Determination of acetylcholinesterase (AChE) activity

AChE assay was performed using an Acetylcholinesterase Assay Kit (Abcam, Cambridge, UK) according to the manufacturer's protocols. Briefly, the brain tissue was homogenized in 0.1M phosphate buffer (Sigma-Aldrich Co.), after which the homogenates were stored at -70℃ until analysis. The sample or standards and AChE reaction mixture were then incubated on a 96-well plate for 20 min at room temperature while protected from the light. Color alterations were read using a Versa max plate reader (Molecular Devices, Sunnyvale, CA, USA) at 405 nm.