Social Defeat Stress Model for Adolescent C57BL/6 Male and Female Mice
March 15th, 2024
We developed an accelerated social defeat stress model for adolescent C57BL/6 mice, which works in both males and females and allows exposure during discrete adolescent periods. Exposure to this model induces social avoidance, but only in a subset of defeated male and female mice.
We investigate the impact of adolescent social adversity on neurodevelopment and behavioral outcomes, specifically focusing on male and female C57BL/6 mice. We model social distress using an adapted version of the chronic social defeat paradigm. Our model, called accelerated social defeat stress, is tailored for its use in adolescent C57BL/6 mice.
The social defeat stress protocol requires aggressive behavior from the resilient mouse. Existing studies are often conducted in the mid-adolescent period or lack a specificity in terms of postnatal day of exposure. Some studies extend into early adulthood or employ strains of mice that are not commonly used.
Implementing the social defeat model in adolescent C57BL/6 mice has been challenging because adult or adolescent mice do not typically attack early adolescent male or female mice and adolescence is a short period of life that encompasses discrete temporal windows of vulnerability. The AcSD model successfully induces social avoidance 24 hours later in both males and females. It is short enough to allow exposure during discrete periods within adolescence.
It allows the segregation of resilient and susceptible mice and is the first model available to study social defeat stress in adolescent C57BL/6 female mice. Our model was generated to be used in adolescent male and female C57BL/6 mice. This four day stress paradigm, with two physical attack sessions per day, uses an adult C57BL/6 male mouse to prime the CD-1 mouse for aggressiveness, ensuring that the CD-1 mouse readily attacks the experimental male or female mouse.
To begin, introduce an adolescent C57BL/6 mouse into the same cage as primed CD-1 mouse. When the CD-1 mouse bites or places its teeth on any part of the adolescent mouse's body, register it as an attack. When the C57BL/6 mouse moves both of its hind paws away from the position they were in initially, it is considered moving away.
Separate the animals with a plastic ruler if the CD-1 mouse bites more than once in succession. Similarly, separate the animals if the CD-1 mouse bites and does not let go, or if the C57BL/6 mouse is trapped in a corner or pinned down by the CD-1 mouse and cannot move away. To screen and prime the CD-1 mice, put on a pair of nitrile examination gloves.
On the first day, introduce an adult male C57BL/6 postnatal day 65 or older mouse as an intruder into the cage of the CD-1 mice for three minutes. Register the latency to the first aggression and how many aggressions are performed. From the second to the last day of screening and priming, introduce an adult male C57BL/6 postnatal day 65 or older for one minute, and then swap it with an adolescent C57BL/6 postnatal day 25 mouse for five minutes.
If the priming is for aggressiveness towards female C57BL/6 mice, perform the screening and priming with adolescent female mice. Register the latency to the first aggression, the number of attacks, and the wounds received by all the C57BL/6 mice. If the CD-1 mouse does not approach the adolescent C57BL/6 mice for two days during the screening or priming, do not include the CD-1 mouse.
To begin, use acrylic glass dividers to separate rack cages into two compartments. Add hard wood chip bedding to both sides of the cage, then place a cotton square on each side. Secure the wire top with binder clips.
Then place the cover lid without the protective cotton over the cage. Place the CD-1 mouse on one side of the divider. Label the cage with a tag placed outside it for easy identification of each mouse.
For the defeat sessions, make a schedule of two sessions per day for four days with a different aggressor for each session. Weigh a C57BL/6 adolescent mouse. Next, introduce a male C57BL/6 postnatal day 65 or older mouse for 30 seconds into the CD-1 side of the defeat cage.
Swap it with an adolescent C57BL/6 postnatal day 24 to 28 mouse for a 10 minute long defeat episode or until 10 attacks occur. Register the latency to the first aggression, the number of attacks, and the wounds received by all the C57BL/6 mice. Separate the animals after each attack with a plastic ruler.
After every session of defeat, check for injuries and treat them with pain relief cream. Register the number of injuries. Place the defeated adolescent C57BL/6 mouse in the free compartment next to its aggressor and leave it there until the next session.
Start a new session with the experimental and aggressor mice that were not paired in the previous session. Monitor the injuries of the adult C57BL/6 male mice used for priming. For the control mice, place two control mice per cage, one on each side of the cage.
House them in the social defeat apparatus in a separate room from the social defeat mice. For every session occurring in the defeat group, rotate the mice in the control group such that each experimental mouse is introduced in the cage of an unfamiliar C57BL/6 mouse. The CD-1 mice attacked the C57BL/6 mice in a consistent manner across multiple cohorts.
Adolescent males received more attacks with primed CD-1 mice during accelerated social defeat than adolescent males exposed to a chronic social defeat protocol. The primed CD-1 mice presented aggressive attacks towards the adolescent C57BL/6 male and female mice. No interaction was found between day and cohort across experiments.
When comparing the number of attacks received by resilient and susceptible mice undergoing accelerated social defeat, no difference is found if experiments are run in males or females.
Overview
This study presents a novel accelerated social defeat stress model designed for adolescent C57BL/6 mice, addressing the impact of social adversity on neurodevelopment and behavior. The model allows for standardized exposure during specific adolescent periods and successfully induces social avoidance in a subset of both male and female mice.
Key Study Components
Area of Science
- Neuroscience
- Behavioral Biology
- Animal Models
Background
- Existing social defeat stress models are often limited in their temporal specificity.
- Adolescence is a critical developmental period fraught with vulnerabilities.
- Prior models have predominantly focused on adult mice or have not effectively measured adolescent responses.
- There is a need for models that include both male and female subjects.
Purpose of Study
- To develop a social defeat model that can be used in adolescent C57BL/6 mice.
- To ascertain the effects of social adversity on behavior and neurodevelopment in both sexes.
- To facilitate the separation of resilient and susceptible responses to stress in adolescent mice.
Methods Used
- The accelerated social defeat stress model involves exposure to aggressive CD-1 mice.
- C57BL/6 mice were subjected to two attack sessions per day over four days.
- Social avoidance was assessed 24 hours post-exposure.
- Injuries and aggression levels were meticulously recorded throughout the study.
- Control mice were housed separately to account for environmental factors.
Main Results
- Adolescent C57BL/6 mice demonstrated significant social avoidance after exposure to the stress model.
- The model effectively distinguished between resilient and susceptible mice responses.
- No differences in aggression responses were observed across sexes in this experimental setup.
Conclusions
- This study establishes an innovative model to investigate social stress effects in adolescent mice.
- The findings enable deeper insights into behavioral changes resulting from adolescent social adversity.
- This model can inform future research on stress-related neurodevelopmental processes.
Frequently Asked Questions
Executive Industry Relevance
Modeling adolescent social adversity in C57BL/6 mice enables biopharma teams to interrogate neurodevelopmental mechanisms underlying stress susceptibility and resilience. The accelerated social defeat stress (AcSD) paradigm provides a standardized, temporally precise system for evaluating behavioral outcomes relevant to psychiatric and neurodevelopmental disorder pipelines. This model supports translational continuity by enabling sex-inclusive, age-specific target validation and mechanistic de-risking in early discovery.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Enables mechanistic interrogation of stress-induced behavioral phenotypes in adolescent brain development.
- Supports functional target validation by distinguishing resilient versus susceptible phenotypes post-stress exposure.
- Facilitates predictive confidence in neuropsychiatric target selection by modeling discrete adolescent vulnerability windows.
Screening & Assay Development
- Provides a validated behavioral assay for quantifying social avoidance as a stress response endpoint.
- Standardizes exposure and readout timing, supporting reproducibility and cross-cohort comparability.
- Enables scalable screening of genetic or pharmacological modifiers of stress susceptibility in both sexes.
Translational & Preclinical Research
- Aligns preclinical behavioral endpoints with human-relevant adolescent stress exposures.
- Supports risk-adjusted advancement of neurodevelopmental disorder models by enabling sex- and age-specific analyses.
- Facilitates continuity from early discovery through preclinical validation of stress-related behavioral biomarkers.
Pipeline & Workflow Integration
The AcSD model integrates into the discovery-to-preclinical continuum by enabling hypothesis-driven testing of stress mechanisms, target validation, and behavioral biomarker development in adolescent mice.
- Discovery Biology: Supports hypothesis testing on neurodevelopmental stress pathways and resilience mechanisms.
- Screening: Delivers reproducible, quantitative social avoidance readouts for compound or genetic screening.
- Analytics: Provides standardized behavioral metrics for cross-condition and cross-cohort statistical analysis.
- Translational Research: Bridges adolescent stress exposure models to preclinical biomarker and endpoint validation.
- Enterprise Reuse: Offers a reusable, sex-inclusive platform for diverse neuropsychiatric R&D programs.
Operational & Enterprise Impact
- Scientific Value: Increases predictive confidence in adolescent stress target validation and mechanistic de-risking.
- Operational Value: Enhances reproducibility, standardization, and scalability of behavioral stress assays.
- Strategic Value: Improves go/no-go decisions for neurodevelopmental disorder portfolios by enabling early risk assessment.
- Portfolio Impact: Supports risk-adjusted prioritization of targets and models for adolescent neuropsychiatric indications.
Implementation Considerations
- Requires expertise in behavioral neuroscience and adolescent rodent handling.
- Needs specialized housing, aggression screening, and injury monitoring infrastructure.
- Demands rigorous cross-team standardization of defeat protocols and behavioral scoring.
- Adaptation across mouse strains or developmental windows may require protocol optimization.
- Short adolescent window and aggression priming steps are practical limitations for throughput.
