Effects of post-weaning social isolation and environmental enrichment on exploratory behavior and anxiety in Wistar rats

Adverse early experience is generally regarded as a risk factor for both externalizing and internalizing behavioral disorders in humans. It can be modeled in rats by a post-weaning social isolation procedure. Effects of social isolation might possibly be ameliorated by environmental enrichment. In the current study, 24 male Wistar rats were divided post-weaning into four rearing conditions: control, environmental enrichment (EE), social isolation (SI) and a combination of the two experimental conditions; (EE+SI). Two observations of the effects of rearing conditions on the rate of social and object interactions were conducted during the juvenile and post-pubertal stages of development. The SI condition led to a marked increase of social interactions during the juvenile phase, but did not affect object interactions. The EE condition increased the level of social interactions during both the juvenile and post-pubertal measurements. The effects of early rearing conditions on adult exploratory behavior were less clear, with a significant difference between the groups obtained in one of three behavioral tests. Results suggest a general robustness in the development of adult exploratory behavior and anxiety when rats were exposed to early social isolation and provided brief opportunities for social play during the juvenile period. Further studies, aimed at distinguishing play-related protective factors serving against long-term adverse effects of juvenile social isolation, are suggested.