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Long-Term Effects of Repeated Social Defeat Stress on Brain Activity during Social Interaction in BALB/c Mice. eNeuro 2022; 9:ENEURO.0068-22.2022. [PMID: 35437264 PMCID: PMC9070729 DOI: 10.1523/eneuro.0068-22.2022] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/26/2022] [Accepted: 04/04/2022] [Indexed: 12/28/2022] Open
Abstract
Understanding the long-term effects of stress on brain function is crucial for understanding the mechanisms of depression. The BALB/c mouse strain has high susceptibility to stress and is thus an effective model for depression. The long-term effects of repeated social defeat stress (SDS) on BALB/c mice, however, are not clear. Here, we investigated the effects of repeated SDS in male BALB/c mice over the subsequent two weeks. Some defeated mice immediately exhibited social avoidance, whereas anxiety-like behavior was only evident at later periods. Furthermore, defeated mice segregated into two groups based on the level of social avoidance, namely, avoidant and nonavoidant mice. The characteristic of avoidance or nonavoidance in each individual was not fixed over the two weeks. In addition, we developed a semi-automated method for analyzing c-Fos expression in the mouse brain to investigate the effect of repeated SDS on brain activity more than two weeks after the end of the stress exposure. Following social interaction, c-Fos expression was reduced in several brain regions in the defeated mice compared with control mice. The correlation of c-Fos expression among these brain areas, with exception of the medial prefrontal cortex (mPFC) and central amygdala (CeA), was increased in defeated mice, suggesting increased synchrony. Notably, c-Fos expression in the lateral habenula (LHb) was different between mice that exhibited social avoidance from immediately after the repeated SDS and those that exhibited social avoidance only at later periods. These observations provide insight into the long-term effects of social stress on behavior and brain activity.
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Tafet GE, Nemeroff CB. Pharmacological Treatment of Anxiety Disorders: The Role of the HPA Axis. Front Psychiatry 2020; 11:443. [PMID: 32499732 PMCID: PMC7243209 DOI: 10.3389/fpsyt.2020.00443] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 05/01/2020] [Indexed: 12/13/2022] Open
Abstract
Stress in general, and early life stress in particular, has been associated with the development of anxiety and mood disorders. The molecular, biological and psychological links between stress exposure and the pathogenesis of anxiety and mood disorders have been extensively studied, resulting in the search of novel psychopharmacological strategies aimed at targets of the hypothalamic-pituitary-adrenal (HPA) axis. Hyperactivity of the HPA axis has been observed in certain subgroups of patients with anxiety and mood disorders. In addition, the effects of different anti-anxiety agents on various components of the HPA axis has been investigated, including benzodiazepines, tricyclic antidepressants (TCAs), and selective serotonin reuptake inhibitors (SSRIs). For example, benzodiazepines, including clonazepam and alprazolam, have been demonstrated to reduce the activity of corticotrophin releasing factor (CRF) neurons in the hypothalamus. TCAs and SSRIs are also effective anti-anxiety agents and these may act, in part, by modulating the HPA axis. In this regard, the SSRI escitalopram inhibits CRF release in the central nucleus of the amygdala, while increasing glucocorticoid receptor (GRs) density in the hippocampus and hypothalamus. The molecular effects of these anti-anxiety agents in the regulation of the HPA axis, taken together with their clinical efficacy, may provide further understanding about the role of the HPA axis in the pathophysiology of mood and anxiety disorders, paving the way for the development of novel therapeutic strategies.
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Affiliation(s)
- Gustavo E. Tafet
- Department of Psychiatry and Neurosciences, Maimónides University, Buenos Aires, Argentina
| | - Charles B. Nemeroff
- Department of Psychiatry, University of Texas at Austin, Austin, TX, United States
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Lieb MW, Weidner M, Arnold MR, Loupy KM, Nguyen KT, Hassell JE, Schnabel KS, Kern R, Day HEW, Lesch KP, Waider J, Lowry CA. Effects of maternal separation on serotonergic systems in the dorsal and median raphe nuclei of adult male Tph2-deficient mice. Behav Brain Res 2019; 373:112086. [PMID: 31319134 DOI: 10.1016/j.bbr.2019.112086] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Revised: 06/18/2019] [Accepted: 07/13/2019] [Indexed: 12/13/2022]
Abstract
Previous studies have highlighted interactions between serotonergic systems and adverse early life experience as important gene x environment determinants of risk of stress-related psychiatric disorders. Evidence suggests that mice deficient in Tph2, the rate-limiting enzyme for brain serotonin synthesis, display disruptions in behavioral phenotypes relevant to stress-related psychiatric disorders. The aim of this study was to determine how maternal separation in wild-type, heterozygous, and Tph2 knockout mice affects mRNA expression of serotonin-related genes. Serotonergic genes studied included Tph2, the high-affinity, low-capacity, sodium-dependent serotonin transporter (Slc6a4), the serotonin type 1a receptor (Htr1a), and the corticosterone-sensitive, low-affinity, high-capacity sodium-independent serotonin transporter, organic cation transporter 3 (Slc22a3). Furthermore, we studied corticotropin-releasing hormone receptors 1 (Crhr1) and 2 (Crhr2), which play important roles in controlling serotonergic neuronal activity. For this study, offspring of Tph2 heterozygous dams were exposed to daily maternal separation for the first two weeks of life. Adult, male wild-type, heterozygous, and homozygous offspring were subsequently used for molecular analysis. Maternal separation differentially altered serotonergic gene expression in a genotype- and topographically-specific manner. For example, maternal separation increased Slc6a4 mRNA expression in the dorsal part of the dorsal raphe nucleus in Tph2 heterozygous mice, but not in wild-type or knockout mice. Overall, these data are consistent with the hypothesis that gene x environment interactions, including serotonergic genes and adverse early life experience, play an important role in vulnerability to stress-related psychiatric disorders.
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Affiliation(s)
- Margaret W Lieb
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Magdalena Weidner
- Division of Molecular Psychiatry, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany; Department of Psychiatry and Psychology, School for Mental Health and Neuroscience (MHeNS), Maastricht University, Maastricht, the Netherlands.
| | - Mathew R Arnold
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Kelsey M Loupy
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Kadi T Nguyen
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - James E Hassell
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - K'Loni S Schnabel
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Raphael Kern
- Division of Molecular Psychiatry, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany.
| | - Heidi E W Day
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, CO 80309, USA; Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309, USA.
| | - Klaus-Peter Lesch
- Division of Molecular Psychiatry, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany; Department of Psychiatry and Psychology, School for Mental Health and Neuroscience (MHeNS), Maastricht University, Maastricht, the Netherlands; Laboratory of Psychiatric Neurobiology, Institute of Molecular Medicine, I.M. Sechenov First Moscow State Medical University, Moscow, Russia.
| | - Jonas Waider
- Division of Molecular Psychiatry, Center of Mental Health, University of Wuerzburg, Wuerzburg, Germany.
| | - Christopher A Lowry
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, CO 80309, USA; Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309, USA; Department of Physical Medicine & Rehabilitation, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Center for Neuroscience, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; Veterans Health Administration, Rocky Mountain Mental Illness Research Education and Clinical Center (MIRECC), Rocky Mountain Regional Veterans Affairs Medical Center (RMRVAMC), Aurora, CO 80045, USA; Military and Veteran Microbiome Consortium for Research and Education (MVM-CoRE), Aurora, CO 80045, USA.
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Vilela-Costa HH, Spiacci A, Bissolli IG, Zangrossi H. A Shift in the Activation of Serotonergic and Non-serotonergic Neurons in the Dorsal Raphe Lateral Wings Subnucleus Underlies the Panicolytic-Like Effect of Fluoxetine in Rats. Mol Neurobiol 2019; 56:6487-6500. [DOI: 10.1007/s12035-019-1536-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 02/22/2019] [Indexed: 01/04/2023]
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Goto S, Ogi H, Fushiki S, Itoh K. Prenatal and lactational bisphenol A exposure does not alter serotonergic neurons morphologically in the murine dorsal raphe nucleus. Brain Dev 2017; 39:475-482. [PMID: 28233694 DOI: 10.1016/j.braindev.2017.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 01/17/2017] [Accepted: 01/23/2017] [Indexed: 10/20/2022]
Abstract
OBJECTIVE There is concern that bisphenol A (BPA), an endocrine-disrupting chemical, affects brain development when exposed to a fetus and/or infant. We previously reported that increased serotonin (5-HT) and its metabolite (5-HIAA) in the dorsal raphe nucleus (DRN) in murine adult brains when they were prenatally exposed to low doses of BPA. This study investigates the morphological alteration of the dorsal raphe nucleus (DRN) in order to explain the disrupted serotonergic system after prenatal and lactational exposure to bisphenol A (BPA). METHODS The murine dams were orally administrated with 500μg/kg/day of BPA from embryonic day 0 to postnatal 3weeks. The DRN, the main region of serotonin production, was morphometrically analyzed at 14weeks, using immunohistochemistry and image analysis combined with 3-dimensional reconstruction. RESULTS No significant differences were revealed in the number of tryptophan hydroxylase 2-immunoreactive neurons in any of the DRN sub-regions or the morphometric parameters, including the whole volume, ventrodorsal, longitudinal, and wing lengths of the DRN among the BPA treatment and sex groups. CONCLUSIONS The murine DRN was not morphologically affected by prenatal and lactational exposure to low doses of BPA. Further studies are necessary regarding the function of serotonergic neurons and the activity of different kinds of related receptors in the brain.
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Affiliation(s)
- Shoko Goto
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan; Department of Pathology, Meiji University of Integrative Medicine, Japan
| | - Hiroshi Ogi
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan
| | - Shinji Fushiki
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan
| | - Kyoko Itoh
- Department of Pathology and Applied Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan.
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Galanin subtype 1 and subtype 2 receptors mediate opposite anxiety-like effects in the rat dorsal raphe nucleus. Behav Brain Res 2016; 314:125-33. [DOI: 10.1016/j.bbr.2016.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 08/01/2016] [Accepted: 08/03/2016] [Indexed: 01/09/2023]
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Lopes DA, Lemes JA, Melo-Thomas L, Schor H, de Andrade JS, Machado CM, Horta-Júnior JA, Céspedes IC, Viana MB. Unpredictable chronic mild stress exerts anxiogenic-like effects and activates neurons in the dorsal and caudal region and in the lateral wings of the dorsal raphe nucleus. Behav Brain Res 2016; 297:180-6. [DOI: 10.1016/j.bbr.2015.10.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 10/01/2015] [Accepted: 10/03/2015] [Indexed: 10/22/2022]
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Spiacci A, Pobbe RLH, Matthiesen M, Zangrossi H. 5-HT1A receptors of the rat dorsal raphe lateral wings and dorsomedial subnuclei differentially control anxiety- and panic-related defensive responses. Neuropharmacology 2015; 107:471-479. [PMID: 26145183 DOI: 10.1016/j.neuropharm.2015.06.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/24/2015] [Accepted: 06/27/2015] [Indexed: 01/04/2023]
Abstract
The dorsal raphe nucleus (DR), the main source of 5-HT projections to brain areas involved in anxiety regulation, is composed by 5 subnuclei that differ morphologically, functionally and neurochemically. Based on immunohistochemical evidence, it has been proposed that whereas 5-HT cells of the dorsomedial (dmDR) and caudal subnuclei are implicated in the pathophysiology of generalized anxiety disorder (GAD), neurons of the lateral wings (lwDR) are associated with panic disorder (PD). We here tested this hypothesis from a behavioral perspective by investigating the consequences of the non-selective stimulation of neurons within the dmDR and lwDR, or the pharmacological manipulation of 5-HT1A receptors located in these nuclei, of male Wistar rats exposed to the elevated T-maze. This test allows the measurement of both a GAD- (i.e. inhibitory avoidance) and a PD- (i.e. escape) related response in the same animal. Intra-dmDR injection of either the excitatory amino acid kainic acid or the 5-HT1A receptor antagonist WAY-100635 facilitated inhibitory avoidance acquisition, suggesting an anxiogenic effect, and inhibited escape expression, a panicolytic-like effect. Microinjection of the 5-HT1A receptor agonist 8-OH-DPAT caused the opposite effect. Administration of the same drugs into the lwDR only altered escape performance. Whereas kainic acid and 8-OH-DPAT facilitated its expression, WAY-100635 inhibited it. At higher doses, kainic acid administration evoked vigorous escape reactions as measured in an open-field. These findings implicate 5-HT neurons of the dmDR in the regulation of both GAD- and PD-related defensive behaviors. They also support a primary role of the lwDR in the mediation of PD-associated responses.
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Affiliation(s)
- Ailton Spiacci
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Roger Luis Henschel Pobbe
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Melina Matthiesen
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Helio Zangrossi
- Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, São Paulo, Brazil.
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9
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Serotonin in anxiety and panic: Contributions of the elevated T-maze. Neurosci Biobehav Rev 2014; 46 Pt 3:397-406. [DOI: 10.1016/j.neubiorev.2014.03.007] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 02/05/2014] [Accepted: 03/03/2014] [Indexed: 11/21/2022]
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10
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Paul ED, Johnson PL, Shekhar A, Lowry CA. The Deakin/Graeff hypothesis: focus on serotonergic inhibition of panic. Neurosci Biobehav Rev 2014; 46 Pt 3:379-96. [PMID: 24661986 PMCID: PMC4170046 DOI: 10.1016/j.neubiorev.2014.03.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 02/15/2014] [Accepted: 03/01/2014] [Indexed: 12/20/2022]
Abstract
The Deakin/Graeff hypothesis proposes that different subpopulations of serotonergic neurons through topographically organized projections to forebrain and brainstem structures modulate the response to acute and chronic stressors, and that dysfunction of these neurons increases vulnerability to affective and anxiety disorders, including panic disorder. We outline evidence supporting the existence of a serotonergic system originally discussed by Deakin/Graeff that is implicated in the inhibition of panic-like behavioral and physiological responses. Evidence supporting this panic inhibition system comes from the following observations: (1) serotonergic neurons located in the 'ventrolateral dorsal raphe nucleus' (DRVL) as well as the ventrolateral periaqueductal gray (VLPAG) inhibit dorsal periaqueductal gray-elicited panic-like responses; (2) chronic, but not acute, antidepressant treatment potentiates serotonin's panicolytic effect; (3) contextual fear activates a central nucleus of the amygdala-DRVL/VLPAG circuit implicated in mediating freezing and inhibiting panic-like escape behaviors; (4) DRVL/VLPAG serotonergic neurons are central chemoreceptors and modulate the behavioral and cardiorespiratory response to panicogenic agents such as sodium lactate and CO2. Implications of the panic inhibition system are discussed.
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Affiliation(s)
- Evan D Paul
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Philip L Johnson
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Anantha Shekhar
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
| | - Christopher A Lowry
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
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Paul ED, Lowry CA. Functional topography of serotonergic systems supports the Deakin/Graeff hypothesis of anxiety and affective disorders. J Psychopharmacol 2013; 27:1090-106. [PMID: 23704363 DOI: 10.1177/0269881113490328] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Over 20 years ago, Deakin and Graeff hypothesized about the role of different serotonergic pathways in controlling the behavioral and physiologic responses to aversive stimuli, and how compromise of these pathways could lead to specific symptoms of anxiety and affective disorders. A growing body of evidence suggests these serotonergic pathways arise from topographically organized subpopulations of serotonergic neurons located in the dorsal and median raphe nuclei. We argue that serotonergic neurons in the dorsal/caudal parts of the dorsal raphe nucleus project to forebrain limbic regions involved in stress/conflict anxiety-related processes, which may be relevant for anxiety and affective disorders. Serotonergic neurons in the "lateral wings" of the dorsal raphe nucleus provide inhibitory control over structures controlling fight-or-flight responses. Dysfunction of this pathway could be relevant for panic disorder. Finally, serotonergic neurons in the median raphe nucleus, and the developmentally and functionally-related interfascicular part of the dorsal raphe nucleus, give rise to forebrain limbic projections that are involved in tolerance and coping with aversive stimuli, which could be important for affective disorders like depression. Elucidating the mechanisms through which stress activates these topographically and functionally distinct serotonergic pathways, and how dysfunction of these pathways leads to symptoms of neuropsychiatric disorders, may lead to the development of novel approaches to both the prevention and treatment of anxiety and affective disorders.
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Affiliation(s)
- Evan D Paul
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, USA
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12
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Fox JH, Lowry CA. Corticotropin-releasing factor-related peptides, serotonergic systems, and emotional behavior. Front Neurosci 2013; 7:169. [PMID: 24065880 PMCID: PMC3778254 DOI: 10.3389/fnins.2013.00169] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 08/30/2013] [Indexed: 12/01/2022] Open
Abstract
Corticotropin-releasing factor (CRF) is a 41-amino acid neuropeptide that is involved in stress-related physiology and behavior, including control of the hypothalamic-pituitary-adrenal (HPA) axis. Members of the CRF family of neuropeptides, including urocortin 1 (UCN 1), UCN 2, and UCN 3, bind to the G protein-coupled receptors, CRF type 1 (CRF1) and CRF2 receptors. In addition, CRF binding protein (CRFBP) binds both CRF and UCN 1 and can modulate their activities. There are multiple mechanisms through which CRF-related peptides may influence emotional behavior, one of which is through altering the activity of brainstem neuromodulatory systems, including serotonergic systems. CRF and CRF-related peptides act within the dorsal raphe nucleus (DR), the major source for serotonin (5-HT) in the brain, to alter the neuronal activity of specific subsets of serotonergic neurons and to influence stress-related behavior. CRF-containing axonal fibers innervate the DR in a topographically organized manner, which may contribute to the ability of CRF to alter the activity of specific subsets of serotonergic neurons. CRF and CRF-related peptides can either increase or decrease serotonergic neuronal firing rates and serotonin release, depending on their concentrations and on the specific CRF receptor subtype(s) involved. This review aims to describe the interactions between CRF-related peptides and serotonergic systems, the consequences for stress-related behavior, and implications for vulnerability to anxiety and affective disorders.
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Affiliation(s)
- James H Fox
- Behavioral Neuroendocrinology Laboratory, Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder Boulder, CO, USA
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Silote GP, Rosal AB, de Souza MM, Beijamini V. Infusion of galanin into the mid-caudal portion of the dorsal raphe nucleus has an anxiolytic effect on rats in the elevated T-maze. Behav Brain Res 2013; 252:312-7. [PMID: 23791934 DOI: 10.1016/j.bbr.2013.06.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 06/14/2013] [Accepted: 06/16/2013] [Indexed: 11/19/2022]
Abstract
Galanin and 5-HT coexist in dorsal raphe nucleus (DRN) neurons. Microinjection of galanin into the DRN reduces the firing rate of serotonin neurons. Serotonergic neurons projecting from the DRN to the amygdala facilitate learned anxiety producing an anxiogenic effect, while those projecting from the periaqueductal grey affect innate anxiety producing a panicolytic effect. We tested the hypothesis that injection of galanin into rat DRN would induce anxiolytic/panicogenic effects in the elevated T-maze (ETM), a model that allows for the evaluation of both of these effects. Galanin infusion into the mid-caudal DRN, but not into the rostral DRN, impaired inhibitory avoidance, suggesting an anxiolytic effect. The effective dose of galanin (0.3 nmol) did not modify locomotor activity in the open field. Contrary to expectations, microinjection of galanin into the DRN did not facilitate the latency of one-way escape in the ETM. Pretreatment with a galanin antagonist, M40, attenuated galanin-induced impairment of inhibitory avoidance. The results show that microinjection of a low dose of galanin only into the mid-caudal DRN has an anxiolytic effect. This effect seems to be mediated, at least in part, by galanin receptors. Further investigation is necessary to identify the receptor subtypes and the DRN subregion involved in the anxiolytic effect of galanin.
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Affiliation(s)
- Gabriela Pandini Silote
- Department of Pharmaceutical Sciences, Health Science Center, Federal University of Espirito Santo, Vitoria, ES 29043-900, Brazil
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Jasinska AJ, Lowry CA, Burmeister M. Serotonin transporter gene, stress and raphe-raphe interactions: a molecular mechanism of depression. Trends Neurosci 2012; 35:395-402. [PMID: 22301434 DOI: 10.1016/j.tins.2012.01.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Revised: 12/02/2011] [Accepted: 01/01/2012] [Indexed: 12/16/2022]
Abstract
Reports of gene-environment interactions (GxE) between the serotonin transporter gene and stress on risk of depression have generated both excitement and controversy. The controversy persists in part because a mechanistic account of this GxE on serotonergic neurotransmission and risk of depression has been lacking. In this Opinion, we draw on recent discoveries in the functional neuroanatomy of the serotonergic dorsal raphe nucleus (DR) to propose such a mechanistic account. We argue that genetically produced variability in serotonin reuptake during stressor-induced raphe-raphe interactions alters the balance in the amygdala-ventromedial prefrontal cortex (VMPFC)-DR circuitry underlying stressor reactivity and emotion regulation. In particular, the recently characterized stressor-responsive serotonergic interneurons originating from the dorsolateral DR may hold a key to unlocking the GxE mechanism of depression.
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Affiliation(s)
- Agnes J Jasinska
- Department of Psychology, University of Michigan, Ann Arbor, Michigan, USA.
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15
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Hale MW, Shekhar A, Lowry CA. Stress-related serotonergic systems: implications for symptomatology of anxiety and affective disorders. Cell Mol Neurobiol 2012; 32:695-708. [PMID: 22484834 DOI: 10.1007/s10571-012-9827-1] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 03/07/2012] [Indexed: 11/30/2022]
Abstract
Previous studies have suggested that serotonergic neurons in the midbrain raphe complex have a functional topographic organization. Recent studies suggest that stimulation of a bed nucleus of the stria terminalis-dorsal raphe nucleus pathway by stress- and anxiety-related stimuli modulates a subpopulation of serotonergic neurons in the dorsal part of the dorsal raphe nucleus (DRD) and caudal part of the dorsal raphe nucleus (DRC) that participates in facilitation of anxiety-like responses. In contrast, recent studies suggest that activation of a spinoparabrachial pathway by peripheral thermal or immune stimuli excites subpopulations of serotonergic neurons in the ventrolateral part of the dorsal raphe nucleus/ventrolateral periaqueducal gray (DRVL/VLPAG) region and interfascicular part of the dorsal raphe nucleus (DRI). Studies support a role for serotonergic neurons in the DRVL/VLPAG in inhibition of panic-like responses, and serotonergic neurons in the DRI in antidepressant-like effects. Thus, data suggest that while some subpopulations of serotonergic neurons in the dorsal raphe nucleus play a role in facilitation of anxiety-like responses, others play a role in inhibition of anxiety- or panic-like responses, while others play a role in antidepressant-like effects. Understanding the anatomical and functional properties of these distinct serotonergic systems may lead to novel therapeutic strategies for the prevention and/or treatment of affective and anxiety disorders. In this review, we describe the anatomical and functional properties of subpopulations of serotonergic neurons in the dorsal raphe nucleus, with a focus on those implicated in symptoms of anxiety and affective disorders, the DRD/DRC, DRVL/VLPAG, and DRI.
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Affiliation(s)
- Matthew W Hale
- School of Psychological Science, La Trobe University, Melbourne, Australia
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Matrov D, Vonk A, Herm L, Rinken A, Harro J. Activating effects of chronic variable stress in rats with different exploratory activity: association with dopamine d(1) receptor function in nucleus accumbens. Neuropsychobiology 2011; 64:110-22. [PMID: 21701229 DOI: 10.1159/000325224] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 01/23/2011] [Indexed: 01/11/2023]
Abstract
BACKGROUND/AIMS Rats display persistent behavioural phenotypes of low (LE) versus high (HE) exploratory activity in the exploration box paradigm. LE rats that prefer passive coping strategies show differential dopaminergic activity in the striatum. The main hypothesis of this study was that chronic variable stress (CVS) would have a higher impact on LE rats. METHODS Animals were submitted to a CVS regimen lasting 32 days that was followed by a behavioural test battery. The functional states of their dopamine D(1) and D(2) receptors were measured in the striatum and nucleus accumbens (NAcc). Cerebral oxidative metabolism was assessed via cytochrome c oxidase histochemistry in 65 brain regions. RESULTS CVS decreased weight gain, to a higher extent in LE rats, and lowered the sucrose preference after the first week, but habituation to the anhedonic effect had developed by the end of the experiment. CVS did not change the behavioural phenotypes initially assigned. No effect of stress on D(2) receptor function was found. Chronically stressed animals exhibited higher levels of social interaction and D(1) receptor-mediated cAMP accumulation in the NAcc, but not in the striatum. CVS was associated with higher oxidative metabolism levels in the anteroventral thalamus, median raphe nuclei and central periaqueductal grey matter. These changes after stress did not depend upon the exploratory phenotype. CONCLUSION This study revealed changes in brain biochemistry after habituation to CVS that might be implicated in successful adaptation to chronic stress.
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Affiliation(s)
- Denis Matrov
- Department of Psychology, Centre of Behavioural and Health Sciences, University of Tartu, Tartu, Estonia
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Hale MW, Lowry CA. Functional topography of midbrain and pontine serotonergic systems: implications for synaptic regulation of serotonergic circuits. Psychopharmacology (Berl) 2011; 213:243-64. [PMID: 21088958 DOI: 10.1007/s00213-010-2089-z] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 10/29/2010] [Indexed: 12/20/2022]
Abstract
RATIONALE Dysfunction of serotonergic systems is thought to play an important role in a number of neurological and psychiatric disorders. Recent studies suggest that there is anatomical and functional diversity among serotonergic systems innervating forebrain systems involved in the control of physiologic and behavioral responses, including the control of emotional states. OBJECTIVE Here, we highlight the methods that have been used to investigate the heterogeneity of serotonergic systems and review the evidence for the unique anatomical, hodological, and functional properties of topographically organized subpopulations of serotonergic neurons in the midbrain and pontine raphe complex. CONCLUSION The emerging understanding of the topographically organized synaptic regulation of brainstem serotonergic systems, the topography of the efferent projections of these systems, and their functional properties, should enable identification of novel therapeutic approaches to treatment of neurological and psychiatric conditions that are associated with dysregulation of serotonergic systems.
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Affiliation(s)
- Matthew W Hale
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA
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Paul ED, Hale MW, Lukkes JL, Valentine MJ, Sarchet DM, Lowry CA. Repeated social defeat increases reactive emotional coping behavior and alters functional responses in serotonergic neurons in the rat dorsal raphe nucleus. Physiol Behav 2011; 104:272-82. [PMID: 21238469 DOI: 10.1016/j.physbeh.2011.01.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 12/16/2010] [Accepted: 01/06/2011] [Indexed: 10/18/2022]
Abstract
Chronic stress is a vulnerability factor for a number of psychiatric disorders, including anxiety and affective disorders. Social defeat in rats has proven to be a useful paradigm to investigate the neural mechanisms underlying physiologic and behavioral adaptation to acute and chronic stress. Previous studies suggest that serotonergic systems may contribute to the physiologic and behavioral adaptation to chronic stress, including social defeat in rodent models. In order to test the hypothesis that repeated social defeat alters the emotional behavior and the excitability of brainstem serotonergic systems implicated in control of emotional behavior, we exposed adult male rats either to home cage control conditions, acute social defeat, or social defeat followed 24h later by a second social defeat encounter. We then assessed behavioral responses during social defeat as well as the excitability of serotonergic neurons within the dorsal raphe nucleus using immunohistochemical staining of tryptophan hydroxylase, a marker of serotonergic neurons, and the protein product of the immediate-early gene, c-fos. Repeated social defeat resulted in a shift away from proactive emotional coping behaviors, such as rearing (explorative escape behavior), and toward reactive emotional coping behaviors such as freezing. Both acute and repeated defeat led to widespread increases in c-Fos expression in serotonergic neurons in the dorsal raphe nucleus. Changes in behavior following a second exposure to social defeat, relative to acute defeat, were associated with decreased c-Fos expression in serotonergic neurons within the dorsal and ventral parts of the mid-rostrocaudal dorsal raphe nucleus, regions that have been implicated in 1) serotonergic modulation of fear- and anxiety-related behavior and 2) defensive behavior in conspecific aggressive encounters, respectively. These data support the hypothesis that serotonergic systems play a role in physiologic and behavioral responses to both acute and repeated social defeat.
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Affiliation(s)
- Evan D Paul
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado, Boulder, CO 80309-0354, USA.
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19
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Urocortin 2 increases c-Fos expression in serotonergic neurons projecting to the ventricular/periventricular system. Exp Neurol 2010; 224:271-81. [PMID: 20382145 DOI: 10.1016/j.expneurol.2010.04.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 03/25/2010] [Accepted: 04/01/2010] [Indexed: 11/21/2022]
Abstract
Serotonin plays an important role in the regulation of anxiety states and physiological responses to aversive stimuli. Intracerebroventricular (i.c.v.) injection of the stress- and anxiety-related neuropeptide urocortin 2 (Ucn 2) increases c-Fos expression in serotonergic neurons in the dorsal (DRD) and caudal (DRC) parts of the dorsal raphe nucleus. These regions contain a subset of serotonergic neurons that projects via the dorsal raphe periventricular tract to periventricular structures, including the subfornical organ and ependymal layer, and to the ventricular system. To determine if Ucn 2 activates ventricle/periventricular-projecting serotonergic neurons in the midbrain raphe complex, we made i.c.v. injections of the retrograde tracer Fluoro-Gold into the lateral ventricle, followed 7 days later by i.c.v. injection of Ucn 2. The DRD at -8.18 mm and the DRC at -8.54 mm and -9.16 mm bregma were analyzed using a combined bright field and immunofluorescence technique. Approximately 40% of the ventricle/periventricular-projecting neurons in the subdivisions sampled were serotonergic. Urocortin 2 increased c-Fos expression in ventricle/periventricular-projecting serotonergic neurons in the DRC and in non-ventricle/periventricular-projecting serotonergic neurons in the DRD and DRC. Of the total population of ventricle/periventricular-projecting serotonergic neurons in the DRC at -8.54 and -9.16 mm bregma, 35% expressed c-Fos following Ucn 2 injections. These data are consistent with previous studies showing that i.c.v. injection of Ucn 2 activates subpopulations of serotonergic neurons restricted to the mid-rostrocaudal DRD and DRC and further demonstrate that these include both subsets of serotonergic neurons that do and do not project to the ventricle/periventricular system.
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20
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Siqueira CC, Rossoni RR, Schenberg LC. Dorsal periaqueductal gray matter-evoked panic-like behaviors are markedly inhibited by a low peripheral dose of thyrotropin releasing hormone. Psychoneuroendocrinology 2010; 35:262-71. [PMID: 19631472 DOI: 10.1016/j.psyneuen.2009.06.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Revised: 05/08/2009] [Accepted: 06/29/2009] [Indexed: 10/20/2022]
Abstract
Stimulation of the dorsal periaqueductal gray matter (DPAG) produces defensive behaviors which are reminiscent of panic attacks. Recent evidence from our laboratory showed that DPAG-evoked defensive behaviors are markedly attenuated in short-term methimazole-induced hypothyroidism. It is not clear, however, whether these effects were due to an increase in thyrotropin releasing hormone (TRH), a decrease in thyroid hormones or to the overall effects of hypothyroidism. Accordingly, here we examined whether the peripheral injection of TRH has any effect either on the panic-like behaviors induced by electrical stimulation of DPAG or anxiety-like behaviors of rats exposed to the elevated plus-maze (EPM). Rats whose stimulation of DPAG produced flight responses (galloping or jumping) with intensities below 60 microA were injected with 1 microg/kg TRH (i.p.) and stimulated 10min after that. The day after, rats were treated with saline and subjected to the same stimulation procedure. Threshold curves were fitted through the logistic model and compared by likelihood-ratio chi(2) tests. TRH and saline effects on EPM performance were appraised in separate groups. Compared to saline-sessions, TRH-injected rats presented thresholds significantly higher for immobility (40%), trotting (33%), galloping (34%), jumping (39%) and exophthalmus (43%). In contrast, TRH had no effects on EPM arm exploration. TRH selective inhibition of DPAG-evoked defensive behaviors adds new evidence that panic attacks may be attenuated by increased levels of this hormone in hypothyroidism.
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Affiliation(s)
- Carla Coelho Siqueira
- Department of Physiological Sciences, Federal University of Espírito Santo, Vitória-ES, Brazil
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21
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Lowry CA, Hale MW. Serotonin and the Neurobiology of Anxious States. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2010. [DOI: 10.1016/s1569-7339(10)70091-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Lowry CA, Hale MW, Evans AK, Heerkens J, Staub DR, Gasser PJ, Shekhar A. Serotonergic systems, anxiety, and affective disorder: focus on the dorsomedial part of the dorsal raphe nucleus. Ann N Y Acad Sci 2009; 1148:86-94. [PMID: 19120094 DOI: 10.1196/annals.1410.004] [Citation(s) in RCA: 203] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Depressed suicide patients have elevated expression of neuronal tryptophan hydroxylase 2 (TPH2) mRNA and protein in midbrain serotonergic neurons, as well as increases in brain serotonin turnover. The mechanisms underlying these changes are uncertain, but increased TPH2 expression and serotonin turnover could result from genetic influences, adverse early life experiences, or acute stressful life events, all of which can alter serotonergic neurotransmission and have been implicated in determining vulnerability to major depression. Emerging evidence suggests that there are several different stress-related subsets of serotonergic neurons, each with a unique role in the integrated stress response. Here we review our current understanding of how genetic and environmental factors may influence TPH2 mRNA expression and serotonergic neurotransmission, focusing in particular on the dorsomedial part of the dorsal raphe nucleus. This subdivision of the dorsal raphe nucleus is selectively innervated by key forebrain structures implicated in regulation of anxiety states, it gives rise to projections to a distributed neural system mediating anxiety states, and serotonergic neurons within this subdivision are selectively activated by a number of stress- and anxiety-related stimuli. A better understanding of the anatomical and functional properties of specific stress- or anxiety-related serotonergic systems should aid our understanding of the neural mechanisms underlying the etiology of anxiety and affective disorders.
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Affiliation(s)
- Christopher A Lowry
- Department of Integrative Physiology, University of Colorado at Boulder, Boulder, Colorado 80309-0354, USA.
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23
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Hale MW, Hay-Schmidt A, Mikkelsen JD, Poulsen B, Bouwknecht JA, Evans AK, Stamper CE, Shekhar A, Lowry CA. Exposure to an open-field arena increases c-Fos expression in a subpopulation of neurons in the dorsal raphe nucleus, including neurons projecting to the basolateral amygdaloid complex. Neuroscience 2008; 157:733-48. [PMID: 18951955 DOI: 10.1016/j.neuroscience.2008.09.050] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 09/12/2008] [Accepted: 09/22/2008] [Indexed: 11/17/2022]
Abstract
Serotonergic systems in the dorsal raphe nucleus are thought to play an important role in the regulation of anxiety states. To investigate responses of neurons in the dorsal raphe nucleus to a mild anxiety-related stimulus, we exposed rats to an open-field, under low-light or high-light conditions. Treatment effects on c-Fos expression in serotonergic and non-serotonergic cells in the midbrain raphe nuclei were determined 2 h following open-field exposure or home cage control (CO) conditions. Rats tested under both light conditions responded with increases in c-Fos expression in serotonergic neurons within subdivisions of the midbrain raphe nuclei compared with CO rats. However, the total numbers of serotonergic neurons involved were small suggesting that exposure to the open-field may affect a subpopulation of serotonergic neurons. To determine if exposure to the open-field activates a subset of neurons in the midbrain raphe complex that projects to forebrain circuits regulating anxiety states, we used cholera toxin B subunit (CTb) as a retrograde tracer to identify neurons projecting to the basolateral amygdaloid complex (BL) in combination with c-Fos immunostaining to identify cells that responded to open-field exposure. Rats received a unilateral injection of CTb into the BL. Seven to 11 days following CTb injection rats were either, 1) exposed to an open-field in low-light conditions, 2) briefly handled or 3) left undisturbed in home cages. Dual immunostaining for c-Fos and CTb revealed an increase in the percentage of c-Fos-immunoreactive BL-projecting neurons in open-field-exposed rats compared with handled and control rats. Dual immunostaining for tryptophan hydroxylase and CTb revealed that a majority (65%) of BL-projecting neurons were serotonergic, leaving open the possibility that activated neurons were serotonergic, non-serotonergic, or both. These data are consistent with the hypothesis that exposure to anxiogenic stimuli activates a subset of neurons in the midbrain raphe complex projecting to amygdala anxiety circuits.
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Affiliation(s)
- M W Hale
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA
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Reyes S, Mitrofanis J. Patterns of FOS expression in the spinal cord and periaqueductal grey matter of 6OHDA-lesioned rats. Int J Neurosci 2008; 118:1053-79. [PMID: 18576208 DOI: 10.1080/00207450701239210] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A less well-known feature of Parkinson disease is that up to 40% of patients experience distinct sensory disturbances, including hyperalgesia and chronic pain. There is a limited understanding of the neural mechanisms that generate these symptoms, however. This study explores the patterns of Fos expression (a well-known marker for changes in cell activity) in the spinal cord and periaqueductal grey matter (PaG), two major sensory (nociceptive) centers, of hemiParkinsonian rats. The medial forebrain bundle (mfb; major tract carrying dopaminergic nigrostriatal axons) was injected with either 6OHDA or saline (controls). A week later, some rats were subjected to mechanical stimulation (pinching) of the hindpaw for 2 h, whereas others received no stimulation. Thereafter, brains were processed using routine tyrosine hydroxylase (marker for dopaminergic cells) or Fos immunocytochemistry. In the PaG, there were many more Fos(+) cells in the 6OHDA-lesioned than in the Control group, in both the stimulation and, in particular, the non-stimulation cases. In the spinal cord, there were also more Fos(+) cells in the 6OHDA-lesioned than in the Control group, but in the stimulation cases only. Overall, the results show distinct changes in Fos expression in the spinal cord and PaG of 6OHDA-lesioned rats, suggesting a substrate for some of the abnormal sensory (nociceptive) circuits that may be evident in parkinsonian cases.
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Affiliation(s)
- Stephanie Reyes
- Department Anatomy and Histology, University of Sydney, Sydney, Australia
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Brambilla D, Franciosi S, Opp MR, Imeri L. Interleukin-1 inhibits firing of serotonergic neurons in the dorsal raphe nucleus and enhances GABAergic inhibitory post-synaptic potentials. Eur J Neurosci 2007; 26:1862-9. [PMID: 17868373 DOI: 10.1111/j.1460-9568.2007.05796.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In vitro electrophysiological data suggest that interleukin-1 may promote non-rapid eye movement sleep by inhibiting spontaneous firing of wake-active serotonergic neurons in the dorsal raphe nucleus (DRN). Interleukin-1 enhances GABA inhibitory effects. DRN neurons are under an inhibitory GABAergic control. This study aimed to test the hypothesis that interleukin-1 inhibits DRN serotonergic neurons by potentiating GABAergic inhibitory effects. In vitro intracellular recordings were performed to assess the responses of physiologically and pharmacologically identified DRN serotonergic neurons to rat recombinant interleukin-1beta. Coronal slices containing DRN were obtained from male Sprague-Dawley rats. The impact of interleukin-1 on firing rate and on evoked post-synaptic potentials was determined. Evoked post-synaptic potentials were induced by stimulation with a bipolar electrode placed on the surface of the slice ventrolateral to DRN. Addition of interleukin-1 (25 ng/mL) to the bath perfusate significantly decreased firing rates of DRN serotonergic neurons from 1.3 +/- 0.2 Hz (before administration) to 0.7 +/- 0.2 Hz. Electrical stimulation induced depolarizing evoked post-synaptic potentials in DRN serotonergic neurons. The application of glutamatergic and GABAergic antagonists unmasked two different post-synaptic potential components: a GABAergic evoked inhibitory post-synaptic potentials and a glutamatergic evoked excitatory post-synaptic potentials, respectively. Interleukin-1 increased GABAergic evoked inhibitory post-synaptic potentials amplitudes by 30.3 +/- 3.8% (n = 6) without affecting glutamatergic evoked excitatory post-synaptic potentials. These results support the hypothesis that interleukin-1 inhibitory effects on DRN serotonergic neurons are mediated by an interleukin-1-induced potentiation of evoked GABAergic inhibitory responses.
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Affiliation(s)
- D Brambilla
- Institute of Human Physiology II, Guiseppe Moruzzi Center for Experimental Sleep Research, University of Milan Medical School, Via Mangiagalli, 32, 20133 Milano, Italy.
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Kishi R, Bongiovanni R, de Nadai TR, Freitas RL, de Oliveira R, Ferreira CMDR, Coimbra NC. Dorsal raphe nucleus and locus coeruleus neural networks and the elaboration of the sweet-substance-induced antinociception. Neurosci Lett 2006; 395:12-7. [PMID: 16289556 DOI: 10.1016/j.neulet.2005.10.046] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Revised: 09/16/2005] [Accepted: 10/17/2005] [Indexed: 11/26/2022]
Abstract
In order to investigate the effects of monoaminergic neurons of the dorsal raphe nucleus (DRN) and locus coeruleus (LC) on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180-200 g received sucrose solution (250 g/L) for 7-14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of ibotenic acid (1.0 microg/0.2 microL) in the DRN or in the LC. The tail withdrawal latencies of the rats in the tail-flick test were measured immediately before and 7 days after this treatment. The neurochemical lesion of locus coeruleus, but not of DRN neural networks with ibotenic acid, after the chronic intake of sweetened solution, decreased the sweet-substance-induced antinociception. These results indicate the involvement of noradrenaline-containing neurons of the LC in the sucrose-induced antinociception. We also consider the possibility of DRN serotonergic neurons exerting some inhibitory effect on the LC neural networks involved with the elaboration of the sweet-substance-induced antinociception.
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Affiliation(s)
- Renato Kishi
- Laboratório de Neuroanatomia e Neuropsicobiologia, Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP), Avenida dos Bandeirantes, 3900 Ribeirão Preto (SP) 14049-900, Brasil
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Miyase CI, Kishi R, de Freitas RL, Paz DA, Coimbra NC. Involvement of pre- and post-synaptic serotonergic receptors of dorsal raphe nucleus neural network in the control of the sweet-substance-induced analgesia in adult Rattus norvegicus (Rodentia, Muridae). Neurosci Lett 2005; 379:169-73. [PMID: 15843057 DOI: 10.1016/j.neulet.2004.12.058] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Revised: 12/19/2004] [Accepted: 12/23/2004] [Indexed: 11/27/2022]
Abstract
In order to investigate the effects of monoaminergic mechanisms of the dorsal raphe nucleus on the elaboration and control of sweet-substance-induced antinociception, male albino Wistar rats weighing 180-200 g received sucrose solution (250 g/L) for 14 days as their only source of liquid. After the chronic consumption of sucrose solution, each animal was pretreated with unilateral microinjection of methiothepin mesylate (5.0 microg/0.2 microL), or methysergide maleate (5.0 microg/0.2 microL) in the dorsal raphe nucleus. Each rat consumed an average of 15.6g sucrose/day. Their tail withdrawal latencies in the tail-flick test were measured immediately before and after this treatment. An analgesia index was calculated from the withdrawal latencies before and after the pharmacological treatment. The blockade of serotonergic receptor in the dorsal raphe nucleus with methysergide after the chronic intake of sucrose decreased the sweet-induced antinociception. However, microinjections of methiothepin in the dorsal raphe nucleus did not cause a similar effect on the tail-flick latencies after the chronic intake of sucrose solution, increasing the sweet-substance-induced analgesia. These results indicate the involvement of serotonin as a neurotransmitter in the sucrose-produced antinociception. Considering that the blockade of pre-synaptic serotonergic receptors of the neural networks of the dorsal raphe nucleus with methiothepin did not decrease the sweet-substance-induced antinociception, and the central blockade of post-synaptic serotonergic receptors decreased the sucrose-induced analgesia, the modulation of the release of serotonin in the neural substrate of the dorsal raphe nucleus seems to be crucial for the organization of this interesting antinociceptive process.
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Affiliation(s)
- Cátia Isumi Miyase
- Laboratório de Neuroanatomia e Neuropsicobiologia, Departamento de Farmacologia, Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo (FMRP-USP), Avenida dos Bandeirantes 3900, Ribeirão Preto (SP) 14049-900, Brazil
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Johnson PL, Lightman SL, Lowry CA. A functional subset of serotonergic neurons in the rat ventrolateral periaqueductal gray implicated in the inhibition of sympathoexcitation and panic. Ann N Y Acad Sci 2004; 1018:58-64. [PMID: 15240352 DOI: 10.1196/annals.1296.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The ability of serotonin (5-HT) to facilitate or attenuate autonomic, endocrine, and behavioral responses to stressful stimuli has received much attention. The effects of 5-HT on physiologic and behavioral responses to stressful stimuli seem to depend on the brain region where it is released and the effector system it acts upon. This and the distinct morphology and topographic organization of subpopulations of serotonergic neurons have led to the hypothesis that subpopulations of serotonergic neurons are functionally distinct. Serotonin's role as a modulator of the "fight-or-flight" response is mediated in part by 5-HT release in the dorsolateral periaqueductal gray (DLPAG) and in the rostral ventrolateral medulla (RVLM), an area that contains sympathoexcitatory C1 adrenergic (A) neurons. The release of 5-HT in either region inhibits stress-induced sympathetic activity in part via actions on 5-HT(1A) receptors. In addition, 5-HT release in the DLPAG inhibits fight-or-flight or "Go" behaviors. The origin of endogenous 5-HT in the DLPAG and RVLM seems to be a subpopulation of serotonergic neurons within the ventrolateral PAG, a region implicated in "freezing" or "No Go" behaviors. These serotonergic neurons are located in the lateral "wings" of the dorsal raphe nucleus (DRN) a region also referred to as the ventrolateral DRN. The existence of a functional subpopulation of serotonergic neurons capable of inhibiting sympathoexcitation and fight-or-flight behavioral responses may be clinically relevant for explaining in part the efficacy of serotonergic drugs in the treatment of hypertension and panic attacks in panic disorder patients.
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Affiliation(s)
- Philip L Johnson
- University Research Centre for Neuroendocrinology, University of Bristol, Marlborough Street, Bristol BS2 8HW, United Kingdom.
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