Neurologic deterioration after massive cerebral infarct should be identified at an early stage for medical and surgical treatments. We investigated the effect of hydrogen sulfide on the excitotoxity of PC12 cells exposed to oxygen–glucose deprivation (OGD) and its effect on the apoptosis of brain tissues in rats with middle cerebral artery occlusion (MCAO). Rats with MCAO were treated with SAM, a cystathionine beta-synthase (CBS) activator, or AOAA, a CBS inhibitor. Hydrogen sulfide content in the brain tissues of infarcted patients or rats wi...