EFFECTS OF ISCHEMIC TOLERANCE ON MESSENGER-RNA LEVELS OF IP(3)R1, BETA-ACTIN, AND NEURON-SPECIFIC ENOLASE IN HIPPOCAMPAL CA1 AREA OF THE GERBIL BRAIN

Global cerebral ischemia induced to Mongolian gerbils by ligation of c ommon carotid arteries (CCAs) is known to result in injury to the hipp ocampal CAI region. In this study, we examined whether neuronal injury can be depicted by measuring levels of mRNA encoding inositol 1,4,5-t risphosphate receptor type 1 (IP(3)R1), neuron specific enolase (NSE) and beta-actin and whether these measurements can be use to assess isc hemic tolerance. Gerbils were subjected either to cerebral ischemia in duced by ligation of both CCAs for 5 min, or to an ischemic tolerance paradigm in which a 2 min ischemic preconditioning was performed 24 hr prior to the 5 min ischemia. At 48 hr after the 5 min ischemic insult , significant decreases in mRNA levels for IP(3)R1 (26%), NSE (38%) an d beta-actin (50%) could be observed in the hippocampal CA1 region. Al though levels of mRNA in the preconditioning group were decreased as c ompared to the sham control, the levels were significantly higher than those in the ischemic group. These results indicate the feasibility o f using mRNA measurement as a parameter to assess cerebral ischemic da mage. In addition, based on the differences in the decline in mRNA lev els between the ischemia group and the preconditioned ischemia group, it can be concluded that this ischemic tolerance paradigm could offer partial protection (around 45%) against the injury due to the 5 min ce rebral ischemic insult.