Evaluation of the Effects of Enlarged Housing on Social Play and Reward Seeking in Rats

The legal minimum dimensions for laboratory rat housing prevent rats from fully performing their behavioural repertoire. In the regular cages, rats cannot run, climb, or even stand upright. The need to house rats in larger cages has been recognized internationally from a welfare perspective, which has led to the development of several commercial cage systems. It is, however, important to evaluate the effect of changes in housing conditions on behaviour in existing animal models. The aim of the study was to determine whether housing animals in larger cages with mandatory enrichment or with additional enrichment would affect play behaviour or sucrose reward sensitivity. This paper describes the effect of housing rats in enlarged cages, the EC4Rats, on social play and for reward seeking. A total of 48 male Lister Hooded rats, PND21-23 at the start of the experiment, were assigned to one of three experimental groups, i.e., (1) standard housing with standard enrichment, (2) EC4Rats housing with standard enrichment and (3) EC4Rats housing with EC4Rats enrichment. The results of the study show that despite subtle differences in social play behaviour, housing rats in these larger cages did not affect reward sensitivity nor the motivation for sucrose self-administration in rats. Taken together, these findings suggest that housing systems that provide rats with more opportunities to engage in natural behaviours do not affect social play or reward-related behaviour.