GDNF and brain ischemia: Using the same model, intravenous injection of microglia 48 h after cerebral ischemia reduced neuronal apoptosis, increased neurotrophic factors including glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and anti-inflammatory cytokines IL-4 and IL-15, and promoted functional neurological recovery (Narantuya et al., 2010a).