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Wong-Lin K, Wang DH, Moustafa AA, Cohen JY, Nakamura K. Toward a multiscale modeling framework for understanding serotonergic function. J Psychopharmacol 2017; 31:1121-1136. [PMID: 28417684 PMCID: PMC5606304 DOI: 10.1177/0269881117699612] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Despite its importance in regulating emotion and mental wellbeing, the complex structure and function of the serotonergic system present formidable challenges toward understanding its mechanisms. In this paper, we review studies investigating the interactions between serotonergic and related brain systems and their behavior at multiple scales, with a focus on biologically-based computational modeling. We first discuss serotonergic intracellular signaling and neuronal excitability, followed by neuronal circuit and systems levels. At each level of organization, we will discuss the experimental work accompanied by related computational modeling work. We then suggest that a multiscale modeling approach that integrates the various levels of neurobiological organization could potentially transform the way we understand the complex functions associated with serotonin.
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Affiliation(s)
- KongFatt Wong-Lin
- Intelligent Systems Research Centre, School of Computing and Intelligent Systems, University of Ulster, Magee Campus, Derry~Londonderry, UK
| | - Da-Hui Wang
- School of Systems Science, and National Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China
| | - Ahmed A Moustafa
- School of Social Sciences and Psychology, and Marcs Institute for Brain and Behaviour, University of Western Sydney, Sydney, Australia
| | - Jeremiah Y Cohen
- Solomon H. Snyder Department of Neuroscience, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, USA
| | - Kae Nakamura
- Department of Physiology, Kansai Medical University, Hirakata, Osaka, Japan
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Spencer WC, Deneris ES. Regulatory Mechanisms Controlling Maturation of Serotonin Neuron Identity and Function. Front Cell Neurosci 2017; 11:215. [PMID: 28769770 PMCID: PMC5515867 DOI: 10.3389/fncel.2017.00215] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 07/05/2017] [Indexed: 11/29/2022] Open
Abstract
The brain serotonin (5-hydroxytryptamine; 5-HT) system has been extensively studied for its role in normal physiology and behavior, as well as, neuropsychiatric disorders. The broad influence of 5-HT on brain function, is in part due to the vast connectivity pattern of 5-HT-producing neurons throughout the CNS. 5-HT neurons are born and terminally specified midway through embryogenesis, then enter a protracted period of maturation, where they functionally integrate into CNS circuitry and then are maintained throughout life. The transcriptional regulatory networks controlling progenitor cell generation and terminal specification of 5-HT neurons are relatively well-understood, yet the factors controlling 5-HT neuron maturation are only recently coming to light. In this review, we first provide an update on the regulatory network controlling 5-HT neuron development, then delve deeper into the properties and regulatory strategies governing 5-HT neuron maturation. In particular, we discuss the role of the 5-HT neuron terminal selector transcription factor (TF) Pet-1 as a key regulator of 5-HT neuron maturation. Pet-1 was originally shown to positively regulate genes needed for 5-HT synthesis, reuptake and vesicular transport, hence 5-HT neuron-type transmitter identity. It has now been shown to regulate, both positively and negatively, many other categories of genes in 5-HT neurons including ion channels, GPCRs, transporters, neuropeptides, and other transcription factors. Its function as a terminal selector results in the maturation of 5-HT neuron excitability, firing characteristics, and synaptic modulation by several neurotransmitters. Furthermore, there is a temporal requirement for Pet-1 in the control of postmitotic gene expression trajectories thus indicating a direct role in 5-HT neuron maturation. Proper regulation of the maturation of cellular identity is critical for normal neuronal functioning and perturbations in the gene regulatory networks controlling these processes may result in long-lasting changes in brain function in adulthood. Further study of 5-HT neuron gene regulatory networks is likely to provide additional insight into how neurons acquire their mature identities and how terminal selector-type TFs function in postmitotic vertebrate neurons.
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Affiliation(s)
- William C Spencer
- Department of Neurosciences, Case Western Reserve UniversityCleveland, OH, United States
| | - Evan S Deneris
- Department of Neurosciences, Case Western Reserve UniversityCleveland, OH, United States
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Chen A, Hubbert KD, Foroudi PF, Lu VF, Janušonis S. Serotonin 5-HT 4 receptors modulate the development of glutamatergic input to the dorsal raphe nucleus. Neurosci Lett 2017; 640:111-116. [PMID: 28108396 DOI: 10.1016/j.neulet.2017.01.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2016] [Revised: 12/19/2016] [Accepted: 01/11/2017] [Indexed: 11/20/2022]
Abstract
The dorsal raphe nucleus (DRN) is a major serotonin (5-hydroxytryptamine, 5-HT)-producing region in the central nervous system. It receives glutamatergic inputs from several brain regions, which are reciprocally modulated by serotonergic signals. We investigated whether serotonin 5-HT4 receptors (5-HT4Rs) play a role in the development of glutamatergic control of the DRN, with an emphasis on cortical inputs. Double-label immunohistochemistry and confocal microscopy were used to quantify vesicular glutamate transporter 1 (vGluT1)-immunoreactive terminals in the DRN of mice with a null-mutation in the 5-HT4R gene. We found no significant change in the overall density of vGluT1-positive terminals in homozygous and heterozygous mice, but heterozygous mice had a significantly higher density of vGluT1-positive terminals contacting serotonergic neurons. These results suggest that altered 5-HT4R expression may affect the development of cortical glutamatergic control of the DRN.
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Affiliation(s)
- Angela Chen
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA
| | - Katherine D Hubbert
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA
| | - Pasha F Foroudi
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA
| | - Vivian F Lu
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA
| | - Skirmantas Janušonis
- Department of Psychological and Brain Sciences, University of California, Santa Barbara, CA 93106-9660, USA.
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Mlinar B, Montalbano A, Piszczek L, Gross C, Corradetti R. Firing Properties of Genetically Identified Dorsal Raphe Serotonergic Neurons in Brain Slices. Front Cell Neurosci 2016; 10:195. [PMID: 27536220 PMCID: PMC4971071 DOI: 10.3389/fncel.2016.00195] [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: 06/26/2016] [Accepted: 07/22/2016] [Indexed: 11/13/2022] Open
Abstract
Tonic spiking of serotonergic neurons establishes serotonin levels in the brain. Since the first observations, slow regular spiking has been considered as a defining feature of serotonergic neurons. Recent studies, however, have revealed the heterogeneity of serotonergic neurons at multiple levels, comprising their electrophysiological properties, suggesting the existence of functionally distinct cellular subpopulations. In order to examine in an unbiased manner whether serotonergic neurons of the dorsal raphe nucleus (DRN) are heterogeneous, we used a non-invasive loose-seal cell-attached method to record α1 adrenergic receptor-stimulated spiking of a large sample of neurons in brain slices obtained from transgenic mice lines that express fluorescent marker proteins under the control of serotonergic system-specific Tph2 and Pet-1 promoters. We found wide homogeneous distribution of firing rates, well fitted by a single Gaussian function (r (2) = 0.93) and independent of anatomical location (P = 0.45), suggesting that in terms of intrinsic firing properties, serotonergic neurons in the DRN represent a single cellular population. Characterization of the population in terms of spiking regularity was hindered by its dependence on the firing rate. For instance, the coefficient of variation of the interspike intervals (ISI), a common measure of spiking irregularity, is of limited usefulness since it correlates negatively with the firing rate (r = -0.33, P < 0.0001). Nevertheless, the majority of neurons exhibited regular, pacemaker-like activity, with coefficient of variance of the ISI lower than 0.5 in ~97% of cases. Unexpectedly, a small percentage of neurons (~1%) exhibited a particular spiking pattern, characterized by low frequency (~0.02-0.1 Hz) oscillations in the firing rate. Transitions between regular and oscillatory firing were observed, suggesting that the oscillatory firing is an alternative firing pattern of serotonergic neurons.
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Affiliation(s)
- Boris Mlinar
- Department of Neuroscience, Psychology, Drug Research and Children's Health, University of Florence Florence, Italy
| | - Alberto Montalbano
- Department of Neuroscience, Psychology, Drug Research and Children's Health, University of Florence Florence, Italy
| | - Lukasz Piszczek
- Mouse Biology Unit, European Molecular Biology Laboratory Monterotondo, Italy
| | - Cornelius Gross
- Mouse Biology Unit, European Molecular Biology Laboratory Monterotondo, Italy
| | - Renato Corradetti
- Department of Neuroscience, Psychology, Drug Research and Children's Health, University of Florence Florence, Italy
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Pet-1 Switches Transcriptional Targets Postnatally to Regulate Maturation of Serotonin Neuron Excitability. J Neurosci 2016; 36:1758-74. [PMID: 26843655 DOI: 10.1523/jneurosci.3798-15.2016] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
UNLABELLED Newborn neurons enter an extended maturation stage, during which they acquire excitability characteristics crucial for development of presynaptic and postsynaptic connectivity. In contrast to earlier specification programs, little is known about the regulatory mechanisms that control neuronal maturation. The Pet-1 ETS (E26 transformation-specific) factor is continuously expressed in serotonin (5-HT) neurons and initially acts in postmitotic precursors to control acquisition of 5-HT transmitter identity. Using a combination of RNA sequencing, electrophysiology, and conditional targeting approaches, we determined gene expression patterns in maturing flow-sorted 5-HT neurons and the temporal requirements for Pet-1 in shaping these patterns for functional maturation of mouse 5-HT neurons. We report a profound disruption of postmitotic expression trajectories in Pet-1(-/-) neurons, which prevented postnatal maturation of 5-HT neuron passive and active intrinsic membrane properties, G-protein signaling, and synaptic responses to glutamatergic, lysophosphatidic, and adrenergic agonists. Unexpectedly, conditional targeting revealed a postnatal stage-specific switch in Pet-1 targets from 5-HT synthesis genes to transmitter receptor genes required for afferent modulation of 5-HT neuron excitability. Five-HT1a autoreceptor expression depended transiently on Pet-1, thus revealing an early postnatal sensitive period for control of 5-HT excitability genes. Chromatin immunoprecipitation followed by sequencing revealed that Pet-1 regulates 5-HT neuron maturation through direct gene activation and repression. Moreover, Pet-1 directly regulates the 5-HT neuron maturation factor Engrailed 1, which suggests Pet-1 orchestrates maturation through secondary postmitotic regulatory factors. The early postnatal switch in Pet-1 targets uncovers a distinct neonatal stage-specific function for Pet-1, during which it promotes maturation of 5-HT neuron excitability. SIGNIFICANCE STATEMENT The regulatory mechanisms that control functional maturation of neurons are poorly understood. We show that in addition to inducing brain serotonin (5-HT) synthesis and reuptake, the Pet-1 ETS (E26 transformation-specific) factor subsequently globally coordinates postmitotic expression trajectories of genes necessary for maturation of 5-HT neuron excitability. Further, Pet-1 switches its transcriptional targets as 5-HT neurons mature from 5-HT synthesis genes to G-protein-coupled receptors, which are necessary for afferent synaptic modulation of 5-HT neuron excitability. Our findings uncover gene-specific switching of downstream targets as a previously unrecognized regulatory strategy through which continuously expressed transcription factors control acquisition of neuronal identity at different stages of development.
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Glutamate input in the dorsal raphe nucleus as a determinant of escalated aggression in male mice. J Neurosci 2015; 35:6452-63. [PMID: 25904796 DOI: 10.1523/jneurosci.2450-14.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although the dorsal raphe nucleus (DRN) has long been linked to neural control of aggression, little is known about the regulatory influences of the DRN when an animal engages in either adaptive species-typical aggressive behavior or escalated aggression. Therefore it is important to explore which neurotransmitter inputs into the DRN determine the escalation of aggression in male mice. Previously, we observed that microinjection of the GABAB receptor agonist baclofen into the DRN escalates aggressive behavior in male mice. Here, we used a serotonin (5-HT) neuron-specific GABAB receptor knock-out mouse to demonstrate that baclofen acts on nonserotonergic neurons to escalate aggression. Intra-DRN baclofen administration increased glutamate release, but did not alter GABA release, within the DRN. Microinjection of l-glutamate into the DRN escalated dose-dependently attack bites toward an intruder. In vivo microdialysis showed that glutamate release increased in the DRN during an aggressive encounter, and the level of glutamate was further increased when the animal was engaged in escalated aggressive behavior after social instigation. Finally, 5-HT release was increased within the DRN and also in the medial prefrontal cortex when animals were provoked by social instigation, and during escalated aggression after social instigation, but this increase in 5-HT release was not observed when animals were engaged in species-typical aggression. In summary, glutamate input into the DRN is enhanced during escalated aggression, which causes a phasic increase of 5-HT release from the DRN 5-HT neurons.
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Sego C, Gonçalves L, Lima L, Furigo IC, Donato J, Metzger M. Lateral habenula and the rostromedial tegmental nucleus innervate neurochemically distinct subdivisions of the dorsal raphe nucleus in the rat. J Comp Neurol 2014; 522:1454-84. [PMID: 24374795 DOI: 10.1002/cne.23533] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 12/23/2013] [Accepted: 12/23/2013] [Indexed: 02/06/2023]
Abstract
The lateral habenula (LHb) is an epithalamic structure differentiated in a medial (LHbM) and a lateral division (LHbL). Together with the rostromedial tegmental nucleus (RMTg), the LHb has been implicated in the processing of aversive stimuli and inhibitory control of monoamine nuclei. The inhibitory LHb influence on midbrain dopamine neurons has been shown to be mainly mediated by the RMTg, a mostly GABAergic nucleus that receives a dominant input from the LHbL. Interestingly, the RMTg also projects to the dorsal raphe nucleus (DR), which also receives direct LHb projections. To compare the organization and transmitter phenotype of LHb projections to the DR, direct and indirect via the RMTg, we first placed injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin into the LHb or the RMTg. We then confirmed our findings by retrograde tracing and investigated a possible GABAergic phenotype of DR-projecting RMTg neurons by combining retrograde tracing with in situ hybridization for GAD67. We found only moderate direct LHb projections to the DR, which mainly emerged from the LHbM and were predominantly directed to the serotonin-rich caudal DR. In contrast, RMTg projections to the DR were more robust, emerged from RMTg neurons enriched in GAD67 mRNA, and were focally directed to a distinctive DR subdivision immunohistochemically characterized as poor in serotonin and enriched in presumptive glutamatergic neurons. Thus, besides its well-acknowledged role as a GABAergic control center for the ventral tegmental area (VTA)-nigra complex, our findings indicate that the RMTg is also a major GABAergic relay between the LHb and the DR.
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Affiliation(s)
- Chemutai Sego
- Department of Physiology & Biophysics, Institute of Biomedical Sciences, University of São Paulo, 05508-900, São Paulo, Brazil; Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, 05508-900, São Paulo, Brazil
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Antidepressant-like effects of cortical deep brain stimulation coincide with pro-neuroplastic adaptations of serotonin systems. Biol Psychiatry 2014; 76:203-12. [PMID: 24503468 PMCID: PMC4072754 DOI: 10.1016/j.biopsych.2013.12.009] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2013] [Revised: 11/27/2013] [Accepted: 12/16/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND Cortical deep brain stimulation (DBS) is a promising therapeutic option for treatment-refractory depression, but its mode of action remains enigmatic. Serotonin (5-HT) systems are engaged indirectly by ventromedial prefrontal cortex (vmPFC) DBS. Resulting neuroplastic changes in 5-HT systems could thus coincide with the long-term therapeutic activity of vmPFC DBS. METHODS We tested this hypothesis by evaluating the antidepressant-like activity of vmPFC DBS in the chronic social defeat stress (CSDS) model of depression (n = 8-13 mice/group). Circuit-wide activation induced by vmPFC DBS was mapped with c-Fos immunolabeling. The effects of chronic vmPFC DBS on the physiology and morphology of genetically identified 5-HT cells from the dorsal raphe nucleus (DRN) were examined with whole-cell recording, somatodendritic three-dimensional reconstructions and morphometric analyses of presynaptic boutons along 5-HT axons. RESULTS Acute DBS drove c-Fos expression locally in the vmPFC and in several distal monosynaptically connected regions, including the DRN. Chronic DBS reversed CSDS-induced social avoidance, restored the disrupted balance of excitatory/inhibitory inputs onto 5-HT neurons, and reversed 5-HT hypoexcitability observed after CSDS. Furthermore, vmPFC DBS reversed CSDS-induced arborization of 5-HT dendrites in the DRN and increased the size and density of 5-HT presynaptic terminals in the dentate gyrus and vmPFC. CONCLUSIONS We validate a new preclinical paradigm to examine cellular mechanisms underlying the antidepressant-like activity of vmPFC DBS and identify dramatic circuit-mediated cellular adaptations that coincide with this treatment. These neuroplastic changes of 5-HT neurons might contribute to the progressive mood improvements reported in patients treated with chronic courses of cortical DBS.
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Dorsal raphe serotonin neurons in mice: immature hyperexcitability transitions to adult state during first three postnatal weeks suggesting sensitive period for environmental perturbation. J Neurosci 2014; 34:4809-21. [PMID: 24695701 DOI: 10.1523/jneurosci.1498-13.2014] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Trauma during early life is a major risk factor for the development of anxiety disorders and suggests that the developing brain may be particularly sensitive to perturbation. Increased vulnerability most likely involves altering neural circuits involved in emotional regulation. The role of serotonin in emotional regulation is well established, but little is known about the postnatal development of the raphe where serotonin is made. Using whole-cell patch-clamp recording and immunohistochemistry, we tested whether serotonin circuitry in the dorsal and median raphe was functionally mature during the first 3 postnatal weeks in mice. Serotonin neurons at postnatal day 4 (P4) were hyperexcitable. The increased excitability was due to depolarized resting membrane potential, increased resistance, increased firing rate, lack of 5-HT1A autoreceptor response, and lack of GABA synaptic activity. Over the next 2 weeks, membrane resistance decreased and resting membrane potential hyperpolarized due in part to potassium current activation. The 5-HT1A autoreceptor-mediated inhibition did not develop until P21. The frequency of spontaneous inhibitory and excitatory events increased as neurons extended and refined their dendritic arbor. Serotonin colocalized with vGlut3 at P4 as in adulthood, suggesting enhanced release of glutamate alongside enhanced serotonin release. Because serotonin affects circuit development in other brain regions, altering the developmental trajectory of serotonin neuron excitability and release could have many downstream consequences. We conclude that serotonin neuron structure and function change substantially during the first 3 weeks of life during which external stressors could potentially alter circuit formation.
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Challis C, Beck SG, Berton O. Optogenetic modulation of descending prefrontocortical inputs to the dorsal raphe bidirectionally bias socioaffective choices after social defeat. Front Behav Neurosci 2014; 8:43. [PMID: 24596546 PMCID: PMC3925846 DOI: 10.3389/fnbeh.2014.00043] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/29/2014] [Indexed: 12/31/2022] Open
Abstract
It has been well established that modulating serotonin (5-HT) levels in humans and animals affects perception and response to social threats, however the circuit mechanisms that control 5-HT output during social interaction are not well understood. A better understanding of these systems could provide groundwork for more precise and efficient therapeutic interventions. Here we examined the organization and plasticity of microcircuits implicated in top-down control of 5-HT neurons in the dorsal raphe nucleus (DRN) by excitatory inputs from the ventromedial prefrontal cortex (vmPFC) and their role in social approach-avoidance decisions. We did this in the context of a social defeat model that induces a long lasting form of social aversion that is reversible by antidepressants. We first used viral tracing and Cre-dependent genetic identification of vmPFC glutamatergic synapses in the DRN to determine their topographic distribution in relation to 5-HT and GABAergic subregions and found that excitatory vmPFC projections primarily localized to GABA-rich areas of the DRN. We then used optogenetics in combination with cFos mapping and slice electrophysiology to establish the functional effects of repeatedly driving vmPFC inputs in DRN. We provide the first direct evidence that vmPFC axons drive synaptic activity and immediate early gene expression in genetically identified DRN GABA neurons through an AMPA receptor-dependent mechanism. In contrast, we did not detect vmPFC-driven synaptic activity in 5-HT neurons and cFos induction in 5-HT neurons was limited. Finally we show that optogenetically increasing or decreasing excitatory vmPFC input to the DRN during sensory exposure to an aggressor's cues enhances or diminishes avoidance bias, respectively. These results clarify the functional organization of vmPFC-DRN pathways and identify GABAergic neurons as a key cellular element filtering top-down vmPFC influences on affect-regulating 5-HT output.
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Affiliation(s)
- Collin Challis
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA ; Neuroscience Graduate Group, University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA
| | - Sheryl G Beck
- Neuroscience Graduate Group, University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA ; Department of Anesthesiology, Children's Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA
| | - Olivier Berton
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA ; Neuroscience Graduate Group, University of Pennsylvania Perelman School of Medicine Philadelphia, PA, USA
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Donaldson ZR, Piel DA, Santos TL, Richardson-Jones J, Leonardo ED, Beck SG, Champagne FA, Hen R. Developmental effects of serotonin 1A autoreceptors on anxiety and social behavior. Neuropsychopharmacology 2014; 39:291-302. [PMID: 23907404 PMCID: PMC3870787 DOI: 10.1038/npp.2013.185] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 06/27/2013] [Accepted: 07/22/2013] [Indexed: 01/13/2023]
Abstract
The serotonin 1A receptor (5-HT1A) has a major role in modulating the effects of serotonin on mood and behavior. Previous studies have shown that knockout of 5-HT1A selectively in the raphe leads to higher levels of anxiety during adulthood. However, it remains unclear whether this phenotype is due to variation in receptor levels specifically during development or throughout life. To test the hypothesis that developmental sensitivity may underlie the effects of 5-HT1A on anxiety, we used an inducible transgenic system to selectively suppress 5-HT1A levels in serotonergic raphe neurons from post-natal days (P) 14 to P30, with a maximal reduction of 40% at P21 and return to regular levels by P30. This developmental decrease in receptor levels has long-lasting consequences, increasing anxiety and decreasing social investigation in adulthood. In addition, post-natal knockdown of autoreceptors leads to long-term increases in the excitability of serotonergic neurons, which may represent a mechanism underlying the effects of post-natal receptor variation on behavior later in life. Finally, we also examined the interplay between receptor variation and juvenile exposure to stress (applied from P14 to P21). Similar to receptor knockdown, juvenile exposure to stress led to increased anxiety phenotypes but did not exacerbate 5-HT1A knockdown-mediated anxiety levels. This work indicates that the effects of 5-HT1A autoreceptors on anxiety and social behaviors are developmentally mediated and suggests that natural variations in the expression of 5-HT1A may act during development to influence individual anxiety levels and contribute to susceptibility to anxiety disorders.
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Affiliation(s)
- Zoe R Donaldson
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY, USA,Division of Integrative Neuroscience, The New York State Psychiatric Institute, New York, NY, USA,Department of Neuroscience and Psychiatry, Columbia University, 1051 Riverside Drive, Kolb 753, New York, NY 10032, USA, Tel: +1 212 543 5173, Fax: +1 212 543 5074, E-mail: or
| | - David A Piel
- Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute and University of Pennsylvania, Philadelphia, PA, USA
| | - Tabia L Santos
- Department of Neuroscience, Barnard College, New York, NY, USA
| | - Jesse Richardson-Jones
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY, USA,Division of Integrative Neuroscience, The New York State Psychiatric Institute, New York, NY, USA
| | - E David Leonardo
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY, USA,Division of Integrative Neuroscience, The New York State Psychiatric Institute, New York, NY, USA
| | - Sheryl G Beck
- Department of Anesthesiology, Children's Hospital of Philadelphia Research Institute and University of Pennsylvania, Philadelphia, PA, USA
| | | | - René Hen
- Departments of Neuroscience and Psychiatry, Columbia University, New York, NY, USA,Division of Integrative Neuroscience, The New York State Psychiatric Institute, New York, NY, USA,Department of Neuroscience and Psychiatry, Columbia University, 1051 Riverside Drive, Kolb 753, New York, NY 10032, USA, Tel: +1 212 543 5173, Fax: +1 212 543 5074, E-mail: or
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Rood BD, Beck SG. Vasopressin indirectly excites dorsal raphe serotonin neurons through activation of the vasopressin1A receptor. Neuroscience 2013; 260:205-16. [PMID: 24345477 DOI: 10.1016/j.neuroscience.2013.12.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 12/04/2013] [Accepted: 12/06/2013] [Indexed: 10/25/2022]
Abstract
The neuropeptide vasopressin (AVP; arginine-vasopressin) is produced in a handful of brain nuclei located in the hypothalamus and extended amygdala and is released both peripherally as a hormone and within the central nervous system as a neurotransmitter. Central projections have been associated with a number of functions including regulation of physiological homeostasis, control of circadian rhythms, and modulation of social behavior. The AVP neurons located in the bed nucleus of the stria terminalis and medial amygdala (i.e., extended amygdala) in particular have been associated with affiliative social behavior in multiple species. It was recently demonstrated that in the mouse AVP projections emanating from extended amygdala neurons innervate a number of forebrain and midbrain brain regions including the dorsal raphe nucleus (DR), the site of origin of most forebrain-projecting serotonin neurons. Based on the presence of AVP fibers in the DR, we hypothesized that AVP would alter the physiology of serotonin neurons via AVP 1A receptor (V1AR) activation. Using whole-cell electrophysiology techniques, we found that AVP increased the frequency and amplitude of excitatory post-synaptic currents (EPSCs) in serotonin neurons of male mice. The indirect stimulation of serotonin neurons was AMPA/kainate receptor dependent and blocked by the sodium channel blocker tetrodotoxin, suggesting an effect of AVP on glutamate neurons. Further, the increase in EPSC frequency induced by AVP was blocked by selective V1AR antagonists. Our data suggest that AVP had an excitatory influence on serotonin neurons. This work highlights a new target (i.e., V1AR) for manipulating serotonin neuron excitability. In light of our data, we propose that some of the diverse effects of AVP on physiology and behavior, including social behavior, may be due to activation of the DR serotonin system.
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Affiliation(s)
- B D Rood
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States.
| | - S G Beck
- Department of Anesthesiology and Critical Care, Children's Hospital of Philadelphia, Philadelphia, PA 19104, United States; Department of Anesthesiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, United States.
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Peng Z, Wang GP, Zeng R, Guo JY, Chen CF, Gong SS. Temporospatial expression and cellular localization of VGLUT3 in the rat cochlea. Brain Res 2013; 1537:100-10. [DOI: 10.1016/j.brainres.2013.09.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 09/11/2013] [Accepted: 09/17/2013] [Indexed: 01/06/2023]
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Abstract
Serotonin (5-HT) modulates neural responses to socioaffective cues and can bias approach or avoidance behavioral decisions, yet the cellular mechanisms underlying its contribution to the regulation of social experiences remain poorly understood. We hypothesized that GABAergic neurons in the dorsal raphe nucleus (DRN) may participate in socioaffective regulation by controlling serotonergic tone during social interaction. We tested this hypothesis using whole-cell recording techniques in genetically identified DRN GABA and 5-HT neurons in mice exposed to social defeat, a model that induces long-lasting avoidance behaviors in a subset of mice responsive to serotonergic antidepressants. Our results revealed that social defeat engaged DRN GABA neurons and drove GABAergic sensitization that strengthened inhibition of 5-HT neurons in mice that were susceptible, but not resilient to social defeat. Furthermore, optogenetic silencing of DRN GABA neurons disinhibited neighboring 5-HT neurons and prevented the acquisition of social avoidance in mice exposed to a social threat, but did not affect a previously acquired avoidance phenotype. We provide the first characterization of GABA neurons in the DRN that monosynaptically inhibit 5-HT neurons and reveal their key role in neuroplastic processes underlying the development of social avoidance.
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Post-weaning social isolation of female rats, anxiety-related behavior, and serotonergic systems. Brain Res 2012; 1443:1-17. [PMID: 22297173 DOI: 10.1016/j.brainres.2012.01.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 01/03/2012] [Accepted: 01/04/2012] [Indexed: 11/23/2022]
Abstract
Our previous studies have shown that post-weaning social isolation of male rats leads to sensitization of serotonergic systems and increases in anxiety-like behavior in adulthood. Although studies in humans suggest that females have an increased sensitivity to stress and risk for the development of neuropsychiatric illnesses, most studies involving laboratory rats have focused on males while females have been insufficiently studied. The objective of this study was to investigate the effects of post-weaning social isolation on subsequent responses of an anxiety-related dorsal raphe nucleus (DR)-basolateral amygdala system to pharmacological challenge with the anxiogenic drug, N-methyl-beta-carboline-3-carboxamide (FG-7142; a partial inverse agonist at the benzodiazepine allosteric site on the γ-aminobutyric acid (GABA)(A) receptor). Juvenile female rats were reared in isolation or in groups of three for a 3-week period from weaning to mid-adolescence, after which all rats were group-reared for an additional 2 weeks. We then used dual immunohistochemical staining for c-Fos and tryptophan hydroxylase in the DR or single immunohistochemical staining for c-Fos in the basolateral amygdala. Isolation-reared rats, but not group-reared rats, injected with FG-7142 had increased c-Fos expression within the basolateral amygdala and in serotonergic neurons in the dorsal, ventrolateral, caudal and interfascicular parts of the DR relative to appropriate vehicle-injected control groups. These data suggest that post-weaning social isolation of female rats sensitizes a DR-basolateral amygdala system to stress-related stimuli, which may lead to an increased sensitivity to stress- and anxiety-related responses in adulthood.
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