The present study investigated the effects of amyloid-beta peptides on nicotinic ACh receptors (Torpedo, alpha4beta2, and alpha7 receptors) and AMPA receptors expressed in Xenopus oocytes by monitoring whole-cell membrane currents. Ten-minutes treatment with amyloid-beta(1-42) (1 muM) inhibited Torpedo ACh receptor currents, reaching 53% of original levels 30 min after treatment. Amyloid-beta(1-40) inhibited the currents in a dose-dependent manner (0.1-10 muM) during treatment, gradually reversing after treatment. Amyloid-beta(1-40) and amyloid-beta(1-42) (0.1 muM) depressed alpha4beta2 receptor currents to each 69% and 62% of original levels at 10-min treatment and lesser depression was obtained with alpha7 receptors. Amyloid-beta(1-42) (0.1 muM) did not significantly inhibit AMPA receptor currents, but amyloid-beta(1-40) (0.1 muM) potentiated the currents to 145-191% of original levels. Amyloid-beta peptides, thus, exert their diverse actions on nicotinic ACh receptors and AMPA receptors, and the inhibitory actions on nicotinic ACh receptors may account for the deterioration of learning and memory in Alzheimer's disease. (C) 2002 Elsevier Science (USA). All rights reserved.