Effects of social and physical enrichment on open field activity differ in male and female Sprague-Dawley rats

Environmental enrichment affects performance of neurologically intact organisms and facilitates recovery of function following CNS injury. Only, a few recent studies have examined the extent to which physical versus social aspects of enriched environments separately contribute to superior performance [Pietropaolo S, Branchi I, Cirulli F, Chiarotti F, Aloe L, Alleva E. Long-term effects of the periadolescent environment on exploratory activity and aggressive behavior in mice: social vs. physical enrichment. Physiol Behav 2004;81:443-53; Schrijver NC, Bahr NI, Weiss IC, Wurbel H. Dissociable effects of isolation rearing and environmental enrichment on exploration, spatial learning and HPA activity in adult rats. Pharmacol Biochem Behav 2002;73:209-24] or the extent to which male and females differ in their response to enrichment [Bardo MT, Kiebaur JE, Valone JM, Deaton C. Environmental enrichment decreases intravenous self-administration of amphetamine in male and female rats. Psychopharm 2001;155:278-84; Daniel JM, Roberts S, Dohanich G. Effects of ovarian hormones and environment on radial maze and water maze performance of female rats. Physiol Behav 1999;66:11-20]. The current experiment examined the separate and combined effects of social enrichment (SE) and physical enrichment (PE) on locomotor activity of male and female Sprague-Dawley rats to determine what aspect of enrichment had the greatest effect to alter activity and to determine whether there were sex differences in these effects. Habituation in the open field was used as an index of simple information-processing and refers to the decrease in activity over time that occurs as an animal becomes acclimated to its environment. Faster habituation indicates greater information-processing. The major findings from the current study were: (1) social enrichment has the greatest effect to improve performance (i.e., increased habituation) for both males and females and (2) the effects of enrichment overall generally appear to be greater for males than for females.