Effects of Ischemic Tolerance on mRNA Levels of IP3R1, β-Actin,and Neuron-Specific Enolase in Hippocampal CA1 Area of the Gerbil Brain

Global cerebral ischemia induced to Mongolian gerbils by ligation of common carotid arteries (CCAs) is known to result in injury to the hippocampal CA1 region. In this study, we examined whether neuronal injury can be depicted by measuring levels of mRNA encoding inositol 1,4,5-trisphosphate receptor type 1 (IP₃R1), neuron specific enolase (NSE) and -actin and whether these measurements can be use to assess ischemic tolerance. Gerbils were subjected either to cerebral ischemia induced 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 IP₃R1 (26%), NSE (38%) and -actin (50%) could be observed in the hippocampal CA1 region. Although levels of mRNA in the preconditioning group were decreased as compared to the sham control, the levels were significantly higher than those in the ischemic group. These results indicate the feasibility of using mRNA measurement as a parameter to assess cerebral ischemic damage. In addition, based on the differences in the decline in mRNA levels 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 cerebral ischemic insult.