Effects of combined pre- and post-natal enrichment on anxiety-like, social, and cognitive behaviours in juvenile and adult rat offspring.

The pre- and post-natal periods are characterized by unrivalled growth and are sensitive to environmental changes. A correctly stimulating early environment is essential for developing natural behaviors and maintaining affective wellness. Five litters of rat progeny were co-housed through gestation until juvenile age in housing providing physical and social enrichment. Five control litters were housed separately in standard conditions. Half of the offspring were tested in the elevated plus-maze and the social interaction test as juveniles (five weeks old) with the other half tested in the Morris water maze. As adults (11 weeks old), the testing groups were reversed. Weight was monitored weekly. Enriched offspring had leaner body weights. In the elevated plus-maze, control juvenile progeny spent a higher percentage of time in the open arms, showed greater locomotor activity, less grooming, and more rearing (males only). In the social interaction test, enriched juvenile offspring were found to sniff their conspecific more, display more self-grooming behaviour as well as show less locomotor activity and body contact. In the Morris water maze probe test, enriched rats demonstrated improved memory for the platform position and more effective search strategies with increased platform crossings, middle crossing as well as more time spent in the platform quadrant and less thigmotaxis behaviour. Adult female rat offspring also demonstrated superior memory for the platform position and crossed the maze middle more often. These results suggest that combined pre- and post-natal environmental enrichment influences physiology and behaviour in offspring rats with some of those influences being long-lasting.