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Gaskins DL, Burke AR, Sajdyk TJ, Truitt WA, Dietrich AD, Shekhar A. Role of Basolateral Amygdalar Somatostatin 2 Receptors in a Rat Model of Chronic Anxiety. Neuroscience 2021; 477:40-49. [PMID: 34487822 PMCID: PMC9744088 DOI: 10.1016/j.neuroscience.2021.08.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 08/25/2021] [Accepted: 08/26/2021] [Indexed: 12/15/2022]
Abstract
Repeated exposure to stress has been implicated in inducing chronic anxiety states. Stress related increases in anxiety responses are likely mediated by activation of corticotropin-releasing factor receptors (CRFR) in the amygdala, particularly the basolateral amygdala (BLA). Within the BLA, acute injections of the CRFR agonist urocortin 1 (Ucn1) leads to acute anxiety, whereas repeated daily injections of subthreshold-doses of Ucn1 produces a long-lasting, persistent anxiety-like phenotype, a phenomenon referred to as Ucn1-priming. Relative gene expressions from the BLA of vehicle and Ucn1-primed rats were analyzed with quantitative RT-PCR using a predesigned panel of 82 neuroscience-related genes. Compared to vehicle-primed rats, only expression of the somatostatin receptor 2 gene (Sstr2) was significantly reduced in the BLA of Ucn1-primed rats. The contribution of Sstr2 on an anxiety phenotype was tested by injecting a Sstr2 antagonist into the BLA in un-primed rats. The Sstr2 antagonist increased anxiety-like behavior. Notably, pretreatment with Sstr2 agonist injected into the BLA blocked anxiety-inducing effects of acute Ucn1 BLA-injections and delayed anxiety expression during Ucn1-priming. However, concomitant Sstr2 agonist pretreatment during Ucn-1 priming did not prevent either the development of a chronic anxiety state or a reduction of BLA Sstr2 expression induced by priming. The data demonstrate that the persistent anxiety-like phenotype observed with Ucn1-priming in the BLA is associated with a selective reduction of Sstr2 gene expression. Although Sstr2 activation in the BLA blocks acute anxiogenic effects of stress and down-regulation of BLA Sstr2, it does not suppress the long-term consequences of prolonged exposure to stress-related challenges.
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Affiliation(s)
- Denise L Gaskins
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA; Graduate Program in Medical Neuroscience, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA
| | - Andrew R Burke
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA; Department of Anatomy Cellular Biology & Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA
| | - Tammy J Sajdyk
- Department of Psychiatry, Indiana University School of Medicine, 355 W. 16th Street, Indianapolis, IN 46202, USA; Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, 410 W 10th St Suite 1000, Indianapolis, IN 46202, USA; Department of Pediatrics, Division of Hematology/Oncology, Indiana University School of Medicine, 705 Riley Hospital Drive, Indianapolis, IN 46202, USA
| | - William A Truitt
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA; Department of Anatomy Cellular Biology & Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA.
| | - Amy D Dietrich
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA; Department of Anatomy Cellular Biology & Physiology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, IN 46202, USA
| | - Anantha Shekhar
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W. 15th Street, Indianapolis, IN 46202, USA; Department of Psychiatry, Indiana University School of Medicine, 355 W. 16th Street, Indianapolis, IN 46202, USA; Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, 410 W 10th St Suite 1000, Indianapolis, IN 46202, USA; Department of Psychiatry, University of Pittsburgh School of Medicine, 3550 Terrace Street, Suite 401, Pittsburgh, PA 15261, USA
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McDonald AJ. Functional neuroanatomy of the basolateral amygdala: Neurons, neurotransmitters, and circuits. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2020; 26:1-38. [PMID: 34220399 PMCID: PMC8248694 DOI: 10.1016/b978-0-12-815134-1.00001-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Alexander J McDonald
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, United States
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3
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Robinson SL, Thiele TE. A role for the neuropeptide somatostatin in the neurobiology of behaviors associated with substances abuse and affective disorders. Neuropharmacology 2020; 167:107983. [PMID: 32027909 DOI: 10.1016/j.neuropharm.2020.107983] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/07/2020] [Accepted: 01/30/2020] [Indexed: 02/06/2023]
Abstract
In recent years, neuropeptides which display potent regulatory control of stress-related behaviors have been extensively demonstrated to play a critical role in regulating behaviors associated with substance abuse and affective disorders. Somatostatin (SST) is one neuropeptide known to significantly contribute to emotionality and stress behaviors. However, the role of SST in regulating behavior has received relatively little attention relative to other stress-involved peptides, such as neuropeptide Y or corticotrophin releasing factor. This review characterizes our current understanding of the role of SST and SST-expressing cells in general in modulating several behaviors intrinsically linked to substance abuse and affective disorders, specifically: anxiety and fear; stress and depression; feeding and drinking; and circadian rhythms. We further summarize evidence of a direct role for the SST system, and specifically somatostatin receptors 2 and 4, in substance abuse disorders. This article is part of the special issue on 'Neuropeptides'.
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Affiliation(s)
- Stacey L Robinson
- Department of Psychology & Neuroscience, University of North Carolina, Chapel Hill, NC, 27599, USA; Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Todd E Thiele
- Department of Psychology & Neuroscience, University of North Carolina, Chapel Hill, NC, 27599, USA; Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, 27599, USA.
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4
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Fogaça MV, Duman RS. Cortical GABAergic Dysfunction in Stress and Depression: New Insights for Therapeutic Interventions. Front Cell Neurosci 2019. [PMID: 30914923 DOI: 10.3389/fncel.2019.00087/full] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Major depressive disorder (MDD) is a debilitating illness characterized by neuroanatomical and functional alterations in limbic structures, notably the prefrontal cortex (PFC), that can be precipitated by exposure to chronic stress. For decades, the monoaminergic deficit hypothesis of depression provided the conceptual framework to understand the pathophysiology of MDD. However, accumulating evidence suggests that MDD and chronic stress are associated with an imbalance of excitation-inhibition (E:I) within the PFC, generated by a deficit of inhibitory synaptic transmission onto principal glutamatergic neurons. MDD patients and chronically stressed animals show a reduction in GABA and GAD67 levels in the brain, decreased expression of GABAergic interneuron markers, and alterations in GABAA and GABAB receptor levels. Moreover, genetically modified animals with deletion of specific GABA receptors subunits or interneuron function show depressive-like behaviors. Here, we provide further evidence supporting the role of cortical GABAergic interneurons, mainly somatostatin- and parvalbumin-expressing cells, required for the optimal E:I balance in the PFC and discuss how the malfunction of these cells can result in depression-related behaviors. Finally, considering the relatively low efficacy of current available medications, we review new fast-acting pharmacological approaches that target the GABAergic system to treat MDD. We conclude that deficits in cortical inhibitory neurotransmission and interneuron function resulting from chronic stress exposure can compromise the integrity of neurocircuits and result in the development of MDD and other stress-related disorders. Drugs that can establish a new E:I balance in the PFC by targeting the glutamatergic and GABAergic systems show promising as fast-acting antidepressants and represent breakthrough strategies for the treatment of depression.
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Affiliation(s)
- Manoela V Fogaça
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
| | - Ronald S Duman
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
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5
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Fogaça MV, Duman RS. Cortical GABAergic Dysfunction in Stress and Depression: New Insights for Therapeutic Interventions. Front Cell Neurosci 2019; 13:87. [PMID: 30914923 PMCID: PMC6422907 DOI: 10.3389/fncel.2019.00087] [Citation(s) in RCA: 203] [Impact Index Per Article: 40.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 02/20/2019] [Indexed: 12/14/2022] Open
Abstract
Major depressive disorder (MDD) is a debilitating illness characterized by neuroanatomical and functional alterations in limbic structures, notably the prefrontal cortex (PFC), that can be precipitated by exposure to chronic stress. For decades, the monoaminergic deficit hypothesis of depression provided the conceptual framework to understand the pathophysiology of MDD. However, accumulating evidence suggests that MDD and chronic stress are associated with an imbalance of excitation-inhibition (E:I) within the PFC, generated by a deficit of inhibitory synaptic transmission onto principal glutamatergic neurons. MDD patients and chronically stressed animals show a reduction in GABA and GAD67 levels in the brain, decreased expression of GABAergic interneuron markers, and alterations in GABAA and GABAB receptor levels. Moreover, genetically modified animals with deletion of specific GABA receptors subunits or interneuron function show depressive-like behaviors. Here, we provide further evidence supporting the role of cortical GABAergic interneurons, mainly somatostatin- and parvalbumin-expressing cells, required for the optimal E:I balance in the PFC and discuss how the malfunction of these cells can result in depression-related behaviors. Finally, considering the relatively low efficacy of current available medications, we review new fast-acting pharmacological approaches that target the GABAergic system to treat MDD. We conclude that deficits in cortical inhibitory neurotransmission and interneuron function resulting from chronic stress exposure can compromise the integrity of neurocircuits and result in the development of MDD and other stress-related disorders. Drugs that can establish a new E:I balance in the PFC by targeting the glutamatergic and GABAergic systems show promising as fast-acting antidepressants and represent breakthrough strategies for the treatment of depression.
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Affiliation(s)
- Manoela V Fogaça
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
| | - Ronald S Duman
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, United States
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6
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Riedemann T, Sutor B. Long-lasting actions of somatostatin on pyramidal cell excitability in the mouse cingulate cortex. Neurosci Lett 2019; 698:217-223. [PMID: 30668961 DOI: 10.1016/j.neulet.2019.01.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/10/2019] [Accepted: 01/18/2019] [Indexed: 02/07/2023]
Abstract
Many neurological diseases are related to disturbances of somatostatin- (SOM-) expressing interneurons in the cingulate cortex. Therefore, their role within the circuitry of the cingulate cortex needs to be investigated. We describe here the physiological time course of SOM effects onto pyramidal cell excitability and action potential discharge pattern. Furthermore, we show that the GRK2 inhibitor Gallein had no effect on the reduced SOM-induced response following repetitive SOM applications.
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Affiliation(s)
- Therese Riedemann
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany.
| | - Bernd Sutor
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany
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Bocchio M, Fisher SP, Unal G, Ellender TJ, Vyazovskiy VV, Capogna M. Sleep and Serotonin Modulate Paracapsular Nitric Oxide Synthase Expressing Neurons of the Amygdala. eNeuro 2016; 3:ENEURO.0177-16.2016. [PMID: 27822504 PMCID: PMC5088777 DOI: 10.1523/eneuro.0177-16.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 09/12/2016] [Indexed: 12/15/2022] Open
Abstract
Unraveling the roles of distinct neuron types is a fundamental challenge to understanding brain function in health and disease. In the amygdala, a brain structure regulating emotional behavior, the diversity of GABAergic neurons has been only partially explored. We report a novel population of GABAergic amygdala neurons expressing high levels of neuronal nitric oxide synthase (nNOS). These cells are predominantly localized along basolateral amygdala (BLA) boundaries. Performing ex vivo patch-clamp recordings from nNOS+ neurons in Nos1-CreER;Ai9 mice, we observed that nNOS+ neurons located along the external capsule display distinctive electrophysiological properties, axonal and dendritic arborization, and connectivity. Examining their c-Fos expression, we found that paracapsular nNOS+ neurons are activated during a period of undisturbed sleep following sleep deprivation, but not during sleep deprivation. Consistently, we found that dorsal raphe serotonin [5-hydroxytryptamine (5-HT)] neurons, which are involved in sleep-wake regulation, innervate nNOS+ neurons. Bath application of 5-HT hyperpolarizes nNOS+ neurons via 5-HT1A receptors. This hyperpolarization produces a reduction in firing rate and, occasionally, a switch from tonic to burst firing mode, thereby contrasting with the classic depolarizing effect of 5-HT on BLA GABAergic cells reported so far. Thus, nNOS+ cells are a distinct cell type of the amygdala that controls the activity of downstream neurons in both amygdaloid and extra-amygdaloid regions in a vigilance state-dependent fashion. Given the strong links among mood, sleep deprivation, and 5-HT, the recruitment of paracapsular nNOS+ neurons following high sleep pressure may represent an important mechanism in emotional regulation.
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Affiliation(s)
- Marco Bocchio
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Oxford OX1 3TH, UK
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Simon P. Fisher
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK
| | - Gunes Unal
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Oxford OX1 3TH, UK
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | - Tommas J. Ellender
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Oxford OX1 3TH, UK
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
| | | | - Marco Capogna
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Oxford OX1 3TH, UK
- Department of Biomedicine, Aarhus University, 8000 Aarhus C, Denmark
- The Danish Research Institute of Translational Neuroscience (DANDRITE), Nordic EMBL Partnership for Molecular Medicine, Aarhus University, 8000 Aarhus C, Denmark
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8
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Jüngling K, Lange MD, Szkudlarek HJ, Lesting J, Erdmann FS, Doengi M, Kügler S, Pape HC. Increased GABAergic Efficacy of Central Amygdala Projections to Neuropeptide S Neurons in the Brainstem During Fear Memory Retrieval. Neuropsychopharmacology 2015; 40:2753-63. [PMID: 25936641 PMCID: PMC4864651 DOI: 10.1038/npp.2015.125] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 04/16/2015] [Accepted: 04/24/2015] [Indexed: 01/26/2023]
Abstract
The canonical view on the central amygdala has evolved from a simple output station towards a highly organized microcircuitry, in which types of GABAergic neurons in centrolateral (CeL) and centromedial (CeM) subnuclei regulate fear expression and generalization. How these specific neuronal populations are connected to extra-amygdaloid target regions remains largely unknown. Here we show in mice that a subpopulation of GABAergic CeL and CeM neurons projects monosynaptically to brainstem neurons expressing neuropeptide S (NPS). The CeL neurons are PKCδ-negative and are activated during conditioned fear. During fear memory retrieval, the efficacy of this GABAergic influence on NPS neurons is enhanced. Moreover, a large proportion of these neurons (~50%) contain prodynorphin and somatostatin, two neuropeptides inhibiting NPS neurons. We conclude that CeL and CeM neurons inhibit NPS neurons in the brainstem by GABA release and that efficacy of this connection is strengthened upon fear memory retrieval. Thereby, this pathway provides a possible feedback mechanism between amygdala and brainstem routes involved in fear and stress coping.
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Affiliation(s)
- Kay Jüngling
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany,Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Robert-Koch-Str. 27a, Münster D-48149, Germany. E-mail: or
| | - Maren D Lange
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Hanna J Szkudlarek
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Jörg Lesting
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Frank S Erdmann
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Michael Doengi
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Sebastian Kügler
- Department of Neurology, Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), Universitätsmedizin Göttingen, Göttingen, Germany
| | - Hans-Christian Pape
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Münster, Germany,Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Robert-Koch-Str. 27a, Münster D-48149, Germany. E-mail: or
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9
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Lucas SJ, Armstrong DL. Protein phosphatase modulation of somatostatin receptor signaling in the mouse hippocampus. Neuropharmacology 2015. [PMID: 26196943 DOI: 10.1016/j.neuropharm.2015.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Many inhibitory interneurones in the hippocampus release the neuropeptide somatostatin (SST) which inhibits neuronal excitability through Gi/Go-coupled receptors. To investigate the signaling pathways underlying the SST inhibition of neuronal excitability in the hippocampus, we performed perforated patch-clamp recordings from CA1 pyramidal neurones in acute brain slices from P14-P18 mice. Bath application of 1 μM SST reversibly reduces the frequency of action potential firing in response to depolarising current steps, and is associated with neuronal hyperpolarisation and a reduction in membrane resistance. This effect is mediated by potassium channels with KCNK-like pharmacology. In addition, in slices that have been cultured in vitro for seven days or more, SST also produces a hyperpolarisation independent reduction in action potential firing, which can be also observed in acute slices when the Ser/Thr protein phosphatases PP2A and PP4 are inhibited selectively with fostriecin. This hyperpolarisation independent effect of SST appears to be mediated by G-protein-activated inwardly rectifying K+ (GIRK) channels. Knockdown of protein phosphatase 5, by Cre recombinase mediated deletion of the floxed Ppp5c gene, blocks the hyperpolarisation independent effect of SST, and reduces the hyperpolarisation dependent effect in a manner consistent with increased SST receptor desensitisation. Thus, reversible protein phosphorylation provides a mechanism to enhance or diminish the inhibitory effect of SST, which could allow system level regulation of circuit excitability in the hippocampus.
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Affiliation(s)
- Sarah J Lucas
- Lab. Neurobiology, National Institute of Environmental Health Sciences, NIH, Durham, NC, 27709, USA.
| | - David L Armstrong
- Lab. Neurobiology, National Institute of Environmental Health Sciences, NIH, Durham, NC, 27709, USA
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Injections of the somatostatin receptor type 2 agonist L-054,264 into the amygdala block expression but not acquisition of conditioned fear in rats. Behav Brain Res 2014; 265:49-52. [PMID: 24548855 DOI: 10.1016/j.bbr.2014.02.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 02/05/2014] [Accepted: 02/07/2014] [Indexed: 01/12/2023]
Abstract
The amygdala is a crucial brain site for acquisition and expression of conditioned fear. Neuropeptides such as somatostatin play a critical role in regulating the activity of the amygdala. In the present study, the specific somatostatin receptor type 2 (SSTR2) agonist L-054,264 was injected into the amygdala of rats either before fear acquisition or before the expression test on conditioned fear measured by fear-potentiated startle. L-054,264 injections strongly attenuated fear expression but did not affect fear acquisition. This suggests that amygdaloid SSTR2 plays an important role in the modulation of fear memory expression.
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11
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Albrecht A, Thiere M, Bergado-Acosta JR, Poranzke J, Müller B, Stork O. Circadian modulation of anxiety: a role for somatostatin in the amygdala. PLoS One 2013; 8:e84668. [PMID: 24376834 PMCID: PMC3869835 DOI: 10.1371/journal.pone.0084668] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/18/2013] [Indexed: 12/30/2022] Open
Abstract
Pharmacological evidence suggests that the neuropeptide somatostatin (SST) exerts anxiolytic action via the amygdala, but findings concerning the putative role of endogenous SST in the regulation of emotional responses are contradictory. We hypothesized that an endogenous regulation of SST expression over the course of the day may determine its function and tested both SST gene expression and the behavior of SST knock out (SST-/-) mice in different aversive tests in relation to circadian rhythm. In an open field and a light/dark avoidance test, SST-/- mice showed significant hyperactivity and anxiety-like behavior during the second, but not during the first half of the active phase, failing to show the circadian modulation of behavior that was evident in their wild type littermates. Behavioral differences occurred independently of changes of intrinsically motivated activity in the home cage. A circadian regulation of SST mRNA and protein expression that was evident in the basolateral complex of the amygdala of wild type mice may provide a neuronal substrate for the observed behavior. However, fear memory towards auditory cue or the conditioning context displayed neither a time- nor genotype-dependent modulation. Together this indicates that SST, in a circadian manner and putatively via its regulation of expression in the amygdala, modulates behavior responding to mildly aversive conditions in mice.
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Affiliation(s)
- Anne Albrecht
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
- * E-mail:
| | - Marlen Thiere
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Jorge Ricardo Bergado-Acosta
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Janine Poranzke
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
| | - Bettina Müller
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
- Center for Behavioural Brain Science, Magdeburg, Germany
| | - Oliver Stork
- Department of Genetics & Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany
- Center for Behavioural Brain Science, Magdeburg, Germany
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Stengel A, Rivier J, Taché Y. Modulation of the adaptive response to stress by brain activation of selective somatostatin receptor subtypes. Peptides 2013; 42:70-7. [PMID: 23287111 PMCID: PMC3633742 DOI: 10.1016/j.peptides.2012.12.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 12/21/2012] [Accepted: 12/21/2012] [Indexed: 01/06/2023]
Abstract
Somatostatin-14 was discovered in 1973 in the hypothalamus as a peptide inhibiting growth hormone release. Somatostatin interacts with five receptor subtypes (sst(1-5)) which are widely distributed in the brain with a distinct, but overlapping, expression pattern. During the last few years, the development of highly selective peptide agonists and antagonists provided new insight to characterize the role of somatostatin receptor subtypes in the pleiotropic actions of somatostatin. Recent evidence in rodents indicates that the activation of selective somatostatin receptor subtypes in the brain blunts stress-corticotropin-releasing factor (CRF) related ACTH release (sst2/5), sympathetic-adrenal activaton (sst5), stimulation of colonic motility (sst1), delayed gastric emptying (sst5), suppression of food intake (sst2) and the anxiogenic-like (sst2) response. These findings suggest that brain somatostatin signaling pathways may play an important role in dampening CRF-mediated endocrine, sympathetic, behavioral and visceral responses to stress.
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Affiliation(s)
- Andreas Stengel
- CURE: Digestive Diseases Research Center and Center for Neurovisceral Sciences & Women's Health, Digestive Diseases Division, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA
- Division of Psychosomatic Medicine & Obesity Center Berlin, Department of Medicine, Charité Medical Center and University, Berlin, Germany
| | - Jean Rivier
- Peptide Biology Laboratories, Salk Institute, La Jolla, California, USA
| | - Yvette Taché
- CURE: Digestive Diseases Research Center and Center for Neurovisceral Sciences & Women's Health, Digestive Diseases Division, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System, Los Angeles, California, USA
- Address: CURE: Digestive Diseases Research Center, Building 115, Room 117, VA Greater Los Angeles Healthcare System, 11301 Wilshire Boulevard, Los Angeles, CA 90073, Phone: 310-312-9275, Fax: 1-310-268-4963,
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Anxiolytic-like effects of somatostatin isoforms SST 14 and SST 28 in two animal models (Rattus norvegicus) after intra-amygdalar and intra-septal microinfusions. Psychopharmacology (Berl) 2011; 216:557-67. [PMID: 21424237 DOI: 10.1007/s00213-011-2248-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 02/25/2011] [Indexed: 12/19/2022]
Abstract
RATIONALE AND OBJECTIVES Somatostatin (SST) isoforms, SST 14 and SST 28, inhibit regulatory hormones in the periphery (e.g., growth hormone) and are widely distributed in the brain. In recent experiments, intracerebroventricular (ICV) SST produced anxiolytic-like effects in both behavioral and electrophysiological models. The sites of action of these anxiolytic effects in the brain, however, and the relative contributions of SST 14 and SST 28 to these effects are unknown. MATERIALS AND METHODS Anxiolytic effects were assessed in the plus-maze and shock-probe tests after (1) intra-amygdalar microinfusion of SST 14 (0.5 or 3 μg per hemisphere) or SST 28 (3 μg per hemisphere), (2) intra-septal microinfusion of SST 14 (0.5 or 1.5 μg per hemisphere) or SST 28 (1.5 μg per hemisphere), or (3) intra-striatal microinfusion of SST 14 (3 μg per hemisphere). RESULTS Intra-amygdalar and intra-septal microinfusions of SST 14 and SST 28 produced robust anxiolytic-like effects in the behavioral tests, unlike intra-striatal microinfusions. The magnitude of the anxiolytic effects in the amygdala and septum were comparable to those found previously with ICV SST 14, ICV L-779976, an SST (sst2) receptor agonist, and ICV diazepam, a classical benzodiazepine anxiolytic. CONCLUSIONS SST receptors in the septum and amygdala are responsive to both SST 14 and SST 28, but not those in the striatum. Although no obvious differences in the anxiolytic-like effects of the isoforms were detected, quantitative or even qualitative differences in their specific anxiolytic effects may occur in different sub-regions of the septum and amygdala, as has been found for benzodiazepine anxiolytics.
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Brockhaus J, Pape HC. Abnormalities in GABAergic synaptic transmission of intralaminar thalamic neurons in a genetic rat model of absence epilepsy. Mol Cell Neurosci 2010; 46:444-51. [PMID: 21112396 DOI: 10.1016/j.mcn.2010.11.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 10/29/2010] [Accepted: 11/18/2010] [Indexed: 10/18/2022] Open
Abstract
Synaptic activity mediated via GABA receptors in thalamic circuits is critically involved in the generation of hypersynchrony associated with absence epilepsy. Neurons of "unspecific" intralaminar thalamic nuclei display characteristic burst patterns during seizure activity, although their synaptic properties remain largely unknown. Here, we used in vitro patch-clamp techniques in neurons of the paracentral (PC) thalamic nucleus, derived from a genetic model of absence epilepsy (WAG-Rij) and a non-epileptic control strain (ACI) to elucidate intrinsic and synaptic properties. PC neurons displayed voltage-dependent low threshold spike bursts or tonic spike firing, typical of thalamic neurons. These parameters, and electrotonic properties, were similar in PC neurons of the two strains. Analyses of miniature inhibitory post synaptic currents (mIPSCs) mediated via GABA(A) receptors revealed no difference in decay time constant and inter-event interval between strains, but a significantly larger amplitude and higher single channel conductance (as assessed by non-stationary variance analysis) in WAG-Rij compared to ACI. By comparison, thalamocortical neurons from the ventrobasal complex of the thalamus showed no difference in mIPSC kinetics and unitary conductance between the two rat strains. In view of the critical role of GABAergic inhibition for synchronous activity in thalamocortical circuits, it is concluded that the increase in unitary conductance of IPSCs in PC neurons contributes to hypersynchrony characterizing seizure activity.
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Affiliation(s)
- Johannes Brockhaus
- Institut für Physiologie I, Westfälische Wilhelms-Universität Münster, Münster, Germany
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15
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Bhattarai JP, Kaszás A, Park SA, Yin H, Park SJ, Herbison AE, Han SK, Abrahám IM. Somatostatin inhibition of gonadotropin-releasing hormone neurons in female and male mice. Endocrinology 2010; 151:3258-66. [PMID: 20410192 DOI: 10.1210/en.2010-0148] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Previous studies indicate that somatostatin regulates gonadotropin secretion. We investigated here whether somatostatin has direct effects on GnRH neurons in the adult male and female mice. Dual-labeling immunofluorescence experiments revealed the presence of somatostatin-immunoreactive fibers adjacent to GnRH neurons, and three-dimensional confocal reconstructions demonstrated apparent somatostatin fiber appositions with 50-60% of GnRH neurons located throughout the brain in both male and female mice. Perforated patch-clamp recordings from GnRH-green fluorescent protein neurons revealed that approximately 70% of GnRH neurons responded in a dose-dependent manner to 10-300 nm somatostatin with an acute membrane hyperpolarization and cessation of firing. This effect persisted in the presence of tetrodotoxin and amino acid receptor antagonists, indicating a direct postsynaptic site of action on the GnRH neuron. The identity of the somatostatin receptors underlying this action was assessed using GnRH neuron single-cell RT-PCR. Of the somatostatin receptor subtypes, the sstr2 transcript was the most prevalent and detected in both males and females. The expression of sstr2 by GnRH neurons was confirmed in the sstr2 knockout/LacZ knock-in mouse line. Electrophysiological studies demonstrated that the sstr2-selective agonist seglitide exerted acute hyperpolarizing actions on GnRH neurons identical to those of somatostatin. Together, these studies reveal somatostatin, acting through sstr2, to be one of the most potent inhibitors of electrical excitability of male and female GnRH neurons identified thus far.
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Affiliation(s)
- Janardhan P Bhattarai
- Department of Oral Physiology and Institute of Oral Bioscience, School of Dentistry, Chonbuk National University, Duck-jin dong, Duck-jin Ku, Jeonju, 561-756, South Korea
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16
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Chung L, Moore S. Neuropeptides modulate compound postsynaptic potentials in basolateral amygdala. Neuroscience 2009; 164:1389-97. [DOI: 10.1016/j.neuroscience.2009.09.061] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 09/22/2009] [Accepted: 09/22/2009] [Indexed: 11/30/2022]
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17
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Engin E, Treit D. Anxiolytic and antidepressant actions of somatostatin: the role of sst2 and sst3 receptors. Psychopharmacology (Berl) 2009; 206:281-9. [PMID: 19609508 DOI: 10.1007/s00213-009-1605-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 06/26/2009] [Indexed: 12/21/2022]
Abstract
RATIONALE AND OBJECTIVES Somatostatin is a cyclic polypeptide that inhibits the release of a variety of regulatory hormones (e.g., growth hormone, insulin, glucagon, and thyrotropin). Somatostatin is also widely distributed within the central nervous system (CNS), acting both as a neurotransmitter and as a neuromodulator. Recently, we showed that intracerebroventricular (i.c.v.) administration of somatostatin reduced anxiety-like and depression-like behaviors in animal models. The somatostatin receptor subtypes that are involved in these behavioral effects, however, have not been investigated. In the CNS, the neurotransmitter actions of somatostatin are mediated through five G-protein coupled receptors (sst1 to sst5). MATERIALS AND METHODS We examined the behavioral effects of i.c.v. microinfusions of different doses of selective agonists of each of the five somatostatin receptor subtypes. Their behavioral effects were assessed in the elevated plus-maze and the forced swim apparatus, rodent models of anxiolytic and antidepressant drug effects, respectively. RESULTS Anxiety-like behavior was reduced following i.c.v. infusions of a selective sst2 receptor agonist, but not after infusions of the other four receptor agonists. An antidepressant-like effect was observed following infusions of either sst2 or sst3 agonists. CONCLUSIONS The results add to our nascent understanding of the role of somatostatin in anxiety- and depression-like behavior and suggest a clinical role for somatostatin agonists for the simultaneous treatment of anxiety and depression, which are often comorbid.
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Affiliation(s)
- Elif Engin
- Department of Psychology, Centre for Neuroscience, University of Alberta, Edmonton, T6G 2E9, AB, Canada
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18
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Chaudhry AM, Marsh-Rollo SE, Aksenov V, Rollo CD, Szechtman H. Modifier Selection by Transgenes: The Case of Growth Hormone Transgenesis and Hyperactive Circling Mice. Evol Biol 2008. [DOI: 10.1007/s11692-008-9036-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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19
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Engin E, Stellbrink J, Treit D, Dickson CT. Anxiolytic and antidepressant effects of intracerebroventricularly administered somatostatin: behavioral and neurophysiological evidence. Neuroscience 2008; 157:666-76. [PMID: 18940236 DOI: 10.1016/j.neuroscience.2008.09.037] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 09/12/2008] [Accepted: 09/16/2008] [Indexed: 11/15/2022]
Abstract
Somatostatin (SST) is a cyclic polypeptide that inhibits the release of a variety of regulatory hormones (e.g. growth hormone, insulin, glucagon, thyrotropin). Moreover, SST is widely distributed within the CNS, acting both as a neurotransmitter and as a neuromodulator of other neurotransmitter systems. However, despite its extensive expression in limbic areas, and its co-localization with GABA, a neurotransmitter previously implicated in emotion, the effects of SST on anxiety and depression have not been investigated. By performing intraventricular infusions in rats we demonstrate, for the first time, that SST has anxiolytic- and antidepressant-like effects in the elevated plus-maze and forced swim test, respectively. In addition, by performing local field potential recordings of hippocampal theta activity evoked by reticular stimulation in urethane-anesthetized rats we also show that SST application suppresses the frequency of theta in a similar fashion to diazepam. This neurophysiological signature, common to all classes of anxiolytic drugs (i.e. benzodiazepines, selective 5-HT reuptake inhibitors, 5-HT1A agonists) provides strong converging evidence for the anxiolytic-like characteristics of SST. Our pharmacological antagonism experiments with bicuculline further suggest that the anxiolytic effect of SST may be attributable to the interaction of SST with GABA, whereas the antidepressant-like effect of SST may be GABA-independent. In addition to contributing to the current understanding of the role of neuropeptides in mood and emotion, these findings support a clinical role for SST (or its analogues) in the treatment of anxiety and depression.
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Affiliation(s)
- E Engin
- Department of Psychology, University of Alberta, P-449 Biological Sciences Building, Edmonton, AB, Canada T6G 2E9
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20
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Sosulina L, Schwesig G, Seifert G, Pape HC. Neuropeptide Y activates a G-protein-coupled inwardly rectifying potassium current and dampens excitability in the lateral amygdala. Mol Cell Neurosci 2008; 39:491-8. [PMID: 18790060 DOI: 10.1016/j.mcn.2008.08.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 08/01/2008] [Accepted: 08/13/2008] [Indexed: 11/26/2022] Open
Abstract
Neuropeptide Y (NPY) reduces anxiety-related behavior in various animal models. Since activity in the lateral amygdala (LA) seems crucial for fear expression of behavior, we studied the mechanisms of NPY in LA projection neurons using whole-cell patch-clamp recordings in slices of the rat amygdala in vitro. Application of NPY activated a membrane K(+) current with inwardly rectifying properties in 92% of tested neurons. Pharmacological properties were indicative of mediation via Y1 receptors. Nonhydrolyzable analogues of guanine nucleotides and SCH23390 blocked the NPY-activated current. Single-cell RT-PCR demonstrated expression of G-protein-coupled inwardly rectifying K(+) channel (GIRK) subunits GIRK1, GIRK2 and GIRK3, suggesting mediation of the NPY response through GIRK type channels. The NPY-activated current depressed action potential firing in LA projection neurons, through membrane hyperpolarization and decreased input resistance. Functionally, the dampening of excitability in projection neurons of the amygdala may contribute to the decrease in anxiogenic behavior during action of NPY.
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Affiliation(s)
- Ludmila Sosulina
- Institut für Physiologie I, Westfälische Wilhelms-Universität Münster, Münster, Germany
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21
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Viollet C, Lepousez G, Loudes C, Videau C, Simon A, Epelbaum J. Somatostatinergic systems in brain: networks and functions. Mol Cell Endocrinol 2008; 286:75-87. [PMID: 17997029 DOI: 10.1016/j.mce.2007.09.007] [Citation(s) in RCA: 142] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 09/10/2007] [Accepted: 09/19/2007] [Indexed: 12/21/2022]
Abstract
Somatostatin is abundantly expressed in mammalian brain. The peptide binds with high affinity to six somatostatin receptors, sst1, sst2A and B, sst3 to 5, all belonging to the G-protein-coupled receptor family. Recent advances in the neuroanatomy of somatostatin neurons and cellular distribution of sst receptors shed light on their functional roles in the neuronal network. Beside their initially described neuroendocrine role, somatostatin systems subserve neuromodulatory roles in the brain, influencing motor activity, sleep, sensory processes and cognitive functions, and are altered in brain diseases like affective disorders, epilepsia and Alzheimer's disease.
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Qiu C, Zeyda T, Johnson B, Hochgeschwender U, de Lecea L, Tallent MK. Somatostatin receptor subtype 4 couples to the M-current to regulate seizures. J Neurosci 2008; 28:3567-76. [PMID: 18385315 PMCID: PMC6671094 DOI: 10.1523/jneurosci.4679-07.2008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Revised: 02/18/2008] [Accepted: 02/22/2008] [Indexed: 11/21/2022] Open
Abstract
The K(+) M-current (I(M), Kv7) is an important regulator of cortical excitability, and mutations in these channels cause a seizure disorder in humans. The neuropeptide somatostatin (SST), which has antiepileptic properties, augments I(M) in hippocampal CA1 pyramidal neurons. We used SST receptor knock-out mice and subtype-selective ligands to investigate the receptor subtype that couples to I(M) and mediates the antiepileptic effects of SST. Using pentylenetetrazole as a chemoconvulsant, SST(2), SST(3), and SST(4) receptor knock-out mice all had shorter latencies to different seizure stages and increased seizure severity when compared with wild-type mice. However, the most robust differences were observed in the SST(4) knock-outs. When seizures were induced by systemic injection of kainate, only SST(4) knock-outs showed an increase in seizure sensitivity. We next examined the action of SST and subtype-selective SST agonists on electrophysiological parameters in hippocampal slices of wild-type and receptor knock-out mice. SST(2) and SST(4) appear to mediate the majority of SST inhibition of epileptiform activity in CA1. SST lacked presynaptic effects in mouse CA1, in contrast to our previous findings in rat. SST increased I(M) in CA1 pyramidal neurons of wild-type and SST(2) knock-out mice, but not SST(4) knock-out mice. Using M-channel blockers, we found that SST(4) coupling to M-channels is critical to its inhibition of epileptiform activity. This is the first demonstration of an endogenous enhancer of I(M) that is important in controlling seizure activity. SST(4) receptors could therefore be an important novel target for developing new antiepileptic and antiepileptogenic drugs.
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Affiliation(s)
- Cuie Qiu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19348
| | - Thomas Zeyda
- John A. Burns School of Medicine, Honolulu, Hawaii 96813
| | - Brian Johnson
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19348
| | | | - Luis de Lecea
- Department of Psychiatry and Behavioral Sciences, Stanford University, Palo Alto, California 94304
| | - Melanie K. Tallent
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19348
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Nanda SA, Qi C, Roseboom PH, Kalin NH. Predator stress induces behavioral inhibition and amygdala somatostatin receptor 2 gene expression. GENES BRAIN AND BEHAVIOR 2008; 7:639-48. [PMID: 18363859 DOI: 10.1111/j.1601-183x.2008.00401.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Psychological stressors precipitate and maintain stress-induced psychopathology, and it is likely that altered amygdala function underlies some of the deleterious effects of psychological stress. To understand the mechanisms underlying the linkage between the response to psychological stressors and maladaptive or psychopathological responses, we have focused on amygdala responsivity in animal models employing species-specific psychological stressors. In the present study, we characterized the effects of a 15-min exposure to a natural predator, the ferret, on rat behavior and the expression of the somatostatin family of genes in the amygdala. We examined the somatostatin family of genes because substantial evidence shows that central somatostatin systems are altered in various neuropsychiatric illnesses. We report that rats respond to acute ferret exposure with a significant increase in fearful and anxious behaviors that is accompanied by robust amygdala activation and an increase in somatostatin receptor 2 (sst2) messenger RNA expression within the amygdala and anterior cingulate cortex. These studies are the first to show stress-induced changes in amygdala sst2 expression and may represent one mechanism by which psychological stress is linked to adaptive and maladaptive behavioral responses.
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Affiliation(s)
- S A Nanda
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI 53719, USA.
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24
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Cervia D, Bagnoli P. An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology. Pharmacol Ther 2007; 116:322-41. [PMID: 17719647 DOI: 10.1016/j.pharmthera.2007.06.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Accepted: 06/28/2007] [Indexed: 12/20/2022]
Abstract
The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.
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Affiliation(s)
- Davide Cervia
- Department of Environmental Sciences, University of Tuscia, largo dell'Università snc, blocco D, 01100 Viterbo, Italy.
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Muller JF, Mascagni F, McDonald AJ. Postsynaptic targets of somatostatin-containing interneurons in the rat basolateral amygdala. J Comp Neurol 2006; 500:513-29. [PMID: 17120289 DOI: 10.1002/cne.21185] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The basolateral amygdala contains several subpopulations of inhibitory interneurons that can be distinguished on the basis of their content of calcium-binding proteins or peptides. Although previous studies have shown that interneuronal subpopulations containing parvalbumin (PV) or vasoactive intestinal peptide (VIP) innervate distinct postsynaptic domains of pyramidal cells as well as other interneurons, very little is known about the synaptic outputs of the interneuronal subpopulation that expresses somatostatin (SOM). The present study utilized dual-labeling immunocytochemical techniques at the light and electron microscopic levels to analyze the innervation of pyramidal cells, PV+ interneurons, and VIP+ interneurons in the anterior basolateral amygdalar nucleus (BLa) by SOM+ axon terminals. Pyramidal cell somata and dendrites were selectively labeled with antibodies to calcium/calmodulin-dependent protein kinase II (CaMK); previous studies have shown that the vast majority of dendritic spines, whether CAMK+ or not, arise from pyramidal cells. Almost all SOM+ axon terminals formed symmetrical synapses. The main postsynaptic targets of SOM+ terminals were small-caliber CaMK+ dendrites and dendritic spines, some of which were CaMK+. These SOM+ synapses with dendrites were often in close proximity to asymmetrical (excitatory) synapses to these same structures formed by unlabeled terminals. Few SOM+ terminals formed synapses with CaMK+ pyramidal cell somata or large-caliber (proximal) dendrites. Likewise, only 15% of SOM+ terminals formed synapses with PV+, VIP+, or SOM+ interneurons. These findings suggest that inhibitory inputs from SOM+ interneurons may interact with excitatory inputs to pyramidal cell distal dendrites in the BLa. These interactions might affect synaptic plasticity related to emotional learning.
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Affiliation(s)
- Jay F Muller
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, South Carolina 29208, USA
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