Surface proteins of cortical cultures were biotinylated and processed for immunoblots. Representative western blots of surface and total (a), GluA1; (b), GluA2; (c), GluN1; (d), GluN2B; (e), GluN2A; and (f), GABAAβ2/3 levels after treatment with Aβ monomers and oligomers from 7PA2-CM and control CHO-CM fractions. Histograms (lower panels) show quantification of surface receptors normalized to total receptor levels. Histograms show oligomers but not monomers lead to significant loss of surface NMDA and AMPA receptors (**p < 0.01; n = 4)