Systemic administration of erythropoietin (EPO) has neuroprotective effects in neonatal hypoxic ischemia (HI) (Matsushita et al., SFN Abstract, 2002). This neuroprotective effect may be related to Bcl-xL, an anti-apoptotic regulatory protein (Renzi et al., Brain Res Mol Brain Res 104:86, 2002, Wen TC et al., J Neurosci Res 67:795, 2002). To understand the mechanism of protective effect of EPO in neonatal period, we examined the effect of EPO on Bcl-xL mRNA expression in neonatal mice after HI. Animals were injected i.p. on postnatal day 7 with 5U/g EPO (n=11) or Vehicle (VEH, n=11). One hour later, a half of the animals in each treatment group were subject to HI. The right common carotid artery was ligated and animals recovered for 90 min. before hypoxic exposure (50 min, 10% O2). The remaining animals received Sham surgery. Brains were removed 3h after hypoxia, immediately frozen on dry ice and cut into 20µm sections. Bcl-xL mRNA level was examined in cortex with in situ hybridization. Bcl-xL mRNA express...