012] [Accepted: 07/13/2012] [Indexed: 01/28/2023]
Abstract
Valid animal models of psychopathology need to include behavioural readouts informed by human findings. In the probabilistic reversal learning (PRL) task, human subjects are confronted with serial reversal of the contingency between two operant stimuli and reward/punishment and, superimposed on this, a low probability (0.2) of punished correct responses/rewarded incorrect responses. In depression, reward-stay and reversals completed are unaffected but response-shift following punished correct response trials, referred to as negative feedback sensitivity (NFS), is increased. The aims of this study were to: establish an operant spatial PRL test appropriate for mice; obtain evidence for the processes mediating reward-stay and punishment-shift responding; and assess effects thereon of genetically- and pharmacologically-altered serotonin (5-HT) function. The study was conducted with wildtype (WT) and heterozygous mutant (HET) mice from a 5-HT transporter (5-HTT) null mutant strain. Mice were mildly food deprived and reward was sugar pellet and punishment was 5-s time out. Mice exhibited high motivation and adaptive reversal performance. Increased probability of punished correct response (PCR) trials per session (p = 0.1, 0.2 or 0.3) led to monotonic decrease in reward-stay and reversals completed, suggesting accurate reward prediction. NFS differed from chance-level at p PCR = 0.1, suggesting accurate punishment prediction, whereas NFS was at chance-level at p = 0.2-0.3. At p PCR = 0.1, HET mice exhibited lower NFS than WT mice. The 5-HTT blocker escitalopram was studied acutely at p PCR = 0.2: a low dose (0.5-1.5 mg/kg) resulted in decreased NFS, increased reward-stay and increased reversals completed, and similarly in WT and HET mice. This study demonstrates that testing PRL in mice can provide evidence on the regulation of reward and punishment processing that is, albeit within certain limits, of relevance to human emotional-cognitive processing, its dysfunction and treatment.
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Affiliation(s)
- Christian Ineichen
- Preclinical Laboratory for Translational Research into Affective Disorders, Clinic for Affective Disorders & General Psychiatry, Psychiatric University Hospital Zurich, August Forel-Strasse 7, CH-8008 Zurich, Switzerland
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Singh YS, Sawarynski LE, Dabiri PD, Choi WR, Andrews AM. Head-to-head comparisons of carbon fiber microelectrode coatings for sensitive and selective neurotransmitter detection by voltammetry. Anal Chem 2011; 83:6658-66. [PMID: 21770471 DOI: 10.1021/ac2011729] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Voltammetry is widely used to investigate neurotransmission and other biological processes but is limited by poor chemical selectivity and fouling of commonly used carbon fiber microelectrodes (CFMs). We performed direct comparisons of three key coating materials purported to impart selectivity and fouling resistance to electrodes: Nafion, base-hydrolyzed cellulose acetate (BCA), and fibronectin. We systematically evaluated the impact on a range of electrode parameters. Fouling due to exposure to brain tissue was investigated using an approach that minimizes the use of animals while enabling evaluation of statistically significant populations of electrodes. We find that BCA is relatively fouling-resistant. Moreover, detection at BCA-coated CFMs can be tuned by altering hydrolysis times to minimize the impact on sensitivity losses while maintaining fouling resistance. Fibronectin coating is associated with moderate losses in sensitivity after coating and fouling. Nafion imparts increased sensitivity for dopamine and norepinephrine but not serotonin, as well as the anticipated selectivity for cationic neurotransmitters over anionic metabolites. Although Nafion has been suggested to resist fouling, both dip-coating and electrodeposition of Nafion are associated with substantial fouling, similar to levels observed at bare electrodes after exposure to brain tissue. Direct comparisons of these coatings identified unique electroanalytical properties of each that can be used to guide selection tailored to the goals and environment of specific studies.
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Affiliation(s)
- Yogesh S Singh
- Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, USA
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