Wilkin, M. M., Menard, J. L. 2020. Social housing ameliorates the enduring effects of intermittent physical stress during mid-adolescence. Physiology & Behavior 214, 112750.

Our prior work showed that exposing single housed rats to intermittent physical stress (IPS) in mid-adolescence (PD35-46) led to increased risk-taking/decreased anxiety behaviour in adulthood, as indexed by their greater willingness to explore the open-arms of an elevated plus maze. We currently tested the hypothesis that the long-lasting impact of IPS during mid-adolescence on open-arm exploration would be ameliorated by social housing. At weaning on PD21, male rats were randomly assigned to one of 3 housing groups: single housed (from weaning at PD21 onward), re-socialized (single housed from PD21–46 and then pair housed from PD47 onward) or pair housed (from PD21 onward). Half of the rats in each housing group were exposed to IPS (elevated platform, foot-shock, water immersion) for 12 days across mid-adolescence and the other half served as housing matched no-stress controls. As hypothesized, the effect of IPS in mid-adolescence on adult levels of open-arm exploration was dependent on housing. Significant IPS-induced increases in open-arm exploration were displayed by single housed rats, and this effect was reduced, but still marginally significant, in re-socialized rats. By contrast, IPS had virtually no effects on open-arm exploration in pair housed rats. In the shock-probe burying test, prior exposure to IPS reduced adult levels of defensive burying in continuously pair housed rats, but had no lasting effects in single housed or re-socialized rats. Taken together, our findings reaffirm that stress during mid-adolescence can have long-lasting effects on adult behavior and highlight the stress reducing properties of social housing.