This study was designed to assess the effects of vitamin D3 pretreatment on the expression of neuronal marker NeuN, subunits of NADPH oxidase, MMP9, and microglial marker (Iba1), as well as on the oxidative stress parameters including the levels of O2·−, malondialdehyde (MDA), and reduced glutathione (GSH) and the activities of glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD), and gamma-glutamylcysteine ligase (γGCL) in the cortex and hippocampus of Mongolian gerbils subjected to global cerebral ischemia followed by 24 hours of reperfusion (I/R). The gene discussed is GSR; the disease is brain ischemia.