Name: Assessment of Post-Chronic Social Defeat Treatment in Mice: Social Threat-Safety Test, Scoring, and Analysis
Uploaded: 2023-12-15T13:20:00
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assessment of post-chronic social defeat treatment in mice: social threat-safety test, scoring, and analysis

Test di sicurezza delle minacce per la suscettibilità o la resilienza allo stress nei modelli murini

Stress is defined as the disruption of homeostasis caused by physical or psychological stimuli1. Stress is a well-known major risk factor for the development of mental disorders such as post-traumatic stress disorder, depression, and anxiety2,3. In particular, social stress is considered a major risk factor for the development of stress-related mental disorders4. One type of social stress that has gained particular importance in research is social subordination stress5. Mice, like humans, are capable of a rich set of social behavior6, rendering them suitable for investigations involving social stress. In the laboratory setting, when adult mice are group housed, they establish a social structure involving the formation of ranks7. Accordingly, the colony model was designed to study the effects of naturally established social hierarchies in mixed-sex groups of mice8. Over the years, variations of the colony model have been developed to utilize social subordination stress, including same-sex group models, the social instability model, and the intruder-colony model. In recent years, however, one particular variant known as the male resident-intruder model has been popularized in literature, simplifying the social complexity to two mice: a resident and an intruder. The animal of interest, known as the intruder, is placed into the cage of a larger, older, and retired breeder, known as the resident or aggressor. The resident then physically attacks the intruder as a method of confrontation, establishing a social hierarchy wherein the resident is dominant and the intruder is subordinate. When confrontations are one-time events, they classify as &#34;acute&#34; (the &#34;acute social defeat model&#34;), whereas repeated confrontations lasting over several days (usually 10) are known as &#34;chronic&#34; (the &#34;chronic social defeat model&#34;). In the chronic social defeat (CSD) model, attacks are intermittent and typically confined to a period of 5-10 min9, termed the physical phase. Following the physical phase, the intruder and resident are kept overnight in the same cage, separated in half with a mesh wall, allowing for all forms of interaction except physical contact. This configuration, known as the sensory phase, induces stress through the continuous appearance of threat instead of direct physical confrontation. In 2018, van der Kooji and colleagues introduced a modified chronic social defeat treatment to focus on the psychosocial component of the model by standardizing and strictly limiting the physical phase10. The modified model limits physical attacks to three 10 s episodes with different residents, occurring in 15 min inter-episode intervals of the sensory phase. Following the third physical episode, the sensory phase lasts overnight. This cycle repeats for 10 consecutive days with new residents per episode. The modified treatment enhances the translational validity of the chronic social defeat model as physical harm of the intruder is minimized, and outcome variability from differential durations of physical attacks is reduced.
Since the CSD model is utilized to study stress-related illness (e.g., depression, anxiety, post-traumatic stress disorder), post-behavioral assays are chosen, including, but not limited to, behavioral assays of aggression, memory, and anhedonia. In recent years, post-CSD behavioral assays in mice often evaluate how and to what extent sociability is affected9. Sociability is defined as the innate preference of mice to socially interact rather than socially avoid a conspecific. Since sociability is subject to stress effects, assays that solely assess social avoidance development were established. Stress-induced social avoidance has a translational relevance as it represents one of the main behavioral symptoms of social anxiety and depression in humans11. Similar to humans, not all mice develop social avoidance following CSD treatment, suggesting the presence of individuality in stress responsiveness. Cohen and colleagues have proposed cut-off behavioral criteria to be a promising approach for studying the neurobiology of individuality12. Selection of animals based on behavior results in group division, underlining the basis for gene-environment studies. Subsequently, different subgroups often show distinct enrichment of specific genetic variants/modifications, which in turn can be investigated under different environmental conditions13. Accordingly, individuality in the development of social avoidance was utilized to divide the single group of chronically socially defeated male mice into two subgroups: stress susceptible (socially avoidant) and stress resilient (socially non-avoidant9,14). However, the interpretation of the social avoidance phenotype in mice as a maladaptive or adaptive behavior should be considered in the overall context of both the treatment (here CSD) and post-treatment behavioral assay. Additionally, the post-treatment behavioral assay of choice would ideally assess other facets of sociability and not solely social avoidance development. Our recent work revealed the involvement of conditioned learning in CSD-induced social avoidance15. Specifically, CSD-induced social avoidance is an aversive conditioned response towards the characterizing traits of the residents&#39; strain serving as the conditioned stimulus to the unconditioned stimulus, namely the attacks by the residents. Moreover, within the socially avoidant subgroup, some individuals can discriminate between the traits of the aversive residents&#39; strain and those of other safe novel strains, while other individuals show generalized social avoidance to both strains. We propose here a refined behavioral post-CSD assay: the Social Threat-Safety Test (STST)15. Unlike other social interaction tests9, the STST enables a simultaneous assessment of social avoidance development as a measurement of the correct aversive conditioned response (i.e., successful conditioned learning) and social threat-safety discrimination ability, both of which are utilized to identify stress-susceptible and stress-resilient individuals within a single group of chronically socially defeated male mice. The assessment of social threat-safety discrimination versus aversive response generalization extends the translational criteria used to classify the single group of chronically socially defeated animals into resilient and susceptible subgroups.

Autore in primo piano: Svelare i meccanismi di resilienza allo stress - Risultati significativi, progressi e ricerche future

Il test di sicurezza contro le minacce sociali scopre i fenotipi legati allo stress psicosociale

Our research seeks to uncover the underlying mechanisms of stress resilience. By understanding those mechanisms, we can employ them to develop better treatment strategies for stress related mental disorders and prevention. Our research has developed a new mouse model with high face validity that allows stratifying a single group of stressed mice into resilience and susceptibility associated phenotypes that are based on the fear circuitry.Also, we provide evidence for the presence of global resilience mechanisms. Our study on stressed mice revealed that they exhibited characteristics that are indicative of both resilience and susceptibility in humans. Specifically, they show different abilities in threat safety discrimination and responsiveness to extinction, which are key features associated with resilience.The resilience and susceptibility associated phenotypes that we identified in mice have face validity and are based on the fear circuitry. This circuitry is highly conserved across species and is arguably one of the best studied circuits. In turn, this allows mechanistic investigations that have the potential to contribute to treatment, development and prevention measures.We'll use our new model to dig deeper into neurobiological mechanisms of resilience and understand how we can actively promote resilience. In addition, we will employ longitudinal analysis to decifer how individual resilience develops over time.

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Assessment of Post-Chronic Social Defeat Treatment in Mice: Social Threat-Safety Test, Scoring, and Analysis  

Valutazione del trattamento post-cronico della sconfitta sociale nei topi: test di sicurezza della minaccia sociale, punteggio e analisi

Iniziare trasferendo tutti i topi cronici, socialmente sconfitti o trattati con CSD e di controllo in nuove gabbie, rispecchiando le condizioni in cui sono arrivati per la prima volta e lasciandoli riposare durante la notte. La mattina seguente, sanificare l'arena a tre camere utilizzando una soluzione di etanolo al 5% e posizionarla sotto la telecamera, garantendo una condizione di luce di 37 lux e la piena visibilità dell'intera arena. Allo stesso modo, pulire gli involucri a rete con etanolo al 5% e posizionarli negli angoli designati.Definire una zona di interazione di due centimetri attorno ai contorni degli involucri mesh. Per la fase di assuefazione, porta l'animale in questione al centro dell'arena e consenti un'esplorazione di sei minuti prima di riportarlo nella sua gabbia di casa. Assegna un punteggio alla durata dell'esplorazione dell'animale, in particolare quando il naso dell'animale si trova all'interno della zona di interazione.Successivamente, posizionare il bersaglio sociale CD-1 nel nuovo bersaglio sociale 129/Sv sotto recinzioni a rete separate. Per iniziare la fase di test, riposizionare immediatamente l'animale in questione al centro dell'arena e consentire l'esplorazione per un periodo di sei minuti. Prendi nota della durata dell'interazione dell'animale con gli obiettivi sociali.Ancora una volta, concentrandosi sull'intervallo quando il naso dell'animale si trova all'interno della zona di interazione. Successivamente, riporta tutti gli animali nel loro habitat individuale. Assicurati di pulire l'arena e i recinti a rete con una soluzione di etanolo al 5% dopo aver valutato ogni animale.Scambia la posizione delle chiusure della rete tra animali diversi per bilanciare qualsiasi potenziale distorsione della posizione. Calcola l'indice di interazione sociale come mostrato. Sulla base dell'indice di interazione sociale, dividi i topi in non evitatori, evitatori indiscriminati e evitatori discriminanti.È stata osservata una differenza significativa nell'indice di interazione sociale con il target sociale CD-1 tra i due gruppi. I sottogruppi degli evitatori discriminanti e degli evitatori indiscriminati avevano un indice di interazione sociale inferiore a 1 con il target sociale CD-1. Riflettendo lo sviluppo dell'evitamento sociale verso lo stimolo delle condizioni, il sottogruppo dei non evitanti aveva un indice di interazione sociale maggiore o equivalente a 1 con lo stesso obiettivo sociale, riflettendo l'apprendimento condizionato avversivo alterato con tale obiettivo.Il sottogruppo degli evitatori discriminanti ha mostrato livelli di socievolezza intatti nei confronti di uno stimolo sicuro o neutro, mentre il sottogruppo degli evitatori indiscriminati ha mostrato una generalizzazione della risposta avversa. L'assenza di bias preferenziali sociali si è riflessa in indici di interazione sociale superiori o equivalenti a 1, con entrambi gli obiettivi sociali all'interno del gruppo di controllo.

assessment-post-chronic-social-defeat-treatment-mice-social-threat

Research

JoVE Journal

Behavior

Assessment of Post-Chronic Social Defeat Treatment in Mice: Social Threat-Safety Test, Scoring, and Analysis

Social Threat-Safety Test Uncovers Psychosocial Stress-Related Phenotypes

Social stress is a major cause of the development of mental disorders. To enhance the translational value of preclinical studies, social stress experience and its behavioral impact on mice should be comparable to humans. Chronic social defeat (CSD) utilizes a type of social stress involving physical attacks and sensory threats to induce mental dysfunctions resembling human affective disorders. To strengthen the psychosocial component of CSD, a 10-day CSD protocol was applied in which daily physical attacks are standardized to three 10 s episodes followed by a 24 h sensory phase. After the 10th sensory phase, the CSD protocol is followed by a refined behavioral assay called the social threat-safety test (STST). Post-stress behavioral assays need to determine how and to what extent the social stressor has influenced behavior. The STST allows chronically socially defeated male mice to interact with 2 novel male individuals (social targets): one social target from the attacking strain encountered during the CSD days and the other from a novel strain. Both are presented simultaneously in different compartments of a three-chambered test arena. The test enables a simultaneous assessment of social avoidance development to measure successful aversive conditioned learning and social threat-safety discrimination ability. The development of social avoidance towards both strains reflects a generalized aversive response and thus, a measurement of stress susceptibility. Meanwhile, the development of social avoidance towards only the attacking strain reflects threat-safety discrimination and thus, a measurement of stress resilience. Finally, the absence of social avoidance towards the attacking strain reflects impaired aversive conditioned learning. The protocol aims to refine the currently used mouse models of stress susceptibility/resilience by including translational criteria, specifically threat-safety discrimination and aversive response generalization, to categorize a single group of chronically socially defeated animals into resilient and susceptible subgroups, eventually advancing future translational approaches.

The social threat-safety test allows a simultaneous assessment of social avoidance development as a measurement of aversive conditioned learning and social threat-safety discrimination ability, both utilized to identify stress-susceptible and stress-resilient individuals within a single group of chronically socially defeated male mice.

Social stress is a major cause of the development of mental disorders. To enhance the translational value of preclinical studies, social stress experience ...

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Comportamento

Begin by relocating all chronic, socially defeated or CSD-treated and control mice into new cages, mirroring the conditions they first arrived in and letting them rest overnight. The following morning, sanitize the three-chambered arena using a 5%ethanol solution and set it up beneath the camera, ensuring a light condition of 37 lux and full visibility of the entire arena. Similarly, clean the mesh enclosures with 5%ethanol and position them in the designated corners.Define a two centimeter interaction zone around the boundaries of the mesh enclosures. For the habituation phase, bring the subject animal into the middle of the arena and allow for a six minute exploration before returning it to its home cage. Score the duration spent by the animal exploring specifically when the animal's nose is inside the interaction zone.Next, place the CD-1 social target in the novel 129/Sv social target under separate mesh enclosures. To initiate the testing phase, immediately place the subject animal back at the center of the arena, and permit exploration for a period of six minutes. Note the duration the animal interacts with the social targets.Again, focusing on the span when the animal's nose is within the interaction zone. Afterward, return all the animals to their individual habitat. Ensure to clean the arena and mesh enclosures with 5%ethanol solution after assessing each animal.Switch the position of the mesh en closures between different animals to balance any potential location bias. Calculate the social interaction index as shown. Based on the social interaction index, divide the mice into the non-avoiders, the indiscriminate-avoiders, and the discriminating-avoiders.A significant difference in the social interaction index with the CD-1 social target between both groups was observed. The discriminating-avoiders and indiscriminate-avoiders subgroups had a social interaction index of less than 1 with the CD-1 social target. Reflecting social avoidance development towards the conditions stimulus, the non-avoiders subgroup had a social interaction index more than or equivalent to 1 with the same social target, reflecting impaired aversive conditioned learning with that target.The discriminating-avoiders subgroup showed intact sociability levels towards a safe or neutral stimulus, while the indiscriminate-avoiders subgroup showed aversive response generalization. The absence of social preferential bias was reflected in social interaction indices of more than or equivalent to 1, with both social targets within the control group.