The expression profile of neurotrophin-3 (NT-3) mRNA in the rat hippocampus after forebrain ischemia was investigated by Northern blot and S1 nuclease protection analyses. The NT-3 transcripts in the hippocampus immediately decreased after ischemic insult, became undetectable within 3 h and remained at undetectable levels for at least 7 days. In contrast, the expression of c-fos and c-jun mRNA transiently increased both in the cerebral cortex and in the hippocampus. These results suggest that brain ischemia triggers dynamic changes in gene expression including a neurotrophic factor, which may cause functional and/or morphological changes of the neuronal network. © 1992.