INDUCTION OF ISCHEMIC TOLERANCE IN GERBIL HIPPOCAMPUS BY PRETREATMENTWITH FOCAL ISCHEMIA

WE investigated the induction of ischaemic tolerance in the hippocampa l CA1 neurones to transient forebrain ischaemia following pretreatment with unilateral middle cerebral artery occlusion (MCAO) in gerbils. H istological evaluation was carried out after 5 min bilateral carotid a rtery occlusion (5BCO) in the gerbils with no MCAO pretreatment, MCAO pretreatment 3 days prior to 5BCO (MCAO-3d-5BCO), MCAO pretreatment 7 days prior to 5BCO and sham MCAO pretreatment 3 days prior to 5BCO. CA 1 neurones were preserved at >40% of normal controls only in the left hippocampus in the MCAO-3d-5BCO gerbils. CA1 neurones in the right sid e of MCAO-3d-5BCO gerbils as well as in both sides of animals in the o ther pretreatment groups almost completely disappeared after 5BCO. Whi le the exact mechanism remains to be resolved, pretreatment with focal ischaemia seems to induce ischaemic tolerance in neurones outside of the primary ischaemic lesion.