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Carpenter RE, Sabirzhanov B, Summers TR, Clark TG, Keifer J, Summers CH. Anxiolytic reversal of classically conditioned / chronic stress-induced gene expression and learning in the Stress Alternatives Model. Behav Brain Res 2023; 440:114258. [PMID: 36521572 PMCID: PMC9872777 DOI: 10.1016/j.bbr.2022.114258] [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: 10/06/2022] [Revised: 11/30/2022] [Accepted: 12/11/2022] [Indexed: 12/14/2022]
Abstract
Social decision-making is critically influenced by neurocircuitries that regulate stress responsiveness. Adaptive choices, therefore, are altered by stress-related neuromodulatory peptide systems, such as corticotropin releasing factor (CRF). Experimental designs that take advantage of ecologically salient fear-inducing stimuli allow for revelation of neural mechanisms that regulate the balance between pro- and anti-stress responsiveness. To accomplish this, we developed a social stress and conditioning protocol, the Stress Alternatives Model (SAM), that utilizes a simple dichotomous choice, and produces distinctive behavioral phenotypes (Escape or Stay). The experiments involve repeated social aggression, a potent unconditioned stimulus (US), from a novel larger conspecific (a 3X larger Rainbow trout). Prior to the social interaction, the smaller test fish is presented with an auditory conditioning stimulus (water off = CS). During the social aggression, an escape route is available, but is only large enough for the smaller test animal. Surprisingly, although the new aggressor provides vigorous attacks each day, only 50% of the test fish choose Escape. Stay fish, treated with the CRF1 antagonist antalarmin, a potent anxiolytic drug, on day 4, promotes Escape behavior for the last 4 days of the SAM protocol. The results suggest that the decision to Escape, required a reduction in stress reactivity. The Stay fish that chose Escape following anxiolytic treatment, learned how to use the escape route prior to stress reduction, as the Escape latency in these fish was significantly faster than first time escapers. In Escape fish, the use of the escape route is learned over several days, reducing the Escape latency over time in the SAM. Fear conditioning (water off + aggression) resulted in elevated hippocampal (DL) Bdnf mRNA levels, with coincident reduction in the AMPA receptor subunit Glua1 expression, a result that is reversed following a one-time treatment (during SAM aggression on day 4) with the anxiolytic CRF1 receptor antagonist antalarmin.
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Affiliation(s)
- Russ E Carpenter
- University Writing Program, University of California Davis, 1 Shields Ave, Davis, CA 95616, USA
| | - Boris Sabirzhanov
- Armed Forces Radiobiology Research Institute, 8901 Wisconsin Ave, Bethesda, MD 20889, USA
| | - Tangi R Summers
- Department of Biology, University of South Dakota, Vermillion, SD 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105, USA
| | - Timothy G Clark
- Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - Joyce Keifer
- Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA
| | - Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105, USA.
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Yaeger JDW, Krupp KT, Summers TR, Summers CH. Contextual generalization of social stress learning is modulated by orexin receptors in basolateral amygdala. Neuropharmacology 2022; 215:109168. [PMID: 35724928 PMCID: PMC9285878 DOI: 10.1016/j.neuropharm.2022.109168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/07/2022] [Accepted: 06/14/2022] [Indexed: 01/22/2023]
Abstract
Fear-associated memories and behavior are often expressed in contexts/environments distinctively different from those in which they are created. This generalization process contributes to psychological disorders, particularly PTSD. Stress-related neurocircuits in the basolateral amygdala (BLA) receive inputs from hypothalamic orexin (Orx) neurons, which mediate neuronal activity by targeting orexin 1 (Orx1R) and orexin 2 (Orx2R) receptors via opposing functions. In BLA, inhibition of Orx1R or activation of Orx2R ameliorate stress responsiveness and behavior. We discovered that most Orx1R+ cells also express CamKIIα, while a majority of Orx2R+ cells are colocalized with GAD67. Further, Orx1R gene Hcrtr1 expression was positively correlated, and Orx2R gene Hcrtr2 expression was negatively correlated, with freezing in a phenotype-dependent fashion (Escape vs Stay) in the Stress Alternatives Model (SAM). The SAM consists of 4-days of social interaction between test mice and novel larger aggressors. Exits positioned at opposite ends of the SAM oval arena provide opportunities to actively avoid aggression. By Day 2, mice commit to behavioral phenotypes: Escape or Stay. Pharmacologically manipulating Orx receptor activity in the BLA, before Day 3 of the SAM, was followed with standard tests of anxiety: Open Field (OF) and Elevated Plus Maze (EPM). In Stay mice, freezing in response to social conflict and locomotion during SAM interaction (not home cage locomotion) were generalized to OF, and blocked by intra-BLA Orx1R antagonism, but not Orx2R antagonism. Moreover, patterns of social avoidance for Escape and Stay mice were recapitulated in OF, with generalization mediated by Orx1R and Orx2R antagonism, plus Orx2R stimulation.
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Affiliation(s)
- Jazmine D W Yaeger
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA; Pediatrics and Rare Diseases Group, Sanford Research, Sioux Falls, SD, 57104, USA
| | - Kevin T Krupp
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA
| | - Tangi R Summers
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA
| | - Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA.
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Orexin 1 Receptor Antagonism in the Basolateral Amygdala Shifts the Balance From Pro- to Antistress Signaling and Behavior. Biol Psychiatry 2022; 91:841-852. [PMID: 35279280 PMCID: PMC9020795 DOI: 10.1016/j.biopsych.2021.12.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 12/18/2021] [Accepted: 12/29/2021] [Indexed: 01/03/2023]
Abstract
BACKGROUND Stress produces differential behavioral responses through select molecular modifications to specific neurocircuitry elements. The orexin (Orx) system targets key components of this neurocircuitry in the basolateral amygdala (BLA). METHODS We assessed the contribution of intra-BLA Orx1 receptors (Orx1Rs) in the expression of stress-induced phenotypes of mice. Using the Stress Alternatives Model, a social stress paradigm that produces two behavioral phenotypes, we characterized the role of intra-BLA Orx1R using acute pharmacological inhibition (SB-674042) and genetic knockdown (AAV-U6-Orx1R-shRNA) strategies. RESULTS In the BLA, we observed that Orx1R (Hcrtr1) messenger RNA is predominantly expressed in CamKIIα+ glutamatergic neurons and rarely in GABAergic (gamma-aminobutyric acidergic) cells. While there is a slight overlap in Hcrtr1 and Orx2 receptor (Hcrtr2) messenger RNA expression in the BLA, we find that these receptors are most often expressed in separate cells. Antagonism of intra-BLA Orx1R after phenotype formation shifted behavioral expression from stress-sensitive (Stay) to stress-resilient (Escape) responses, an effect that was mimicked by genetic knockdown. Acute inhibition of Orx1R in the BLA also reduced contextual and cued fear freezing responses in Stay animals. This phenotype-specific behavioral change was accompanied by biased molecular transcription favoring Hcrtr2 over Hcrtr1 and Mapk3 over Plcb1 cell signaling cascades and enhanced Bdnf messenger RNA. CONCLUSIONS Functional reorganization of intra-BLA gene expression is produced by antagonism of Orx1R, which promotes elevated Hcrtr2, greater Mapk3, and increased Bdnf expression. Together, these results provide evidence for a receptor-driven mechanism that balances pro- and antistress responses within the BLA.
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Korzan WJ, Summers CH. Evolution of stress responses refine mechanisms of social rank. Neurobiol Stress 2021; 14:100328. [PMID: 33997153 PMCID: PMC8105687 DOI: 10.1016/j.ynstr.2021.100328] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/07/2021] [Accepted: 04/09/2021] [Indexed: 02/08/2023] Open
Abstract
Social rank functions to facilitate coping responses to socially stressful situations and conditions. The evolution of social status appears to be inseparably connected to the evolution of stress. Stress, aggression, reward, and decision-making neurocircuitries overlap and interact to produce status-linked relationships, which are common among both male and female populations. Behavioral consequences stemming from social status and rank relationships are molded by aggressive interactions, which are inherently stressful. It seems likely that the balance of regulatory elements in pro- and anti-stress neurocircuitries results in rapid but brief stress responses that are advantageous to social dominance. These systems further produce, in coordination with reward and aggression circuitries, rapid adaptive responding during opportunities that arise to acquire food, mates, perch sites, territorial space, shelter and other resources. Rapid acquisition of resources and aggressive postures produces dominant individuals, who temporarily have distinct fitness advantages. For these reasons also, change in social status can occur rapidly. Social subordination results in slower and more chronic neural and endocrine reactions, a suite of unique defensive behaviors, and an increased propensity for anxious and depressive behavior and affect. These two behavioral phenotypes are but distinct ends of a spectrum, however, they may give us insights into the troubling mechanisms underlying the myriad of stress-related disorders to which they appear to be evolutionarily linked.
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Affiliation(s)
| | - Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD 57069 USA.,Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069, USA.,Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105 USA
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Pang TY, Yaeger JDW, Summers CH, Mitra R. Cardinal role of the environment in stress induced changes across life stages and generations. Neurosci Biobehav Rev 2021; 124:137-150. [PMID: 33549740 DOI: 10.1016/j.neubiorev.2021.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Revised: 11/20/2020] [Accepted: 01/08/2021] [Indexed: 12/21/2022]
Abstract
The stress response in rodents and humans is exquisitely dependent on the environmental context. The interactive element of the environment is typically studied by creating laboratory models of stress-induced plasticity manifested in behavior or the underlying neuroendocrine mediators of the behavior. Here, we discuss three representative sets of studies where the role of the environment in mediating stress sensitivity or stress resilience is considered across varying windows of time. Collectively, these studies testify that environmental variation at an earlier time point modifies the relationship between stressor and stress response at a later stage. The metaplastic effects of the environment on the stress response remain possible across various endpoints, including behavior, neuroendocrine regulation, region-specific neural plasticity, and regulation of receptors. The timescale of such variation spans adulthood, across stages of life history and generational boundaries. Thus, environmental variables are powerful determinants of the observed diversity in stress response. The predominant role of the environment suggests that it is possible to promote stress resilience through purposeful modification of the environment.
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Affiliation(s)
- Terence Y Pang
- Florey Institute of Neuroscience and Mental Health, Parkville, 3052, VIC, Australia; Department of Anatomy and Neuroscience, The University of Melbourne, 3010, VIC, Australia
| | - Jazmine D W Yaeger
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA
| | - Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA
| | - Rupshi Mitra
- School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
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Korzan WJ, Summers TR, Summers CH. Neural and endocrine responses to social stress differ during actual and virtual aggressive interactions or physiological sign stimuli. Behav Processes 2021; 182:104294. [PMID: 33290833 PMCID: PMC7872145 DOI: 10.1016/j.beproc.2020.104294] [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: 08/13/2020] [Revised: 10/05/2020] [Accepted: 12/01/2020] [Indexed: 12/19/2022]
Abstract
Neural and endocrine responses provide quantitative measures that can be used for discriminating behavioral output analyses. Experimental design differences often make it difficult to compare results with respect to the mechanisms producing behavioral actions. We hypothesize that comparisons of distinctive behavioral paradigms or modification of social signals can aid in teasing apart the subtle differences in animal responses to social stress. Eyespots are a unique sympathetically activated sign stimulus of the lizard Anolis carolinensis that influence aggression and social dominance. Eyespot formation along with measurements of central and plasma monoamines enable comparison of paired male aggressive interactions with those provoked by a mirror image. The results suggest that experiments employing artificial application of sign stimuli in dyadic interactions amplify behavioral, neural and endocrine responses, and foreshorten behavioral interactions compared to those that develop among pairs naturally. While the use of mirrors to induce aggressive behavior produces simulated interactions that appear normal, some behavioral, neural, and endocrine responses are amplified in these experiments as well. In contrast, mirror image interactions also limit the level of certain behavioral and neuroendocrine responses. As true social communication does not occur during interaction with mirror images, rank relationships can never be established. Multiple experimental approaches, such as combining naturalistic social interactions with virtual exchanges and/or manipulation of sign stimuli, can often provide added depth to understanding the motivation, context, and mechanisms that produce specific behaviors. The addition of endocrine and neural measurements helps identify the contributions of specific behavioral elements to the social processes proceeding.
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Affiliation(s)
| | - Tangi R Summers
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA
| | - Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD, 57069, USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD, 57069, USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD, 57105, USA.
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Alfonso S, Sadoul B, Gesto M, Joassard L, Chatain B, Geffroy B, Bégout ML. Coping styles in European sea bass: The link between boldness, stress response and neurogenesis. Physiol Behav 2019; 207:76-85. [PMID: 31047951 DOI: 10.1016/j.physbeh.2019.04.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 04/24/2019] [Accepted: 04/24/2019] [Indexed: 12/12/2022]
Abstract
Coping styles consist of a coherent set of individual physiological and behavioral differences in stress responses that are consistent across time and context. Such consistent inter-individual differences in behavior have already been shown in European sea bass (Dicentrarchus labrax), but the associated mechanisms are still poorly understood. Here, we combine physiological measurements with individual behavioral responses in order to characterize coping styles in fish. Fish were tagged and placed in a tank for group risk-taking tests (GRT) at 8 months of age to evaluate boldness using the proxy latency of leaving a sheltered area towards an open area. A subsample of these fish were individually challenged 16 months later using an open field test (OFT), in which the boldness was assessed after being placed in a shelter within an open arena. Latency to exit the shelter, time spent in the shelter, and distance travelled were recorded for this purpose. The blood and brain were then collected to evaluate plasma cortisol concentration and neurotransmitter levels (dopamine, norepinephrine, serotonin, and related metabolites), as well as brain transcription of key genes involved in stress axis regulation (gr1, gr2, mr, crf), neurogenesis (neurod1, neurod2, pcna), and neuronal development (egr1). Fish acting bolder in the GRT were not necessarily those acting bolder in the OFT, highlighting the relatively low consistency across different types of tests performed with a 16-months interval. There was, however, a significant correlation between stress markers and boldness. Indeed, mRNA levels of mr, crf, gr2, egr1, and neurod2, as well as norepinephrine levels were higher in shy than bold fish, whereas brain serotonergic activity was lower in shy fish. Overall, our study highlights the fact that boldness was not consistent over time when testing context differed (group vs. alone). This is in agreement with previous literature suggesting that social context play a key role in boldness measurement and that the particular life history of each individual may account in shaping the personality fate of a fish.
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Affiliation(s)
- Sébastien Alfonso
- MARBEC, Univ. Montpellier, CNRS, Ifremer, IRD, Palavas-les-flots, France; Laboratoire Ressources Halieutiques, Ifremer, Place Gaby Coll, F-17137 L'Houmeau, France.
| | - Bastien Sadoul
- MARBEC, Univ. Montpellier, CNRS, Ifremer, IRD, Palavas-les-flots, France
| | - Manuel Gesto
- Technical University of Denmark, Willemoesvej 2 Building Hovedbygning, D-9850 Hirtshals, Denmark
| | - Lucette Joassard
- Laboratoire Ressources Halieutiques, Ifremer, Place Gaby Coll, F-17137 L'Houmeau, France
| | - Béatrice Chatain
- MARBEC, Univ. Montpellier, CNRS, Ifremer, IRD, Palavas-les-flots, France
| | - Benjamin Geffroy
- MARBEC, Univ. Montpellier, CNRS, Ifremer, IRD, Palavas-les-flots, France
| | - Marie-Laure Bégout
- Laboratoire Ressources Halieutiques, Ifremer, Place Gaby Coll, F-17137 L'Houmeau, France
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Summers CH, Yaeger JDW, Staton CD, Arendt DH, Summers TR. Orexin/hypocretin receptor modulation of anxiolytic and antidepressive responses during social stress and decision-making: Potential for therapy. Brain Res 2018; 1731:146085. [PMID: 30590027 DOI: 10.1016/j.brainres.2018.12.036] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 12/15/2018] [Accepted: 12/21/2018] [Indexed: 12/12/2022]
Abstract
Hypothalmic orexin/hypocretin (Orx) neurons in the lateral and dorsomedial perifornical region (LH-DMH/PeF) innervate broadly throughout the brain, and receive similar inputs. This wide distribution, as well as two Orx peptides (OrxA and OrxB) and two Orx receptors (Orx1 and Orx2) allow for functionally related but distinctive behavioral outcomes, that include arousal, sleep-wake regulation, food seeking, metabolism, feeding, reward, addiction, and learning. These are all motivational functions, and tie the orexin systems to anxiety and depression as well. We present evidence, that for affective behavior, Orx1 and Orx2 receptors appear to have opposing functions. The majority of research on anxiety- and depression-related outcomes has focused on Orx1 receptors, which appear to have primarily anxiogenic and pro-depressive actions. Although there is significant research suggesting contrary findings, the primary potential for pharmacotherapies linked to the Orx1 receptor is via antagonists to block anxious and depressive behavior. Dual orexin receptor antagonists have been approved for treatment of sleep disorders, and are likely candidates for adaptation for affect disorder treatments. However, we present evidence here that demonstrates the Orx2 receptors are anxiolytic and antidepressive. Using a new experimental pre-clinical model of anxious and depressive behavior stimulated by social stress and decision-making that produces two stable behavioral phenotypes, Escape/Resilient and Stay/Susceptible, we tested the effects of intracerebroventricular injections of Orx2 agonist and antagonist drugs. Over ten behavioral measures, we have demonstrated that Orx2 agonists promote resilience, as well as anxiolytic and antidepressive behavior. In contrast, Orx2 antagonists or knockdown kindle anxious and pro-depressive behavior plus increase susceptibility. The results suggest that the Orx2 receptor may be a useful target for pharmacotherapies to treat anxiety and depression.
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Affiliation(s)
- Cliff H Summers
- Department of Biology, University of South Dakota, Vermillion, SD 57069 USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069 USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105 USA.
| | - Jazmine D W Yaeger
- Department of Biology, University of South Dakota, Vermillion, SD 57069 USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069 USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105 USA
| | - Clarissa D Staton
- Department of Biology, University of South Dakota, Vermillion, SD 57069 USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069 USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105 USA
| | - David H Arendt
- Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069 USA
| | - Tangi R Summers
- Department of Biology, University of South Dakota, Vermillion, SD 57069 USA; Neuroscience Group, Division of Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, SD 57069 USA; Veterans Affairs Research Service, Sioux Falls VA Health Care System, Sioux Falls, SD 57105 USA
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Orexin 2 receptor stimulation enhances resilience, while orexin 2 inhibition promotes susceptibility, to social stress, anxiety and depression. Neuropharmacology 2018; 143:79-94. [PMID: 30240784 DOI: 10.1016/j.neuropharm.2018.09.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Revised: 08/28/2018] [Accepted: 09/11/2018] [Indexed: 02/08/2023]
Abstract
Knockdown of orexin/hypocretin 2 receptor (Orx2) in the basolateral amygdala (BLA) affects anxious and depressive behavior. We use a new behavioral paradigm, the Stress Alternatives Model (SAM), designed to improve translational impact. The SAM induces social stress in adult male mice by aggression from larger mice, allowing for adaptive decision-making regarding escape. In this model, mice remain (Stay) in the oval SAM arena or escape from social aggression (Escape) via routes only large enough for the smaller mouse. We hypothesized intracerebroventricular (icv) stimulation of Orx2 receptors would be anxiolytic and antidepressive in SAM-related social behavior and the Social Interaction/Preference (SIP) test. Conversely, we predicted that icv antagonism of Orx2 receptors would promote anxious and depressive behavior in these same tests. Anxious behaviors such as freezing (both cued and conflict) and startle are exhibited more often in Stay compared with Escape phenotype mice. Time spent attentive to the escape route is more frequent in Escape mice. In Stay mice, stimulation of Orx2 receptors reduces fear conditioning, conflict freezing and startle, and promotes greater attention to the escape hole. This anxiolysis was accompanied by activation of a cluster of inhibitory neurons in the amygdala. A small percentage of those Stay mice also begin escaping; whereas Escape is reversed by the Orx2 antagonist. Escape mice were also Resilient, and Stay mice Susceptible to stress (SIP), with both conditions reversed by Orx2 antagonism or stimulation respectively. Together, these results suggest that the Orx2 receptor may be a useful potential target for anxiolytic or antidepressive therapeutics.
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Culbert BM, Gilmour KM, Balshine S. Stress axis regulation during social ascension in a group-living cichlid fish. Horm Behav 2018; 103:121-128. [PMID: 29932951 DOI: 10.1016/j.yhbeh.2018.06.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/17/2018] [Accepted: 06/15/2018] [Indexed: 01/15/2023]
Abstract
Animals living in groups often form social hierarchies, with characteristic behaviours and physiologies associated with rank. However, when social opportunities arise and a subordinate ascends into a dominant position, quick adjustments are necessary to secure this position. Such periods of social transition are typically associated with elevated glucocorticoid production, but the precise regulation of the stress axis during these occasions is not well understood. Using the group-living cichlid, Neolamprologus pulcher, the effects of social ascension on the stress axis were assessed. Ascenders rapidly filled experimentally created vacancies, adopting a dominant behavioural phenotype within 72 h-elevating aggression, activity, and workload, while receiving high rates of affiliative behaviours from their group members. Despite assuming behavioural dominance within their groups, ascenders displayed higher cortisol levels than dominants three days post-ascension. Additionally, compared to subordinates, ascenders had increased transcript abundance of steroidogenic acute regulatory protein (star) and cytochrome p450 side-chain cleavage enzyme (p450scc) in the head kidney, indicating activation of the stress axis. Cortisol levels were lowest in ascenders that displayed low rates of aggression, potentially reflecting the reestablishment of social stability in these groups. Increased transcript abundance of both glucocorticoid receptors (gr1 and gr2) in the brain's preoptic area (POA) of ascenders compared to dominants suggested an enhanced capacity for cortisol regulation via negative feedback. Our results reveal a regulatory cascade of behavioural and physiological interactions and highlight the importance of investigating the underlying mechanisms regulating the stress axis.
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Affiliation(s)
- Brett M Culbert
- Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main St W, Hamilton, Ontario L8S 4K1, Canada.
| | - Kathleen M Gilmour
- Department of Biology, University of Ottawa, 20 Marie Curie Private, Ottawa, Ontario K1N 6N5, Canada
| | - Sigal Balshine
- Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main St W, Hamilton, Ontario L8S 4K1, Canada
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Al-Naimi OAS, Delvalle JR, Carryl SS, Rodriguez NA, Aliou F, Cambi M, Bamshad M. Socio-Ecological Disruptions at Critical Periods During Development Alter Stress Responses and Hippocampal Dendritic Morphology of Prairie Voles: Implications for Social Monogamy. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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