RESUMEN
Amyloid-beta peptide oligomers (AßO) have been considered "primum movens" for a cascade of events that ultimately cause selective neuronal death in Alzheimer's disease (AD). However, initial events triggered by AßO have not been clearly defined. Synaptic (Syn) N-methyl-d-aspartate receptors (NMDAR) are known to activate cAMP response element-binding protein (CREB), a transcriptional factor involved in gene expression related to cell survival, memory formation and synaptic plasticity, whereas activation of extrasynaptic (ESyn) NMDARs was linked to excitotoxic events. In AD brain, CREB phosphorylation/activation was shown to be altered, along with dyshomeostasis of intracellular Ca2+ (Ca2+ i). Thus, in this work, we analyze acute/early and long-term AßO-mediated changes in CREB activation involving Syn or ESyn NMDARs in mature rat cortical neurons. Our findings show that acute AßO exposure produce early increase in phosphorylated CREB, reflecting CREB activity, in a process occurring through Syn NMDAR-mediated Ca2+ influx. Data also demonstrate that AßO long-term (24 h) exposure compromises synaptic function related to Ca2+-dependent CREB phosphorylation/activation and nuclear CREB levels and related target genes, namely Bdnf, Gadd45γ, and Btg2. Data suggest a dual effect of AßO following early or prolonged exposure in mature cortical neurons through the activation of the CREB signaling pathway, linked to the activation of Syn NMDARs.