Neural viability was measured using a MTT reduction kit (Sigma, USA). Briefly, primary cultured neurons were exposed to designated periods of OGD. Twenty-four hours after the reperfusion, neurons were incubated with 500 μg/ml MTT in culture medium at 37°C for 4 h. Next, the medium was removed, and 100 μL DMSO was added into each well of 96 well multiplates to dissolve the crystals. The absorbance at 550 nm was measured with a microplate reader (PerkinElmer, USA). Neural death was determined by measuring the concentration of LDH released from the damaged cells with a LDH assay kit (Dojindo, Japan) following manufacturer’s instruction.