Do social play deprived rats have a different responsivity to stress? The importance of social play behaviour for stress resilience

Abstract

Social play behaviour is a healthy form of interaction during the early phases of life of humans and most non-human mammals. Social play is thought to be important for the regulation of stress responses and appropriate behavioural responses to changing social situations in adulthood. In this study, the effects of social play deprivation on behaviour andstress responsivity were investigated. Two stress tests were performed, in which the corticosterone response to stressful stimuli has been determined in social play deprived (SPD) rats and was compared to control rats that were not isolated during early development.

There was no significant difference in the responsivity to stress between SPD rats and control rats. However, the increase of the plasma corticosterone level between baseline and at 15 minutes after exposure to social stress was found to be moderately positively correlated with a few behavioural acts for the SPD group, including the total freezing time and the total amount of submissive posture, but not for the control group. A positive correlation was also found between the amount of clinch attacks and the total freezing time of the SPD group, though this correlation was not significant for the control group. This may indicate that social play deprivation causes a higher sensitivity of the hypothalamic-pituitary-adrenocortical (HPA) axis. Furthermore, there were significant differences among the various time points of the corticosterone response in both stress tests. There was also a statistically significant interaction between the effects of the experiment day on plasma corticosterone levels after exposure to a novel environment. This demonstrates the dynamics of the corticosterone response and suggests a sensitivity of corticosterone to stressors and environmental factors.