INCREASED F1 GAP-43 MESSENGER-RNA ACCUMULATION IN GERBIL HIPPOCAMPUS AFTER BRAIN ISCHEMIA/

To assess whether ischemia could induce GAP-Q mRNA expression, we perf ormed in situ hybridization in gerbil brains that had been subjected t o 5 min of global ischemia. In control dentate granule cells, little h ybridization was detected in contrast to the intense signal generated by pyramidal neurons of the adult hippocampal formation. After ischemi a, we detected a robust GAP-43 signal over hippocampal granule cells a t 3 h of reperfusion, persisting through 7 days, and disappearing by 1 4 days. This demonstrated GAP-43 gene induction after ischemia, and su ggests that GAP-43 may be involved in reactive events, including fiber sprouting and synaptic reorganization, that follow ischemia.