Abstract: Objective To observe the effect of over-expressed amyloid procursor protein (APP) gene, one of AD-related genes and overproduction of β-amyloid (Aβ) peptides, on the cholinergic receptor binding and the ChAT activity in human neuroblastoma cell line SH-SY5Y. METHODS SH-SY5Y cells were stably transfected with pCMV695 plasmid containing wild type human APP695 gene by Lipofectamine 2000 method. The expression of APP was detected by Western blot. Aβcontents were test by ELISA assay in over-expression SH-SY5Y cell clones (SH-SY5Y-APP). The special binding of muscarinic and nicotinic cholinergic receptors in those Aβ-overproducing cell clones were determined by radio-ligand binding method. The cholinergic acetyl transferase (ChAT) activity was assayed by radiao-immunoassay. RESULTS No evident morphologic changes of cytotoxicity were detected after transfection. When Aβproduction was 2～2.6 times as much as that of normal cells (i.e. it was below the concentrations of 115～150 pmol/L), muscarinic receptor binding was decreased from 18.5 % to 21.9 % (P<0.05) compared with normal cells. However, no marked alterations in nicotinic receptor binding and the ChAT activity were found. CONCLUSION In this experiment, we found that muscarinic receptor binding inhibition was showed before cytotoxicity, nicotinic receptor binding and ChAT activity changes in SH-SY5Y-APP. It is suggested that the increase of Aβproduction could independently caused the cholinergic dysfunction in early stage of AD brain tissues by muscarinic receptor binding inhibition.