351
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Wellman CL, Izquierdo A, Garrett JE, Martin KP, Carroll J, Millstein R, Lesch KP, Murphy DL, Holmes A. Impaired stress-coping and fear extinction and abnormal corticolimbic morphology in serotonin transporter knock-out mice. J Neurosci 2007; 27:684-91. [PMID: 17234600 PMCID: PMC6672805 DOI: 10.1523/jneurosci.4595-06.2007] [Citation(s) in RCA: 285] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A lesser-expressing form of the human 5-HT transporter (5-HTT) gene has been associated with increased fear and anxiety and vulnerability to the effects of stress. These phenotypic abnormalities are linked to functional and anatomical disturbances in a neural pathway connecting the prefrontal cortex (PFC) and amygdala. Likewise, rodent and nonhuman primate studies indicate a major role for PFC and amygdala in the mediation of fear- and stress-related behaviors. We used a 5-HTT knock-out (KO) mouse to examine the effects of genetically driven loss of 5-HTT function for the following: (1) depression-related behavior in response to repeated stress, and pavlovian fear conditioning, extinction, and extinction recall; and (2) dendritic morphology and spine density of Golgi-stained pyramidal neurons in the infralimbic cortex (IL) and the basolateral amygdala (BLA). 5-HTT KO mice exhibited increased depressive-like immobility after repeated exposure to forced swim stress, compared with wild-type (WT) controls. Whereas fear conditioning and fear extinction was normal, 5-HTT KO mice exhibited a significant deficit in extinction recall. The apical dendritic branches of IL pyramidal neurons in 5-HTT KO mice were significantly increased in length relative to WT mice. Pyramidal neurons in BLA had normal dendritic morphology but significantly greater spine density in 5-HT KO mice compared with WT mice. Together, the present findings demonstrate a specific phenotypic profile of fear- and stress-related deficits in 5-HTT KO mice, accompanied by morphological abnormalities in two key neural loci. These data provide insight into the behavioral sequelae of loss of 5-HTT gene function and identify potential neural substrates underlying these phenotypes.
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Affiliation(s)
- C. L. Wellman
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405
| | - A. Izquierdo
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcoholism and Alcohol Abuse, National Institutes of Health, Bethesda, Maryland 20852
| | - J. E. Garrett
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405
| | - K. P. Martin
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405
| | - J. Carroll
- Laboratory of Clinical Science, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, and
| | - R. Millstein
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcoholism and Alcohol Abuse, National Institutes of Health, Bethesda, Maryland 20852
| | - K.-P. Lesch
- Molecular and Clinical Psychobiology, Department of Psychiatry and Psychotherapy, University of Würzburg, Würzberg 97080, Germany
| | - D. L. Murphy
- Laboratory of Clinical Science, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, and
| | - A. Holmes
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcoholism and Alcohol Abuse, National Institutes of Health, Bethesda, Maryland 20852
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352
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Akirav I, Maroun M. The role of the medial prefrontal cortex-amygdala circuit in stress effects on the extinction of fear. Neural Plast 2007; 2007:30873. [PMID: 17502909 PMCID: PMC1838961 DOI: 10.1155/2007/30873] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 11/16/2006] [Accepted: 11/16/2006] [Indexed: 11/18/2022] Open
Abstract
Stress exposure, depending on its intensity and duration, affects cognition and learning in an adaptive or maladaptive manner. Studies addressing the effects of stress on cognitive processes have mainly focused on conditioned fear, since it is suggested that fear-motivated learning lies at the root of affective and anxiety disorders. Inhibition of fear-motivated response can be accomplished by experimental extinction of the fearful response to the fear-inducing stimulus. Converging evidence indicates that extinction of fear memory requires plasticity in both the medial prefrontal cortex and the amygdala. These brain areas are also deeply involved in mediating the effects of exposure to stress on memory. Moreover, extensive evidence indicates that gamma-aminobutyric acid (GABA) transmission plays a primary role in the modulation of behavioral sequelae resulting from a stressful experience, and may also partially mediate inhibitory learning during extinction. In this review, we present evidence that exposure to a stressful experience may impair fear extinction and the possible involvement of the GABA system. Impairment of fear extinction learning is particularly important as it may predispose some individuals to the development of posttraumatic stress disorder. We further discuss a possible dysfunction in the medial prefrontal cortex-amygdala circuit following a stressful experience that may explain the impaired extinction caused by exposure to a stressor.
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Affiliation(s)
- Irit Akirav
- Department of Psychology, The Brain and Behavior Research Center, University of Haifa, Haifa 31905, Israel
| | - Mouna Maroun
- Department of Neurobiology and Ethology, The Brain and Behavior Research Center, Faculty of Science and Science Education, University of Haifa, Haifa 31905, Israel
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353
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Stevenson CW, Halliday DM, Marsden CA, Mason R. Systemic administration of the benzodiazepine receptor partial inverse agonist FG-7142 disrupts corticolimbic network interactions. Synapse 2007; 61:646-63. [PMID: 17503486 DOI: 10.1002/syn.20414] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The medial prefrontal cortex (mPFC) and basolateral amygdala (BLA) coordinate various stress responses. Although the effects of stressors on mPFC and BLA activity have been previously examined, it remains unclear to what extent stressors affect functional interactions between these regions. In vivo electrophysiology in the anesthetized rat was used to examine mPFC and BLA activity simultaneously in response to FG-7142, a benzodiazepine receptor partial inverse agonist that mimics various stress responses, in an attempt to model the effects of stressors on corticolimbic functional connectivity. Extracellular unit and local field potential (LFP) recordings, using multielectrode arrays positioned in mPFC and BLA, were conducted under basal conditions and in response to systemic FG-7142 administration. This drug increased mPFC and BLA unit firing at the lowest dose tested, whereas higher doses of FG-7142 decreased various burst firing parameters in both regions. Moreover, LFP power was attenuated at lower (<1 Hz) and potentiated at higher frequencies in mPFC (1-12 Hz) and BLA (4-8 Hz). Interestingly, FG-7142 diminished synchronized unit firing, both within and between mPFC and BLA. Finally, FG-7142 decreased LFP synchronization between these regions. In a separate group of animals, pretreatment with the selective benzodiazepine receptor antagonist flumazenil blocked the changes in burst firing, LFP power and synchronized activity induced by FG-7142, confirming direct benzodiazepine receptor-mediated effects. These results indicate that FG-7142 disrupts corticolimbic network interactions via benzodiazepine receptor partial inverse agonism. Perturbation of mPFC-BLA functional connectivity induced by FG-7142 may provide a useful model of corticolimbic dysfunction induced by stressors.
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Affiliation(s)
- Carl W Stevenson
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom.
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354
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Radley JJ, Arias CM, Sawchenko PE. Regional differentiation of the medial prefrontal cortex in regulating adaptive responses to acute emotional stress. J Neurosci 2006; 26:12967-76. [PMID: 17167086 PMCID: PMC6674963 DOI: 10.1523/jneurosci.4297-06.2006] [Citation(s) in RCA: 303] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 11/03/2006] [Indexed: 01/02/2023] Open
Abstract
The medial prefrontal cortex (mPFC) is an important neural substrate for integrating cognitive-affective information and regulating the hypothalamo-pituitary-adrenal (HPA) axis response to emotional stress. mPFC modulation of stress responses is effected in part via the paraventricular hypothalamic nucleus (PVH), which houses both autonomic (sympathoadrenal) and neuroendocrine (HPA) effector mechanisms. Although the weight of evidence suggests that mPFC influences on stress-related PVH outputs are inhibitory, discordant findings have been reported, and such work has tended to treat this cortical region as a unitary structure. Here we compared the effects of lesions of the dorsal versus ventral aspects of mPFC, centered in the prelimbic and infralimbic fields, respectively, on acute restraint stress-induced activation of PVH cell groups mediating autonomic and neuroendocrine responses. Lesions to the dorsal mPFC enhanced restraint-induced Fos and corticotropin-releasing factor (CRF) mRNA expression in the neurosecretory region of PVH. Ablation of the ventral mPFC decreased stress-induced Fos protein and CRF mRNA expression in this compartment but increased Fos induction in PVH regions involved in central autonomic control. Repetition of the experiments in rats bearing retrograde tracer deposits to label PVH-autonomic projections confirmed that ventral mPFC lesions selectively increased stress-induced Fos expression in identified preautonomic neurons. Finally, hormonal indices of HPA activation in response to acute stress were augmented after dorsal mPFC lesions and attenuated after ventral mPFC lesions. These results suggest that dorsal and ventral aspects of the mPFC differentially regulate neuroendocrine and autonomic PVH outputs in response to emotional stress.
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Affiliation(s)
- Jason J. Radley
- Laboratory of Neuronal Structure and Function, The Salk Institute for Biological Studies, and Foundation for Medical Research, La Jolla, California 92037
| | - Carlos M. Arias
- Laboratory of Neuronal Structure and Function, The Salk Institute for Biological Studies, and Foundation for Medical Research, La Jolla, California 92037
| | - Paul E. Sawchenko
- Laboratory of Neuronal Structure and Function, The Salk Institute for Biological Studies, and Foundation for Medical Research, La Jolla, California 92037
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355
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Hefner K, Holmes A. Ontogeny of fear-, anxiety- and depression-related behavior across adolescence in C57BL/6J mice. Behav Brain Res 2006; 176:210-5. [PMID: 17098297 PMCID: PMC1831838 DOI: 10.1016/j.bbr.2006.10.001] [Citation(s) in RCA: 144] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2006] [Revised: 09/26/2006] [Accepted: 10/02/2006] [Indexed: 11/20/2022]
Abstract
Adolescence is characterized by behavioral traits such as emotional lability and impulsivity that are associated with increased vulnerability to affective illness and addictions. Research in rodents has found that adolescent rats and mice differ from adults on measures of anxiety-like behavior, novelty seeking and stress-responsivity. The present study sought to extend these data by evaluating fear-, anxiety- and depression-related behaviors in male C57BL/6J mice aged four (early adolescent), six (peri-adolescent) or eight (early adult) weeks of age. Age groups were compared on: Pavlovian fear conditioning and extinction, anxiety-like behavior and exploratory locomotion (using elevated plus-maze and novel open field), and depression-related behavior (via forced swim test). Results showed that early adolescent mice exhibited enhanced fear conditioning, but extinguished at a similar rate as adults. There were no major differences in anxiety-like behavior across age groups, although early adolescent and peri-adolescent mice exhibited less exploratory locomotion than adults. Depression-related immobility behavior in the forced swim test was lower in early adolescents than adult mice across three test exposures. Present findings in the C57BL/6J inbred strain add to growing evidence of changes in rodent fear- and stress-related behaviors across the developmental transition from juvenility through adulthood. Understanding the neural basis of these ontogenic changes could provide insight into the pathogenesis and treatment of affective disorders that have their origins in adolescence.
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Affiliation(s)
- Kathryn Hefner
- Section on Behavioral Science and Genetics, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institute of Mental Health, Rockville, MD 20852, USA
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356
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Maroun M. Stress reverses plasticity in the pathway projecting from the ventromedial prefrontal cortex to the basolateral amygdala. Eur J Neurosci 2006; 24:2917-22. [PMID: 17156214 DOI: 10.1111/j.1460-9568.2006.05169.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We have previously shown that high-frequency stimulation to the basolateral amygdala (BLA) induces long-term potentiation (LTP) in the ventromedial prefrontal cortex (vmPFC) and that prior exposure to inescapable stress inhibits the induction of LTP in this pathway [Maroun & Richter-Levin (2003)J. Neurosci., 23, 4406-4409]. Here, we show that the reciprocal pathway projecting from the vmPFC to the BLA is resistant to the induction of LTP. Conversely, long-term depression (LTD) is robustly induced in the BLA in response to low-frequency stimulation to the vmPFC. Furthermore, prior exposure to inescapable stress reverses plasticity in this pathway, resulting in the promotion of LTP and the inhibition of LTD. Our findings suggest that, under normal and safe conditions, the vmPFC is unable to exert excitatory synaptic plasticity over the BLA; rather, LTD, which encodes memory of safety in the BLA, is favoured. Following stressful experiences, LTP in the BLA is promoted to encode memory of fear.
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Affiliation(s)
- Mouna Maroun
- The Brain and Behaviour Research Center, Department of Neurobiology and Ethology, Faculty of Science and Science Education, University of Haifa, Haifa 31905, Israel.
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