Norepinephrine (NE) induces endoplasmic reticulum (ER) unfolded protein response and reduces maturation and translocation of NE transporter to cell membrane via enhanced formation of reactive oxygen species in PC12 cells. Here we investigated if ER stress is also implicated in the pro-apoptotic effect of NE. We found that the apoptotic effect of NE was associated with increased processing of ER-resident pro-caspase-12, cleavage of caspase-9 and -3, and mitochondrial release of cytochrome c. ER stress was evidenced by up-regulation of ER chaperone GRP78 and transcription factor CHOP, and the translocation of XBP-1 from the ER to the nucleus by NE. NE also reduced phospho-Akt (Ser473), indicating suppression of the phosphatidylinositol 3 kinase (PI3K)-Akt survival pathway. Similar findings were produced by thapsigargin. Nerve growth factor (NGF), which promotes the PI3K-Akt activity, reduced the effects of NE and thapsigargin on apoptosis and activation of caspase-12 and -3. However, the effects of NE, but not of thapsigargin, were abolished by pretreatment with superoxide dismutase (SOD) and catalase. In contrast, the PI3K inhibitors LY294002 and wortmannin abolished the protective effects of both SOD/catalase and NGF on NE-induced apoptosis. The functional importance of caspase-12 activation was supported by the use of Z-ATAD-FMK which reduced the NE-induced procession of caspase-12 and cell apoptosis, but the caspase-12, -9 and -3 inhihitors had no effects on the increase of cytosolic cytochrome c produced by NE. In contrast, the release of mitochondrial cytochrome c was abolished by SOD/catalase and NGF. The results indicate that NE induces cell apoptosis by both ER stress and mitochondrial death pathway, and that the effects of NE were mediated via oxidative stress and inhibition of the PI3K-Akt survival pathway.