Impacts of prolonged different social (equality and inequality) conditions on spatial learning and memory deficits, as well as obsessive-compulsive disorder-like behaviors in male rats

Abstract

INTRODUCTION: Observing others' suffering and being observed during stress may differentially influence behavioral patterns and brain functions such as learning, memory, and mood. This study investigated the effects of prolonged social equality and inequality on spatial learning and memory deficits, as well as obsessive-compulsive disorder (OCD)-like behaviors in rats. METHODS: Male rats were randomly divided into six groups: control (Co), pseudo-observer (Pse-Ob), pseudo-demonstrator (Pse-De), observer (Ob), demonstrator (De), and co-demonstrator (Co-De). All groups except the control underwent restraint stress induction (2 h/day for 21 days) using both social equality and inequality models. The social inequality model consisted of a restrained demonstrator and a free-moving observer, while the social equality model used two restrained co-demonstrators. Spatial learning and memory, as well as OCD-like behaviors, were assessed using the Barnes Maze (BM) and Marble Burying (MB) tests, respectively. RESULTS: Escape latency and traveled distance were significantly increased in all stressed groups relative to the control group during both the training and probe trials in the BM test. In these trials, these variables were significantly reduced in the Ob and Co-De groups relative to the De group. The number of buried marbles was significantly higher in the De and Co-De groups than in the Co and Pse-De groups in the MB test. Furthermore, a significant increase was observed in the Co-De group relative to the Ob group. CONCLUSION: Social inequality-induced stress impairs spatial learning and memory, but this can be significantly mitigated by the presence of a familiar conspecific in a similar situation. Restraint stress in the presence of others was able to induce OCD-like behaviors under both equal and inequal conditions.