Environmental enrichment in BALB/c mice - Effects in classical tests of anxiety and exposure to a predatory odor

Early stimulation by environmental enrichment generally leads to improved l earning abilities in rodents. However, the effects of environmental enrichm ent on emotional reactivity remain more questionable and were mostly studie d by using classical tests of anxiety based on confrontation with a novel e nvironment. The main goal of our study was to use different tests of anxiet y to compare BALB/c mice reared in either a standard condition (SC) or enri ched condition (EC). Exposure to cat feces was used to assess anxiety accor ding to an ethoexperimental approach and a comparison was made with the ele vated plus maze and the open field as classical tests of anxiety. In accord ance with previous works, our results show that EC mice were more active th an SC mice in the elevated plus maze and the open field. Thus, possibly as a direct consequence of frequent changes in their breeding conditions, reac tivity to a novel environment was reduced in EC mice. However, the cat odor test revealed no intergroup differences for behavior, although corticoster one levels were reduced in EC mice. These results indicate that classical ( i.e. reaction to novel environments) and ethoexperimental-based tests (i.e. exposure to predator cues) measure different aspects of emotional reactivi ty. Further studies using ECs should be useful for the delineation of the n eurobiological substrates of these different reactions. (C) 2001 Elsevier S cience Inc. All rights reserved.