Natural flavonoids ameliorate amyloid-β peptide (Aβ)-induced neurotoxicity. We examined whether the fustin flavonoid affects Aβ-induced learning impairment in mice. Repeated treatment with fustin significantly attenuated Aβ (1-42)-induced conditioned fear and passive avoidance behaviors. This effect was comparable to that of EGb761, a standard extract of ginkgo. Fustin treatment significantly prevented decreases in acetylcholine (ACh) levels, choline acetyltransferase (ChAT) activity, and ChAT gene expression induced by Aβ (1-42). Fustin also consistently suppressed increases in acetyl cholinesterase (AChE) activity and AChE gene expression induced by Aβ (1-42). In addition, fustin significantly attenuated Aβ (1-42)-induced selective decreases in muscarinic M1 receptor gene expression and muscarinic M1 receptor binding activity (as determined by [3H] pirenzepine binding) by modulating extracellular signal-regulated kinase 1/2 (ERK 1/2) and cAMP response-element binding protein (CREB) phosphorylation and brain-derived neurotrophic factor (BDNF) expression. These effects of fustin were reversed by treatment with dicyclomine, a muscarinic M1 receptor antagonist, and SL327, a selective ERK inhibitor, but not by chelerythrine, a pan-protein kinase C (PKC) inhibitor. Taken together, our results suggest that fustin attenuates Aβ (1-42)-impaired learning, and that the ERK/CREB/BDNF pathway is important for the M1 receptor-mediated cognition-enhancing effects of fustin.
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