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Ahlbrand R, Wilson A, Woller P, Sachdeva Y, Lai J, Davis N, Wiggins J, Sah R. Sex-specific threat responding and neuronal engagement in carbon dioxide associated fear and extinction: Noradrenergic involvement in female mice. Neurobiol Stress 2024; 30:100617. [PMID: 38433995 PMCID: PMC10907837 DOI: 10.1016/j.ynstr.2024.100617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/12/2024] [Accepted: 02/13/2024] [Indexed: 03/05/2024] Open
Abstract
Difficulty in appropriately responding to threats is a key feature of psychiatric disorders, especially fear-related conditions such as panic disorder (PD) and posttraumatic stress disorder (PTSD). Most prior work on threat and fear regulation involves exposure to external threatful cues. However, fear can also be triggered by aversive, within-the-body, sensations. This interoceptive signaling of fear is highly relevant to PD and PTSD but is not well understood, especially in the context of sex. Using female and male mice, the current study investigated fear-associated spontaneous and conditioned behaviors to carbon dioxide (CO2) inhalation, a potent interoceptive threat that induces fear and panic. We also investigated whether behavioral sensitivity to CO2 is associated with delayed PTSD-relevant behaviors. CO2 evoked heterogenous freezing behaviors in both male and female animals. However, active, rearing behavior was significantly reduced in CO2-exposed male but not female mice. Interestingly, behavioral sensitivity to CO2 was associated with compromised fear extinction, independent of sex. However, in comparison to CO2-exposed males, females elicited less freezing and higher rearing during extinction suggesting an engagement of active versus passive defensive coping. Persistent neuronal activation marker ΔFosB immuno-mapping revealed attenuated engagement of infralimbic-prefrontal areas in both sexes but higher activation of brain stem locus coeruleus (LC) area in females. Inter-regional co-activation mapping revealed sex-independent disruptions in the infralimbic-amygdala associations but altered LC associations only in CO2-exposed female mice. Lastly, dopamine β hydroxylase positive (DβH + ve) noradrenergic neuronal cell counts in the LC correlated with freezing and rearing behaviors during CO2 inhalation and extinction only in female but not male mice. Collectively, these data provide evidence for higher active defensive responding to interoceptive threat CO2-associated fear in females that may stem from increased recruitment of the brainstem noradrenergic system. Our findings reveal distinct contributory mechanisms that may promote sex differences in fear and panic associated pathologies.
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Affiliation(s)
- Rebecca Ahlbrand
- Department of Pharmacology and Systems Physiology, University of Cincinnati, USA
- Veterans Affairs Medical Center, Cincinnati, OH, USA
| | - Allison Wilson
- Neuroscience Undergraduate Program, University of Cincinnati, USA
| | - Patrick Woller
- Neuroscience Graduate Program, University of Cincinnati, USA
| | - Yuv Sachdeva
- Department of Pharmacology and Systems Physiology, University of Cincinnati, USA
| | - Jayden Lai
- Department of Pharmacology and Systems Physiology, University of Cincinnati, USA
| | - Nikki Davis
- Neuroscience Undergraduate Program, University of Cincinnati, USA
| | - James Wiggins
- Neuroscience Undergraduate Program, University of Cincinnati, USA
| | - Renu Sah
- Department of Pharmacology and Systems Physiology, University of Cincinnati, USA
- Neuroscience Graduate Program, University of Cincinnati, USA
- Veterans Affairs Medical Center, Cincinnati, OH, USA
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2
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Souza INO, Andrade BS, Frost PS, Neris RLS, Gavino-Leopoldino D, Da Poian AT, Assunção-Miranda I, Figueiredo CP, Clarke JR, Neves GA. Different outcomes of neonatal and adult Zika virus infection on startle reflex and prepulse inhibition in mice. Behav Brain Res 2023; 451:114519. [PMID: 37263423 DOI: 10.1016/j.bbr.2023.114519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 05/20/2023] [Accepted: 05/28/2023] [Indexed: 06/03/2023]
Abstract
Zika virus (ZIKV) infection causes severe neurological consequences in both gestationally-exposed infants and adults. Sensorial gating deficits strongly correlate to the motor, sensorial and cognitive impairments observed in ZIKV-infected patients. However, no startle response or prepulse inhibition (PPI) assessment has been made in patients or animal models. In this study, we identified different outcomes according to the age of infection and sex in mice: neonatally infected animals presented an increase in PPI and delayed startle latency. However, adult-infected male mice presented lower startle amplitude, while a PPI impairment was observed 14 days after infection in both sexes. Our data further the understanding of the functional impacts of ZIKV on the developing and mature nervous system, which could help explain other behavioral and cognitive alterations caused by the virus. With this study, we support the startle reflex testing in ZIKV-exposed patients, especially infants, allowing for early detection of functional neuromotor damage and early intervention.
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Affiliation(s)
- Isis N O Souza
- Laboratory of Molecular Pharmacology, Institute of Biomedical Sciences, Universidade Federal do Rio de Janeiro, Brazil; School of Pharmacy, Universidade Federal do Rio de Janeiro, Brazil
| | - Brenda S Andrade
- Laboratory of Molecular Pharmacology, Institute of Biomedical Sciences, Universidade Federal do Rio de Janeiro, Brazil
| | - Paula S Frost
- School of Pharmacy, Universidade Federal do Rio de Janeiro, Brazil
| | - Romulo L S Neris
- Institute of Microbiology Paulo de Goes, Universidade Federal do Rio de Janeiro, Brazil
| | | | - Andrea T Da Poian
- Institute of Medical Biochemistry Leopoldo de Meis (IBqM), Universidade Federal do Rio de Janeiro, Brazil
| | | | | | - Julia R Clarke
- School of Pharmacy, Universidade Federal do Rio de Janeiro, Brazil
| | - Gilda A Neves
- Laboratory of Molecular Pharmacology, Institute of Biomedical Sciences, Universidade Federal do Rio de Janeiro, Brazil.
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3
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Hu C, Wang Z, Liu B, Huang H, Zhang N, Xu Y. Validation of a system for automatic quantitative analysis of laboratory mice behavior based on locomotor pose. Comput Biol Med 2022; 150:105960. [PMID: 36122441 DOI: 10.1016/j.compbiomed.2022.105960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 07/28/2022] [Accepted: 08/06/2022] [Indexed: 11/17/2022]
Abstract
Automatic recognition and accurate quantitative analysis of rodent behavior play an important role in brain neuroscience, pharmacological and toxicological. Currently, most behavior recognition systems used in experiments mainly focus on the indirect measurements of animal movement trajectories, while neglecting the changes of animal body pose that can indicate more psychological factors. Thus, this paper developed and validated an hourglass network-based behavioral quantification system (HNBQ), which uses a combination of body pose and movement parameters to quantify the activity of mice in an enclosed experimental chamber. In addition, The HNBQ was employed to record behavioral abnormalities of head scanning in the presence of food gradients in open field test (OFT). The results proved that the HNBQ in the new object recognition (NOR) experiment was highly correlated with the scores of manual observers during the latent exploration period and the cumulative exploration time. Moreover, in the OFT, HNBQ was able to capture the subtle differences in head scanning behavior of mice in the gradient experimental groups. Satisfactory results support that the combination of body pose and motor parameters can regard as a new alternative approach for quantification of animal behavior in laboratory.
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Affiliation(s)
- Chunhai Hu
- School of Electrical Engineering, Yanshan University, Qinhuangdao, 066044, China
| | - Zhongjian Wang
- School of Electrical Engineering, Yanshan University, Qinhuangdao, 066044, China
| | - Bin Liu
- School of Electrical Engineering, Yanshan University, Qinhuangdao, 066044, China.
| | - Hong Huang
- Centre for Pharmacological and Toxicological Research, Institute of Medicinal Plants, Beijing, 100193, China
| | - Ning Zhang
- School of Electrical Engineering, Yanshan University, Qinhuangdao, 066044, China
| | - Yanguang Xu
- School of Electrical Engineering, Yanshan University, Qinhuangdao, 066044, China
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4
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Abrous DN, Koehl M, Lemoine M. A Baldwin interpretation of adult hippocampal neurogenesis: from functional relevance to physiopathology. Mol Psychiatry 2022; 27:383-402. [PMID: 34103674 PMCID: PMC8960398 DOI: 10.1038/s41380-021-01172-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 05/03/2021] [Accepted: 05/12/2021] [Indexed: 02/05/2023]
Abstract
Hippocampal adult neurogenesis has been associated to many cognitive, emotional, and behavioral functions and dysfunctions, and its status as a selected effect or an "appendix of the brain" has been debated. In this review, we propose to understand hippocampal neurogenesis as the process underlying the "Baldwin effect", a particular situation in evolution where fitness does not rely on the natural selection of genetic traits, but on "ontogenetic adaptation" to a changing environment. This supports the view that a strong distinction between developmental and adult hippocampal neurogenesis is made. We propose that their functions are the constitution and the lifelong adaptation, respectively, of a basic repertoire of cognitive and emotional behaviors. This lifelong adaptation occurs through new forms of binding, i.e., association or dissociation of more basic elements. This distinction further suggests that a difference is made between developmental vulnerability (or resilience), stemming from dysfunctional (or highly functional) developmental hippocampal neurogenesis, and adult vulnerability (or resilience), stemming from dysfunctional (or highly functional) adult hippocampal neurogenesis. According to this hypothesis, developmental and adult vulnerability are distinct risk factors for various mental disorders in adults. This framework suggests new avenues for research on hippocampal neurogenesis and its implication in mental disorders.
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Affiliation(s)
- Djoher Nora Abrous
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, Neurogenesis and Pathophysiology group, F-33000, Bordeaux, France.
| | - Muriel Koehl
- grid.412041.20000 0001 2106 639XUniv. Bordeaux, INSERM, Neurocentre Magendie, U1215, Neurogenesis and Pathophysiology group, F-33000 Bordeaux, France
| | - Maël Lemoine
- grid.412041.20000 0001 2106 639XUniversity Bordeaux, CNRS, ImmunoConcEpT, UMR 5164, Bordeaux, France
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5
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Shida Y, Endo H, Owada S, Inagaki Y, Sumiyoshi H, Kamiya A, Eto T, Tatemichi M. Branched-chain amino acids govern the high learning ability phenotype in Tokai high avoider (THA) rats. Sci Rep 2021; 11:23104. [PMID: 34845278 PMCID: PMC8630195 DOI: 10.1038/s41598-021-02591-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/19/2021] [Indexed: 11/09/2022] Open
Abstract
To fully understand the mechanisms governing learning and memory, animal models with minor interindividual variability and higher cognitive function are required. THA rats established by crossing those with high learning capacity exhibit excellent learning and memory abilities, but the factors underlying their phenotype are completely unknown. In the current study, we compare the hippocampi of parental strain Wistar rats to those of THA rats via metabolomic analysis in order to identify molecules specific to the THA rat hippocampus. Higher branched-chain amino acid (BCAA) levels and enhanced activation of BCAA metabolism-associated enzymes were observed in THA rats, suggesting that acetyl-CoA and acetylcholine are synthesized through BCAA catabolism. THA rats maintained high blood BCAA levels via uptake of BCAAs in the small intestine and suppression of BCAA catabolism in the liver. Feeding THA rats with a BCAA-reduced diet decreased acetylcholine levels and learning ability, thus, maintaining high BCAA levels while their proper metabolism in the hippocampus is the mechanisms underlying the high learning ability in THA rats. Identifying appropriate BCAA nutritional supplements and activation methods may thus hold potential for the prevention and amelioration of higher brain dysfunction, including learning disabilities and dementia.
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Affiliation(s)
- Yukari Shida
- Center for Molecular Prevention and Environmental Medicine, Department of Preventive Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
| | - Hitoshi Endo
- Center for Molecular Prevention and Environmental Medicine, Department of Preventive Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan.
| | - Satoshi Owada
- Center for Molecular Prevention and Environmental Medicine, Department of Preventive Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
| | - Yutaka Inagaki
- Center for Matrix Biology and Medicine, Department of Innovative Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
| | - Hideaki Sumiyoshi
- Center for Matrix Biology and Medicine, Department of Innovative Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
| | - Akihide Kamiya
- Department of Molecular Life Sciences, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
| | - Tomoo Eto
- Central Institute for Experimental Animals, 3-25-12 Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa, 210-0821, Japan
| | - Masayuki Tatemichi
- Center for Molecular Prevention and Environmental Medicine, Department of Preventive Medicine, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259-1193, Japan
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Ding T, Magarinos AM, Kow LM, Milner TA, Pfaff DW. Kv2.1 expression in giant reticular neurons of the postnatal mouse brain. J Chem Neuroanat 2021; 117:102005. [PMID: 34280489 PMCID: PMC8464498 DOI: 10.1016/j.jchemneu.2021.102005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 06/03/2021] [Accepted: 07/15/2021] [Indexed: 10/20/2022]
Abstract
Previous experiments charted the development of behavioral arousal in postnatal mice. From Postnatal Day 3 (P3) to Postnatal Day 6 (P6) mice (a) become significantly more active, "arousable"; and (b) in large reticular neurons, nucleus gigantocellularis (NGC), patch clamp recordings reveal a significantly increased ability to fire high frequency trains of action potentials as are associated with elevated cortical arousal. These action potential trains depend on delayed rectifiers such as Kv2.1. Here we report tracking the development of expression of a delayed rectifier, Kv2.1 in NGC neurons crucial for initiating CNS arousal. In tissue sections, light microscope immunohistochemistry revealed that expression of Kv2.1 in NGC neurons is greater at day P6 than at P3. Electron microscope immunohistochemistry revealed Kv2.1 labeling on the plasmalemmal surface of soma and dendrites, greater on P6 than P3. In brainstem reticular neuron cell culture, Kv2.1 immunocytochemistry increased monotonically from Days-In-Vitro 3-10, paralleling the ability of such neurons to fire action potential trains. The increase of Kv2.1 expression from P3 to P6, perhaps in conjunction with other delayed rectifier currents, could permit the ability to fire action potential trains in NGC neurons. Further work with genetically identified NGC neurons is indicated.
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Affiliation(s)
- Ting Ding
- Laboratory of Neurobiology and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, United States; Department of Obstetrics and Gynecology, National Clinical Research Center for Obstetrical and Gynecological Diseases, Tongji Medical College, Tongji Hospital, Huazhong University of Science and Technology, Wuhan, 430030, China.
| | - Ana Maria Magarinos
- Laboratory of Neurobiology and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, United States.
| | - Lee-Ming Kow
- Laboratory of Neurobiology and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, United States.
| | - Teresa A Milner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, 407 East 61st Street, New York, NY, 10065, United States; Harold and Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, United States.
| | - Donald W Pfaff
- Laboratory of Neurobiology and Behavior, The Rockefeller University, 1230 York Avenue, New York, NY, 10065, United States.
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7
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Turner AD, Sullivan T, Drury K, Hall TA, Williams CN, Guilliams KP, Murphy S, Iqbal O’Meara AM. Cognitive Dysfunction After Analgesia and Sedation: Out of the Operating Room and Into the Pediatric Intensive Care Unit. Front Behav Neurosci 2021; 15:713668. [PMID: 34483858 PMCID: PMC8415404 DOI: 10.3389/fnbeh.2021.713668] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 07/26/2021] [Indexed: 11/13/2022] Open
Abstract
In the midst of concerns for potential neurodevelopmental effects after surgical anesthesia, there is a growing awareness that children who require sedation during critical illness are susceptible to neurologic dysfunctions collectively termed pediatric post-intensive care syndrome, or PICS-p. In contrast to healthy children undergoing elective surgery, critically ill children are subject to inordinate neurologic stress or injury and need to be considered separately. Despite recognition of PICS-p, inconsistency in techniques and timing of post-discharge assessments continues to be a significant barrier to understanding the specific role of sedation in later cognitive dysfunction. Nonetheless, available pediatric studies that account for analgesia and sedation consistently identify sedative and opioid analgesic exposures as risk factors for both in-hospital delirium and post-discharge neurologic sequelae. Clinical observations are supported by animal models showing neuroinflammation, increased neuronal death, dysmyelination, and altered synaptic plasticity and neurotransmission. Additionally, intensive care sedation also contributes to sleep disruption, an important and overlooked variable during acute illness and post-discharge recovery. Because analgesia and sedation are potentially modifiable, understanding the underlying mechanisms could transform sedation strategies to improve outcomes. To move the needle on this, prospective clinical studies would benefit from cohesion with regard to datasets and core outcome assessments, including sleep quality. Analyses should also account for the wide range of diagnoses, heterogeneity of this population, and the dynamic nature of neurodevelopment in age cohorts. Much of the related preclinical evidence has been studied in comparatively brief anesthetic exposures in healthy animals during infancy and is not generalizable to critically ill children. Thus, complementary animal models that more accurately "reverse translate" critical illness paradigms and the effect of analgesia and sedation on neuropathology and functional outcomes are needed. This review explores the interactive role of sedatives and the neurologic vulnerability of critically ill children as it pertains to survivorship and functional outcomes, which is the next frontier in pediatric intensive care.
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Affiliation(s)
- Ashley D. Turner
- Division of Pediatric Critical Care, Department of Pediatrics, Washington University in St. Louis, St. Louis, MO, United States
| | - Travis Sullivan
- Department of Surgery, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Kurt Drury
- Department of Pediatrics, Division of Pediatric Critical Care, Doernbecher Children’s Hospital, Oregon Health & Science University, Portland, OR, United States
| | - Trevor A. Hall
- Department of Pediatrics, Division of Pediatric Psychology, Pediatric Critical Care and Neurotrauma Recovery Program, Doernbecher Children’s Hospital, Oregon Health & Science University, Portland, OR, United States
| | - Cydni N. Williams
- Department of Pediatrics, Division of Pediatric Critical Care, Doernbecher Children’s Hospital, Oregon Health & Science University, Portland, OR, United States
| | - Kristin P. Guilliams
- Division of Pediatric Critical Care, Department of Pediatrics, Washington University in St. Louis, St. Louis, MO, United States
- Division of Pediatric Neurology, Department of Neurology, Washington University in St. Louis, St. Louis, MO, United States
- Division of Neuroradiology, Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, United States
| | - Sarah Murphy
- Department of Pediatrics, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States
| | - A. M. Iqbal O’Meara
- Department of Pediatrics, Child Health Research Institute, Children’s Hospital of Richmond at Virginia Commonwealth University School of Medicine, Richmond, VA, United States
- Department of Pediatrics, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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Guilherme EM, Gianlorenço ACL. The Effects of Intravermis Cerebellar Microinjections of Dopaminergic Agents in Motor Learning and Aversive Memory Acquisition in Mice. Front Behav Neurosci 2021; 15:628357. [PMID: 33716682 PMCID: PMC7947320 DOI: 10.3389/fnbeh.2021.628357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 01/28/2021] [Indexed: 01/01/2023] Open
Abstract
The cerebellum receives dopaminergic innervation and expresses the five types of described dopaminergic receptors. The cerebellar function involves both motor movement and cognition, but the role of cerebellar dopaminergic system on these processes remain unclear. The present study explores the behavioral responses to intracerebellar microinjection of dopaminergic agents in motor and emotional memory. For this, naïve Swiss mice had their cerebellar vermis implanted with a guide canula, received a intravermis microinjection of Dopamine, D1-like antagonist SCH-23390 or D2-like antagonist Eticlopride, and underwent a behavioral analysis of motor learning (by a Rotarod and balance beam learning protocol) or aversive memory acquisition (by the inhibitory avoidance task). The mixed-effects analysis was used to evaluate groups performance, followed by Tukey’s post hoc when appropriated. In this study, Dopamine, SCH-23390 and Eticlopride at the doses used did not affected motor control and motor learning. In addition, the administration of Dopamine and SCH-233390 had no effects on emotional memory acquisition, but the animals that received the highest dose of Eticlopride had an improvement in aversive memory acquisition, shown by a suppression of its innate preference for the dark compartment of the inhibitory avoidance apparatus following an exposure to a foot shock. We propose that cerebellar dopaminergic D2 receptors seem to participate on the modulation of aversive memory processes, without influencing motor performance at the doses used in this study.
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Affiliation(s)
- Evelyn M Guilherme
- Laboratory of Neuroscience, Department of Physical Therapy, Center of Biological Sciences and Health, Federal University of São Carlos, São Carlos, Brazil
| | - Anna Carolyna L Gianlorenço
- Laboratory of Neuroscience, Department of Physical Therapy, Center of Biological Sciences and Health, Federal University of São Carlos, São Carlos, Brazil
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Arakawa H. Restraint stress activates defensive behaviors in male rats depending on age and housing condition. Physiol Behav 2020; 224:113073. [PMID: 32659391 DOI: 10.1016/j.physbeh.2020.113073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 07/08/2020] [Accepted: 07/09/2020] [Indexed: 10/23/2022]
Abstract
Restraint is a widely used experimental stress manipulation in animal models. It is still unclear, however, whether restraint is associated with physical fatigue leading to overall behavioral inhibition, or if it induces activation of defensive behaviors and strategies to protect against subsequent challenges. The aim of this study was to systematically investigate restraint effects in rats based on housing condition (isolation- vs. pair-housed) and age at the time of testing, both of which are relevant to the expression of defensive strategies. Restraint induced behavioral inhibition in male rats younger than postnatal day 65 in an open-field paradigm, while it activated defensive behaviors in adult rats, depending on their housing condition; thereby pair-housed adult rats exhibited a heightened stretch-attend postures (SAPs) and it was suppressed by restraint, while isolation-housed adult rats displayed lower SAPs but it was enhanced by restraint. Restraint also enhanced pain tolerance, but not pain sensitivity, across all ages, regardless of housing conditions. These results suggest that restraint stress activates defensive systems of male rats, including sensory defenses and exploratory strategies in a novel environment, and these expression patterns vary with age from overall inhibition to changes in defensive behavior strategies. Understanding differential changes in these models could lead to greater consistency and better standardization of rodent models commonly used to assess the impact of stress on anxiety and defensive behaviors.
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Affiliation(s)
- Hiroyuki Arakawa
- Department of Psychology, Tokiwa University, 1-430-1 Miwa, Mito, Ibaraki 310-8585 Japan.
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