Induction of cytosolic and ER stress genes after transient cerebral ischemia. Brain sections were obtained from sham-operated control rats and rats subjected to 15 mins of ischemia followed by 4, 24, and 48 h of reperfusion. Ribo-probes were used for in situ hybridization. Cytosolic stress gene hsp70 is dramatically upregulated, whereas ER chaperone grp78 is mildly or moderately induced in 24 h of reperfusion in CA1 neurons undergoing delayed neuronal death after ischemia. At 48 h of reperfusion, however, both HSP70 and GRP78 mRNAs decline because delayed neuronal death occurred in CA1 neurons after transient cerebral ischemia (BR Hu, unpublished observation).