Influence of an enriched environment and cortical grafting on functional outcome in brain infarcts of adult rats.

The purpose of this work was to study if enriched housing conditions and fetal neocortical transplantation could enhance the functional outcome after focal brain ischemia in adult rats. The right middle cerebral artery (MCA) was ligated in 34 inbred, spontaneously hypertensive male rats, which were then randomly divided into three groups. Groups A and B were transferred to an enriched environment, i.e., a large cage with opportunities for various activities but not forcing the rats to do any particular tasks; group C was kept in standard laboratory cages. Three weeks after the MCA occlusion blocks of fetal neocortical tissue (Embryonic Day 17) were transplanted to the infarct cavity in groups B and C. Rats in group A (n = 11) and group B (n = 11) performed equally well and significantly better than rats in group C (n = 10) when placed on an inclined plane and when traversing a rotating pole 6 and 9 weeks after the MCA occlusion and in a leg placement test at 9, but not 6 and 12 weeks. Skilled forelimb function did not differ between the groups. Infarct size and thalamic atrophy did not differ between the groups and graft size was similar in group B and C. There was no correlation between infarct size and motor function in any of the tests in rats housed in an enriched environment. Since the environment can significantly alter functional outcome without reducing infarct size we suggest that more attention should be given to the role of the laboratory environment and to long term behavioral outcome in experimental stroke.