ISCHEMIC PRECONDITIONING - A LONG-TERM SURVIVAL STUDY USING BEHAVIORAL AND HISTOLOGICAL END-POINTS

In this study we sought to determine if ischemic preconditioning provi ded long term behavioral and histological protection. A second goal wa s to see if ischemic preconditioning conveys its protective effect on CA1 neurons by altering post-ischemic brain temperature. While precond itioning episodes of short duration ischemia (i.e. 1.5 min) provided s ignificant histological protection of CA1 pyramidal cells against a su bsequent severe ischemic insult (i.e. 5 min), this did not result in c omplete behavioural protection. Preconditioned ischemic animals initia lly displayed habituation deficits in an open field test that were com parable to untreated ischemic gerbils. A significant decline in CA1 pr eservation in preconditioned animals was observed when survival time w as extended from 10 (81% protection) to 30 (53% protection) days. In a ddition, protection was not observed in the subiculum and CA2 sector o f the hippocampus where consistent damage was observed in 21/22 gerbil s. Ischemic preconditioning did not markedly affect post-ischemic brai n temperature suggesting that the observed protection was not due to a reduction in temperature during or after the severe ischemic insult. The lack of functional protection within the first 10 days after ische mia, along with the decline of cellular preservation over time, sugges ts that this paradigm may not provide permanent protection.