Caspase-3 activity assay

After drug treatment, caspase-3 activity assay was carried out according to the manufacturer's protocol (Abcam, ab39401). Pure hippocampal neurons were lysed with 50 µl chilled cell lysis buffer and incubated, centrifuged, and analyzed for total protein using a Bradford assay. The samples were diluted in a ratio of 50 µg protein in 50 µl cell lysis buffer for each assay, then 2× reaction buffer and DEVD-p-NA substrate were added to each sample. After incubation, absorbance was read at a wavelength of 405 nm using a microplate multi-label counter system (Perkin-Elmer, Boston, MA).