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Tsukasa Koyama - One of the best experts on this subject based on the ideXlab platform.
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Effect of the coadministration of citalopram with mirtazapine or atipamezole on rat contextual conditioned fear.
Neuropsychiatric Disease and Treatment, 2014Co-Authors: Takahiro Masuda, Yan An, Yuji Kitaichi, Shin Nakagawa, Tsukasa Koyama, Takeshi Inoue, Naoki Takamura, Ichiro KusumiAbstract:Background Mirtazapine, a noradrenergic and specific serotonergic antidepressant, which blocks the α2-adrenergic autoreceptors and heteroreceptors, has shown anxiolytic properties in clinical trials and preclinical animal experiments. The addition of mirtazapine to selective serotonin reuptake inhibitors (SSRIs) is clinically suggested to be more effective for anxiety disorders. In this study, we examined the combined effects of mirtazapine and citalopram, an SSRI, on the Freezing Behavior of rats, which was induced by contextual conditioned fear as an index of anxiety or fear.
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anxiolytic like effect of mirtazapine mediates its effect in the median raphe nucleus
European Journal of Pharmacology, 2013Co-Authors: Yan An, Yuji Kitaichi, Takeshi Izumi, Xiaobai Li, Shin Nakagawa, Takeshi Inoue, Ning Song, Chong Chen, Tsukasa KoyamaAbstract:Abstract Mirtazapine, a noradrenergic and specific serotonergic antidepressant (NaSSA), blocks the α2-adrenergic autoreceptors and heteroreceptors, which are responsible for controlling noradrenaline and 5-hydroxytryptamine (5-HT) release. Though preclinical and clinical studies have shown that mirtazapine exerts an anxiolytic action, its precise brain target sites remain unclear. In the present study, we investigated the brain area(s) in which mirtazapine exerts its anxiolytic-like effects on the expression of contextual conditioned Freezing in rats. Mirtazapine (3 μg/site) was directly injected into three brain structures, the median raphe nucleus (MRN), hippocampus and amygdala. Freezing Behavior tests were carried out 10 min after injections. Our results showed that the intra-MRN injection of mirtazapine reduced Freezing significantly, whereas injections into the hippocampus or the amygdala did not. In addition, the intra-MRN injection of mirtazapine did not affect locomotor activity. These results suggest that the anxiolytic-like effect of mirtazapine might be mediated by its action on the MRN.
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monoamine oxidase inhibitors reduce conditioned fear stress induced Freezing Behavior in rats
European Journal of Pharmacology, 2000Co-Authors: Yuji Maki, Yuji Kitaichi, Ihoko Muraki, Takeshi Izumi, Xiaobai Li, Takeshi Inoue, Tsukasa KoyamaAbstract:Abstract The present study examined the acute anxiolytic effects of monoamine oxidase inhibitors on Freezing Behavior, a putative index of anxiety induced by conditioned fear stress. The selective serotonin 1A receptor agonist tandospirone (0.1–10 mg/kg) inhibited Freezing dose dependently. The irreversible, non-selective monoamine oxidase inhibitors tranylcypromine (3 and 15 mg/kg) and phenelzine (30 and 80 mg/kg) reduced Freezing significantly. Clorgyline (10 mg/kg, irreversible selective monoamine oxidase A inhibitor), N-(2-aminoethyl)-5-(m-fluorophenyl)-4-thiazole carboxamide (Ro 41-1049) (30 mg/kg, reversible selective monoamine oxidase A inhibitor), selegiline (3 mg/kg, irreversible selective monoamine oxidase B inhibitor) and lazabemide (10 mg/kg, reversible selective monoamine oxidase B inhibitor) had no effect on Freezing Behavior. However, combined administration of clorgyline (10 mg/kg) and selegiline (3 mg/kg) reduced Freezing significantly, as well as combined administration of clorgyline (10 mg/kg) and lazabemide (10 mg/kg), Ro 41-1049 (30 mg/kg) and selegiline (3 mg/kg), or Ro 41-1049 (30 mg/kg) and lazabemide (10 mg/kg). These effects of monoamine oxidase inhibitors on Freezing were not due to non-specific motor effects. These results suggest that acute inhibition of both monoamine oxidase A and B reduced anxiety or fear, while inhibition of monoamine oxidase A or B alone failed to reduce anxiety or fear.
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effects of conditioned fear stress on serotonin neurotransmission and Freezing Behavior in rats
European Journal of Pharmacology, 1999Co-Authors: S Hashimoto, Takeshi Inoue, Tsukasa KoyamaAbstract:In an attempt to clarify the role of the brain serotonergic system in the psychopathology of anxiety, we examined the effect of a psychological stress, conditioned fear stress, on extracellular serotonin (5-hydroxytryptamine, 5-HT) concentrations in the rat medial prefrontal cortex using the method of in vivo microdialysis, while simultaneously observing conditioned fear stress-induced Freezing Behavior, an index of anxiety. Conditioned fear stress increased extracellular 5-HT levels in the medial prefrontal cortex, and this 5-HT level increase was followed by a resolution of the Freezing Behavior. A dose of 10 mg/kg of a selective 5-HT reuptake inhibitor, citalopram, administered 60 min before exposure to conditioned fear stress increased extracellular 5-HT concentrations immediately and potently, reducing Freezing Behavior. These findings strongly suggest that facilitation of brain 5-HT neurotransmission decreases anxiety, which is in agreement with the clinical reports that selective 5-HT reuptake inhibitors are effective in the treatment of anxiety disorders.
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effects of typical and atypical antipsychotic drugs on Freezing Behavior induced by conditioned fear
Pharmacology Biochemistry and Behavior, 1996Co-Authors: Takeshi Inoue, Kiyoshi Tsuchiya, Tsukasa KoyamaAbstract:Atypical antipsychotic drugs (atypical APDs), such as clozapine, ORG5222, and olanzapine, have been suggested to possess anxiolytic activity in the conflict test and elevated plus-maze test, while several studies have suggested that typical APDs are not anxiolytic in several models of anxiety. We investigated the effects of typical and atypical APDs on the acquisition and expression of conditioned fear-induced Freezing. Drugs were administered subcutaneously to male Sprague-Dawley rats 30 min before foot shock stress (the VI60s schedule, 2.5 mA for 30 min). Twenty-four hours after foot shock, Freezing Behavior of rats was observed in the shock chamber without shocks. The atypical APD clozapine (0.3–10 mg/kg) dose-dependently inhibited the acquisition of conditioned Freezing. Candidates for atypical APDs, ORG5222 (0.1–1 mg/kg), olanzapine (1–10 mg/kg), and raclopride (3–30 mg/kg), also reduced the acquisition of conditioned Freezing in a dose-dependent manner. Typical APDs, haloperidol (3 mg/kg), spiperone (0.1–1 mg/kg) and nemonapride (1 mg/kg) had significant inhibitory effects on the acquisition of conditioned Freezing, but their effects were reduced at higher doses. Chlorpromazine, a typical APD, showed about 50% inhibition of the acquisition of conditioned Freezing at the dose of 10 mg/kg, but did not reveal significant inhibition at any of the doses (3–30 mg/kg). The ED50s (mg/kg) for inhibiting the acquisition of conditioned Freezing significantly correlated with the ki values for D4 dopaminergic receptors, but not with the Ki values for other monoamine and acetylcholine receptors. On the other hand, clozapine or haloperidol did not change the expression of conditioned Freezing. These results suggest that protective effects of clozapine and other antipsychotic drugs on the acquisition of conditioned Freezing may be mediated by blockade of D4 receptors.
Takeshi Inoue - One of the best experts on this subject based on the ideXlab platform.
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Effect of the coadministration of citalopram with mirtazapine or atipamezole on rat contextual conditioned fear.
Neuropsychiatric Disease and Treatment, 2014Co-Authors: Takahiro Masuda, Yan An, Yuji Kitaichi, Shin Nakagawa, Tsukasa Koyama, Takeshi Inoue, Naoki Takamura, Ichiro KusumiAbstract:Background Mirtazapine, a noradrenergic and specific serotonergic antidepressant, which blocks the α2-adrenergic autoreceptors and heteroreceptors, has shown anxiolytic properties in clinical trials and preclinical animal experiments. The addition of mirtazapine to selective serotonin reuptake inhibitors (SSRIs) is clinically suggested to be more effective for anxiety disorders. In this study, we examined the combined effects of mirtazapine and citalopram, an SSRI, on the Freezing Behavior of rats, which was induced by contextual conditioned fear as an index of anxiety or fear.
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anxiolytic like effect of mirtazapine mediates its effect in the median raphe nucleus
European Journal of Pharmacology, 2013Co-Authors: Yan An, Yuji Kitaichi, Takeshi Izumi, Xiaobai Li, Shin Nakagawa, Takeshi Inoue, Ning Song, Chong Chen, Tsukasa KoyamaAbstract:Abstract Mirtazapine, a noradrenergic and specific serotonergic antidepressant (NaSSA), blocks the α2-adrenergic autoreceptors and heteroreceptors, which are responsible for controlling noradrenaline and 5-hydroxytryptamine (5-HT) release. Though preclinical and clinical studies have shown that mirtazapine exerts an anxiolytic action, its precise brain target sites remain unclear. In the present study, we investigated the brain area(s) in which mirtazapine exerts its anxiolytic-like effects on the expression of contextual conditioned Freezing in rats. Mirtazapine (3 μg/site) was directly injected into three brain structures, the median raphe nucleus (MRN), hippocampus and amygdala. Freezing Behavior tests were carried out 10 min after injections. Our results showed that the intra-MRN injection of mirtazapine reduced Freezing significantly, whereas injections into the hippocampus or the amygdala did not. In addition, the intra-MRN injection of mirtazapine did not affect locomotor activity. These results suggest that the anxiolytic-like effect of mirtazapine might be mediated by its action on the MRN.
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juvenile stress attenuates the dorsal hippocampal postsynaptic 5 ht1a receptor function in adult rats
Psychopharmacology, 2011Co-Authors: Hirokazu Matsuzaki, Takeshi Izumi, Takeshi Inoue, Takahiro Horinouchi, Shuken Boku, Taku Yamaguchi, Takayuki Yoshida, Machiko Matsumoto, Hiroko Togashi, Soichi MiwaAbstract:Traumatic events in early life are associated with an increased risk of psychiatric diseases in adulthood. 5-hydroxytryptamine (5-HT)1A receptors play a pivotal role in the 5-HTergic mechanisms associated with the etiology of stress-related disorders. The goal of the present study was to investigate whether juvenile stress influences emotional control via postsynaptic 5-HT1A receptor in the hippocampus and amygdala using contextual fear conditioning test in adult rats. The rats were subjected to aversive footshock (FS) during the third week of the postnatal period (3wFS group). During the postadolescent period (10–14 weeks postnatal), experiments were performed. The systemic administration of the 5-HT1A receptor agonist R-(+)-8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) (0.2 mg/kg, i.p.) attenuated the Freezing Behavior in the non-FS group, but not in the 3wFS group. The bilateral local injection of 8-OH-DPAT (1 μg/side) into the amygdala decreased the Freezing Behavior in the non-FS group and the 3wFS group. However, the local injection of 8-OH-DPAT (1 μg/side) into the hippocampus decreased the Freezing Behavior in the non-FS group, but not in the 3wFS group. In a 5-HT1A receptor binding study, the Bmax of the 3wFS group decreased in the dorsal hippocampus, but not the amygdala in comparison with the non-FS group. The juvenile stress attenuated the hippocampal postsynaptic 5-HT1A receptor function in context-dependent conditioned fear.
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monoamine oxidase inhibitors reduce conditioned fear stress induced Freezing Behavior in rats
European Journal of Pharmacology, 2000Co-Authors: Yuji Maki, Yuji Kitaichi, Ihoko Muraki, Takeshi Izumi, Xiaobai Li, Takeshi Inoue, Tsukasa KoyamaAbstract:Abstract The present study examined the acute anxiolytic effects of monoamine oxidase inhibitors on Freezing Behavior, a putative index of anxiety induced by conditioned fear stress. The selective serotonin 1A receptor agonist tandospirone (0.1–10 mg/kg) inhibited Freezing dose dependently. The irreversible, non-selective monoamine oxidase inhibitors tranylcypromine (3 and 15 mg/kg) and phenelzine (30 and 80 mg/kg) reduced Freezing significantly. Clorgyline (10 mg/kg, irreversible selective monoamine oxidase A inhibitor), N-(2-aminoethyl)-5-(m-fluorophenyl)-4-thiazole carboxamide (Ro 41-1049) (30 mg/kg, reversible selective monoamine oxidase A inhibitor), selegiline (3 mg/kg, irreversible selective monoamine oxidase B inhibitor) and lazabemide (10 mg/kg, reversible selective monoamine oxidase B inhibitor) had no effect on Freezing Behavior. However, combined administration of clorgyline (10 mg/kg) and selegiline (3 mg/kg) reduced Freezing significantly, as well as combined administration of clorgyline (10 mg/kg) and lazabemide (10 mg/kg), Ro 41-1049 (30 mg/kg) and selegiline (3 mg/kg), or Ro 41-1049 (30 mg/kg) and lazabemide (10 mg/kg). These effects of monoamine oxidase inhibitors on Freezing were not due to non-specific motor effects. These results suggest that acute inhibition of both monoamine oxidase A and B reduced anxiety or fear, while inhibition of monoamine oxidase A or B alone failed to reduce anxiety or fear.
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effects of conditioned fear stress on serotonin neurotransmission and Freezing Behavior in rats
European Journal of Pharmacology, 1999Co-Authors: S Hashimoto, Takeshi Inoue, Tsukasa KoyamaAbstract:In an attempt to clarify the role of the brain serotonergic system in the psychopathology of anxiety, we examined the effect of a psychological stress, conditioned fear stress, on extracellular serotonin (5-hydroxytryptamine, 5-HT) concentrations in the rat medial prefrontal cortex using the method of in vivo microdialysis, while simultaneously observing conditioned fear stress-induced Freezing Behavior, an index of anxiety. Conditioned fear stress increased extracellular 5-HT levels in the medial prefrontal cortex, and this 5-HT level increase was followed by a resolution of the Freezing Behavior. A dose of 10 mg/kg of a selective 5-HT reuptake inhibitor, citalopram, administered 60 min before exposure to conditioned fear stress increased extracellular 5-HT concentrations immediately and potently, reducing Freezing Behavior. These findings strongly suggest that facilitation of brain 5-HT neurotransmission decreases anxiety, which is in agreement with the clinical reports that selective 5-HT reuptake inhibitors are effective in the treatment of anxiety disorders.
Marcus Lira Brandao - One of the best experts on this subject based on the ideXlab platform.
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different patterns of Freezing Behavior organized in the periaqueductal gray of rats association with different types of anxiety
Behavioural Brain Research, 2008Co-Authors: Marcus Lira Brandao, Janaina Menezes Zanoveli, Raquel C Ruizmartinez, Luciana Chrystine Oliveira, J LandeirafernandezAbstract:Freezing defined as the complete absence of body movements is a normal response of animals to unavoidable fear stimuli. The present review presents a series of evidence relating different defensive patterns with specific anxiety disorders. There are at least four different kinds of Freezing with specific neural substrates. The immobility induced by stimulation of the ventral column of the periaqueductal gray (vPAG) has been considered a quiescence characteristic of the recovery component of defense-recuperative processes. There is an isomorphism between Freezing response to contextual stimuli paired with electrical shocks and generalized anxiety disorder. Besides, two types of Freezing emerge with the electrical stimulation of the dorsal aspects of the periaqueductal gray (dPAG): the dPAG-evoked Freezing and the dPAG post-stimulation Freezing. Evidence is presented in support of the hypothesis that whereas dPAG-evoked Freezing would serve as a model of panic attacks, the dPAG post-stimulation Freezing appears to be a model of panic disorder. It is also proposed that conditioned Freezing plus dPAG electrical stimulation might also mimic panic disorder with agoraphobia. A model of serotoninergic modulation through on- and off-cells of the defense reaction generated in the dPAG is also presented. The understanding of how the periaqueductal gray generates and elaborates different types of Freezing is of relevance for our better knowledge of distinct types of anxiety such as panic disorder or generalized anxiety disorder.
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conditioned and unconditioned fear organized in the periaqueductal gray are differentially sensitive to injections of muscimol into amygdaloid nuclei
Neurobiology of Learning and Memory, 2006Co-Authors: Raquel Chacon Ruiz Martinez, Amanda Ribeiro De Oliveira, Marcus Lira BrandaoAbstract:The lateral and basolateral nuclei of the amygdala (LaA and BLA, respectively) serve as a filter for unconditioned and conditioned aversive information that ascends to higher structures from the brainstem, whereas the central nucleus of the amygdala (CeA) is considered to be the main output for the defense reaction. It has been shown that the dorsal periaqueductal gray (dPAG) is activated by threatening stimuli and has important functional links with the amygdala through two-way anatomical connections. In this work, we examined the influence of chemical inactivation of these nuclei of amygdala on the Freezing and escape responses induced by electrical stimulation through electrodes implanted in the dPAG of Wistar rats. Each rat also bore a cannula implanted in the LaA, BLA or CeA for injections of muscimol (0.5 microg/0.5 microL) or its vehicle. The duration of Freezing Behavior that outlasts electrical stimulation of the dPAG was also measured. On the following day, these animals were submitted to a contextual fear-conditioning using foot shocks as unconditioned stimulus. Conditioned Freezing to contextual cues previously associated with foot shocks was also inhibited by injections of muscimol into these amygdaloid nuclei. The contextual conditioned Freezing Behavior is generated in the neural circuits of conditioned fear in the amygdala. The data obtained also show that injections of muscimol into the three amygdaloid nuclei did not change the aversive threshold of Freezing, but disrupted the dPAG post-stimulation Freezing. Previous findings that the latter Freezing results directly from dPAG stimulation and that it is not sensitive to a context shift suggest that it is unconditioned in nature. Thus, the amygdala can affect some, but not all, aspects of unconditioned Freezing. Post-stimulation Freezing may reflect the process of transferring aversive information from dPAG to higher brain structures.
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analysis of Freezing Behavior and ultrasonic vocalization in response to foot shocks ultrasound signals and gabaergic inhibition in the inferior colliculus effects of muscimol and midazolam
European Neuropsychopharmacology, 2004Co-Authors: Manoel Jorge Nobre, Marcus Lira BrandaoAbstract:Freezing Behavior is a common response to distal threatening stimuli. It has been reported that experimenter-presented 20-kHz tones produce Freezing in Wistar rats. The present studies were designed to determine the acoustic specificity for induction of the emission of ultrasound vocalizations (USV) and Freezing of rats to either ultrasound tones or to a standard stressor, foot-shocks. We also examined whether GABA-benzodiazepine mechanisms, known for modulating anxiety-related processes, are involved in the regulation of defensive responses to these two aversive unconditioned stimuli. It was found that emission of USV was only observed with foot-shocks. Moreover, rats exhibited Freezing when they were exposed to foot-shocks and 20-25-kHz ultrasound signals. Likewise, removal of the GABAergic inhibitory control on the neural substrates of aversion in the inferior colliculus by local microinjections of semicarbazide, a blocker of the glutamic acid decarboxylase, caused Freezing Behavior without emission of USV. All these responses were significantly reduced by midazolam and muscimol. It is suggested that the neural substrates of aversion in the inferior colliculus are under inhibitory control of GABAergic mechanisms and are different from those triggered by foot-shocks.
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antinociception induced by stimulation of ventrolateral periaqueductal gray at the Freezing threshold is regulated by opioid and 5 ht2a receptors as assessed by the tail flick and formalin tests
Pharmacology Biochemistry and Behavior, 2003Co-Authors: Maria Cecilia Zanoto De Luca, Marcus Lira Brandao, J Landeirafernandez, Vitor Augusto MottaAbstract:It has been suggested that antinociception is part of the animal's defensive reaction to threatening situations. Chemical or electrical stimulation of the ventrolateral portion of the periaqueductal gray (vlPAG) produces both defensive Freezing Behavior and antinociception, supporting the view that the vlPAG is a critical structure in the coordination of the defensive reaction. The present study indicated that electrical stimulation of the vlPAG, at a current intensity sufficient to induce defensive Freezing, caused a decrease in reactivity to a phasic escapable noxious stimulus (as measured in the tail-flick test) and to a tonic, inescapable noxious stimulus (as measured in the formalin test). These antinociceptive effects were reversed by microinjections of the opioid antagonist naltrexone or the specific 5-HT2A receptor antagonist ketanserin into the stimulation sites. These results suggest that (a) activation of neural circuits of the vlPAG, responsible for the production of Freezing Behavior, reduces the reactivity to nociceptive stimuli (as evaluated by the tail-flick and formalin tests) and that (b) opioid- and 5-HT2A-mediated mechanisms are called into action for regulating the antinociceptive response that accompanies the Freezing Behavior induced by vlPAG stimulation.
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defensive Freezing evoked by electrical stimulation of the periaqueductal gray comparison between dorsolateral and ventrolateral regions
Neuroreport, 2001Co-Authors: Daniel Machado Vianna, Marcus Lira Brandao, F G Graeff, J LandeirafernandezAbstract:Previous reports indicated that ventrolateral periaqueductal gray (vlPAG) plays a role in the expression of Freezing Behavior whereas dorsolateral periaqueductal gray (dlPAG) is involved on both Freezing and active forms of defensive Behaviors. In order to evaluate the role of each of these areas in the occurrence of defensive reactions, rats were electrically stimulated either in the dlPAG or vlPAG with different stimulus frequencies. Stepwise increases in the electrical stimulation of both dlPAG or vlPAG induced initially Freezing and then a jumping response. Freezing induced by vlPAG stimulation had a tendency to disappear when the stimulation was turned off whereas Freezing induced by dlPAG stimulation remained high in the absence of the stimulation. These results suggest that dlPAG and vlPAG are involved on defensive Freezing probably through different neural circuitries.
Stephen Maren - One of the best experts on this subject based on the ideXlab platform.
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role of the bed nucleus of the stria terminalis in aversive learning and memory
Learning & Memory, 2017Co-Authors: Travis D Goode, Stephen MarenAbstract:Surviving threats in the environment requires brain circuits for detecting (or anticipating) danger and for coordinating appropriate defensive responses (e.g., increased cardiac output, stress hormone release, and Freezing Behavior). The bed nucleus of the stria terminalis (BNST) is a critical interface between the "affective forebrain"-including the amygdala, ventral hippocampus, and medial prefrontal cortex-and the hypothalamic and brainstem areas that have been implicated in neuroendocrine, autonomic, and Behavioral responses to actual or anticipated threats. However, the precise contribution of the BNST to defensive Behavior is unclear, both in terms of the antecedent stimuli that mobilize BNST activity and the consequent defensive reactions. For example, it is well known that the BNST is essential for contextual fear conditioning, but dispensable for fear conditioning to discrete conditioned stimuli (CSs), at least as indexed by Freezing Behavior. However, recent evidence suggests that there are circumstances in which contextual Freezing may persist independent of the BNST. Furthermore, the BNST is involved in the reinstatement (or relapse) of conditioned Freezing to extinguished discrete CSs. As such, there are critical gaps in understanding how the BNST contributes to fundamental processes involved in Pavlovian fear conditioning. Here, we attempt to provide an integrative account of BNST function in fear conditioning. We discuss distinctions between unconditioned stress and conditioned fear and the role of BNST circuits in organizing Behaviors associated with these states. We propose that the BNST mediates conditioned defensive responses-not based on the modality or duration of the antecedent threat or the duration of the Behavioral response to the threat-but rather as consequence the ability of an antecedent stimulus to predict when an aversive outcome will occur (i.e., its temporal predictability). We argue that the BNST is not uniquely mobilized by sustained threats or uniquely involved in organizing sustained fear responses. In contrast, we argue that the BNST is involved in organizing fear responses to stimuli that poorly predict when danger will occur, no matter the duration, modality, or complexity of those stimuli. The concepts discussed in this review are critical to understanding the contribution of the human BNST to fear and anxiety disorders.
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hippocampus and pavlovian fear conditioning in rats muscimol infusions into the ventral but not dorsal hippocampus impair the acquisition of conditional Freezing to an auditory conditional stimulus
Behavioral Neuroscience, 2004Co-Authors: Stephen Maren, William HoltAbstract:The authors compared the effects of pharmacological inactivation of the dorsal hippocampus (DH) or ventral hippocampus (VH) on Pavlovian fear conditioning in rats. Freezing Behavior served as the measure of fear. Pretraining infusions of muscimol, a GABAA receptor agonist, into the VH disrupted auditory, but not contextual, fear conditioning; DH infusions did not affect fear conditioning. Pretesting inactivation of the VH or DH did not affect the expression of conditional Freezing. Pretraining electrolytic lesions of the VH reproduced the effects of muscimol infusions, whereas posttraining VH lesions disrupted both auditory and contextual Freezing. Hence, neurons in the VH are importantly involved in the acquisition of auditory fear conditioning and the expression of auditory and contextual fear under some conditions. An abundance of evidence indicates that the hippocampus is importantly involved in associative learning and memory (Anagnostaras, Gale, & Fanselow, 2001; Douglas, 1967; Eichenbaum,
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is there savings for pavlovian fear conditioning after neurotoxic basolateral amygdala lesions in rats
Neurobiology of Learning and Memory, 2001Co-Authors: Stephen MarenAbstract:Considerable evidence indicates an important role for amygdaloid nuclei in both the acquisition and expression of Pavlovian fear conditioning. Recent reports from my laboratory have focused on the impact of neurotoxic lesions of the basolateral complex of the amygdala (BLA) on conditional Freezing Behavior in rats. In these studies, I have observed severe effects of posttraining BLA lesions on the expression of conditional Freezing even after extensive presurgical overtraining (25–75 trials). Moreover, I have found no evidence for sparing of fear memory (i.e., savings) in these rats when I assess their rate of reacquisition relative to BLA rats receiving minimal training (1 trial). In these experiments, Freezing Behavior was assessed using a conventional time-sampling procedure and expressed as a response probability. Although this measure is well established in the literature, it is conceivable that it is not sensitive to spared memory in rats with BLA lesions. To address this issue, I present a more detailed analysis of Freezing Behavior that quantifies latency to freeze, the number of Freezing bouts, the duration of Freezing bouts, and the probability distribution of bout lengths. I also include control data from untrained (no-shock) rats. Consistent with my earlier reports, I find no evidence of savings of fear memory in rats with neurotoxic BLA lesions using several measures of Freezing Behavior. These results reiterate the conclusion that fear memory, as it is expressed in Freezing Behavior, requires neurons in the BLA.
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The startled seahorse: is the hippocampus necessary for contextual fear conditioning?
Trends in cognitive sciences, 1998Co-Authors: Stephen Maren, Stephan G. Anagnostaras, Michael S. FanselowAbstract:are not known, although it is assumedthat configural strategies normally supersede elemental strategies.The lion’s share of work implicat-ing the hippocampus in contextualconditioning has been derived fromstudies of fear conditioning in rats. Infear conditioning tasks, discrete and/orcontextual CSs that are paired withfootshock come to evoke conditionalfear responses (CRs) such as defecation,potentiated acoustic startle, elevatedblood pressure and Freezing. In manylaboratories, contextual fear is assessedby returning the rats to the condition-ing chamber and measuring Freezing.That the hippocampus plays an impor-tant role in contextual fear condition-ing is indicated by studies demonstrat-ing that dorsal hippocampal lesionsattenuate Freezing to contextual CSs,but do not alter Freezing Behavior todiscrete CSs (Refs 2,3). Hippocampal le-sions also impair contextual fear condi-tioning following unsignaled train-ing
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Retrograde abolition of conditional fear after excitotoxic lesions in the basolateral amygdala of rats: Absence of a temporal gradient.
Behavioral Neuroscience, 1996Co-Authors: Stephen Maren, Gal Aharonov, Michael S. FanselowAbstract:The role of the basolateral amygdala (BLA) in the acquisition and expression of Pavlovian fear conditioning was examined in 80 rats. Excitotoxic lesions were made in the BLA using N-methyl-o-aspartate 7 days before or 1, 14, or 28 days after Pavlovian fear conditioning. Conditioning consisted of three pairings of a tone with an aversive footshock in a novel chamber, and Freezing Behavior served as an index of conditional fear. BLA lesions abolished conditional Freezing to both the contextual and acoustic conditional stimuli at all training-to-lesion intervals, and the magnitude of the impairment did not vary as a function of the training-to-lesion interval. Reacquisition training elevated levels of Freezing in rats with BLA lesions but did not reduce the magnitude of their deficit in relation to that of controls. These results reveal that neurons in the BLA have an enduring role in the expression of conditional fear.
Frank Stratmann - One of the best experts on this subject based on the ideXlab platform.
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laboratory generated mixtures of mineral dust particles with biological substances characterization of the particle mixing state and immersion Freezing Behavior
Atmospheric Chemistry and Physics, 2016Co-Authors: Stefanie Augustinbauditz, S. Hartmann, Martin Ebert, Johannes Schneider, Cyrielle Denjean, Susann Schmidt, Frank StratmannAbstract:Abstract. Biological particles such as bacteria, fungal spores or pollen are known to be efficient ice nucleating particles. Their ability to nucleate ice is due to ice nucleation active macromolecules (INMs). It has been suggested that these INMs maintain their nucleating ability even when they are separated from their original carriers. This opens the possibility of an accumulation of such INMs in soils, resulting in an internal mixture of mineral dust and INMs. If particles from such soils which contain biological INMs are then dispersed into the atmosphere due to wind erosion or agricultural processes, they could induce ice nucleation at temperatures typical for biological substances, i.e., above −20 up to almost 0 °C, while they might be characterized as mineral dust particles due to a possibly low content of biological material. We conducted a study within the research unit INUIT (Ice Nucleation research UnIT), where we investigated the ice nucleation Behavior of mineral dust particles internally mixed with INM. Specifically, we mixed a pure mineral dust sample (illite-NX) with ice active biological material (birch pollen washing water) and quantified the immersion Freezing Behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). A very important topic concerning the investigations presented here as well as for atmospheric application is the characterization of the mixing state of aerosol particles. In the present study we used different methods like single-particle aerosol mass spectrometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and a Volatility–Hygroscopicity Tandem Differential Mobility Analyser (VH-TDMA) to investigate the mixing state of our generated aerosol. Not all applied methods performed similarly well in detecting small amounts of biological material on the mineral dust particles. Measuring the hygroscopicity/volatility of the mixed particles with the VH-TDMA was the most sensitive method. We found that internally mixed particles, containing ice active biological material, follow the ice nucleation Behavior observed for the pure biological particles. We verified this by modeling the Freezing Behavior of the mixed particles with the Soccerball model (SBM). It can be concluded that a single INM located on a mineral dust particle determines the Freezing Behavior of that particle with the result that Freezing occurs at temperatures at which pure mineral dust particles are not yet ice active.
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can we define an asymptotic value for the ice active surface site density for heterogeneous ice nucleation
EGUGA, 2015Co-Authors: Dennis Niedermeier, Stefanie Augustinbauditz, Susan Hartmann, Heike Wex, Karoliina Ignatius, Frank StratmannAbstract:The immersion Freezing Behavior of droplets containing size-segregated, monodisperse feldspar particles was investigated. For all particle sizes investigated, a leveling off of the frozen droplet fraction was observed reaching a plateau within the heterogeneous Freezing temperature regime (T >− 38°C). The frozen fraction in the plateau region was proportional to the particle surface area. Based on these findings, an asymptotic value for ice active surface site density ns, which we named ns⋆, could be determined for the investigated feldspar sample. The comparison of these results with those of other studies not only elucidates the general feasibility of determining such an asymptotic value but also shows that the value of ns⋆ strongly depends on the method of the particle surface area determination. However, such an asymptotic value might be an important input parameter for atmospheric modeling applications. At least it shows that care should be taken when ns is extrapolated to lower or higher temperature.
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heterogeneous ice nucleation exploring the transition from stochastic to singular Freezing Behavior
Atmospheric Chemistry and Physics, 2011Co-Authors: Dennis Niedermeier, Jens Voigtlander, Raymond A. Shaw, S. Hartmann, Heike Wex, T Clauss, Frank StratmannAbstract:Abstract. Heterogeneous ice nucleation, a primary pathway for ice formation in the atmosphere, has been described alternately as being stochastic, in direct analogy with homogeneous nucleation, or singular, with ice nuclei initiating Freezing at deterministic temperatures. We present an idealized, conceptual model to explore the transition between stochastic and singular ice nucleation. This "soccer ball" model treats particles as being covered with surface sites (patches of finite area) characterized by different nucleation barriers, but with each surface site following the stochastic nature of ice embryo formation. The model provides a phenomenological explanation for seemingly contradictory experimental results obtained in our research groups. Even with ice nucleation treated fundamentally as a stochastic process this process can be masked by the heterogeneity of surface properties, as might be typical for realistic atmospheric particle populations. Full evaluation of the model findings will require experiments with well characterized ice nucleating particles and the ability to vary both temperature and waiting time for Freezing.
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homogeneous and heterogeneous ice nucleation at lacis operating principle and theoretical studies
Atmospheric Chemistry and Physics, 2011Co-Authors: S. Hartmann, Dennis Niedermeier, Jens Voigtlander, Thomas Clauss, Alexei Kiselev, Raymond A. Shaw, Frank StratmannAbstract:Abstract. At the Leipzig Aerosol Cloud Interaction Simulator (LACIS) experiments investigating homogeneous and heterogeneous nucleation of ice (particularly immersion Freezing in the latter case) have been carried out. Here both the physical LACIS setup and the numerical model developed to design experiments at LACIS and interpret their results are presented in detail. Combining results from the numerical model with experimental data, it was found that for the experimental parameter space considered, classical homogeneous ice nucleation theory is able to predict the Freezing Behavior of highly diluted ammonium sulfate solution droplets, while classical heterogeneous ice nucleation theory, together with the assumption of a constant contact angle, fails to predict the immersion Freezing Behavior of surrogate mineral dust particles (Arizona Test Dust, ATD). The main reason for this failure is the compared to experimental data apparently overly strong temperature dependence of the nucleation rate coefficient. Assuming, in the numerical model, Classical Nucleation Theory (CNT) for homogeneous ice nucleation and a CNT-based parameterization for the nucleation rate coefficient in the immersion Freezing mode, recently published by our group, it was found that even for a relatively effective ice nucleating agent such as pure ATD, there is a temperature range where homogeneous ice nucleation is dominant. The main explanation is the apparently different temperature dependencies of the two Freezing mechanisms. Finally, reviewing the assumptions made during the derivation of the CNT-based parameterization for immersion Freezing, it was found that the assumption of constant temperature during ice nucleation and the chosen ice nucleation time were justified, underlining the applicability of the method to determine the fitting coefficients in the parameterization equation.
