Foetal grafts from hippocampal regio superior alleviate ischaemic-induced behavioural deficits.

Transitory global cerebral ischaemia produced in rats by four vessel occlusion for 15 min produced substantial loss of CA1 cells in dorsal hippocampus and minimal other intra- and extra-hippocampal damage. Ischaemic rats showed a long-lasting impairment in spatial navigation in the water maze, and such impairment was sensitive to task difficulty. Groups of ischaemic animals were implanted with foetal tissue dissected from hippocampal regio superior (SUP--containing CA1 field), regio inferior (INF--containing dentate gyrus), and basal forebrain, with grafts sited in the alveus above the damaged CA1 region. Behavioral testing in the water maze (acquisition, retention and a working memory task) was conducted over a period of 4 to 12 weeks after grafting. Only rats receiving the SUP graft showed consistent improvement in water maze performance, relative to ischaemic controls, when tested in retention and working memory. Although the selective effect of CA1-containing grafts suggests repairing of the damaged host circuit, functional recovery may have been related to the greater ability of SUP grafts to survive and grow in the host ischaemic hippocampus.