The effects of dietary fatty acid composition combined with environmental enrichment on brain and behavior in mice.

Abstract

In this study we investigated the effects of dietary fatty acid (FA) composition combined with postweaning environmental enrichment on brain fatty acid composition and behavior in mice. There were three dietary conditions: a saturated fat group deficient in essential fatty acids, a group deficient in n-3 fatty acids only, and a control group containing both n-3 and n-6 fatty acids in a ratio of 0.27. Animals were fed these diets during pregnancy and lactation and after weaning. Brain fatty acid composition was determined on days 1, 9, 17 and 25 after birth and in adult animals at 3 months. At weaning two females from each litter were assigned randomly to either an enriched or standard environmental condition. After six weeks in these environments they were tested in the Morris water maze and open field. Adult percentages of 22:6n-3 were present in the brain within the first week after birth. These values were reduced by 50% in the n-3 deficient diet and by 80% in the saturated fat diet; adult animals on the saturated fat diet were also severely retarded in growth. Animals fed the saturated fat diet were initially slightly slower in locating the hidden platform in the Morris maze relative to the control group, but this was not apparent in the reversal learning phase; a cued learning task using a visible platform indicated that these effects did not appear to be related to differences in motor or motivational capacities. The n-3 deficient group did not differ from either the saturated fat group or the controls. All dietary groups showed beneficial effects of environmental enrichment in decreasing their latency to locate the hidden platform, and these effects appeared to be partially independent of the increased swimming speed of the enriched animals. Enriched animals in all groups showed less rearing activity in the open field and spent more time stationary; the animals fed saturated fat reared less and travelled shorter distances more slowly. In all cases the effects of diet and environment were additive, thereby providing little support for the hypothesis that dietary fatty acid composition would affect the animals' capacity to benefit from the functional effects of environmental enrichment.