Effect of Acute Stress on Social Behavior

Effect of acute stress on social behavior: a three chambered approach

Abstract:

Introduction: Social interaction plays a pivotal role in mental well being of an individual. Despite its critical importance in our lives, our understanding of the neurological control of social behaviour is limited. The neurobiology of stress and social behavior are deeply intertwined. The social environment interacts with stress on almost every front: social interactions can buffer the response to an external stressor; and social behavior often changes in response to stressful life experience. Herein we explored the alterations caused by stress in social behavior of mice, with particular attention to different social contexts.

Aims & Objectives: Objective of this study was to assess the various neurobehavioral changes in mice after exposure to acute restraint stress. We assessed the alterations in a) sociability and preference for social novelty (social interaction); and b) social affiliation and preference for opposite sex.

Material and Methods: Animals (Balb/C mice) were divided into two groups viz Group I-control and Group II –stress with 12 animals (6 males/6 females) each. The restraint stress group mice were placed in specially constructed restraint meshes for 1 hour in the morning and then subjected to social behavior analysis by using crawley’s three chambered apparatus.

Results: We report that acute stress causes significant impairment in the social behavior, with pronounced changes in preference for sociability, social novelty and social affiliation (between same and opposite sex). In a nutshell, there is an increase in sociability and a significant decrease in social novelty profile. Additionally opposite sex preferences also show marked changes following acute stress.

Conclusion: Restraint stress produces an inescapable physical and mental stress which significantly impairs social behavior, social affiliation and social interaction.

Key Words: Acute stress, social behavior, social interaction, opposite-sex social behavior, social affiliation, three chambered apparatus.

1. Introduction

Like humans social world of animals is filled with diverse types of interactions and this social experience interacts with organismal stress on various levels. Use of rodent models has improved our understanding of the role of stressor type, timing, and other factors impacting physiology and behavior. Social interactions can act as stress absorbers, thereby buffering potentially adverse impacts on behavior.

In humans, stressful situations can promote affiliative behavior [1-3] and anticipation of stressful events can promote group cohesion and liking for group members [4, 5]. However, and in some cases, social behavior is reduced after a stressor; in fact social withdrawal is one of the diagnostic criteria for post-traumatic stress disorder (DSM V) [6]. While effects of stress on social behavior are evident in humans, most of our understanding of these impacts, their underlying molecular and cellular mechanisms, comes from rodent studies (mostly prairie voles). In rodents, several stressors and manipulations of the hypothalamic pituitary adrenal (HPA) hormonal axis have been shown to impact a variety of subsequent social behaviors. For instance, stress has marked contrasting effect on opposite sex preference in prairie voles. In males, stressful experiences mildly enhance the ability to form partner preferences while it’s the opposite in females [7]. In rats also stress impacts opposite-sex social behavior. In particular, stress has been shown to inhibit mating behavior in males and in naturally cycling females, via elevation of the inhibitory hypothalamic hormone RF-amide related peptide 1 [8, 9].

Not much data is available as to whether or not stress impairs same-sex social interaction. In an unpublished data same-sex social interaction behavior in prairie voles was enhanced following a stressor (unpublished data referenced in [10]). Stress exposure prior to pairing impairs preference formation for a same-sex individual in female prairie voles [11]. In addition, familiarity of the conspecific prior to the stressor may influence whether social behavior is increased or decreased. In male rats, social defeat stress lead to social avoidance measured by reduced time spent in social contact with an unfamiliar non-aggressive rat [12] and avoidance of the dominant rat [13]. Non-social stressors may have the opposite effect, for example, in groups of familiar male rats, rats spend more time huddling in large groups during an immediate stressor [14, 15]. To unfold this mystery (solve this puzzle) our study aimed at assessing the social interaction behavior after acute stress in mice.

We consider two main classes of effects: the effect of acute stress on social interaction (sociability and preference for social novelty) and the effect of stress on subsequent social affiliation (preferences for same and opposite sex) (Fig. 1).

2. Materials and Methods:

Materials: Stop watch, 20 % ethanol, tissue papers, three chambered apparatus, restrainer, steel wire meshed pencil cups, water.

Animals: Male and female Balb/C mice were purchased 5 weeks postpartum from National Institute of Pharmaceutical Education and Research (NIPER), Mohali and housed under 12-h light/12-h dark (LD) cycles over 2 weeks. Males and females were caged separately. All protocols using animals in this study were approved by the IAEC.

Acute Restraint Stress: Mice were restrained for 1 h in a 31-mm, inner diameter, × 85-mm acryl tube and then subjected to social behavior analysis [16].

Crawley’s three-chambered social approach task

Social approach was tested in an three-chambered apparatus using methods previously described with slight modification [17]. The apparatus (60cm × 23cm × 23cm (h)) was a rectangular, three-chambered box made from matte white finish acrylic. Opaque retractable doors (12cm × 33cm) were designed to create optimum entryways and encourage exploration across chamber openings (5cm × 10cm). The test requires use of same sex animals but in addition we used opposite sex mice to study male female interactions. Subjects in home cage were placed in testing room 1hr before behavioral analysis for habituation and to minimize effects of stress on behavior. Testing procedures comprised of three following phases:

A) Habituation: Doors to side chambers were closed and animal was placed in the center chamber. After 10min of habituation subject was guided back to center chamber, and doors were closed. Urine was soaked up, fecal pellets were removed, and side chambers were cleaned with water.

B) Sociability: One steel pencil cup was added to each side chamber. Object mouse #1 was placed under cup in left chamber and novel object was placed under cup in right chamber. Plastic cups were placed on top of steel pencil cups to prevent subject from climbing on top. After 10min Sociability trial, subject was guided back to center chamber, and doors were closed. Cups were removed for cleaning and object mouse #1 was returned to home cage. Urine was soaked up, fecal pellets were removed, and side chambers were cleaned with water.

C) Social Novelty: New steel cups were added, one to each side chamber. Object mouse #1 was placed under cup in right chamber and object mouse #2 was placed under cup in left chamber. Same plastic cups were placed on top of steel cups to prevent subject from climbing on top. After 10min Social Novelty trial, subject was guided back to center chamber, and doors were closed. Subject was returned to home cage, cups were removed for cleaning, and the object mouse was returned to home cage. All cups and chambers were cleaned with 20% ethanol between subjects.

Behavioral analysis: The test in overall comprised of three animals viz subject, object and the novel. We used different set of combinations using sex (male/female) and condition (stressed/non-stressed) as variables to analyse the behavioral pattern of control and stressed mice. Time spent in each chamber was recorded manually using an observation chart.

Statistical Analysis: Statistical Analysis Values were represented as mean ± SEM. Data was analyzed using one-way analysis of variance (ANOVA) and group means were compared by performing Dunnett’s multiple comparison test using GraphPad prism v5.03 software (GraphPad Software, Inc.). P < 0.05 was considered significant.

3. Results:

1. Altered Social interaction behavior (Fig-2): In case of social interaction behavior (involving mice with same sex), after exposure to stress we observed a slight increase in sociability of mice indicated by increased time spent with object animal as compared to control. This is a clear indication of stressed mice will to be with a conspecific rather than a novel object, which means stress exposure increases bonding and group affiliation. In the second half of the experiment, we observed an inversion in the behavior for preference for social novelty. Stressed mice spent a significantly higher time with the familiar mice than the novel mice as compared to controls. This indicated that the natural tendency of mice to explore novel situations is notably reduced after stress exposure.
2. Altered opposite sex affiliation (Fig-3): One of the highlight of this study was that the stress caused a significant change in opposite sex behavior. Normal mice have a higher tendency to bond with opposite sex conspecific than of the same sex. While in this case, stress exposure led to an increased affiliation for same sex conspecific than opposite sex conspecific.

4. Acknowledgement: The authors would like to acknowledge Jaypee University of Information Technology, Waknaghat.

5. Conclusions

Social interactions can ameliorate the impact of stress on social behavior and vice-versa. Molecular and morphological signatures are not the only aftermath of a neurological disorder. In addition a disturbed social life is also a major setback. In this study we observed that acute stress leads to significant alterations in social behavior. While it increased bonding and affiliation as seen by increased sociability, it reduced the preferences for social novelty. These effects may happen all together or at different times, and vary with individual genetic background, experience, sex, species, and other factors. While it is not feasible to study all such factors in a single study, we tried to study how stress reflects in social behavior between same and opposite sex. In this study we studied the interaction time which is a longstanding measure of social behavior in understanding preferences for familiar versus novel individuals.

This study is one small step in the direction of a more of social behavior oriented view of a neurological or in that case any disorder. Our next step is be to study the effect of chronic stress and depression on social behavior and whether or not drug treatment corrects the behavioral abnormalities than just molecular ones.

Figures

Figure 1: Work plan for studying the effect of acute stress on social behavior.

Figure 2: Left- Sociability profile of control and stressed mice. There is a slight increase in sociability in stressed mice as compared to that of control. Right- Social novelty profile of control and stressed mice. There is a significant reduction in social novelty in stressed mice indicating a reduced preference for exploring new conspecifics as compared to control.

Figure 3: Left- Stressed mice show a significant increase in the time spent with a cagemate compared to control indicating increased social bonding. Additionally stressed mice show a highly reduced preference for opposite sex. Right- Stressed mice show a reduced preference for novel mice (opposite sex) and an increased preference for the familiar one (opposite sex) indicating reduced preference for social novelty as compared to control mice.