Synthetic Aβ-induced spine loss can be rescued by blockade of NMDA receptors, but not by blockade of action potentials or nAChRs. The CA1 region of hippocampal slice cultures was infected with EGFP virus and incubated in normal medium or in medium containing Aβ (1–42) and AP5, TTX or α-bungarotoxin as indicated. Spine density was measured after 24 h of infection and drug treatment (no treatment: 17 dendrites, 9 slices; Aβ42: 24 dendrites, 10 slices; Aβ42 + AP5: 15 dendrites, 9 slices; Aβ42 + TTX: 13 dendrites, 7 slices; Aβ42 + α-bungarotoxin: 14 dendrites, 7 slices; ANOVA, F = 7.27, P < 0.0001; t test between no treatment and drug-treated groups, *P < 0.002). Error bars represent s.e.m.