EFFECTS OF ENRICHED HOUSING ENVIRONMENT ON THE BEHAVIOR OF YOUNG MALEAND FEMALE MICE IN 4 EXPLORATORY TASKS

Two groups of NMRI outbred mice were reared in different housing condi tions from weaning until testing. 68 subjects were allocated to groups of four sex-mates. Individuals of the control groups (C-mice, 20 fema les, 16 males) were kept in standard laboratory cages (Makrolon type I II) without any contents except wood shavings on the floor; individual s of the experimental groups (E-mice, 16 females, 16 males) were kept in Makrolon type III cages which were enriched with two insets, a plas tic box with several openings and a wooden scaffolding. When 9 to 10 w eeks old, the young mice were tested in four exploratory tasks. In two behavioural tests that require climbing over an obstacle, E-mice clim bed over a barrier and out of a Petri dish after a considerably shorte r latency period than C-mice (both: p < 0.001). In a specific behaviou ral test for anxiety, the elevated plus-maze test, E-males showed a hi gher tendency than C-males to visit the open arms of the maze (p < 0.0 01), which indicates reduced anxiety, whereas no difference occurred b etween females. A higher open-field activity compared to controls was apparent in E-mice of both sexes (females: p < 0.01; males: p < 0.05). It is suggested that the enriched rearing environment has a combined effect on emotionality, activity and sensorimotor skills.