In this study, we analyzed whether ER Ca2+ release, induced by amyloid-beta (Abeta) and prion (PrP) peptides activates the mitochondrial-mediated apoptotic pathway. In cortical neurons, addition of the synthetic Abeta1-40 or PrP106-126 peptides depletes ER Ca2+ content, leading to cytosolic Ca2+ overload. The Ca2+ released through ryanodine (RyR) and inositol 1,4,5-trisphosphate (IP3R) receptors was shown to be involved in the loss of mitochondrial membrane potential, Bax translocation to mitochondria and apoptotic death. Our data further demonstrate that Ca2+ released from the ER leads to the depletion of endogenous GSH levels and accumulation of reactive oxygen species, which were also involved in the depolarization of the mitochondrial membrane. These results illustrate that the early Abeta- and PrP -induced perturbation of ER Ca2+ homeostasis affects mitochondrial function, activating the mitochondrial-mediated apoptotic pathway and help to clarify the mechanism implicated in neuronal death that occurs in AD and PrD.