Fustin flavonoid attenuates Delta b-amyloid (1-42)-induced learning impairment

Natural flavonoids ameliorate amyloid- Delta *b peptide (A Delta *b)-induced neurotoxicity. We examined whether the fustin flavonoid affects A Delta *b-induced learning impairment in mice. Repeated treatment with fustin significantly attenuated A Delta *b (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 A Delta *b (1-42). Fustin also consistently suppressed increases in acetyl cholinesterase (AChE) activity and AChE gene expression induced by A Delta *b (1-42). In addition, fustin significantly attenuated A Delta *b (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 A Delta *b (1-42)-impaired learning, and that the ERK/CREB/BDNF pathway is important for the M1 receptor-mediated cognition-enhancing effects of fustin. [copy 2009 Wiley-Liss, Inc.